[PATCH bpf-next v5 00/25] Local kptrs, BPF linked lists

[PATCH bpf-next v5 00/25] Local kptrs, BPF linked lists

[Kumar Kartikeya Dwivedi]

This series introduces user defined BPF objects, by introducing local
kptrs. These are kptrs (strongly typed pointers) that refer to objects
of a user defined type, hence called "local" kptrs. This allows BPF
programs to allocate their own objects, build their own object
hierarchies, and use the basic building blocks provided by BPF runtime
to build their own data structures flexibly.

Then, we introduce the support for single ownership BPF linked lists,
which can be put inside BPF maps, or local kptrs, and hold such
allocated local kptrs as elements. It works as an instrusive collection,
which is done to allow making local kptrs part of multiple data
structures at the same time in the future.

The eventual goal of this and future patches is to allow one to do some
limited form of kernel style programming in BPF C, and allow programmers
to build their own complex data structures flexibly out of basic
building blocks.

The key difference will be that such programs are verified to be safe,
preserve runtime integrity of the system, and are proven to be bug free
as far as the invariants of BPF specific APIs are concerned.

One immediate use case that will be using the entire infrastructure this
series is introducing will be managing percpu NMI safe linked lists
inside BPF programs.

The other use case this will serve in the near future will be linking
kernel structures like XDP frame and sk_buff directly into user data
structures (rbtree, pifomap, etc.) for packet queueing. This will follow
single ownership concept included in this series.

The user has complete control of the internal locking, and hence also
the batching of operations for each critical section.

The features are:
- Local kptrs - User defined kernel objects.
- bpf_obj_new, bpf_obj_drop to allocate and free them.
- Single ownership BPF linked lists.
  - Support for them in BPF maps.
  - Support for them in local kptrs.
- Global spin locks.
- Spin locks inside local kptrs.

Some other notable things:
- Completely static verification of locking.
- Kfunc argument handling has been completely reworked.
- Argument rewriting support for kfuncs.
- Search pruning now understands non-size precise registers.
- A new bpf_experimental.h header as a dumping ground for these APIs.

Any functionality exposed in this series is NOT part of UAPI. It is only
available through use of kfuncs, and structs that can be added to map
value may also change their size or name in the future. Hence, every
feature in this series must be considered experimental.

Follow-ups:
-----------
 * Support for kptrs (local and kernel) in local storage and percpu maps + kptr tests
 * Fixes for helper access checks rebasing on top of this series

Next steps:
-----------
 * NMI safe percpu single ownership linked lists (using local_t protection).
 * Lockless linked lists.
 * Allow RCU protected local kptrs. This then allows RCU protected list
   lookups, since spinlock protection for readers does not scale.
 * Introduce bpf_refcount for local kptrs, shared ownership.
 * Introduce shared ownership linked lists.
 * Documentation.

Changelog:
----------
 v4 -> v5
 v4: https://lore.kernel.org/bpf/20221103191013.1236066-1-memxor@gmail.com

  * Add a lot more selftests (failure, success, runtime, BTF)
  * Make sure series is bisect friendly
  * Move list draining out of spin lock
    * This exposed an issue where bpf_mem_free can now be called in
      map_free path without migrate_disable, also fixed that.
  * Rename MEM_ALLOC -> MEM_RINGBUF, MEM_TYPE_LOCAL -> MEM_ALLOC (Alexei)
  * Group lock identity into a struct active_lock { ptr, id } (Dave)
  * Split set_release_on_unlock logic into separate patch (Alexei)

 v3 -> v4
 v3: https://lore.kernel.org/bpf/20221102202658.963008-1-memxor@gmail.com

  * Fix compiler error for !CONFIG_BPF_SYSCALL (Kernel Test Robot)
  * Fix error due to BUILD_BUG_ON on 32-bit platforms (Kernel Test Robot)

 v2 -> v3
 v2: https://lore.kernel.org/bpf/20221013062303.896469-1-memxor@gmail.com

  * Add ack from Dave for patch 5
  * Rename btf_type_fields -> btf_record, btf_type_fields_off ->
    btf_field_offs, rename functions similarly (Alexei)
  * Remove 'kind' component from contains declaration tag (Alexei)
  * Move bpf_list_head, bpf_list_node definitions to UAPI bpf.h (Alexei)
  * Add note in commit log about modifying btf_struct_access API (Dave)
  * Downgrade WARN_ON_ONCE to verbose(env, "...") and return -EFAULT (Dave)
  * Add type_is_local_kptr wrapper to avoid noisy checks (Dave)
  * Remove unused flags parameter from bpf_kptr_new (Alexei)
  * Rename bpf_kptr_new -> bpf_obj_new, bpf_kptr_drop -> bpf_obj_drop (Alexei)
  * Reword comment in ref_obj_id_set_release_on_unlock (Dave)
  * Fix return type of ref_obj_id_set_release_on_unlock (Dave)
  * Introduce is_bpf_list_api_kfunc to dedup checks (Dave)
  * Disallow BPF_WRITE to untrusted local kptrs
  * Add details about soundness of check_reg_allocation_locked logic
  * List untrusted local kptrs for PROBE_MEM handling

 v1 -> v2
 v1: https://lore.kernel.org/bpf/20221011012240.3149-1-memxor@gmail.com

  * Rebase on bpf-next to resolve merge conflict in DENYLIST.s390x
  * Fix a couple of mental lapses in bpf_list_head_free

 RFC v1 -> v1
 RFC v1: https://lore.kernel.org/bpf/20220904204145.3089-1-memxor@gmail.com

  * Mostly a complete rewrite of BTF parsing, refactor existing code (Kartikeya)
  * Rebase kfunc rewrite for bpf-next, add support for more changes
  * Cache type metadata in BTF to avoid recomputation inside verifier (Kartikeya)
  * Remove __kernel tag, make things similar to map values, reserve bpf_ prefix
  * bpf_kptr_new, bpf_kptr_drop
  * Rename precision state enum values (Alexei)
  * Drop explicit constructor/destructor support (Alexei)
  * Rewrite code for constructing/destructing objects and offload to runtime
  * Minimize duplication in bpf_map_value_off_desc handling (Alexei)
  * Expose global memory allocator (Alexei)
  * Address other nits from Alexei
  * Split out local kptrs in maps, more kptrs in maps support into a follow up

Links:
------
 * Dave's BPF RB-Tree RFC series
   v1 (Discussion thread)
     https://lore.kernel.org/bpf/20220722183438.3319790-1-davemarchevsky@fb.com
   v2 (With support for static locks)
     https://lore.kernel.org/bpf/20220830172759.4069786-1-davemarchevsky@fb.com
 * BPF Linked Lists Discussion
   https://lore.kernel.org/bpf/CAP01T74U30+yeBHEgmgzTJ-XYxZ0zj71kqCDJtTH9YQNfTK+Xw@mail.gmail.com
 * BPF Memory Allocator from Alexei
   https://lore.kernel.org/bpf/20220902211058.60789-1-alexei.starovoitov@gmail.com
 * BPF Memory Allocator UAPI Discussion
   https://lore.kernel.org/bpf/d3f76b27f4e55ec9e400ae8dcaecbb702a4932e8.camel@fb.com

Kumar Kartikeya Dwivedi (25):
  bpf: Remove BPF_MAP_OFF_ARR_MAX
  bpf: Fix copy_map_value, zero_map_value
  bpf: Support bpf_list_head in map values
  bpf: Rename RET_PTR_TO_ALLOC_MEM
  bpf: Rename MEM_ALLOC to MEM_RINGBUF
  bpf: Introduce local kptrs
  bpf: Recognize bpf_{spin_lock,list_head,list_node} in local kptrs
  bpf: Verify ownership relationships for user BTF types
  bpf: Allow locking bpf_spin_lock in local kptr
  bpf: Allow locking bpf_spin_lock global variables
  bpf: Allow locking bpf_spin_lock in inner map values
  bpf: Rewrite kfunc argument handling
  bpf: Drop kfunc bits from btf_check_func_arg_match
  bpf: Support constant scalar arguments for kfuncs
  bpf: Teach verifier about non-size constant arguments
  bpf: Introduce bpf_obj_new
  bpf: Introduce bpf_obj_drop
  bpf: Permit NULL checking pointer with non-zero fixed offset
  bpf: Introduce single ownership BPF linked list API
  bpf: Add 'release on unlock' logic for bpf_list_push_{front,back}
  selftests/bpf: Add __contains macro to bpf_experimental.h
  selftests/bpf: Update spinlock selftest
  selftests/bpf: Add failure test cases for spin lock pairing
  selftests/bpf: Add BPF linked list API tests
  selftests/bpf: Add BTF sanity tests

 Documentation/bpf/kfuncs.rst                  |   30 +
 include/linux/bpf.h                           |  113 +-
 include/linux/bpf_verifier.h                  |   24 +-
 include/linux/btf.h                           |   67 +-
 include/linux/filter.h                        |    8 +-
 include/uapi/linux/bpf.h                      |   10 +
 kernel/bpf/btf.c                              |  808 +++++-----
 kernel/bpf/core.c                             |   16 +
 kernel/bpf/helpers.c                          |  143 +-
 kernel/bpf/map_in_map.c                       |    5 -
 kernel/bpf/ringbuf.c                          |    6 +-
 kernel/bpf/syscall.c                          |   30 +-
 kernel/bpf/verifier.c                         | 1346 +++++++++++++++--
 net/bpf/bpf_dummy_struct_ops.c                |   14 +-
 net/core/filter.c                             |   34 +-
 net/ipv4/bpf_tcp_ca.c                         |   13 +-
 net/netfilter/nf_conntrack_bpf.c              |   17 +-
 tools/include/uapi/linux/bpf.h                |   10 +
 tools/testing/selftests/bpf/DENYLIST.s390x    |    1 +
 .../testing/selftests/bpf/bpf_experimental.h  |   68 +
 .../testing/selftests/bpf/prog_tests/dynptr.c |    2 +-
 .../bpf/prog_tests/kfunc_dynptr_param.c       |    2 +-
 .../selftests/bpf/prog_tests/linked_list.c    |  524 +++++++
 .../selftests/bpf/prog_tests/spin_lock.c      |  133 ++
 .../selftests/bpf/prog_tests/spinlock.c       |   45 -
 .../testing/selftests/bpf/progs/linked_list.c |  370 +++++
 .../testing/selftests/bpf/progs/linked_list.h |   56 +
 .../selftests/bpf/progs/linked_list_fail.c    |  581 +++++++
 .../selftests/bpf/progs/test_spin_lock.c      |    4 +-
 .../selftests/bpf/progs/test_spin_lock_fail.c |  204 +++
 tools/testing/selftests/bpf/verifier/calls.c  |    2 +-
 .../selftests/bpf/verifier/ref_tracking.c     |    4 +-
 .../testing/selftests/bpf/verifier/ringbuf.c  |    2 +-
 .../selftests/bpf/verifier/spill_fill.c       |    2 +-
 34 files changed, 4012 insertions(+), 682 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/bpf_experimental.h
 create mode 100644 tools/testing/selftests/bpf/prog_tests/linked_list.c
 create mode 100644 tools/testing/selftests/bpf/prog_tests/spin_lock.c
 delete mode 100644 tools/testing/selftests/bpf/prog_tests/spinlock.c
 create mode 100644 tools/testing/selftests/bpf/progs/linked_list.c
 create mode 100644 tools/testing/selftests/bpf/progs/linked_list.h
 create mode 100644 tools/testing/selftests/bpf/progs/linked_list_fail.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_spin_lock_fail.c


base-commit: 25906092edb4bcf94cb669bd1ed03a0ef2f4120c
prerequisite-patch-id: c763e9eecf8258840e7db20e4475c26f4c7800bc
prerequisite-patch-id: 553e0a3f3035d36a96bdcc798793cbecc519d3e7
-- 
2.38.1

[PATCH bpf-next v5 01/25] bpf: Remove BPF_MAP_OFF_ARR_MAX

[Kumar Kartikeya Dwivedi]

In f71b2f64177a ("bpf: Refactor map->off_arr handling"), map->off_arr
was refactored to be btf_field_offs. The number of field offsets is
equal to maximum possible fields limited by BTF_FIELDS_MAX. Hence, reuse
BTF_FIELDS_MAX as spin_lock and timer no longer are to be handled
specially for offset sorting, fix the comment, and remove incorrect
WARN_ON as its rec->cnt can never exceed this value. The reason to keep
separate constant was the it was always more 2 more than total kptrs.
This is no longer the case.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 include/linux/bpf.h | 9 ++++-----
 kernel/bpf/btf.c    | 2 +-
 2 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 798aec816970..1a66a1df1af1 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -165,9 +165,8 @@ struct bpf_map_ops {
 };
 
 enum {
-	/* Support at most 8 pointers in a BTF type */
-	BTF_FIELDS_MAX	      = 10,
-	BPF_MAP_OFF_ARR_MAX   = BTF_FIELDS_MAX,
+	/* Support at most 10 fields in a BTF type */
+	BTF_FIELDS_MAX	   = 10,
 };
 
 enum btf_field_type {
@@ -203,8 +202,8 @@ struct btf_record {
 
 struct btf_field_offs {
 	u32 cnt;
-	u32 field_off[BPF_MAP_OFF_ARR_MAX];
-	u8 field_sz[BPF_MAP_OFF_ARR_MAX];
+	u32 field_off[BTF_FIELDS_MAX];
+	u8 field_sz[BTF_FIELDS_MAX];
 };
 
 struct bpf_map {
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 5579ff3a5b54..12361d7b2498 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -3584,7 +3584,7 @@ struct btf_field_offs *btf_parse_field_offs(struct btf_record *rec)
 	u8 *sz;
 
 	BUILD_BUG_ON(ARRAY_SIZE(foffs->field_off) != ARRAY_SIZE(foffs->field_sz));
-	if (IS_ERR_OR_NULL(rec) || WARN_ON_ONCE(rec->cnt > sizeof(foffs->field_off)))
+	if (IS_ERR_OR_NULL(rec))
 		return NULL;
 
 	foffs = kzalloc(sizeof(*foffs), GFP_KERNEL | __GFP_NOWARN);
-- 
2.38.1

[PATCH bpf-next v5 02/25] bpf: Fix copy_map_value, zero_map_value

[Kumar Kartikeya Dwivedi]

The current offset needs to also skip over the already copied region in
addition to the size of the next field. This case manifests where there
are gaps between adjacent special fields.

It was observed that for a map value with size 48, having fields at:
off:  0, 16, 32
size: 4, 16, 16

The current code does:

memcpy(dst + 0, src + 0, 0)
memcpy(dst + 4, src + 4, 12)
memcpy(dst + 20, src + 20, 12)
memcpy(dst + 36, src + 36, 12)

With the fix, it is done correctly as:

memcpy(dst + 0, src + 0, 0)
memcpy(dst + 4, src + 4, 12)
memcpy(dst + 32, src + 32, 0)
memcpy(dst + 48, src + 48, 0)

Fixes: 4d7d7f69f4b1 ("bpf: Adapt copy_map_value for multiple offset case")
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 include/linux/bpf.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 1a66a1df1af1..f08eb2d27de0 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -360,7 +360,7 @@ static inline void bpf_obj_memcpy(struct btf_field_offs *foffs,
 		u32 sz = next_off - curr_off;
 
 		memcpy(dst + curr_off, src + curr_off, sz);
-		curr_off += foffs->field_sz[i];
+		curr_off += foffs->field_sz[i] + sz;
 	}
 	memcpy(dst + curr_off, src + curr_off, size - curr_off);
 }
@@ -390,7 +390,7 @@ static inline void bpf_obj_memzero(struct btf_field_offs *foffs, void *dst, u32
 		u32 sz = next_off - curr_off;
 
 		memset(dst + curr_off, 0, sz);
-		curr_off += foffs->field_sz[i];
+		curr_off += foffs->field_sz[i] + sz;
 	}
 	memset(dst + curr_off, 0, size - curr_off);
 }
-- 
2.38.1

[PATCH bpf-next v5 03/25] bpf: Support bpf_list_head in map values

[Kumar Kartikeya Dwivedi]

Add the support on the map side to parse, recognize, verify, and build
metadata table for a new special field of the type struct bpf_list_head.
To parameterize the bpf_list_head for a certain value type and the
list_node member it will accept in that value type, we use BTF
declaration tags.

The definition of bpf_list_head in a map value will be done as follows:

struct foo {
	struct bpf_list_node node;
	int data;
};

struct map_value {
	struct bpf_list_head head __contains(foo, node);
};

Then, the bpf_list_head only allows adding to the list 'head' using the
bpf_list_node 'node' for the type struct foo.

The 'contains' annotation is a BTF declaration tag composed of four
parts, "contains:name:node" where the name is then used to look up the
type in the map BTF, with its kind hardcoded to BTF_KIND_STRUCT during
the lookup. The node defines name of the member in this type that has
the type struct bpf_list_node, which is actually used for linking into
the linked list. For now, 'kind' part is hardcoded as struct.

This allows building intrusive linked lists in BPF, using container_of
to obtain pointer to entry, while being completely type safe from the
perspective of the verifier. The verifier knows exactly the type of the
nodes, and knows that list helpers return that type at some fixed offset
where the bpf_list_node member used for this list exists. The verifier
also uses this information to disallow adding types that are not
accepted by a certain list.

For now, no elements can be added to such lists. Support for that is
coming in future patches, hence draining and freeing items is done with
a TODO that will be resolved in a future patch.

Note that the bpf_list_head_free function moves the list out to a local
variable under the lock and releases it, doing the actual draining of
the list items outside the lock. While this helps with not holding the
lock for too long pessimizing other concurrent list operations, it is
also necessary for deadlock prevention: unless every function called in
the critical section would be notrace, a fentry/fexit program could
attach and call bpf_map_update_elem again on the map, leading to the
same lock being acquired if the key matches and lead to a deadlock.
While this requires some special effort on part of the BPF programmer to
trigger and is highly unlikely to occur in practice, it is always better
if we can avoid such a condition.

While notrace would prevent this, doing the draining outside the lock
has advantages of its own, hence it is used to also fix the deadlock
related problem.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 include/linux/bpf.h            |  17 ++++
 include/uapi/linux/bpf.h       |  10 +++
 kernel/bpf/btf.c               | 143 ++++++++++++++++++++++++++++++++-
 kernel/bpf/helpers.c           |  32 ++++++++
 kernel/bpf/syscall.c           |  22 ++++-
 kernel/bpf/verifier.c          |   7 ++
 tools/include/uapi/linux/bpf.h |  10 +++
 7 files changed, 237 insertions(+), 4 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index f08eb2d27de0..05f98e9e5c48 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -175,6 +175,7 @@ enum btf_field_type {
 	BPF_KPTR_UNREF = (1 << 2),
 	BPF_KPTR_REF   = (1 << 3),
 	BPF_KPTR       = BPF_KPTR_UNREF | BPF_KPTR_REF,
+	BPF_LIST_HEAD  = (1 << 4),
 };
 
 struct btf_field_kptr {
@@ -184,11 +185,18 @@ struct btf_field_kptr {
 	u32 btf_id;
 };
 
+struct btf_field_list_head {
+	struct btf *btf;
+	u32 value_btf_id;
+	u32 node_offset;
+};
+
 struct btf_field {
 	u32 offset;
 	enum btf_field_type type;
 	union {
 		struct btf_field_kptr kptr;
+		struct btf_field_list_head list_head;
 	};
 };
 
@@ -266,6 +274,8 @@ static inline const char *btf_field_type_name(enum btf_field_type type)
 	case BPF_KPTR_UNREF:
 	case BPF_KPTR_REF:
 		return "kptr";
+	case BPF_LIST_HEAD:
+		return "bpf_list_head";
 	default:
 		WARN_ON_ONCE(1);
 		return "unknown";
@@ -282,6 +292,8 @@ static inline u32 btf_field_type_size(enum btf_field_type type)
 	case BPF_KPTR_UNREF:
 	case BPF_KPTR_REF:
 		return sizeof(u64);
+	case BPF_LIST_HEAD:
+		return sizeof(struct bpf_list_head);
 	default:
 		WARN_ON_ONCE(1);
 		return 0;
@@ -298,6 +310,8 @@ static inline u32 btf_field_type_align(enum btf_field_type type)
 	case BPF_KPTR_UNREF:
 	case BPF_KPTR_REF:
 		return __alignof__(u64);
+	case BPF_LIST_HEAD:
+		return __alignof__(struct bpf_list_head);
 	default:
 		WARN_ON_ONCE(1);
 		return 0;
@@ -403,6 +417,9 @@ static inline void zero_map_value(struct bpf_map *map, void *dst)
 void copy_map_value_locked(struct bpf_map *map, void *dst, void *src,
 			   bool lock_src);
 void bpf_timer_cancel_and_free(void *timer);
+void bpf_list_head_free(const struct btf_field *field, void *list_head,
+			struct bpf_spin_lock *spin_lock);
+
 int bpf_obj_name_cpy(char *dst, const char *src, unsigned int size);
 
 struct bpf_offload_dev;
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 94659f6b3395..dd381086bad9 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -6887,6 +6887,16 @@ struct bpf_dynptr {
 	__u64 :64;
 } __attribute__((aligned(8)));
 
+struct bpf_list_head {
+	__u64 :64;
+	__u64 :64;
+} __attribute__((aligned(8)));
+
+struct bpf_list_node {
+	__u64 :64;
+	__u64 :64;
+} __attribute__((aligned(8)));
+
 struct bpf_sysctl {
 	__u32	write;		/* Sysctl is being read (= 0) or written (= 1).
 				 * Allows 1,2,4-byte read, but no write.
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 12361d7b2498..d8f083b09e5e 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -3205,9 +3205,15 @@ enum {
 struct btf_field_info {
 	enum btf_field_type type;
 	u32 off;
-	struct {
-		u32 type_id;
-	} kptr;
+	union {
+		struct {
+			u32 type_id;
+		} kptr;
+		struct {
+			const char *node_name;
+			u32 value_btf_id;
+		} list_head;
+	};
 };
 
 static int btf_find_struct(const struct btf *btf, const struct btf_type *t,
@@ -3261,6 +3267,63 @@ static int btf_find_kptr(const struct btf *btf, const struct btf_type *t,
 	return BTF_FIELD_FOUND;
 }
 
+static const char *btf_find_decl_tag_value(const struct btf *btf,
+					   const struct btf_type *pt,
+					   int comp_idx, const char *tag_key)
+{
+	int i;
+
+	for (i = 1; i < btf_nr_types(btf); i++) {
+		const struct btf_type *t = btf_type_by_id(btf, i);
+		int len = strlen(tag_key);
+
+		if (!btf_type_is_decl_tag(t))
+			continue;
+		if (pt != btf_type_by_id(btf, t->type) ||
+		    btf_type_decl_tag(t)->component_idx != comp_idx)
+			continue;
+		if (strncmp(__btf_name_by_offset(btf, t->name_off), tag_key, len))
+			continue;
+		return __btf_name_by_offset(btf, t->name_off) + len;
+	}
+	return NULL;
+}
+
+static int btf_find_list_head(const struct btf *btf, const struct btf_type *pt,
+			      const struct btf_type *t, int comp_idx,
+			      u32 off, int sz, struct btf_field_info *info)
+{
+	const char *value_type;
+	const char *list_node;
+	s32 id;
+
+	if (!__btf_type_is_struct(t))
+		return BTF_FIELD_IGNORE;
+	if (t->size != sz)
+		return BTF_FIELD_IGNORE;
+	value_type = btf_find_decl_tag_value(btf, pt, comp_idx, "contains:");
+	if (!value_type)
+		return -EINVAL;
+	list_node = strstr(value_type, ":");
+	if (!list_node)
+		return -EINVAL;
+	value_type = kstrndup(value_type, list_node - value_type, GFP_KERNEL | __GFP_NOWARN);
+	if (!value_type)
+		return -ENOMEM;
+	id = btf_find_by_name_kind(btf, value_type, BTF_KIND_STRUCT);
+	kfree(value_type);
+	if (id < 0)
+		return id;
+	list_node++;
+	if (str_is_empty(list_node))
+		return -EINVAL;
+	info->type = BPF_LIST_HEAD;
+	info->off = off;
+	info->list_head.value_btf_id = id;
+	info->list_head.node_name = list_node;
+	return BTF_FIELD_FOUND;
+}
+
 static int btf_get_field_type(const char *name, u32 field_mask, u32 *seen_mask,
 			      int *align, int *sz)
 {
@@ -3284,6 +3347,12 @@ static int btf_get_field_type(const char *name, u32 field_mask, u32 *seen_mask,
 			goto end;
 		}
 	}
+	if (field_mask & BPF_LIST_HEAD) {
+		if (!strcmp(name, "bpf_list_head")) {
+			type = BPF_LIST_HEAD;
+			goto end;
+		}
+	}
 	/* Only return BPF_KPTR when all other types with matchable names fail */
 	if (field_mask & BPF_KPTR) {
 		type = BPF_KPTR_REF;
@@ -3317,6 +3386,8 @@ static int btf_find_struct_field(const struct btf *btf,
 			return field_type;
 
 		off = __btf_member_bit_offset(t, member);
+		if (i && !off)
+			return -EFAULT;
 		if (off % 8)
 			/* valid C code cannot generate such BTF */
 			return -EINVAL;
@@ -3339,6 +3410,12 @@ static int btf_find_struct_field(const struct btf *btf,
 			if (ret < 0)
 				return ret;
 			break;
+		case BPF_LIST_HEAD:
+			ret = btf_find_list_head(btf, t, member_type, i, off, sz,
+						 idx < info_cnt ? &info[idx] : &tmp);
+			if (ret < 0)
+				return ret;
+			break;
 		default:
 			return -EFAULT;
 		}
@@ -3373,6 +3450,8 @@ static int btf_find_datasec_var(const struct btf *btf, const struct btf_type *t,
 			return field_type;
 
 		off = vsi->offset;
+		if (i && !off)
+			return -EFAULT;
 		if (vsi->size != sz)
 			continue;
 		if (off % align)
@@ -3393,6 +3472,12 @@ static int btf_find_datasec_var(const struct btf *btf, const struct btf_type *t,
 			if (ret < 0)
 				return ret;
 			break;
+		case BPF_LIST_HEAD:
+			ret = btf_find_list_head(btf, var, var_type, -1, off, sz,
+						 idx < info_cnt ? &info[idx] : &tmp);
+			if (ret < 0)
+				return ret;
+			break;
 		default:
 			return -EFAULT;
 		}
@@ -3491,6 +3576,46 @@ static int btf_parse_kptr(const struct btf *btf, struct btf_field *field,
 	return ret;
 }
 
+static int btf_parse_list_head(const struct btf *btf, struct btf_field *field,
+			       struct btf_field_info *info)
+{
+	const struct btf_type *t, *n = NULL;
+	const struct btf_member *member;
+	u32 offset;
+	int i;
+
+	t = btf_type_by_id(btf, info->list_head.value_btf_id);
+	/* We've already checked that value_btf_id is a struct type. We
+	 * just need to figure out the offset of the list_node, and
+	 * verify its type.
+	 */
+	for_each_member(i, t, member) {
+		if (strcmp(info->list_head.node_name, __btf_name_by_offset(btf, member->name_off)))
+			continue;
+		/* Invalid BTF, two members with same name */
+		if (n)
+			return -EINVAL;
+		n = btf_type_by_id(btf, member->type);
+		if (!__btf_type_is_struct(n))
+			return -EINVAL;
+		if (strcmp("bpf_list_node", __btf_name_by_offset(btf, n->name_off)))
+			return -EINVAL;
+		offset = __btf_member_bit_offset(n, member);
+		if (offset % 8)
+			return -EINVAL;
+		offset /= 8;
+		if (offset % __alignof__(struct bpf_list_node))
+			return -EINVAL;
+
+		field->list_head.btf = (struct btf *)btf;
+		field->list_head.value_btf_id = info->list_head.value_btf_id;
+		field->list_head.node_offset = offset;
+	}
+	if (!n)
+		return -ENOENT;
+	return 0;
+}
+
 struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type *t,
 				    u32 field_mask, u32 value_size)
 {
@@ -3539,12 +3664,24 @@ struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type
 			if (ret < 0)
 				goto end;
 			break;
+		case BPF_LIST_HEAD:
+			ret = btf_parse_list_head(btf, &rec->fields[i], &info_arr[i]);
+			if (ret < 0)
+				goto end;
+			break;
 		default:
 			ret = -EFAULT;
 			goto end;
 		}
 		rec->cnt++;
 	}
+
+	/* bpf_list_head requires bpf_spin_lock */
+	if (btf_record_has_field(rec, BPF_LIST_HEAD) && rec->spin_lock_off < 0) {
+		ret = -EINVAL;
+		goto end;
+	}
+
 	return rec;
 end:
 	btf_record_free(rec);
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 283f55bbeb70..7bc71995f17c 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -1706,6 +1706,38 @@ bpf_base_func_proto(enum bpf_func_id func_id)
 	}
 }
 
+void bpf_list_head_free(const struct btf_field *field, void *list_head,
+			struct bpf_spin_lock *spin_lock)
+{
+	struct list_head *head = list_head, *orig_head = list_head;
+
+	BUILD_BUG_ON(sizeof(struct list_head) > sizeof(struct bpf_list_head));
+	BUILD_BUG_ON(__alignof__(struct list_head) > __alignof__(struct bpf_list_head));
+
+	/* Do the actual list draining outside the lock to not hold the lock for
+	 * too long, and also prevent deadlocks if tracing programs end up
+	 * executing on entry/exit of functions called inside the critical
+	 * section, and end up doing map ops that call bpf_list_head_free for
+	 * the same map value again.
+	 */
+	__bpf_spin_lock_irqsave(spin_lock);
+	if (!head->next || list_empty(head))
+		goto unlock;
+	head = head->next;
+unlock:
+	INIT_LIST_HEAD(orig_head);
+	__bpf_spin_unlock_irqrestore(spin_lock);
+
+	while (head != orig_head) {
+		void *obj = head;
+
+		obj -= field->list_head.node_offset;
+		head = head->next;
+		/* TODO: Rework later */
+		kfree(obj);
+	}
+}
+
 BTF_SET8_START(tracing_btf_ids)
 #ifdef CONFIG_KEXEC_CORE
 BTF_ID_FLAGS(func, crash_kexec, KF_DESTRUCTIVE)
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 85532d301124..fdbae52f463f 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -536,6 +536,9 @@ void btf_record_free(struct btf_record *rec)
 				module_put(rec->fields[i].kptr.module);
 			btf_put(rec->fields[i].kptr.btf);
 			break;
+		case BPF_LIST_HEAD:
+			/* Nothing to release for bpf_list_head */
+			break;
 		default:
 			WARN_ON_ONCE(1);
 			continue;
@@ -578,6 +581,9 @@ struct btf_record *btf_record_dup(const struct btf_record *rec)
 				goto free;
 			}
 			break;
+		case BPF_LIST_HEAD:
+			/* Nothing to acquire for bpf_list_head */
+			break;
 		default:
 			ret = -EFAULT;
 			WARN_ON_ONCE(1);
@@ -637,6 +643,11 @@ void bpf_obj_free_fields(const struct btf_record *rec, void *obj)
 		case BPF_KPTR_REF:
 			field->kptr.dtor((void *)xchg((unsigned long *)field_ptr, 0));
 			break;
+		case BPF_LIST_HEAD:
+			if (WARN_ON_ONCE(rec->spin_lock_off < 0))
+				continue;
+			bpf_list_head_free(field, field_ptr, obj + rec->spin_lock_off);
+			break;
 		default:
 			WARN_ON_ONCE(1);
 			continue;
@@ -965,7 +976,8 @@ static int map_check_btf(struct bpf_map *map, const struct btf *btf,
 	if (!value_type || value_size != map->value_size)
 		return -EINVAL;
 
-	map->record = btf_parse_fields(btf, value_type, BPF_SPIN_LOCK | BPF_TIMER | BPF_KPTR,
+	map->record = btf_parse_fields(btf, value_type,
+				       BPF_SPIN_LOCK | BPF_TIMER | BPF_KPTR | BPF_LIST_HEAD,
 				       map->value_size);
 	if (!IS_ERR_OR_NULL(map->record)) {
 		int i;
@@ -1012,6 +1024,14 @@ static int map_check_btf(struct bpf_map *map, const struct btf *btf,
 					goto free_map_tab;
 				}
 				break;
+			case BPF_LIST_HEAD:
+				if (map->map_type != BPF_MAP_TYPE_HASH &&
+				    map->map_type != BPF_MAP_TYPE_LRU_HASH &&
+				    map->map_type != BPF_MAP_TYPE_ARRAY) {
+					ret = -EOPNOTSUPP;
+					goto free_map_tab;
+				}
+				break;
 			default:
 				/* Fail if map_type checks are missing for a field type */
 				ret = -EOPNOTSUPP;
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index d3b75aa0c54d..0374f03d1f56 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -12805,6 +12805,13 @@ static int check_map_prog_compatibility(struct bpf_verifier_env *env,
 {
 	enum bpf_prog_type prog_type = resolve_prog_type(prog);
 
+	if (btf_record_has_field(map->record, BPF_LIST_HEAD)) {
+		if (is_tracing_prog_type(prog_type)) {
+			verbose(env, "tracing progs cannot use bpf_list_head yet\n");
+			return -EINVAL;
+		}
+	}
+
 	if (btf_record_has_field(map->record, BPF_SPIN_LOCK)) {
 		if (prog_type == BPF_PROG_TYPE_SOCKET_FILTER) {
 			verbose(env, "socket filter progs cannot use bpf_spin_lock yet\n");
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 94659f6b3395..dd381086bad9 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -6887,6 +6887,16 @@ struct bpf_dynptr {
 	__u64 :64;
 } __attribute__((aligned(8)));
 
+struct bpf_list_head {
+	__u64 :64;
+	__u64 :64;
+} __attribute__((aligned(8)));
+
+struct bpf_list_node {
+	__u64 :64;
+	__u64 :64;
+} __attribute__((aligned(8)));
+
 struct bpf_sysctl {
 	__u32	write;		/* Sysctl is being read (= 0) or written (= 1).
 				 * Allows 1,2,4-byte read, but no write.
-- 
2.38.1

[PATCH bpf-next v5 04/25] bpf: Rename RET_PTR_TO_ALLOC_MEM

[Kumar Kartikeya Dwivedi]

Currently, the verifier has two return types, RET_PTR_TO_ALLOC_MEM, and
RET_PTR_TO_ALLOC_MEM_OR_NULL, however the former is confusingly named to
imply that it carries MEM_ALLOC, while only the latter does. This causes
confusion during code review leading to conclusions like that the return
value of RET_PTR_TO_DYNPTR_MEM_OR_NULL (which is RET_PTR_TO_ALLOC_MEM |
PTR_MAYBE_NULL) may be consumable by bpf_ringbuf_{submit,commit}.

Rename it to make it clear MEM_ALLOC needs to be tacked on top of
RET_PTR_TO_MEM.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 include/linux/bpf.h   | 6 +++---
 kernel/bpf/verifier.c | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 05f98e9e5c48..2fe3ec620d54 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -607,7 +607,7 @@ enum bpf_return_type {
 	RET_PTR_TO_SOCKET,		/* returns a pointer to a socket */
 	RET_PTR_TO_TCP_SOCK,		/* returns a pointer to a tcp_sock */
 	RET_PTR_TO_SOCK_COMMON,		/* returns a pointer to a sock_common */
-	RET_PTR_TO_ALLOC_MEM,		/* returns a pointer to dynamically allocated memory */
+	RET_PTR_TO_MEM,			/* returns a pointer to memory */
 	RET_PTR_TO_MEM_OR_BTF_ID,	/* returns a pointer to a valid memory or a btf_id */
 	RET_PTR_TO_BTF_ID,		/* returns a pointer to a btf_id */
 	__BPF_RET_TYPE_MAX,
@@ -617,8 +617,8 @@ enum bpf_return_type {
 	RET_PTR_TO_SOCKET_OR_NULL	= PTR_MAYBE_NULL | RET_PTR_TO_SOCKET,
 	RET_PTR_TO_TCP_SOCK_OR_NULL	= PTR_MAYBE_NULL | RET_PTR_TO_TCP_SOCK,
 	RET_PTR_TO_SOCK_COMMON_OR_NULL	= PTR_MAYBE_NULL | RET_PTR_TO_SOCK_COMMON,
-	RET_PTR_TO_ALLOC_MEM_OR_NULL	= PTR_MAYBE_NULL | MEM_ALLOC | RET_PTR_TO_ALLOC_MEM,
-	RET_PTR_TO_DYNPTR_MEM_OR_NULL	= PTR_MAYBE_NULL | RET_PTR_TO_ALLOC_MEM,
+	RET_PTR_TO_ALLOC_MEM_OR_NULL	= PTR_MAYBE_NULL | MEM_ALLOC | RET_PTR_TO_MEM,
+	RET_PTR_TO_DYNPTR_MEM_OR_NULL	= PTR_MAYBE_NULL | RET_PTR_TO_MEM,
 	RET_PTR_TO_BTF_ID_OR_NULL	= PTR_MAYBE_NULL | RET_PTR_TO_BTF_ID,
 
 	/* This must be the last entry. Its purpose is to ensure the enum is
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 0374f03d1f56..2407e3b179ec 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -7621,7 +7621,7 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
 		mark_reg_known_zero(env, regs, BPF_REG_0);
 		regs[BPF_REG_0].type = PTR_TO_TCP_SOCK | ret_flag;
 		break;
-	case RET_PTR_TO_ALLOC_MEM:
+	case RET_PTR_TO_MEM:
 		mark_reg_known_zero(env, regs, BPF_REG_0);
 		regs[BPF_REG_0].type = PTR_TO_MEM | ret_flag;
 		regs[BPF_REG_0].mem_size = meta.mem_size;
-- 
2.38.1

[PATCH bpf-next v5 05/25] bpf: Rename MEM_ALLOC to MEM_RINGBUF

[Kumar Kartikeya Dwivedi]

Currently, verifier uses MEM_ALLOC type tag to specially tag memory
returned from bpf_ringbuf_reserve helper. However, this is currently
only used for this purpose and there is an implicit assumption that it
only refers to ringbuf memory (e.g. the check for ARG_PTR_TO_ALLOC_MEM
in check_func_arg_reg_off).

Hence, rename MEM_ALLOC to MEM_RINGBUF to indicate this special
relationship and instead open the use of MEM_ALLOC for more generic
allocations made for user types.

Also, since ARG_PTR_TO_ALLOC_MEM_OR_NULL is unused, simply drop it.

Finally, update selftests using 'alloc_' verifier string to 'ringbuf_'.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 include/linux/bpf.h                               | 11 ++++-------
 kernel/bpf/ringbuf.c                              |  6 +++---
 kernel/bpf/verifier.c                             | 14 +++++++-------
 tools/testing/selftests/bpf/prog_tests/dynptr.c   |  2 +-
 tools/testing/selftests/bpf/verifier/ringbuf.c    |  2 +-
 tools/testing/selftests/bpf/verifier/spill_fill.c |  2 +-
 6 files changed, 17 insertions(+), 20 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 2fe3ec620d54..afc1c51b59ff 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -488,10 +488,8 @@ enum bpf_type_flag {
 	 */
 	MEM_RDONLY		= BIT(1 + BPF_BASE_TYPE_BITS),
 
-	/* MEM was "allocated" from a different helper, and cannot be mixed
-	 * with regular non-MEM_ALLOC'ed MEM types.
-	 */
-	MEM_ALLOC		= BIT(2 + BPF_BASE_TYPE_BITS),
+	/* MEM points to BPF ring buffer reservation. */
+	MEM_RINGBUF		= BIT(2 + BPF_BASE_TYPE_BITS),
 
 	/* MEM is in user address space. */
 	MEM_USER		= BIT(3 + BPF_BASE_TYPE_BITS),
@@ -565,7 +563,7 @@ enum bpf_arg_type {
 	ARG_PTR_TO_LONG,	/* pointer to long */
 	ARG_PTR_TO_SOCKET,	/* pointer to bpf_sock (fullsock) */
 	ARG_PTR_TO_BTF_ID,	/* pointer to in-kernel struct */
-	ARG_PTR_TO_ALLOC_MEM,	/* pointer to dynamically allocated memory */
+	ARG_PTR_TO_RINGBUF_MEM,	/* pointer to dynamically reserved ringbuf memory */
 	ARG_CONST_ALLOC_SIZE_OR_ZERO,	/* number of allocated bytes requested */
 	ARG_PTR_TO_BTF_ID_SOCK_COMMON,	/* pointer to in-kernel sock_common or bpf-mirrored bpf_sock */
 	ARG_PTR_TO_PERCPU_BTF_ID,	/* pointer to in-kernel percpu type */
@@ -582,7 +580,6 @@ enum bpf_arg_type {
 	ARG_PTR_TO_MEM_OR_NULL		= PTR_MAYBE_NULL | ARG_PTR_TO_MEM,
 	ARG_PTR_TO_CTX_OR_NULL		= PTR_MAYBE_NULL | ARG_PTR_TO_CTX,
 	ARG_PTR_TO_SOCKET_OR_NULL	= PTR_MAYBE_NULL | ARG_PTR_TO_SOCKET,
-	ARG_PTR_TO_ALLOC_MEM_OR_NULL	= PTR_MAYBE_NULL | ARG_PTR_TO_ALLOC_MEM,
 	ARG_PTR_TO_STACK_OR_NULL	= PTR_MAYBE_NULL | ARG_PTR_TO_STACK,
 	ARG_PTR_TO_BTF_ID_OR_NULL	= PTR_MAYBE_NULL | ARG_PTR_TO_BTF_ID,
 	/* pointer to memory does not need to be initialized, helper function must fill
@@ -617,7 +614,7 @@ enum bpf_return_type {
 	RET_PTR_TO_SOCKET_OR_NULL	= PTR_MAYBE_NULL | RET_PTR_TO_SOCKET,
 	RET_PTR_TO_TCP_SOCK_OR_NULL	= PTR_MAYBE_NULL | RET_PTR_TO_TCP_SOCK,
 	RET_PTR_TO_SOCK_COMMON_OR_NULL	= PTR_MAYBE_NULL | RET_PTR_TO_SOCK_COMMON,
-	RET_PTR_TO_ALLOC_MEM_OR_NULL	= PTR_MAYBE_NULL | MEM_ALLOC | RET_PTR_TO_MEM,
+	RET_PTR_TO_RINGBUF_MEM_OR_NULL	= PTR_MAYBE_NULL | MEM_RINGBUF | RET_PTR_TO_MEM,
 	RET_PTR_TO_DYNPTR_MEM_OR_NULL	= PTR_MAYBE_NULL | RET_PTR_TO_MEM,
 	RET_PTR_TO_BTF_ID_OR_NULL	= PTR_MAYBE_NULL | RET_PTR_TO_BTF_ID,
 
diff --git a/kernel/bpf/ringbuf.c b/kernel/bpf/ringbuf.c
index 9e832acf4692..80f4b4d88aaf 100644
--- a/kernel/bpf/ringbuf.c
+++ b/kernel/bpf/ringbuf.c
@@ -447,7 +447,7 @@ BPF_CALL_3(bpf_ringbuf_reserve, struct bpf_map *, map, u64, size, u64, flags)
 
 const struct bpf_func_proto bpf_ringbuf_reserve_proto = {
 	.func		= bpf_ringbuf_reserve,
-	.ret_type	= RET_PTR_TO_ALLOC_MEM_OR_NULL,
+	.ret_type	= RET_PTR_TO_RINGBUF_MEM_OR_NULL,
 	.arg1_type	= ARG_CONST_MAP_PTR,
 	.arg2_type	= ARG_CONST_ALLOC_SIZE_OR_ZERO,
 	.arg3_type	= ARG_ANYTHING,
@@ -490,7 +490,7 @@ BPF_CALL_2(bpf_ringbuf_submit, void *, sample, u64, flags)
 const struct bpf_func_proto bpf_ringbuf_submit_proto = {
 	.func		= bpf_ringbuf_submit,
 	.ret_type	= RET_VOID,
-	.arg1_type	= ARG_PTR_TO_ALLOC_MEM | OBJ_RELEASE,
+	.arg1_type	= ARG_PTR_TO_RINGBUF_MEM | OBJ_RELEASE,
 	.arg2_type	= ARG_ANYTHING,
 };
 
@@ -503,7 +503,7 @@ BPF_CALL_2(bpf_ringbuf_discard, void *, sample, u64, flags)
 const struct bpf_func_proto bpf_ringbuf_discard_proto = {
 	.func		= bpf_ringbuf_discard,
 	.ret_type	= RET_VOID,
-	.arg1_type	= ARG_PTR_TO_ALLOC_MEM | OBJ_RELEASE,
+	.arg1_type	= ARG_PTR_TO_RINGBUF_MEM | OBJ_RELEASE,
 	.arg2_type	= ARG_ANYTHING,
 };
 
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 2407e3b179ec..5fca156eca43 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -577,8 +577,8 @@ static const char *reg_type_str(struct bpf_verifier_env *env,
 
 	if (type & MEM_RDONLY)
 		strncpy(prefix, "rdonly_", 32);
-	if (type & MEM_ALLOC)
-		strncpy(prefix, "alloc_", 32);
+	if (type & MEM_RINGBUF)
+		strncpy(prefix, "ringbuf_", 32);
 	if (type & MEM_USER)
 		strncpy(prefix, "user_", 32);
 	if (type & MEM_PERCPU)
@@ -5780,7 +5780,7 @@ static const struct bpf_reg_types mem_types = {
 		PTR_TO_MAP_KEY,
 		PTR_TO_MAP_VALUE,
 		PTR_TO_MEM,
-		PTR_TO_MEM | MEM_ALLOC,
+		PTR_TO_MEM | MEM_RINGBUF,
 		PTR_TO_BUF,
 	},
 };
@@ -5798,7 +5798,7 @@ static const struct bpf_reg_types int_ptr_types = {
 static const struct bpf_reg_types fullsock_types = { .types = { PTR_TO_SOCKET } };
 static const struct bpf_reg_types scalar_types = { .types = { SCALAR_VALUE } };
 static const struct bpf_reg_types context_types = { .types = { PTR_TO_CTX } };
-static const struct bpf_reg_types alloc_mem_types = { .types = { PTR_TO_MEM | MEM_ALLOC } };
+static const struct bpf_reg_types ringbuf_mem_types = { .types = { PTR_TO_MEM | MEM_RINGBUF } };
 static const struct bpf_reg_types const_map_ptr_types = { .types = { CONST_PTR_TO_MAP } };
 static const struct bpf_reg_types btf_ptr_types = { .types = { PTR_TO_BTF_ID } };
 static const struct bpf_reg_types spin_lock_types = { .types = { PTR_TO_MAP_VALUE } };
@@ -5831,7 +5831,7 @@ static const struct bpf_reg_types *compatible_reg_types[__BPF_ARG_TYPE_MAX] = {
 	[ARG_PTR_TO_BTF_ID]		= &btf_ptr_types,
 	[ARG_PTR_TO_SPIN_LOCK]		= &spin_lock_types,
 	[ARG_PTR_TO_MEM]		= &mem_types,
-	[ARG_PTR_TO_ALLOC_MEM]		= &alloc_mem_types,
+	[ARG_PTR_TO_RINGBUF_MEM]	= &ringbuf_mem_types,
 	[ARG_PTR_TO_INT]		= &int_ptr_types,
 	[ARG_PTR_TO_LONG]		= &int_ptr_types,
 	[ARG_PTR_TO_PERCPU_BTF_ID]	= &percpu_btf_ptr_types,
@@ -5952,14 +5952,14 @@ int check_func_arg_reg_off(struct bpf_verifier_env *env,
 	case PTR_TO_MAP_VALUE:
 	case PTR_TO_MEM:
 	case PTR_TO_MEM | MEM_RDONLY:
-	case PTR_TO_MEM | MEM_ALLOC:
+	case PTR_TO_MEM | MEM_RINGBUF:
 	case PTR_TO_BUF:
 	case PTR_TO_BUF | MEM_RDONLY:
 	case SCALAR_VALUE:
 		/* Some of the argument types nevertheless require a
 		 * zero register offset.
 		 */
-		if (base_type(arg_type) != ARG_PTR_TO_ALLOC_MEM)
+		if (base_type(arg_type) != ARG_PTR_TO_RINGBUF_MEM)
 			return 0;
 		break;
 	/* All the rest must be rejected, except PTR_TO_BTF_ID which allows
diff --git a/tools/testing/selftests/bpf/prog_tests/dynptr.c b/tools/testing/selftests/bpf/prog_tests/dynptr.c
index 8fc4e6c02bfd..b0c06f821cb8 100644
--- a/tools/testing/selftests/bpf/prog_tests/dynptr.c
+++ b/tools/testing/selftests/bpf/prog_tests/dynptr.c
@@ -17,7 +17,7 @@ static struct {
 	{"ringbuf_missing_release2", "Unreleased reference id=2"},
 	{"ringbuf_missing_release_callback", "Unreleased reference id"},
 	{"use_after_invalid", "Expected an initialized dynptr as arg #3"},
-	{"ringbuf_invalid_api", "type=mem expected=alloc_mem"},
+	{"ringbuf_invalid_api", "type=mem expected=ringbuf_mem"},
 	{"add_dynptr_to_map1", "invalid indirect read from stack"},
 	{"add_dynptr_to_map2", "invalid indirect read from stack"},
 	{"data_slice_out_of_bounds_ringbuf", "value is outside of the allowed memory range"},
diff --git a/tools/testing/selftests/bpf/verifier/ringbuf.c b/tools/testing/selftests/bpf/verifier/ringbuf.c
index b64d33e4833c..84838feba47f 100644
--- a/tools/testing/selftests/bpf/verifier/ringbuf.c
+++ b/tools/testing/selftests/bpf/verifier/ringbuf.c
@@ -28,7 +28,7 @@
 	},
 	.fixup_map_ringbuf = { 1 },
 	.result = REJECT,
-	.errstr = "dereference of modified alloc_mem ptr R1",
+	.errstr = "dereference of modified ringbuf_mem ptr R1",
 },
 {
 	"ringbuf: invalid reservation offset 2",
diff --git a/tools/testing/selftests/bpf/verifier/spill_fill.c b/tools/testing/selftests/bpf/verifier/spill_fill.c
index e23f07175e1b..9bb302dade23 100644
--- a/tools/testing/selftests/bpf/verifier/spill_fill.c
+++ b/tools/testing/selftests/bpf/verifier/spill_fill.c
@@ -84,7 +84,7 @@
 	},
 	.fixup_map_ringbuf = { 1 },
 	.result = REJECT,
-	.errstr = "R0 pointer arithmetic on alloc_mem_or_null prohibited",
+	.errstr = "R0 pointer arithmetic on ringbuf_mem_or_null prohibited",
 },
 {
 	"check corrupted spill/fill",
-- 
2.38.1

[PATCH bpf-next v5 06/25] bpf: Introduce local kptrs

[Kumar Kartikeya Dwivedi]

Introduce local kptrs, i.e. PTR_TO_BTF_ID that point to a type in
program BTF. This is indicated by the presence of MEM_ALLOC type flag in
reg->type to avoid having to check btf_is_kernel when trying to match
argument types in helpers.

Refactor btf_struct_access callback to just take bpf_reg_state instead
of btf and btf_type paramters. Note that the call site in
check_map_access now simulates access to a PTR_TO_BTF_ID by creating a
dummy reg on stack. Since only the type, btf, and btf_id of the register
matter for the checks, it can be done so without complicating the usual
cases elsewhere in the verifier where reg->btf and reg->btf_id is used
verbatim.

Whenever walking such types, any pointers being walked will always yield
a SCALAR instead of pointer. In the future we might permit kptr inside
local kptr (either kernel or local), and it would be permitted only in
that case.

For now, these local kptrs will always be referenced in verifier
context, hence ref_obj_id == 0 for them is a bug. It is allowed to write
to such objects, as long fields that are special are not touched
(support for which will be added in subsequent patches). Note that once
such a local kptr is marked PTR_UNTRUSTED, it is no longer allowed to
write to it.

No PROBE_MEM handling is therefore done for loads into this type unless
PTR_UNTRUSTED is part of the register type, since they can never be in
an undefined state, and their lifetime will always be valid.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 include/linux/bpf.h              | 28 ++++++++++++++++--------
 include/linux/filter.h           |  8 +++----
 kernel/bpf/btf.c                 | 16 ++++++++++----
 kernel/bpf/verifier.c            | 37 ++++++++++++++++++++++++++------
 net/bpf/bpf_dummy_struct_ops.c   | 14 ++++++------
 net/core/filter.c                | 34 ++++++++++++-----------------
 net/ipv4/bpf_tcp_ca.c            | 13 ++++++-----
 net/netfilter/nf_conntrack_bpf.c | 17 ++++++---------
 8 files changed, 99 insertions(+), 68 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index afc1c51b59ff..75dbd2ecf80a 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -524,6 +524,11 @@ enum bpf_type_flag {
 	/* Size is known at compile time. */
 	MEM_FIXED_SIZE		= BIT(10 + BPF_BASE_TYPE_BITS),
 
+	/* MEM is of a type from program BTF, not kernel BTF. This is used to
+	 * tag PTR_TO_BTF_ID allocated using bpf_obj_new.
+	 */
+	MEM_ALLOC		= BIT(11 + BPF_BASE_TYPE_BITS),
+
 	__BPF_TYPE_FLAG_MAX,
 	__BPF_TYPE_LAST_FLAG	= __BPF_TYPE_FLAG_MAX - 1,
 };
@@ -771,6 +776,7 @@ struct bpf_prog_ops {
 			union bpf_attr __user *uattr);
 };
 
+struct bpf_reg_state;
 struct bpf_verifier_ops {
 	/* return eBPF function prototype for verification */
 	const struct bpf_func_proto *
@@ -792,9 +798,8 @@ struct bpf_verifier_ops {
 				  struct bpf_insn *dst,
 				  struct bpf_prog *prog, u32 *target_size);
 	int (*btf_struct_access)(struct bpf_verifier_log *log,
-				 const struct btf *btf,
-				 const struct btf_type *t, int off, int size,
-				 enum bpf_access_type atype,
+				 const struct bpf_reg_state *reg,
+				 int off, int size, enum bpf_access_type atype,
 				 u32 *next_btf_id, enum bpf_type_flag *flag);
 };
 
@@ -2080,9 +2085,9 @@ static inline bool bpf_tracing_btf_ctx_access(int off, int size,
 	return btf_ctx_access(off, size, type, prog, info);
 }
 
-int btf_struct_access(struct bpf_verifier_log *log, const struct btf *btf,
-		      const struct btf_type *t, int off, int size,
-		      enum bpf_access_type atype,
+int btf_struct_access(struct bpf_verifier_log *log,
+		      const struct bpf_reg_state *reg,
+		      int off, int size, enum bpf_access_type atype,
 		      u32 *next_btf_id, enum bpf_type_flag *flag);
 bool btf_struct_ids_match(struct bpf_verifier_log *log,
 			  const struct btf *btf, u32 id, int off,
@@ -2333,9 +2338,8 @@ static inline struct bpf_prog *bpf_prog_by_id(u32 id)
 }
 
 static inline int btf_struct_access(struct bpf_verifier_log *log,
-				    const struct btf *btf,
-				    const struct btf_type *t, int off, int size,
-				    enum bpf_access_type atype,
+				    const struct bpf_reg_state *reg,
+				    int off, int size, enum bpf_access_type atype,
 				    u32 *next_btf_id, enum bpf_type_flag *flag)
 {
 	return -EACCES;
@@ -2792,4 +2796,10 @@ struct bpf_key {
 	bool has_ref;
 };
 #endif /* CONFIG_KEYS */
+
+static inline bool type_is_local_kptr(u32 type)
+{
+	return type & MEM_ALLOC;
+}
+
 #endif /* _LINUX_BPF_H */
diff --git a/include/linux/filter.h b/include/linux/filter.h
index efc42a6e3aed..787d35dbf5b0 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -568,10 +568,10 @@ struct sk_filter {
 DECLARE_STATIC_KEY_FALSE(bpf_stats_enabled_key);
 
 extern struct mutex nf_conn_btf_access_lock;
-extern int (*nfct_btf_struct_access)(struct bpf_verifier_log *log, const struct btf *btf,
-				     const struct btf_type *t, int off, int size,
-				     enum bpf_access_type atype, u32 *next_btf_id,
-				     enum bpf_type_flag *flag);
+extern int (*nfct_btf_struct_access)(struct bpf_verifier_log *log,
+				     const struct bpf_reg_state *reg,
+				     int off, int size, enum bpf_access_type atype,
+				     u32 *next_btf_id, enum bpf_type_flag *flag);
 
 typedef unsigned int (*bpf_dispatcher_fn)(const void *ctx,
 					  const struct bpf_insn *insnsi,
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index d8f083b09e5e..4d6c8577bf17 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -6015,20 +6015,28 @@ static int btf_struct_walk(struct bpf_verifier_log *log, const struct btf *btf,
 	return -EINVAL;
 }
 
-int btf_struct_access(struct bpf_verifier_log *log, const struct btf *btf,
-		      const struct btf_type *t, int off, int size,
-		      enum bpf_access_type atype __maybe_unused,
+int btf_struct_access(struct bpf_verifier_log *log,
+		      const struct bpf_reg_state *reg,
+		      int off, int size, enum bpf_access_type atype __maybe_unused,
 		      u32 *next_btf_id, enum bpf_type_flag *flag)
 {
+	const struct btf *btf = reg->btf;
 	enum bpf_type_flag tmp_flag = 0;
+	const struct btf_type *t;
+	u32 id = reg->btf_id;
 	int err;
-	u32 id;
 
+	t = btf_type_by_id(btf, id);
 	do {
 		err = btf_struct_walk(log, btf, t, off, size, &id, &tmp_flag);
 
 		switch (err) {
 		case WALK_PTR:
+			/* For local types, the destination register cannot
+			 * become a pointer again.
+			 */
+			if (type_is_local_kptr(reg->type))
+				return SCALAR_VALUE;
 			/* If we found the pointer or scalar on t+off,
 			 * we're done.
 			 */
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 5fca156eca43..7dcb4629f764 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -4682,17 +4682,28 @@ static int check_ptr_to_btf_access(struct bpf_verifier_env *env,
 		return -EACCES;
 	}
 
-	if (env->ops->btf_struct_access) {
-		ret = env->ops->btf_struct_access(&env->log, reg->btf, t,
-						  off, size, atype, &btf_id, &flag);
+	if (env->ops->btf_struct_access && !type_is_local_kptr(reg->type)) {
+		if (!btf_is_kernel(reg->btf)) {
+			verbose(env, "verifier internal error: reg->btf must be kernel btf\n");
+			return -EFAULT;
+		}
+		ret = env->ops->btf_struct_access(&env->log, reg, off, size, atype, &btf_id, &flag);
 	} else {
-		if (atype != BPF_READ) {
+		/* Writes are permitted with default btf_struct_access for local
+		 * kptrs (which always have ref_obj_id > 0), but not for
+		 * _untrusted_ local kptrs.
+		 */
+		if (atype != BPF_READ && reg->type != (PTR_TO_BTF_ID | MEM_ALLOC)) {
 			verbose(env, "only read is supported\n");
 			return -EACCES;
 		}
 
-		ret = btf_struct_access(&env->log, reg->btf, t, off, size,
-					atype, &btf_id, &flag);
+		if (type_is_local_kptr(reg->type) && !reg->ref_obj_id) {
+			verbose(env, "verifier internal error: ref_obj_id for local kptr must be non-zero\n");
+			return -EFAULT;
+		}
+
+		ret = btf_struct_access(&env->log, reg, off, size, atype, &btf_id, &flag);
 	}
 
 	if (ret < 0)
@@ -4718,6 +4729,7 @@ static int check_ptr_to_map_access(struct bpf_verifier_env *env,
 {
 	struct bpf_reg_state *reg = regs + regno;
 	struct bpf_map *map = reg->map_ptr;
+	struct bpf_reg_state map_reg;
 	enum bpf_type_flag flag = 0;
 	const struct btf_type *t;
 	const char *tname;
@@ -4756,7 +4768,10 @@ static int check_ptr_to_map_access(struct bpf_verifier_env *env,
 		return -EACCES;
 	}
 
-	ret = btf_struct_access(&env->log, btf_vmlinux, t, off, size, atype, &btf_id, &flag);
+	/* Simulate access to a PTR_TO_BTF_ID */
+	memset(&map_reg, 0, sizeof(map_reg));
+	mark_btf_ld_reg(env, &map_reg, 0, PTR_TO_BTF_ID, btf_vmlinux, *map->ops->map_btf_id, 0);
+	ret = btf_struct_access(&env->log, &map_reg, off, size, atype, &btf_id, &flag);
 	if (ret < 0)
 		return ret;
 
@@ -5966,6 +5981,7 @@ int check_func_arg_reg_off(struct bpf_verifier_env *env,
 	 * fixed offset.
 	 */
 	case PTR_TO_BTF_ID:
+	case PTR_TO_BTF_ID | MEM_ALLOC:
 		/* When referenced PTR_TO_BTF_ID is passed to release function,
 		 * it's fixed offset must be 0.	In the other cases, fixed offset
 		 * can be non-zero.
@@ -13648,6 +13664,13 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env)
 			break;
 		case PTR_TO_BTF_ID:
 		case PTR_TO_BTF_ID | PTR_UNTRUSTED:
+		/* PTR_TO_BTF_ID | MEM_ALLOC always has a valid lifetime, unlike
+		 * PTR_TO_BTF_ID, and an active ref_obj_id, but the same cannot
+		 * be said once it is marked PTR_UNTRUSTED, hence we must handle
+		 * any faults for loads into such types. BPF_WRITE is disallowed
+		 * for this case.
+		 */
+		case PTR_TO_BTF_ID | MEM_ALLOC | PTR_UNTRUSTED:
 			if (type == BPF_READ) {
 				insn->code = BPF_LDX | BPF_PROBE_MEM |
 					BPF_SIZE((insn)->code);
diff --git a/net/bpf/bpf_dummy_struct_ops.c b/net/bpf/bpf_dummy_struct_ops.c
index e78dadfc5829..2d434c1f4617 100644
--- a/net/bpf/bpf_dummy_struct_ops.c
+++ b/net/bpf/bpf_dummy_struct_ops.c
@@ -156,29 +156,29 @@ static bool bpf_dummy_ops_is_valid_access(int off, int size,
 }
 
 static int bpf_dummy_ops_btf_struct_access(struct bpf_verifier_log *log,
-					   const struct btf *btf,
-					   const struct btf_type *t, int off,
-					   int size, enum bpf_access_type atype,
+					   const struct bpf_reg_state *reg,
+					   int off, int size, enum bpf_access_type atype,
 					   u32 *next_btf_id,
 					   enum bpf_type_flag *flag)
 {
 	const struct btf_type *state;
+	const struct btf_type *t;
 	s32 type_id;
 	int err;
 
-	type_id = btf_find_by_name_kind(btf, "bpf_dummy_ops_state",
+	type_id = btf_find_by_name_kind(reg->btf, "bpf_dummy_ops_state",
 					BTF_KIND_STRUCT);
 	if (type_id < 0)
 		return -EINVAL;
 
-	state = btf_type_by_id(btf, type_id);
+	t = btf_type_by_id(reg->btf, reg->btf_id);
+	state = btf_type_by_id(reg->btf, type_id);
 	if (t != state) {
 		bpf_log(log, "only access to bpf_dummy_ops_state is supported\n");
 		return -EACCES;
 	}
 
-	err = btf_struct_access(log, btf, t, off, size, atype, next_btf_id,
-				flag);
+	err = btf_struct_access(log, reg, off, size, atype, next_btf_id, flag);
 	if (err < 0)
 		return err;
 
diff --git a/net/core/filter.c b/net/core/filter.c
index cb3b635e35be..199632e6a7cb 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -8651,28 +8651,25 @@ static bool tc_cls_act_is_valid_access(int off, int size,
 DEFINE_MUTEX(nf_conn_btf_access_lock);
 EXPORT_SYMBOL_GPL(nf_conn_btf_access_lock);
 
-int (*nfct_btf_struct_access)(struct bpf_verifier_log *log, const struct btf *btf,
-			      const struct btf_type *t, int off, int size,
-			      enum bpf_access_type atype, u32 *next_btf_id,
-			      enum bpf_type_flag *flag);
+int (*nfct_btf_struct_access)(struct bpf_verifier_log *log,
+			      const struct bpf_reg_state *reg,
+			      int off, int size, enum bpf_access_type atype,
+			      u32 *next_btf_id, enum bpf_type_flag *flag);
 EXPORT_SYMBOL_GPL(nfct_btf_struct_access);
 
 static int tc_cls_act_btf_struct_access(struct bpf_verifier_log *log,
-					const struct btf *btf,
-					const struct btf_type *t, int off,
-					int size, enum bpf_access_type atype,
-					u32 *next_btf_id,
-					enum bpf_type_flag *flag)
+					const struct bpf_reg_state *reg,
+					int off, int size, enum bpf_access_type atype,
+					u32 *next_btf_id, enum bpf_type_flag *flag)
 {
 	int ret = -EACCES;
 
 	if (atype == BPF_READ)
-		return btf_struct_access(log, btf, t, off, size, atype, next_btf_id,
-					 flag);
+		return btf_struct_access(log, reg, off, size, atype, next_btf_id, flag);
 
 	mutex_lock(&nf_conn_btf_access_lock);
 	if (nfct_btf_struct_access)
-		ret = nfct_btf_struct_access(log, btf, t, off, size, atype, next_btf_id, flag);
+		ret = nfct_btf_struct_access(log, reg, off, size, atype, next_btf_id, flag);
 	mutex_unlock(&nf_conn_btf_access_lock);
 
 	return ret;
@@ -8738,21 +8735,18 @@ void bpf_warn_invalid_xdp_action(struct net_device *dev, struct bpf_prog *prog,
 EXPORT_SYMBOL_GPL(bpf_warn_invalid_xdp_action);
 
 static int xdp_btf_struct_access(struct bpf_verifier_log *log,
-				 const struct btf *btf,
-				 const struct btf_type *t, int off,
-				 int size, enum bpf_access_type atype,
-				 u32 *next_btf_id,
-				 enum bpf_type_flag *flag)
+				 const struct bpf_reg_state *reg,
+				 int off, int size, enum bpf_access_type atype,
+				 u32 *next_btf_id, enum bpf_type_flag *flag)
 {
 	int ret = -EACCES;
 
 	if (atype == BPF_READ)
-		return btf_struct_access(log, btf, t, off, size, atype, next_btf_id,
-					 flag);
+		return btf_struct_access(log, reg, off, size, atype, next_btf_id, flag);
 
 	mutex_lock(&nf_conn_btf_access_lock);
 	if (nfct_btf_struct_access)
-		ret = nfct_btf_struct_access(log, btf, t, off, size, atype, next_btf_id, flag);
+		ret = nfct_btf_struct_access(log, reg, off, size, atype, next_btf_id, flag);
 	mutex_unlock(&nf_conn_btf_access_lock);
 
 	return ret;
diff --git a/net/ipv4/bpf_tcp_ca.c b/net/ipv4/bpf_tcp_ca.c
index 6da16ae6a962..d15c91de995f 100644
--- a/net/ipv4/bpf_tcp_ca.c
+++ b/net/ipv4/bpf_tcp_ca.c
@@ -69,18 +69,17 @@ static bool bpf_tcp_ca_is_valid_access(int off, int size,
 }
 
 static int bpf_tcp_ca_btf_struct_access(struct bpf_verifier_log *log,
-					const struct btf *btf,
-					const struct btf_type *t, int off,
-					int size, enum bpf_access_type atype,
-					u32 *next_btf_id,
-					enum bpf_type_flag *flag)
+					const struct bpf_reg_state *reg,
+					int off, int size, enum bpf_access_type atype,
+					u32 *next_btf_id, enum bpf_type_flag *flag)
 {
+	const struct btf_type *t;
 	size_t end;
 
 	if (atype == BPF_READ)
-		return btf_struct_access(log, btf, t, off, size, atype, next_btf_id,
-					 flag);
+		return btf_struct_access(log, reg, off, size, atype, next_btf_id, flag);
 
+	t = btf_type_by_id(reg->btf, reg->btf_id);
 	if (t != tcp_sock_type) {
 		bpf_log(log, "only read is supported\n");
 		return -EACCES;
diff --git a/net/netfilter/nf_conntrack_bpf.c b/net/netfilter/nf_conntrack_bpf.c
index 8639e7efd0e2..24002bc61e07 100644
--- a/net/netfilter/nf_conntrack_bpf.c
+++ b/net/netfilter/nf_conntrack_bpf.c
@@ -191,19 +191,16 @@ BTF_ID(struct, nf_conn___init)
 
 /* Check writes into `struct nf_conn` */
 static int _nf_conntrack_btf_struct_access(struct bpf_verifier_log *log,
-					   const struct btf *btf,
-					   const struct btf_type *t, int off,
-					   int size, enum bpf_access_type atype,
-					   u32 *next_btf_id,
-					   enum bpf_type_flag *flag)
+					   const struct bpf_reg_state *reg,
+					   int off, int size, enum bpf_access_type atype,
+					   u32 *next_btf_id, enum bpf_type_flag *flag)
 {
-	const struct btf_type *ncit;
-	const struct btf_type *nct;
+	const struct btf_type *ncit, *nct, *t;
 	size_t end;
 
-	ncit = btf_type_by_id(btf, btf_nf_conn_ids[1]);
-	nct = btf_type_by_id(btf, btf_nf_conn_ids[0]);
-
+	ncit = btf_type_by_id(reg->btf, btf_nf_conn_ids[1]);
+	nct = btf_type_by_id(reg->btf, btf_nf_conn_ids[0]);
+	t = btf_type_by_id(reg->btf, reg->btf_id);
 	if (t != nct && t != ncit) {
 		bpf_log(log, "only read is supported\n");
 		return -EACCES;
-- 
2.38.1

[PATCH bpf-next v5 07/25] bpf: Recognize bpf_{spin_lock,list_head,list_node} in local kptrs

[Kumar Kartikeya Dwivedi]

Allow specifying bpf_spin_lock, bpf_list_head, bpf_list_node fields in a
local kptr.

Update btf_struct_access callback to reject direct access to these
special fields in local kptrs.

A bpf_list_head allows implementing map-in-map style use cases, where
local kptr with bpf_list_head is linked into a list in a map value. This
would require embedding a bpf_list_node, support for which is also
included.

Lastly, while we strictly don't require to hold a bpf_spin_lock while
manipulating the bpf_list_head of a local kptr, as when have access to
it, we have complete ownership of the object, the locking constraint is
still kept and may be conditionally lifted in the future.

Note that the specification of such types can be done just like map
values, e.g.:

struct bar {
	struct bpf_list_node node;
};

struct foo {
	struct bpf_spin_lock lock;
	struct bpf_list_head head __contains(bar, node);
	struct bpf_list_node node;
};

struct map_value {
	struct bpf_spin_lock lock;
	struct bpf_list_head head __contains(foo, node);
};

To recognize such types in user BTF, we build a btf_struct_metas array
of metadata items corresponding to each BTF ID. This is done once during
the btf_parse stage to avoid having to do it each time during the
verification process's requirement to inspect the metadata.

Moreover, the computed metadata needs to be passed to some helpers in
future patches which requires allocating them and storing them in the
BTF that is pinned by the program itself, so that valid access can be
assumed to such data during program runtime.

A key thing to note is that once a btf_struct_meta is available for a
type, both the btf_record and btf_field_offs should be available. It is
critical that btf_field_offs is available in case special fields are
present, as we extensively rely on special fields being zeroed out in
map values and local kptrs in later patches. The code ensures that by
bailing out in case of errors and ensuring both are available together.
If the record is not available, the special fields won't be recognized,
so not having both is also fine (in terms of being a verification error
and not a runtime bug).

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 include/linux/bpf.h  |   7 ++
 include/linux/btf.h  |  35 ++++++++
 kernel/bpf/btf.c     | 196 +++++++++++++++++++++++++++++++++++++++----
 kernel/bpf/syscall.c |   4 +
 4 files changed, 224 insertions(+), 18 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 75dbd2ecf80a..dfcd34e36025 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -176,6 +176,7 @@ enum btf_field_type {
 	BPF_KPTR_REF   = (1 << 3),
 	BPF_KPTR       = BPF_KPTR_UNREF | BPF_KPTR_REF,
 	BPF_LIST_HEAD  = (1 << 4),
+	BPF_LIST_NODE  = (1 << 5),
 };
 
 struct btf_field_kptr {
@@ -276,6 +277,8 @@ static inline const char *btf_field_type_name(enum btf_field_type type)
 		return "kptr";
 	case BPF_LIST_HEAD:
 		return "bpf_list_head";
+	case BPF_LIST_NODE:
+		return "bpf_list_node";
 	default:
 		WARN_ON_ONCE(1);
 		return "unknown";
@@ -294,6 +297,8 @@ static inline u32 btf_field_type_size(enum btf_field_type type)
 		return sizeof(u64);
 	case BPF_LIST_HEAD:
 		return sizeof(struct bpf_list_head);
+	case BPF_LIST_NODE:
+		return sizeof(struct bpf_list_node);
 	default:
 		WARN_ON_ONCE(1);
 		return 0;
@@ -312,6 +317,8 @@ static inline u32 btf_field_type_align(enum btf_field_type type)
 		return __alignof__(u64);
 	case BPF_LIST_HEAD:
 		return __alignof__(struct bpf_list_head);
+	case BPF_LIST_NODE:
+		return __alignof__(struct bpf_list_node);
 	default:
 		WARN_ON_ONCE(1);
 		return 0;
diff --git a/include/linux/btf.h b/include/linux/btf.h
index d80345fa566b..a01a8da20021 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -6,6 +6,8 @@
 
 #include <linux/types.h>
 #include <linux/bpfptr.h>
+#include <linux/bsearch.h>
+#include <linux/btf_ids.h>
 #include <uapi/linux/btf.h>
 #include <uapi/linux/bpf.h>
 
@@ -78,6 +80,17 @@ struct btf_id_dtor_kfunc {
 	u32 kfunc_btf_id;
 };
 
+struct btf_struct_meta {
+	u32 btf_id;
+	struct btf_record *record;
+	struct btf_field_offs *field_offs;
+};
+
+struct btf_struct_metas {
+	u32 cnt;
+	struct btf_struct_meta types[];
+};
+
 typedef void (*btf_dtor_kfunc_t)(void *);
 
 extern const struct file_operations btf_fops;
@@ -408,6 +421,23 @@ static inline struct btf_param *btf_params(const struct btf_type *t)
 	return (struct btf_param *)(t + 1);
 }
 
+static inline int btf_id_cmp_func(const void *a, const void *b)
+{
+	const int *pa = a, *pb = b;
+
+	return *pa - *pb;
+}
+
+static inline bool btf_id_set_contains(const struct btf_id_set *set, u32 id)
+{
+	return bsearch(&id, set->ids, set->cnt, sizeof(u32), btf_id_cmp_func) != NULL;
+}
+
+static inline void *btf_id_set8_contains(const struct btf_id_set8 *set, u32 id)
+{
+	return bsearch(&id, set->pairs, set->cnt, sizeof(set->pairs[0]), btf_id_cmp_func);
+}
+
 #ifdef CONFIG_BPF_SYSCALL
 struct bpf_prog;
 
@@ -423,6 +453,7 @@ int register_btf_kfunc_id_set(enum bpf_prog_type prog_type,
 s32 btf_find_dtor_kfunc(struct btf *btf, u32 btf_id);
 int register_btf_id_dtor_kfuncs(const struct btf_id_dtor_kfunc *dtors, u32 add_cnt,
 				struct module *owner);
+struct btf_struct_meta *btf_find_struct_meta(const struct btf *btf, u32 btf_id);
 #else
 static inline const struct btf_type *btf_type_by_id(const struct btf *btf,
 						    u32 type_id)
@@ -454,6 +485,10 @@ static inline int register_btf_id_dtor_kfuncs(const struct btf_id_dtor_kfunc *dt
 {
 	return 0;
 }
+static inline struct btf_struct_meta *btf_find_struct_meta(const struct btf *btf, u32 btf_id)
+{
+	return NULL;
+}
 #endif
 
 static inline bool btf_type_is_struct_ptr(struct btf *btf, const struct btf_type *t)
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 4d6c8577bf17..5e3cffe4bc37 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -237,6 +237,7 @@ struct btf {
 	struct rcu_head rcu;
 	struct btf_kfunc_set_tab *kfunc_set_tab;
 	struct btf_id_dtor_kfunc_tab *dtor_kfunc_tab;
+	struct btf_struct_metas *struct_meta_tab;
 
 	/* split BTF support */
 	struct btf *base_btf;
@@ -1642,8 +1643,30 @@ static void btf_free_dtor_kfunc_tab(struct btf *btf)
 	btf->dtor_kfunc_tab = NULL;
 }
 
+static void btf_struct_metas_free(struct btf_struct_metas *tab)
+{
+	int i;
+
+	if (!tab)
+		return;
+	for (i = 0; i < tab->cnt; i++) {
+		btf_record_free(tab->types[i].record);
+		kfree(tab->types[i].field_offs);
+	}
+	kfree(tab);
+}
+
+static void btf_free_struct_meta_tab(struct btf *btf)
+{
+	struct btf_struct_metas *tab = btf->struct_meta_tab;
+
+	btf_struct_metas_free(tab);
+	btf->struct_meta_tab = NULL;
+}
+
 static void btf_free(struct btf *btf)
 {
+	btf_free_struct_meta_tab(btf);
 	btf_free_dtor_kfunc_tab(btf);
 	btf_free_kfunc_set_tab(btf);
 	kvfree(btf->types);
@@ -3353,6 +3376,12 @@ static int btf_get_field_type(const char *name, u32 field_mask, u32 *seen_mask,
 			goto end;
 		}
 	}
+	if (field_mask & BPF_LIST_NODE) {
+		if (!strcmp(name, "bpf_list_node")) {
+			type = BPF_LIST_NODE;
+			goto end;
+		}
+	}
 	/* Only return BPF_KPTR when all other types with matchable names fail */
 	if (field_mask & BPF_KPTR) {
 		type = BPF_KPTR_REF;
@@ -3398,6 +3427,7 @@ static int btf_find_struct_field(const struct btf *btf,
 		switch (field_type) {
 		case BPF_SPIN_LOCK:
 		case BPF_TIMER:
+		case BPF_LIST_NODE:
 			ret = btf_find_struct(btf, member_type, off, sz, field_type,
 					      idx < info_cnt ? &info[idx] : &tmp);
 			if (ret < 0)
@@ -3460,6 +3490,7 @@ static int btf_find_datasec_var(const struct btf *btf, const struct btf_type *t,
 		switch (field_type) {
 		case BPF_SPIN_LOCK:
 		case BPF_TIMER:
+		case BPF_LIST_NODE:
 			ret = btf_find_struct(btf, var_type, off, sz, field_type,
 					      idx < info_cnt ? &info[idx] : &tmp);
 			if (ret < 0)
@@ -3669,6 +3700,8 @@ struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type
 			if (ret < 0)
 				goto end;
 			break;
+		case BPF_LIST_NODE:
+			break;
 		default:
 			ret = -EFAULT;
 			goto end;
@@ -5139,6 +5172,118 @@ static int btf_parse_hdr(struct btf_verifier_env *env)
 	return btf_check_sec_info(env, btf_data_size);
 }
 
+static const char *local_kptr_fields[] = {
+	"bpf_spin_lock",
+	"bpf_list_head",
+	"bpf_list_node",
+};
+
+static struct btf_struct_metas *
+btf_parse_struct_metas(struct bpf_verifier_log *log, struct btf *btf)
+{
+	union {
+		struct btf_id_set set;
+		struct {
+			u32 _cnt;
+			u32 _ids[ARRAY_SIZE(local_kptr_fields)];
+		} _arr;
+	} lkf;
+	struct btf_struct_metas *tab = NULL;
+	int i, n, id, ret;
+
+	memset(&lkf, 0, sizeof(lkf));
+
+	for (i = 0; i < ARRAY_SIZE(local_kptr_fields); i++) {
+		/* Try to find whether this special type exists in user BTF, and
+		 * if so remember its ID so we can easily find it among members
+		 * of structs that we iterate in the next loop.
+		 */
+		id = btf_find_by_name_kind(btf, local_kptr_fields[i], BTF_KIND_STRUCT);
+		if (id < 0)
+			continue;
+		lkf.set.ids[lkf.set.cnt++] = id;
+	}
+
+	if (!lkf.set.cnt)
+		return NULL;
+	sort(&lkf.set.ids, lkf.set.cnt, sizeof(lkf.set.ids[0]), btf_id_cmp_func, NULL);
+
+	n = btf_nr_types(btf);
+	for (i = 1; i < n; i++) {
+		const struct btf_member *member;
+		struct btf_field_offs *foffs;
+		struct btf_struct_meta *type;
+		struct btf_record *record;
+		const struct btf_type *t;
+		int j;
+
+		t = btf_type_by_id(btf, i);
+		if (!t) {
+			ret = -EINVAL;
+			goto free;
+		}
+		if (!__btf_type_is_struct(t))
+			continue;
+
+		cond_resched();
+
+		for_each_member(j, t, member) {
+			if (btf_id_set_contains(&lkf.set, member->type))
+				goto parse;
+		}
+		continue;
+	parse:
+		if (!tab) {
+			tab = kzalloc(offsetof(struct btf_struct_metas, types[1]),
+				      GFP_KERNEL | __GFP_NOWARN);
+			if (!tab)
+				return ERR_PTR(-ENOMEM);
+		} else {
+			struct btf_struct_metas *new_tab;
+
+			new_tab = krealloc(tab, offsetof(struct btf_struct_metas, types[tab->cnt + 1]),
+					   GFP_KERNEL | __GFP_NOWARN);
+			if (!new_tab) {
+				ret = -ENOMEM;
+				goto free;
+			}
+			tab = new_tab;
+		}
+		type = &tab->types[tab->cnt];
+
+		type->btf_id = i;
+		record = btf_parse_fields(btf, t, BPF_SPIN_LOCK | BPF_LIST_HEAD | BPF_LIST_NODE, t->size);
+		if (IS_ERR_OR_NULL(record)) {
+			ret = PTR_ERR_OR_ZERO(record) ?: -EFAULT;
+			goto free;
+		}
+		foffs = btf_parse_field_offs(record);
+		if (WARN_ON_ONCE(IS_ERR_OR_NULL(foffs))) {
+			btf_record_free(record);
+			ret = -EFAULT;
+			goto free;
+		}
+		type->record = record;
+		type->field_offs = foffs;
+		tab->cnt++;
+	}
+	return tab;
+free:
+	btf_struct_metas_free(tab);
+	return ERR_PTR(ret);
+}
+
+struct btf_struct_meta *btf_find_struct_meta(const struct btf *btf, u32 btf_id)
+{
+	struct btf_struct_metas *tab;
+
+	BUILD_BUG_ON(offsetof(struct btf_struct_meta, btf_id) != 0);
+	tab = btf->struct_meta_tab;
+	if (!tab)
+		return NULL;
+	return bsearch(&btf_id, tab->types, tab->cnt, sizeof(tab->types[0]), btf_id_cmp_func);
+}
+
 static int btf_check_type_tags(struct btf_verifier_env *env,
 			       struct btf *btf, int start_id)
 {
@@ -5189,6 +5334,7 @@ static int btf_check_type_tags(struct btf_verifier_env *env,
 static struct btf *btf_parse(bpfptr_t btf_data, u32 btf_data_size,
 			     u32 log_level, char __user *log_ubuf, u32 log_size)
 {
+	struct btf_struct_metas *struct_meta_tab;
 	struct btf_verifier_env *env = NULL;
 	struct bpf_verifier_log *log;
 	struct btf *btf = NULL;
@@ -5257,15 +5403,24 @@ static struct btf *btf_parse(bpfptr_t btf_data, u32 btf_data_size,
 	if (err)
 		goto errout;
 
+	struct_meta_tab = btf_parse_struct_metas(log, btf);
+	if (IS_ERR(struct_meta_tab)) {
+		err = PTR_ERR(struct_meta_tab);
+		goto errout;
+	}
+	btf->struct_meta_tab = struct_meta_tab;
+
 	if (log->level && bpf_verifier_log_full(log)) {
 		err = -ENOSPC;
-		goto errout;
+		goto errout_meta;
 	}
 
 	btf_verifier_env_free(env);
 	refcount_set(&btf->refcnt, 1);
 	return btf;
 
+errout_meta:
+	btf_free_struct_meta_tab(btf);
 errout:
 	btf_verifier_env_free(env);
 	if (btf)
@@ -6026,6 +6181,28 @@ int btf_struct_access(struct bpf_verifier_log *log,
 	u32 id = reg->btf_id;
 	int err;
 
+	while (type_is_local_kptr(reg->type)) {
+		struct btf_struct_meta *meta;
+		struct btf_record *rec;
+		int i;
+
+		meta = btf_find_struct_meta(btf, id);
+		if (!meta)
+			break;
+		rec = meta->record;
+		for (i = 0; i < rec->cnt; i++) {
+			struct btf_field *field = &rec->fields[i];
+			u32 offset = field->offset;
+			if (off < offset + btf_field_type_size(field->type) && offset < off + size) {
+				bpf_log(log,
+					"direct access to %s is disallowed\n",
+					btf_field_type_name(field->type));
+				return -EACCES;
+			}
+		}
+		break;
+	}
+
 	t = btf_type_by_id(btf, id);
 	do {
 		err = btf_struct_walk(log, btf, t, off, size, &id, &tmp_flag);
@@ -7267,23 +7444,6 @@ bool btf_is_module(const struct btf *btf)
 	return btf->kernel_btf && strcmp(btf->name, "vmlinux") != 0;
 }
 
-static int btf_id_cmp_func(const void *a, const void *b)
-{
-	const int *pa = a, *pb = b;
-
-	return *pa - *pb;
-}
-
-bool btf_id_set_contains(const struct btf_id_set *set, u32 id)
-{
-	return bsearch(&id, set->ids, set->cnt, sizeof(u32), btf_id_cmp_func) != NULL;
-}
-
-static void *btf_id_set8_contains(const struct btf_id_set8 *set, u32 id)
-{
-	return bsearch(&id, set->pairs, set->cnt, sizeof(set->pairs[0]), btf_id_cmp_func);
-}
-
 enum {
 	BTF_MODULE_F_LIVE = (1 << 0),
 };
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index fdbae52f463f..c96039a4e57f 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -537,6 +537,7 @@ void btf_record_free(struct btf_record *rec)
 			btf_put(rec->fields[i].kptr.btf);
 			break;
 		case BPF_LIST_HEAD:
+		case BPF_LIST_NODE:
 			/* Nothing to release for bpf_list_head */
 			break;
 		default:
@@ -582,6 +583,7 @@ struct btf_record *btf_record_dup(const struct btf_record *rec)
 			}
 			break;
 		case BPF_LIST_HEAD:
+		case BPF_LIST_NODE:
 			/* Nothing to acquire for bpf_list_head */
 			break;
 		default:
@@ -648,6 +650,8 @@ void bpf_obj_free_fields(const struct btf_record *rec, void *obj)
 				continue;
 			bpf_list_head_free(field, field_ptr, obj + rec->spin_lock_off);
 			break;
+		case BPF_LIST_NODE:
+			break;
 		default:
 			WARN_ON_ONCE(1);
 			continue;
-- 
2.38.1

[PATCH bpf-next v5 08/25] bpf: Verify ownership relationships for user BTF types

[Kumar Kartikeya Dwivedi]

Ensure that there can be no ownership cycles among different types by
way of having owning objects that can hold some other type as their
element. For instance, a map value can only hold local kptrs, but these
are allowed to have another bpf_list_head. To prevent unbounded
recursion while freeing resources, elements of bpf_list_head in local
kptrs can never have a bpf_list_head which are part of list in a map
value. Later patches will verify this by having dedicated BTF selftests.

Also, to make runtime destruction easier, once btf_struct_metas is fully
populated, we can stash the metadata of the value type directly in the
metadata of the list_head fields, as that allows easier access to the
value type's layout to destruct it at runtime from the btf_field entry
of the list head itself.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 include/linux/bpf.h  |  1 +
 include/linux/btf.h  |  1 +
 kernel/bpf/btf.c     | 71 ++++++++++++++++++++++++++++++++++++++++++++
 kernel/bpf/syscall.c |  4 +++
 4 files changed, 77 insertions(+)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index dfcd34e36025..88ac4c12bab0 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -190,6 +190,7 @@ struct btf_field_list_head {
 	struct btf *btf;
 	u32 value_btf_id;
 	u32 node_offset;
+	struct btf_record *value_rec;
 };
 
 struct btf_field {
diff --git a/include/linux/btf.h b/include/linux/btf.h
index a01a8da20021..42d8f3730a8d 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -178,6 +178,7 @@ int btf_find_spin_lock(const struct btf *btf, const struct btf_type *t);
 int btf_find_timer(const struct btf *btf, const struct btf_type *t);
 struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type *t,
 				    u32 field_mask, u32 value_size);
+int btf_check_and_fixup_fields(const struct btf *btf, struct btf_record *rec);
 struct btf_field_offs *btf_parse_field_offs(struct btf_record *rec);
 bool btf_type_is_void(const struct btf_type *t);
 s32 btf_find_by_name_kind(const struct btf *btf, const char *name, u8 kind);
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 5e3cffe4bc37..685a6998432b 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -3721,6 +3721,67 @@ struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type
 	return ERR_PTR(ret);
 }
 
+int btf_check_and_fixup_fields(const struct btf *btf, struct btf_record *rec)
+{
+	int i;
+
+	/* There are two owning types, kptr_ref and bpf_list_head. The former
+	 * only supports storing kernel types, which can never store references
+	 * to program allocated local types, atleast not yet. Hence we only need
+	 * to ensure that bpf_list_head ownership does not form cycles.
+	 */
+	if (IS_ERR_OR_NULL(rec) || !(rec->field_mask & BPF_LIST_HEAD))
+		return 0;
+	for (i = 0; i < rec->cnt; i++) {
+		struct btf_struct_meta *meta;
+		u32 btf_id;
+
+		if (!(rec->fields[i].type & BPF_LIST_HEAD))
+			continue;
+		btf_id = rec->fields[i].list_head.value_btf_id;
+		meta = btf_find_struct_meta(btf, btf_id);
+		if (!meta)
+			return -EFAULT;
+		rec->fields[i].list_head.value_rec = meta->record;
+
+		if (!(rec->field_mask & BPF_LIST_NODE))
+			continue;
+
+		/* We need to ensure ownership acyclicity among all types. The
+		 * proper way to do it would be to topologically sort all BTF
+		 * IDs based on the ownership edges, since there can be multiple
+		 * bpf_list_head in a type. Instead, we use the following
+		 * reasoning:
+		 *
+		 * - A type can only be owned by another type in user BTF if it
+		 *   has a bpf_list_node.
+		 * - A type can only _own_ another type in user BTF if it has a
+		 *   bpf_list_head.
+		 *
+		 * We ensure that if a type has both bpf_list_head and
+		 * bpf_list_node, its element types cannot be owning types.
+		 *
+		 * To ensure acyclicity:
+		 *
+		 * When A only has bpf_list_head, ownership chain can be:
+		 *	A -> B -> C
+		 * Where:
+		 * - B has both bpf_list_head and bpf_list_node.
+		 * - C only has bpf_list_node.
+		 *
+		 * When A has both bpf_list_head and bpf_list_node, some other
+		 * type already owns it in the BTF domain, hence it can not own
+		 * another owning type through any of the bpf_list_head edges.
+		 *	A -> B
+		 * Where:
+		 * - B only has bpf_list_node.
+		 */
+		if (meta->record->field_mask & BPF_LIST_HEAD)
+			return -ELOOP;
+	}
+	return 0;
+}
+
 static int btf_field_offs_cmp(const void *_a, const void *_b, const void *priv)
 {
 	const u32 a = *(const u32 *)_a;
@@ -5410,6 +5471,16 @@ static struct btf *btf_parse(bpfptr_t btf_data, u32 btf_data_size,
 	}
 	btf->struct_meta_tab = struct_meta_tab;
 
+	if (struct_meta_tab) {
+		int i;
+
+		for (i = 0; i < struct_meta_tab->cnt; i++) {
+			err = btf_check_and_fixup_fields(btf, struct_meta_tab->types[i].record);
+			if (err < 0)
+				goto errout_meta;
+		}
+	}
+
 	if (log->level && bpf_verifier_log_full(log)) {
 		err = -ENOSPC;
 		goto errout_meta;
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index c96039a4e57f..4669020bb47d 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1044,6 +1044,10 @@ static int map_check_btf(struct bpf_map *map, const struct btf *btf,
 		}
 	}
 
+	ret = btf_check_and_fixup_fields(btf, map->record);
+	if (ret < 0)
+		goto free_map_tab;
+
 	if (map->ops->map_check_btf) {
 		ret = map->ops->map_check_btf(map, btf, key_type, value_type);
 		if (ret < 0)
-- 
2.38.1

[PATCH bpf-next v5 09/25] bpf: Allow locking bpf_spin_lock in local kptr

[Kumar Kartikeya Dwivedi]

Allow locking a bpf_spin_lock embedded in local kptr, in addition to
already support map value pointers. The handling is similar to that of
map values, by just preserving the reg->id of local kptrs as well, and
adjusting process_spin_lock to work with non-PTR_TO_MAP_VALUE and
remember the id in verifier state.

Refactor the existing process_spin_lock to work with PTR_TO_BTF_ID |
MEM_ALLOC in addition to PTR_TO_MAP_VALUE. We need to update the
reg_may_point_to_spin_lock which is used in mark_ptr_or_null_reg to
preserve reg->id, that will be used in env->cur_state->active_spin_lock
to remember the currently held spin lock.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 kernel/bpf/helpers.c  |  2 ++
 kernel/bpf/verifier.c | 70 ++++++++++++++++++++++++++++++++-----------
 2 files changed, 55 insertions(+), 17 deletions(-)

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 7bc71995f17c..5bc0b9f0f306 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -336,6 +336,7 @@ const struct bpf_func_proto bpf_spin_lock_proto = {
 	.gpl_only	= false,
 	.ret_type	= RET_VOID,
 	.arg1_type	= ARG_PTR_TO_SPIN_LOCK,
+	.arg1_btf_id    = BPF_PTR_POISON,
 };
 
 static inline void __bpf_spin_unlock_irqrestore(struct bpf_spin_lock *lock)
@@ -358,6 +359,7 @@ const struct bpf_func_proto bpf_spin_unlock_proto = {
 	.gpl_only	= false,
 	.ret_type	= RET_VOID,
 	.arg1_type	= ARG_PTR_TO_SPIN_LOCK,
+	.arg1_btf_id    = BPF_PTR_POISON,
 };
 
 void copy_map_value_locked(struct bpf_map *map, void *dst, void *src,
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 7dcb4629f764..f1170e9db699 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -453,8 +453,16 @@ static bool reg_type_not_null(enum bpf_reg_type type)
 
 static bool reg_may_point_to_spin_lock(const struct bpf_reg_state *reg)
 {
-	return reg->type == PTR_TO_MAP_VALUE &&
-	       btf_record_has_field(reg->map_ptr->record, BPF_SPIN_LOCK);
+	struct btf_record *rec = NULL;
+
+	if (reg->type == PTR_TO_MAP_VALUE) {
+		rec = reg->map_ptr->record;
+	} else if (reg->type == (PTR_TO_BTF_ID | MEM_ALLOC)) {
+		struct btf_struct_meta *meta = btf_find_struct_meta(reg->btf, reg->btf_id);
+		if (meta)
+			rec = meta->record;
+	}
+	return btf_record_has_field(rec, BPF_SPIN_LOCK);
 }
 
 static bool type_is_rdonly_mem(u32 type)
@@ -5583,8 +5591,10 @@ static int process_spin_lock(struct bpf_verifier_env *env, int regno,
 	struct bpf_reg_state *regs = cur_regs(env), *reg = &regs[regno];
 	struct bpf_verifier_state *cur = env->cur_state;
 	bool is_const = tnum_is_const(reg->var_off);
-	struct bpf_map *map = reg->map_ptr;
 	u64 val = reg->var_off.value;
+	struct bpf_map *map = NULL;
+	struct btf_record *rec;
+	struct btf *btf = NULL;
 
 	if (!is_const) {
 		verbose(env,
@@ -5592,19 +5602,32 @@ static int process_spin_lock(struct bpf_verifier_env *env, int regno,
 			regno);
 		return -EINVAL;
 	}
-	if (!map->btf) {
-		verbose(env,
-			"map '%s' has to have BTF in order to use bpf_spin_lock\n",
-			map->name);
-		return -EINVAL;
+	if (reg->type == PTR_TO_MAP_VALUE) {
+		map = reg->map_ptr;
+		if (!map->btf) {
+			verbose(env,
+				"map '%s' has to have BTF in order to use bpf_spin_lock\n",
+				map->name);
+			return -EINVAL;
+		}
+		rec = map->record;
+	} else {
+		struct btf_struct_meta *meta;
+
+		btf = reg->btf;
+		meta = btf_find_struct_meta(reg->btf, reg->btf_id);
+		if (meta)
+			rec = meta->record;
 	}
-	if (!btf_record_has_field(map->record, BPF_SPIN_LOCK)) {
-		verbose(env, "map '%s' has no valid bpf_spin_lock\n", map->name);
+
+	if (!btf_record_has_field(rec, BPF_SPIN_LOCK)) {
+		verbose(env, "%s '%s' has no valid bpf_spin_lock\n", map ? "map" : "local",
+			map ? map->name : "kptr");
 		return -EINVAL;
 	}
-	if (map->record->spin_lock_off != val + reg->off) {
+	if (rec->spin_lock_off != val + reg->off) {
 		verbose(env, "off %lld doesn't point to 'struct bpf_spin_lock' that is at %d\n",
-			val + reg->off, map->record->spin_lock_off);
+			val + reg->off, rec->spin_lock_off);
 		return -EINVAL;
 	}
 	if (is_lock) {
@@ -5810,13 +5833,19 @@ static const struct bpf_reg_types int_ptr_types = {
 	},
 };
 
+static const struct bpf_reg_types spin_lock_types = {
+	.types = {
+		PTR_TO_MAP_VALUE,
+		PTR_TO_BTF_ID | MEM_ALLOC,
+	}
+};
+
 static const struct bpf_reg_types fullsock_types = { .types = { PTR_TO_SOCKET } };
 static const struct bpf_reg_types scalar_types = { .types = { SCALAR_VALUE } };
 static const struct bpf_reg_types context_types = { .types = { PTR_TO_CTX } };
 static const struct bpf_reg_types ringbuf_mem_types = { .types = { PTR_TO_MEM | MEM_RINGBUF } };
 static const struct bpf_reg_types const_map_ptr_types = { .types = { CONST_PTR_TO_MAP } };
 static const struct bpf_reg_types btf_ptr_types = { .types = { PTR_TO_BTF_ID } };
-static const struct bpf_reg_types spin_lock_types = { .types = { PTR_TO_MAP_VALUE } };
 static const struct bpf_reg_types percpu_btf_ptr_types = { .types = { PTR_TO_BTF_ID | MEM_PERCPU } };
 static const struct bpf_reg_types func_ptr_types = { .types = { PTR_TO_FUNC } };
 static const struct bpf_reg_types stack_ptr_types = { .types = { PTR_TO_STACK } };
@@ -5941,6 +5970,11 @@ static int check_reg_type(struct bpf_verifier_env *env, u32 regno,
 				return -EACCES;
 			}
 		}
+	} else if (type_is_local_kptr(reg->type)) {
+		if (meta->func_id != BPF_FUNC_spin_lock && meta->func_id != BPF_FUNC_spin_unlock) {
+			verbose(env, "verifier internal error: unimplemented handling of local kptr\n");
+			return -EFAULT;
+		}
 	}
 
 	return 0;
@@ -6057,7 +6091,8 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 		goto skip_type_check;
 
 	/* arg_btf_id and arg_size are in a union. */
-	if (base_type(arg_type) == ARG_PTR_TO_BTF_ID)
+	if (base_type(arg_type) == ARG_PTR_TO_BTF_ID ||
+	    base_type(arg_type) == ARG_PTR_TO_SPIN_LOCK)
 		arg_btf_id = fn->arg_btf_id[arg];
 
 	err = check_reg_type(env, regno, arg_type, arg_btf_id, meta);
@@ -6675,9 +6710,10 @@ static bool check_btf_id_ok(const struct bpf_func_proto *fn)
 	int i;
 
 	for (i = 0; i < ARRAY_SIZE(fn->arg_type); i++) {
-		if (base_type(fn->arg_type[i]) == ARG_PTR_TO_BTF_ID && !fn->arg_btf_id[i])
-			return false;
-
+		if (base_type(fn->arg_type[i]) == ARG_PTR_TO_BTF_ID)
+			return !!fn->arg_btf_id[i];
+		if (base_type(fn->arg_type[i]) == ARG_PTR_TO_SPIN_LOCK)
+			return fn->arg_btf_id[i] == BPF_PTR_POISON;
 		if (base_type(fn->arg_type[i]) != ARG_PTR_TO_BTF_ID && fn->arg_btf_id[i] &&
 		    /* arg_btf_id and arg_size are in a union. */
 		    (base_type(fn->arg_type[i]) != ARG_PTR_TO_MEM ||
-- 
2.38.1

[PATCH bpf-next v5 10/25] bpf: Allow locking bpf_spin_lock global variables

[Kumar Kartikeya Dwivedi]

Global variables reside in maps accessible using direct_value_addr
callbacks, so giving each load instruction's rewrite a unique reg->id
disallows us from holding locks which are global.

The reason for preserving reg->id as a unique value for registers that
may point to spin lock is that two separate lookups are treated as two
separate memory regions, and any possible aliasing is ignored for the
purposes of spin lock correctness.

This is not great especially for the global variable case, which are
served from maps that have max_entries == 1, i.e. they always lead to
map values pointing into the same map value.

So refactor the active_spin_lock into a 'active_lock' structure which
represents the lock identity, and instead of the reg->id, remember two
fields, a pointer and the reg->id. The pointer will store reg->map_ptr
or reg->btf. It's only necessary to distinguish for the id == 0 case of
global variables, but always setting the pointer to a non-NULL value and
using the pointer to check whether the lock is held simplifies code in
the verifier.

This is generic enough to allow it for global variables, map lookups,
and local kptr registers at the same time.

Note that while whether a lock is held can be answered by just comparing
active_lock.ptr to NULL, to determine whether the register is pointing
to the same held lock requires comparing _both_ ptr and id.

Finally, as a result of this refactoring, pseudo load instructions are
not given a unique reg->id, as they are doing lookup for the same map
value (max_entries is never greater than 1).

Essentially, we consider that the tuple of (ptr, id) will always be
unique for any kind of argument to bpf_spin_{lock,unlock}.

Note that this can be extended in the future to also remember offset
used for locking, so that we can introduce multiple bpf_spin_lock fields
in the same allocation.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 include/linux/bpf_verifier.h |  5 ++++-
 kernel/bpf/verifier.c        | 41 ++++++++++++++++++++++++------------
 2 files changed, 32 insertions(+), 14 deletions(-)

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 1a32baa78ce2..70cccac62a15 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -323,7 +323,10 @@ struct bpf_verifier_state {
 	u32 branches;
 	u32 insn_idx;
 	u32 curframe;
-	u32 active_spin_lock;
+	struct {
+		void *ptr;
+		u32 id;
+	} active_lock;
 	bool speculative;
 
 	/* first and last insn idx of this verifier state */
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index f1170e9db699..281a6a04a0d8 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1210,7 +1210,8 @@ static int copy_verifier_state(struct bpf_verifier_state *dst_state,
 	}
 	dst_state->speculative = src->speculative;
 	dst_state->curframe = src->curframe;
-	dst_state->active_spin_lock = src->active_spin_lock;
+	dst_state->active_lock.ptr = src->active_lock.ptr;
+	dst_state->active_lock.id = src->active_lock.id;
 	dst_state->branches = src->branches;
 	dst_state->parent = src->parent;
 	dst_state->first_insn_idx = src->first_insn_idx;
@@ -5582,7 +5583,7 @@ int check_kfunc_mem_size_reg(struct bpf_verifier_env *env, struct bpf_reg_state
  * Since only one bpf_spin_lock is allowed the checks are simpler than
  * reg_is_refcounted() logic. The verifier needs to remember only
  * one spin_lock instead of array of acquired_refs.
- * cur_state->active_spin_lock remembers which map value element got locked
+ * cur_state->active_lock remembers which map value element got locked
  * and clears it after bpf_spin_unlock.
  */
 static int process_spin_lock(struct bpf_verifier_env *env, int regno,
@@ -5631,22 +5632,35 @@ static int process_spin_lock(struct bpf_verifier_env *env, int regno,
 		return -EINVAL;
 	}
 	if (is_lock) {
-		if (cur->active_spin_lock) {
+		if (cur->active_lock.ptr) {
 			verbose(env,
 				"Locking two bpf_spin_locks are not allowed\n");
 			return -EINVAL;
 		}
-		cur->active_spin_lock = reg->id;
+		if (map)
+			cur->active_lock.ptr = map;
+		else
+			cur->active_lock.ptr = btf;
+		cur->active_lock.id = reg->id;
 	} else {
-		if (!cur->active_spin_lock) {
+		void *ptr;
+
+		if (map)
+			ptr = map;
+		else
+			ptr = btf;
+
+		if (!cur->active_lock.ptr) {
 			verbose(env, "bpf_spin_unlock without taking a lock\n");
 			return -EINVAL;
 		}
-		if (cur->active_spin_lock != reg->id) {
+		if (cur->active_lock.ptr != ptr ||
+		    cur->active_lock.id != reg->id) {
 			verbose(env, "bpf_spin_unlock of different lock\n");
 			return -EINVAL;
 		}
-		cur->active_spin_lock = 0;
+		cur->active_lock.ptr = NULL;
+		cur->active_lock.id = 0;
 	}
 	return 0;
 }
@@ -10573,8 +10587,8 @@ static int check_ld_imm(struct bpf_verifier_env *env, struct bpf_insn *insn)
 	    insn->src_reg == BPF_PSEUDO_MAP_IDX_VALUE) {
 		dst_reg->type = PTR_TO_MAP_VALUE;
 		dst_reg->off = aux->map_off;
-		if (btf_record_has_field(map->record, BPF_SPIN_LOCK))
-			dst_reg->id = ++env->id_gen;
+		WARN_ON_ONCE(map->max_entries != 1);
+		/* We want reg->id to be same (0) as map_value is not distinct */
 	} else if (insn->src_reg == BPF_PSEUDO_MAP_FD ||
 		   insn->src_reg == BPF_PSEUDO_MAP_IDX) {
 		dst_reg->type = CONST_PTR_TO_MAP;
@@ -10652,7 +10666,7 @@ static int check_ld_abs(struct bpf_verifier_env *env, struct bpf_insn *insn)
 		return err;
 	}
 
-	if (env->cur_state->active_spin_lock) {
+	if (env->cur_state->active_lock.ptr) {
 		verbose(env, "BPF_LD_[ABS|IND] cannot be used inside bpf_spin_lock-ed region\n");
 		return -EINVAL;
 	}
@@ -11918,7 +11932,8 @@ static bool states_equal(struct bpf_verifier_env *env,
 	if (old->speculative && !cur->speculative)
 		return false;
 
-	if (old->active_spin_lock != cur->active_spin_lock)
+	if (old->active_lock.ptr != cur->active_lock.ptr ||
+	    old->active_lock.id != cur->active_lock.id)
 		return false;
 
 	/* for states to be equal callsites have to be the same
@@ -12563,7 +12578,7 @@ static int do_check(struct bpf_verifier_env *env)
 					return -EINVAL;
 				}
 
-				if (env->cur_state->active_spin_lock &&
+				if (env->cur_state->active_lock.ptr &&
 				    (insn->src_reg == BPF_PSEUDO_CALL ||
 				     insn->imm != BPF_FUNC_spin_unlock)) {
 					verbose(env, "function calls are not allowed while holding a lock\n");
@@ -12600,7 +12615,7 @@ static int do_check(struct bpf_verifier_env *env)
 					return -EINVAL;
 				}
 
-				if (env->cur_state->active_spin_lock) {
+				if (env->cur_state->active_lock.ptr) {
 					verbose(env, "bpf_spin_unlock is missing\n");
 					return -EINVAL;
 				}
-- 
2.38.1

[PATCH bpf-next v5 11/25] bpf: Allow locking bpf_spin_lock in inner map values

[Kumar Kartikeya Dwivedi]

There is no need to restrict users from locking bpf_spin_lock in map
values of inner maps. Each inner map lookup gets a unique reg->id
assigned to the returned PTR_TO_MAP_VALUE which will be preserved after
the NULL check. Distinct lookups into different inner map get unique
IDs, and distinct lookups into same inner map also get unique IDs.

Hence, lift the restriction by removing the check return -ENOTSUPP in
map_in_map.c. Later commits will add comprehensive test cases to ensure
that invalid cases are rejected.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 kernel/bpf/map_in_map.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/kernel/bpf/map_in_map.c b/kernel/bpf/map_in_map.c
index 8ca0cca39d49..f31893a123a2 100644
--- a/kernel/bpf/map_in_map.c
+++ b/kernel/bpf/map_in_map.c
@@ -29,11 +29,6 @@ struct bpf_map *bpf_map_meta_alloc(int inner_map_ufd)
 		return ERR_PTR(-ENOTSUPP);
 	}
 
-	if (btf_record_has_field(inner_map->record, BPF_SPIN_LOCK)) {
-		fdput(f);
-		return ERR_PTR(-ENOTSUPP);
-	}
-
 	inner_map_meta_size = sizeof(*inner_map_meta);
 	/* In some cases verifier needs to access beyond just base map. */
 	if (inner_map->ops == &array_map_ops)
-- 
2.38.1

[PATCH bpf-next v5 12/25] bpf: Rewrite kfunc argument handling

[Kumar Kartikeya Dwivedi]

As we continue to add more features, argument types, kfunc flags, and
different extensions to kfuncs, the code to verify the correctness of
the kfunc prototype wrt the passed in registers has become ad-hoc and
ugly to read. To make life easier, and make a very clear split between
different stages of argument processing, move all the code into
verifier.c and refactor into easier to read helpers and functions.

This also makes sharing code within the verifier easier with kfunc
argument processing. This will be more and more useful in later patches
as we are now moving to implement very core BPF helpers as kfuncs, to
keep them experimental before baking into UAPI.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 include/linux/btf.h                           |  31 +-
 kernel/bpf/btf.c                              |  16 +-
 kernel/bpf/verifier.c                         | 547 +++++++++++++++++-
 .../bpf/prog_tests/kfunc_dynptr_param.c       |   2 +-
 tools/testing/selftests/bpf/verifier/calls.c  |   2 +-
 .../selftests/bpf/verifier/ref_tracking.c     |   4 +-
 6 files changed, 569 insertions(+), 33 deletions(-)

diff --git a/include/linux/btf.h b/include/linux/btf.h
index 42d8f3730a8d..d5b26380a60f 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -338,6 +338,16 @@ static inline bool btf_type_is_struct(const struct btf_type *t)
 	return kind == BTF_KIND_STRUCT || kind == BTF_KIND_UNION;
 }
 
+static inline bool __btf_type_is_struct(const struct btf_type *t)
+{
+	return BTF_INFO_KIND(t->info) == BTF_KIND_STRUCT;
+}
+
+static inline bool btf_type_is_array(const struct btf_type *t)
+{
+	return BTF_INFO_KIND(t->info) == BTF_KIND_ARRAY;
+}
+
 static inline u16 btf_type_vlen(const struct btf_type *t)
 {
 	return BTF_INFO_VLEN(t->info);
@@ -439,9 +449,10 @@ static inline void *btf_id_set8_contains(const struct btf_id_set8 *set, u32 id)
 	return bsearch(&id, set->pairs, set->cnt, sizeof(set->pairs[0]), btf_id_cmp_func);
 }
 
-#ifdef CONFIG_BPF_SYSCALL
 struct bpf_prog;
+struct bpf_verifier_log;
 
+#ifdef CONFIG_BPF_SYSCALL
 const struct btf_type *btf_type_by_id(const struct btf *btf, u32 type_id);
 const char *btf_name_by_offset(const struct btf *btf, u32 offset);
 struct btf *btf_parse_vmlinux(void);
@@ -455,6 +466,12 @@ s32 btf_find_dtor_kfunc(struct btf *btf, u32 btf_id);
 int register_btf_id_dtor_kfuncs(const struct btf_id_dtor_kfunc *dtors, u32 add_cnt,
 				struct module *owner);
 struct btf_struct_meta *btf_find_struct_meta(const struct btf *btf, u32 btf_id);
+const struct btf_member *
+btf_get_prog_ctx_type(struct bpf_verifier_log *log, const struct btf *btf,
+		      const struct btf_type *t, enum bpf_prog_type prog_type,
+		      int arg);
+bool btf_types_are_same(const struct btf *btf1, u32 id1,
+			const struct btf *btf2, u32 id2);
 #else
 static inline const struct btf_type *btf_type_by_id(const struct btf *btf,
 						    u32 type_id)
@@ -490,6 +507,18 @@ static inline struct btf_struct_meta *btf_find_struct_meta(const struct btf *btf
 {
 	return NULL;
 }
+static inline const struct btf_member *
+btf_get_prog_ctx_type(struct bpf_verifier_log *log, const struct btf *btf,
+		      const struct btf_type *t, enum bpf_prog_type prog_type,
+		      int arg)
+{
+	return NULL;
+}
+static inline bool btf_types_are_same(const struct btf *btf1, u32 id1,
+				      const struct btf *btf2, u32 id2)
+{
+	return false;
+}
 #endif
 
 static inline bool btf_type_is_struct_ptr(struct btf *btf, const struct btf_type *t)
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 685a6998432b..9d374c76b4a4 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -478,16 +478,6 @@ static bool btf_type_nosize_or_null(const struct btf_type *t)
 	return !t || btf_type_nosize(t);
 }
 
-static bool __btf_type_is_struct(const struct btf_type *t)
-{
-	return BTF_INFO_KIND(t->info) == BTF_KIND_STRUCT;
-}
-
-static bool btf_type_is_array(const struct btf_type *t)
-{
-	return BTF_INFO_KIND(t->info) == BTF_KIND_ARRAY;
-}
-
 static bool btf_type_is_datasec(const struct btf_type *t)
 {
 	return BTF_INFO_KIND(t->info) == BTF_KIND_DATASEC;
@@ -5533,7 +5523,7 @@ static u8 bpf_ctx_convert_map[] = {
 #undef BPF_MAP_TYPE
 #undef BPF_LINK_TYPE
 
-static const struct btf_member *
+const struct btf_member *
 btf_get_prog_ctx_type(struct bpf_verifier_log *log, const struct btf *btf,
 		      const struct btf_type *t, enum bpf_prog_type prog_type,
 		      int arg)
@@ -6319,8 +6309,8 @@ int btf_struct_access(struct bpf_verifier_log *log,
  * end up with two different module BTFs, but IDs point to the common type in
  * vmlinux BTF.
  */
-static bool btf_types_are_same(const struct btf *btf1, u32 id1,
-			       const struct btf *btf2, u32 id2)
+bool btf_types_are_same(const struct btf *btf1, u32 id1,
+			const struct btf *btf2, u32 id2)
 {
 	if (id1 != id2)
 		return false;
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 281a6a04a0d8..7e50772f9f08 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -7850,19 +7850,523 @@ static void mark_btf_func_reg_size(struct bpf_verifier_env *env, u32 regno,
 	}
 }
 
+struct bpf_kfunc_call_arg_meta {
+	/* In parameters */
+	struct btf *btf;
+	u32 func_id;
+	u32 kfunc_flags;
+	const struct btf_type *func_proto;
+	const char *func_name;
+	/* Out parameters */
+	u32 ref_obj_id;
+	u8 release_regno;
+	bool r0_rdonly;
+	u64 r0_size;
+};
+
+static bool is_kfunc_acquire(struct bpf_kfunc_call_arg_meta *meta)
+{
+	return meta->kfunc_flags & KF_ACQUIRE;
+}
+
+static bool is_kfunc_ret_null(struct bpf_kfunc_call_arg_meta *meta)
+{
+	return meta->kfunc_flags & KF_RET_NULL;
+}
+
+static bool is_kfunc_release(struct bpf_kfunc_call_arg_meta *meta)
+{
+	return meta->kfunc_flags & KF_RELEASE;
+}
+
+static bool is_kfunc_trusted_args(struct bpf_kfunc_call_arg_meta *meta)
+{
+	return meta->kfunc_flags & KF_TRUSTED_ARGS;
+}
+
+static bool is_kfunc_sleepable(struct bpf_kfunc_call_arg_meta *meta)
+{
+	return meta->kfunc_flags & KF_SLEEPABLE;
+}
+
+static bool is_kfunc_destructive(struct bpf_kfunc_call_arg_meta *meta)
+{
+	return meta->kfunc_flags & KF_DESTRUCTIVE;
+}
+
+static bool is_kfunc_arg_kptr_get(struct bpf_kfunc_call_arg_meta *meta, int arg)
+{
+	return arg == 0 && (meta->kfunc_flags & KF_KPTR_GET);
+}
+
+static bool is_kfunc_arg_mem_size(const struct btf *btf,
+				  const struct btf_param *arg,
+				  const struct bpf_reg_state *reg)
+{
+	int len, sfx_len = sizeof("__sz") - 1;
+	const struct btf_type *t;
+	const char *param_name;
+
+	t = btf_type_skip_modifiers(btf, arg->type, NULL);
+	if (!btf_type_is_scalar(t) || reg->type != SCALAR_VALUE)
+		return false;
+
+	/* In the future, this can be ported to use BTF tagging */
+	param_name = btf_name_by_offset(btf, arg->name_off);
+	if (str_is_empty(param_name))
+		return false;
+	len = strlen(param_name);
+	if (len < sfx_len)
+		return false;
+	param_name += len - sfx_len;
+	if (strncmp(param_name, "__sz", sfx_len))
+		return false;
+
+	return true;
+}
+
+static bool is_kfunc_arg_ret_buf_size(const struct btf *btf,
+				      const struct btf_param *arg,
+				      const struct bpf_reg_state *reg,
+				      const char *name)
+{
+	int len, target_len = strlen(name);
+	const struct btf_type *t;
+	const char *param_name;
+
+	t = btf_type_skip_modifiers(btf, arg->type, NULL);
+	if (!btf_type_is_scalar(t) || reg->type != SCALAR_VALUE)
+		return false;
+
+	param_name = btf_name_by_offset(btf, arg->name_off);
+	if (str_is_empty(param_name))
+		return false;
+	len = strlen(param_name);
+	if (len != target_len)
+		return false;
+	if (strcmp(param_name, name))
+		return false;
+
+	return true;
+}
+
+enum {
+	KF_ARG_DYNPTR_ID,
+};
+
+BTF_ID_LIST(kf_arg_btf_ids)
+BTF_ID(struct, bpf_dynptr_kern)
+
+static bool is_kfunc_arg_dynptr(const struct btf *btf,
+				const struct btf_param *arg)
+{
+	const struct btf_type *t;
+	u32 res_id;
+
+	t = btf_type_skip_modifiers(btf, arg->type, NULL);
+	if (!t)
+		return false;
+	if (!btf_type_is_ptr(t))
+		return false;
+	t = btf_type_skip_modifiers(btf, t->type, &res_id);
+	if (!t)
+		return false;
+	return btf_types_are_same(btf, res_id, btf_vmlinux, kf_arg_btf_ids[KF_ARG_DYNPTR_ID]);
+}
+
+/* Returns true if struct is composed of scalars, 4 levels of nesting allowed */
+static bool __btf_type_is_scalar_struct(struct bpf_verifier_env *env,
+					const struct btf *btf,
+					const struct btf_type *t, int rec)
+{
+	const struct btf_type *member_type;
+	const struct btf_member *member;
+	u32 i;
+
+	if (!btf_type_is_struct(t))
+		return false;
+
+	for_each_member(i, t, member) {
+		const struct btf_array *array;
+
+		member_type = btf_type_skip_modifiers(btf, member->type, NULL);
+		if (btf_type_is_struct(member_type)) {
+			if (rec >= 3) {
+				verbose(env, "max struct nesting depth exceeded\n");
+				return false;
+			}
+			if (!__btf_type_is_scalar_struct(env, btf, member_type, rec + 1))
+				return false;
+			continue;
+		}
+		if (btf_type_is_array(member_type)) {
+			array = btf_array(member_type);
+			if (!array->nelems)
+				return false;
+			member_type = btf_type_skip_modifiers(btf, array->type, NULL);
+			if (!btf_type_is_scalar(member_type))
+				return false;
+			continue;
+		}
+		if (!btf_type_is_scalar(member_type))
+			return false;
+	}
+	return true;
+}
+
+
+static u32 *reg2btf_ids[__BPF_REG_TYPE_MAX] = {
+#ifdef CONFIG_NET
+	[PTR_TO_SOCKET] = &btf_sock_ids[BTF_SOCK_TYPE_SOCK],
+	[PTR_TO_SOCK_COMMON] = &btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON],
+	[PTR_TO_TCP_SOCK] = &btf_sock_ids[BTF_SOCK_TYPE_TCP],
+#endif
+};
+
+enum kfunc_ptr_arg_type {
+	KF_ARG_PTR_TO_CTX,
+	KF_ARG_PTR_TO_KPTR_STRONG,   /* PTR_TO_KPTR but type specific */
+	KF_ARG_PTR_TO_DYNPTR,
+	KF_ARG_PTR_TO_BTF_ID,	     /* Also covers reg2btf_ids conversions */
+	KF_ARG_PTR_TO_MEM,
+	KF_ARG_PTR_TO_MEM_SIZE,	     /* Size derived from next argument, skip it */
+};
+
+static enum kfunc_ptr_arg_type
+get_kfunc_ptr_arg_type(struct bpf_verifier_env *env,
+		       struct bpf_kfunc_call_arg_meta *meta,
+		       const struct btf_type *t, const struct btf_type *ref_t,
+		       const char *ref_tname, const struct btf_param *args,
+		       int argno, int nargs)
+{
+	u32 regno = argno + 1;
+	struct bpf_reg_state *regs = cur_regs(env);
+	struct bpf_reg_state *reg = &regs[regno];
+	bool arg_mem_size = false;
+
+	/* In this function, we verify the kfunc's BTF as per the argument type,
+	 * leaving the rest of the verification with respect to the register
+	 * type to our caller. When a set of conditions hold in the BTF type of
+	 * arguments, we resolve it to a known kfunc_ptr_arg_type.
+	 */
+	if (btf_get_prog_ctx_type(&env->log, meta->btf, t, resolve_prog_type(env->prog), argno))
+		return KF_ARG_PTR_TO_CTX;
+
+	if (is_kfunc_arg_kptr_get(meta, argno)) {
+		if (!btf_type_is_ptr(ref_t)) {
+			verbose(env, "arg#0 BTF type must be a double pointer for kptr_get kfunc\n");
+			return -EINVAL;
+		}
+		ref_t = btf_type_by_id(meta->btf, ref_t->type);
+		ref_tname = btf_name_by_offset(meta->btf, ref_t->name_off);
+		if (!btf_type_is_struct(ref_t)) {
+			verbose(env, "kernel function %s args#0 pointer type %s %s is not supported\n",
+				meta->func_name, btf_type_str(ref_t), ref_tname);
+			return -EINVAL;
+		}
+		return KF_ARG_PTR_TO_KPTR_STRONG;
+	}
+
+	if (is_kfunc_arg_dynptr(meta->btf, &args[argno]))
+		return KF_ARG_PTR_TO_DYNPTR;
+
+	if ((base_type(reg->type) == PTR_TO_BTF_ID || reg2btf_ids[base_type(reg->type)])) {
+		if (!btf_type_is_struct(ref_t)) {
+			verbose(env, "kernel function %s args#%d pointer type %s %s is not supported\n",
+				meta->func_name, argno, btf_type_str(ref_t), ref_tname);
+			return -EINVAL;
+		}
+		return KF_ARG_PTR_TO_BTF_ID;
+	}
+
+	if (argno + 1 < nargs && is_kfunc_arg_mem_size(meta->btf, &args[argno + 1], &regs[regno + 1]))
+		arg_mem_size = true;
+
+	/* This is the catch all argument type of register types supported by
+	 * check_helper_mem_access. However, we only allow when argument type is
+	 * pointer to scalar, or struct composed (recursively) of scalars. When
+	 * arg_mem_size is true, the pointer can be void *.
+	 */
+	if (!btf_type_is_scalar(ref_t) && !__btf_type_is_scalar_struct(env, meta->btf, ref_t, 0) &&
+	    (arg_mem_size ? !btf_type_is_void(ref_t) : 1)) {
+		verbose(env, "arg#%d pointer type %s %s must point to %sscalar, or struct with scalar\n",
+			argno, btf_type_str(ref_t), ref_tname, arg_mem_size ? "void, " : "");
+		return -EINVAL;
+	}
+	return arg_mem_size ? KF_ARG_PTR_TO_MEM_SIZE : KF_ARG_PTR_TO_MEM;
+}
+
+static int process_kf_arg_ptr_to_btf_id(struct bpf_verifier_env *env,
+					struct bpf_reg_state *reg,
+					const struct btf_type *ref_t,
+					const char *ref_tname, u32 ref_id,
+					struct bpf_kfunc_call_arg_meta *meta,
+					int argno)
+{
+	const struct btf_type *reg_ref_t;
+	bool strict_type_match = false;
+	const struct btf *reg_btf;
+	const char *reg_ref_tname;
+	u32 reg_ref_id;
+
+	if (reg->type == PTR_TO_BTF_ID) {
+		reg_btf = reg->btf;
+		reg_ref_id = reg->btf_id;
+	} else {
+		reg_btf = btf_vmlinux;
+		reg_ref_id = *reg2btf_ids[base_type(reg->type)];
+	}
+
+	if (is_kfunc_trusted_args(meta) || (is_kfunc_release(meta) && reg->ref_obj_id))
+		strict_type_match = true;
+
+	reg_ref_t = btf_type_skip_modifiers(reg_btf, reg_ref_id, &reg_ref_id);
+	reg_ref_tname = btf_name_by_offset(reg_btf, reg_ref_t->name_off);
+	if (!btf_struct_ids_match(&env->log, reg_btf, reg_ref_id, reg->off, meta->btf, ref_id, strict_type_match)) {
+		verbose(env, "kernel function %s args#%d expected pointer to %s %s but R%d has a pointer to %s %s\n",
+			meta->func_name, argno, btf_type_str(ref_t), ref_tname, argno + 1,
+			btf_type_str(reg_ref_t), reg_ref_tname);
+		return -EINVAL;
+	}
+	return 0;
+}
+
+static int process_kf_arg_ptr_to_kptr_strong(struct bpf_verifier_env *env,
+					     struct bpf_reg_state *reg,
+					     const struct btf_type *ref_t,
+					     const char *ref_tname,
+					     struct bpf_kfunc_call_arg_meta *meta,
+					     int argno)
+{
+	struct btf_field *kptr_field;
+
+	/* check_func_arg_reg_off allows var_off for
+	 * PTR_TO_MAP_VALUE, but we need fixed offset to find
+	 * off_desc.
+	 */
+	if (!tnum_is_const(reg->var_off)) {
+		verbose(env, "arg#0 must have constant offset\n");
+		return -EINVAL;
+	}
+
+	kptr_field = btf_record_find(reg->map_ptr->record, reg->off + reg->var_off.value, BPF_KPTR);
+	if (!kptr_field || kptr_field->type != BPF_KPTR_REF) {
+		verbose(env, "arg#0 no referenced kptr at map value offset=%llu\n",
+			reg->off + reg->var_off.value);
+		return -EINVAL;
+	}
+
+	if (!btf_struct_ids_match(&env->log, meta->btf, ref_t->type, 0, kptr_field->kptr.btf,
+				  kptr_field->kptr.btf_id, true)) {
+		verbose(env, "kernel function %s args#%d expected pointer to %s %s\n",
+			meta->func_name, argno, btf_type_str(ref_t), ref_tname);
+		return -EINVAL;
+	}
+	return 0;
+}
+
+static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_arg_meta *meta)
+{
+	const char *func_name = meta->func_name, *ref_tname;
+	const struct btf *btf = meta->btf;
+	const struct btf_param *args;
+	u32 i, nargs;
+	int ret;
+
+	args = (const struct btf_param *)(meta->func_proto + 1);
+	nargs = btf_type_vlen(meta->func_proto);
+	if (nargs > MAX_BPF_FUNC_REG_ARGS) {
+		verbose(env, "Function %s has %d > %d args\n", func_name, nargs,
+			MAX_BPF_FUNC_REG_ARGS);
+		return -EINVAL;
+	}
+
+	/* Check that BTF function arguments match actual types that the
+	 * verifier sees.
+	 */
+	for (i = 0; i < nargs; i++) {
+		struct bpf_reg_state *regs = cur_regs(env), *reg = &regs[i + 1];
+		const struct btf_type *t, *ref_t, *resolve_ret;
+		enum bpf_arg_type arg_type = ARG_DONTCARE;
+		u32 regno = i + 1, ref_id, type_size;
+		bool is_ret_buf_sz = false;
+		int kf_arg_type;
+
+		t = btf_type_skip_modifiers(btf, args[i].type, NULL);
+		if (btf_type_is_scalar(t)) {
+			if (reg->type != SCALAR_VALUE) {
+				verbose(env, "R%d is not a scalar\n", regno);
+				return -EINVAL;
+			}
+			if (is_kfunc_arg_ret_buf_size(btf, &args[i], reg, "rdonly_buf_size")) {
+					meta->r0_rdonly = true;
+					is_ret_buf_sz = true;
+			} else if (is_kfunc_arg_ret_buf_size(btf, &args[i], reg, "rdwr_buf_size")) {
+					is_ret_buf_sz = true;
+			}
+
+			if (is_ret_buf_sz) {
+				if (meta->r0_size) {
+					verbose(env, "2 or more rdonly/rdwr_buf_size parameters for kfunc");
+					return -EINVAL;
+				}
+
+				if (!tnum_is_const(reg->var_off)) {
+					verbose(env, "R%d is not a const\n", regno);
+					return -EINVAL;
+				}
+
+				meta->r0_size = reg->var_off.value;
+				ret = mark_chain_precision(env, regno);
+				if (ret)
+					return ret;
+			}
+			continue;
+		}
+
+		if (!btf_type_is_ptr(t)) {
+			verbose(env, "Unrecognized arg#%d type %s\n", i, btf_type_str(t));
+			return -EINVAL;
+		}
+
+		if (reg->ref_obj_id) {
+			if (is_kfunc_release(meta) && meta->ref_obj_id) {
+				verbose(env, "verifier internal error: more than one arg with ref_obj_id R%d %u %u\n",
+					regno, reg->ref_obj_id,
+					meta->ref_obj_id);
+				return -EFAULT;
+			}
+			meta->ref_obj_id = reg->ref_obj_id;
+			if (is_kfunc_release(meta))
+				meta->release_regno = regno;
+		}
+
+		ref_t = btf_type_skip_modifiers(btf, t->type, &ref_id);
+		ref_tname = btf_name_by_offset(btf, ref_t->name_off);
+
+		kf_arg_type = get_kfunc_ptr_arg_type(env, meta, t, ref_t, ref_tname, args, i, nargs);
+		if (kf_arg_type < 0)
+			return kf_arg_type;
+
+		switch (kf_arg_type) {
+		case KF_ARG_PTR_TO_BTF_ID:
+			if (!is_kfunc_trusted_args(meta))
+				break;
+			if (!reg->ref_obj_id) {
+				verbose(env, "R%d must be referenced\n", regno);
+				return -EINVAL;
+			}
+			fallthrough;
+		case KF_ARG_PTR_TO_CTX:
+			/* Trusted arguments have the same offset checks as release arguments */
+			arg_type |= OBJ_RELEASE;
+			break;
+		case KF_ARG_PTR_TO_KPTR_STRONG:
+		case KF_ARG_PTR_TO_DYNPTR:
+		case KF_ARG_PTR_TO_MEM:
+		case KF_ARG_PTR_TO_MEM_SIZE:
+			/* Trusted by default */
+			break;
+		default:
+			WARN_ON_ONCE(1);
+			return -EFAULT;
+		}
+
+		if (is_kfunc_release(meta) && reg->ref_obj_id)
+			arg_type |= OBJ_RELEASE;
+		ret = check_func_arg_reg_off(env, reg, regno, arg_type);
+		if (ret < 0)
+			return ret;
+
+		switch (kf_arg_type) {
+		case KF_ARG_PTR_TO_CTX:
+			if (reg->type != PTR_TO_CTX) {
+				verbose(env, "arg#%d expected pointer to ctx, but got %s\n", i, btf_type_str(t));
+				return -EINVAL;
+			}
+			break;
+		case KF_ARG_PTR_TO_KPTR_STRONG:
+			if (reg->type != PTR_TO_MAP_VALUE) {
+				verbose(env, "arg#0 expected pointer to map value\n");
+				return -EINVAL;
+			}
+			ret = process_kf_arg_ptr_to_kptr_strong(env, reg, ref_t, ref_tname, meta, i);
+			if (ret < 0)
+				return ret;
+			break;
+		case KF_ARG_PTR_TO_DYNPTR:
+			if (reg->type != PTR_TO_STACK) {
+				verbose(env, "arg#%d expected pointer to stack\n", i);
+				return -EINVAL;
+			}
+
+			if (!is_dynptr_reg_valid_init(env, reg)) {
+				verbose(env, "arg#%d pointer type %s %s must be valid and initialized\n",
+					i, btf_type_str(ref_t), ref_tname);
+				return -EINVAL;
+			}
+
+			if (!is_dynptr_type_expected(env, reg, ARG_PTR_TO_DYNPTR | DYNPTR_TYPE_LOCAL)) {
+				verbose(env, "arg#%d pointer type %s %s points to unsupported dynamic pointer type\n",
+					i, btf_type_str(ref_t), ref_tname);
+				return -EINVAL;
+			}
+			break;
+		case KF_ARG_PTR_TO_BTF_ID:
+			/* Only base_type is checked, further checks are done here */
+			if (reg->type != PTR_TO_BTF_ID &&
+			    (!reg2btf_ids[base_type(reg->type)] || type_flag(reg->type))) {
+				verbose(env, "arg#%d expected pointer to btf or socket\n", i);
+				return -EINVAL;
+			}
+			ret = process_kf_arg_ptr_to_btf_id(env, reg, ref_t, ref_tname, ref_id, meta, i);
+			if (ret < 0)
+				return ret;
+			break;
+		case KF_ARG_PTR_TO_MEM:
+			resolve_ret = btf_resolve_size(btf, ref_t, &type_size);
+			if (IS_ERR(resolve_ret)) {
+				verbose(env, "arg#%d reference type('%s %s') size cannot be determined: %ld\n",
+					i, btf_type_str(ref_t), ref_tname, PTR_ERR(resolve_ret));
+				return -EINVAL;
+			}
+			ret = check_mem_reg(env, reg, regno, type_size);
+			if (ret < 0)
+				return ret;
+			break;
+		case KF_ARG_PTR_TO_MEM_SIZE:
+			ret = check_kfunc_mem_size_reg(env, &regs[regno + 1], regno + 1);
+			if (ret < 0) {
+				verbose(env, "arg#%d arg#%d memory, len pair leads to invalid memory access\n", i, i + 1);
+				return ret;
+			}
+			/* Skip next '__sz' argument */
+			i++;
+			break;
+		}
+	}
+
+	if (is_kfunc_release(meta) && !meta->release_regno) {
+		verbose(env, "release kernel function %s expects refcounted PTR_TO_BTF_ID\n",
+			func_name);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
 static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 			    int *insn_idx_p)
 {
 	const struct btf_type *t, *func, *func_proto, *ptr_type;
 	struct bpf_reg_state *regs = cur_regs(env);
-	struct bpf_kfunc_arg_meta meta = { 0 };
 	const char *func_name, *ptr_type_name;
+	struct bpf_kfunc_call_arg_meta meta;
 	u32 i, nargs, func_id, ptr_type_id;
 	int err, insn_idx = *insn_idx_p;
 	const struct btf_param *args;
 	struct btf *desc_btf;
 	u32 *kfunc_flags;
-	bool acq;
 
 	/* skip for now, but return error when we find this in fixup_kfunc_call */
 	if (!insn->imm)
@@ -7883,24 +8387,34 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 			func_name);
 		return -EACCES;
 	}
-	if (*kfunc_flags & KF_DESTRUCTIVE && !capable(CAP_SYS_BOOT)) {
-		verbose(env, "destructive kfunc calls require CAP_SYS_BOOT capabilities\n");
+
+	/* Prepare kfunc call metadata */
+	memset(&meta, 0, sizeof(meta));
+	meta.btf = desc_btf;
+	meta.func_id = func_id;
+	meta.kfunc_flags = *kfunc_flags;
+	meta.func_proto = func_proto;
+	meta.func_name = func_name;
+
+	if (is_kfunc_destructive(&meta) && !capable(CAP_SYS_BOOT)) {
+		verbose(env, "destructive kfunc calls require CAP_SYS_BOOT capability\n");
 		return -EACCES;
 	}
 
-	acq = *kfunc_flags & KF_ACQUIRE;
-
-	meta.flags = *kfunc_flags;
+	if (is_kfunc_sleepable(&meta) && !env->prog->aux->sleepable) {
+		verbose(env, "program must be sleepable to call sleepable kfunc %s\n", func_name);
+		return -EACCES;
+	}
 
 	/* Check the arguments */
-	err = btf_check_kfunc_arg_match(env, desc_btf, func_id, regs, &meta);
+	err = check_kfunc_args(env, &meta);
 	if (err < 0)
 		return err;
 	/* In case of release function, we get register number of refcounted
-	 * PTR_TO_BTF_ID back from btf_check_kfunc_arg_match, do the release now
+	 * PTR_TO_BTF_ID in bpf_kfunc_arg_meta, do the release now.
 	 */
-	if (err) {
-		err = release_reference(env, regs[err].ref_obj_id);
+	if (meta.release_regno) {
+		err = release_reference(env, regs[meta.release_regno].ref_obj_id);
 		if (err) {
 			verbose(env, "kfunc %s#%d reference has not been acquired before\n",
 				func_name, func_id);
@@ -7914,7 +8428,7 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 	/* Check return type */
 	t = btf_type_skip_modifiers(desc_btf, func_proto->type, NULL);
 
-	if (acq && !btf_type_is_struct_ptr(desc_btf, t)) {
+	if (is_kfunc_acquire(&meta) && !btf_type_is_struct_ptr(meta.btf, t)) {
 		verbose(env, "acquire kernel function does not return PTR_TO_BTF_ID\n");
 		return -EINVAL;
 	}
@@ -7953,20 +8467,23 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 			regs[BPF_REG_0].type = PTR_TO_BTF_ID;
 			regs[BPF_REG_0].btf_id = ptr_type_id;
 		}
-		if (*kfunc_flags & KF_RET_NULL) {
+		if (is_kfunc_ret_null(&meta)) {
 			regs[BPF_REG_0].type |= PTR_MAYBE_NULL;
 			/* For mark_ptr_or_null_reg, see 93c230e3f5bd6 */
 			regs[BPF_REG_0].id = ++env->id_gen;
 		}
 		mark_btf_func_reg_size(env, BPF_REG_0, sizeof(void *));
-		if (acq) {
+		if (is_kfunc_acquire(&meta)) {
 			int id = acquire_reference_state(env, insn_idx);
 
 			if (id < 0)
 				return id;
-			regs[BPF_REG_0].id = id;
+			if (is_kfunc_ret_null(&meta))
+				regs[BPF_REG_0].id = id;
 			regs[BPF_REG_0].ref_obj_id = id;
 		}
+		if (reg_may_point_to_spin_lock(&regs[BPF_REG_0]) && !regs[BPF_REG_0].id)
+			regs[BPF_REG_0].id = ++env->id_gen;
 	} /* else { add_kfunc_call() ensures it is btf_type_is_void(t) } */
 
 	nargs = btf_type_vlen(func_proto);
diff --git a/tools/testing/selftests/bpf/prog_tests/kfunc_dynptr_param.c b/tools/testing/selftests/bpf/prog_tests/kfunc_dynptr_param.c
index c210657d4d0a..55d641c1f126 100644
--- a/tools/testing/selftests/bpf/prog_tests/kfunc_dynptr_param.c
+++ b/tools/testing/selftests/bpf/prog_tests/kfunc_dynptr_param.c
@@ -22,7 +22,7 @@ static struct {
 	 "arg#0 pointer type STRUCT bpf_dynptr_kern points to unsupported dynamic pointer type", 0},
 	{"not_valid_dynptr",
 	 "arg#0 pointer type STRUCT bpf_dynptr_kern must be valid and initialized", 0},
-	{"not_ptr_to_stack", "arg#0 pointer type STRUCT bpf_dynptr_kern not to stack", 0},
+	{"not_ptr_to_stack", "arg#0 expected pointer to stack", 0},
 	{"dynptr_data_null", NULL, -EBADMSG},
 };
 
diff --git a/tools/testing/selftests/bpf/verifier/calls.c b/tools/testing/selftests/bpf/verifier/calls.c
index e1a937277b54..86d6fef2e3b4 100644
--- a/tools/testing/selftests/bpf/verifier/calls.c
+++ b/tools/testing/selftests/bpf/verifier/calls.c
@@ -109,7 +109,7 @@
 	},
 	.prog_type = BPF_PROG_TYPE_SCHED_CLS,
 	.result = REJECT,
-	.errstr = "arg#0 pointer type STRUCT prog_test_ref_kfunc must point",
+	.errstr = "arg#0 expected pointer to btf or socket",
 	.fixup_kfunc_btf_id = {
 		{ "bpf_kfunc_call_test_acquire", 3 },
 		{ "bpf_kfunc_call_test_release", 5 },
diff --git a/tools/testing/selftests/bpf/verifier/ref_tracking.c b/tools/testing/selftests/bpf/verifier/ref_tracking.c
index f18ce867271f..4784471b0b7f 100644
--- a/tools/testing/selftests/bpf/verifier/ref_tracking.c
+++ b/tools/testing/selftests/bpf/verifier/ref_tracking.c
@@ -142,7 +142,7 @@
 	.kfunc = "bpf",
 	.expected_attach_type = BPF_LSM_MAC,
 	.flags = BPF_F_SLEEPABLE,
-	.errstr = "arg#0 pointer type STRUCT bpf_key must point to scalar, or struct with scalar",
+	.errstr = "arg#0 expected pointer to btf or socket",
 	.fixup_kfunc_btf_id = {
 		{ "bpf_lookup_user_key", 2 },
 		{ "bpf_key_put", 4 },
@@ -163,7 +163,7 @@
 	.kfunc = "bpf",
 	.expected_attach_type = BPF_LSM_MAC,
 	.flags = BPF_F_SLEEPABLE,
-	.errstr = "arg#0 pointer type STRUCT bpf_key must point to scalar, or struct with scalar",
+	.errstr = "arg#0 expected pointer to btf or socket",
 	.fixup_kfunc_btf_id = {
 		{ "bpf_lookup_system_key", 1 },
 		{ "bpf_key_put", 3 },
-- 
2.38.1

[PATCH bpf-next v5 13/25] bpf: Drop kfunc bits from btf_check_func_arg_match

[Kumar Kartikeya Dwivedi]

Remove all kfunc related bits now from btf_check_func_arg_match, as
users have been converted away to refactored kfunc argument handling.

This is split into a separate commit to aid review, in order to compare
what has been preserved from the removed bits easily instead of mixing
removed hunks with previous patch.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 include/linux/bpf.h          |  11 --
 include/linux/bpf_verifier.h |   2 -
 kernel/bpf/btf.c             | 364 +----------------------------------
 kernel/bpf/verifier.c        |   4 +-
 4 files changed, 10 insertions(+), 371 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 88ac4c12bab0..7ccd90fd19ba 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2108,22 +2108,11 @@ int btf_distill_func_proto(struct bpf_verifier_log *log,
 			   const char *func_name,
 			   struct btf_func_model *m);
 
-struct bpf_kfunc_arg_meta {
-	u64 r0_size;
-	bool r0_rdonly;
-	int ref_obj_id;
-	u32 flags;
-};
-
 struct bpf_reg_state;
 int btf_check_subprog_arg_match(struct bpf_verifier_env *env, int subprog,
 				struct bpf_reg_state *regs);
 int btf_check_subprog_call(struct bpf_verifier_env *env, int subprog,
 			   struct bpf_reg_state *regs);
-int btf_check_kfunc_arg_match(struct bpf_verifier_env *env,
-			      const struct btf *btf, u32 func_id,
-			      struct bpf_reg_state *regs,
-			      struct bpf_kfunc_arg_meta *meta);
 int btf_prepare_func_args(struct bpf_verifier_env *env, int subprog,
 			  struct bpf_reg_state *reg);
 int btf_check_type_match(struct bpf_verifier_log *log, const struct bpf_prog *prog,
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 70cccac62a15..f3a601d33fb3 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -592,8 +592,6 @@ int check_ptr_off_reg(struct bpf_verifier_env *env,
 int check_func_arg_reg_off(struct bpf_verifier_env *env,
 			   const struct bpf_reg_state *reg, int regno,
 			   enum bpf_arg_type arg_type);
-int check_kfunc_mem_size_reg(struct bpf_verifier_env *env, struct bpf_reg_state *reg,
-			     u32 regno);
 int check_mem_reg(struct bpf_verifier_env *env, struct bpf_reg_state *reg,
 		   u32 regno, u32 mem_size);
 bool is_dynptr_reg_valid_init(struct bpf_verifier_env *env,
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 9d374c76b4a4..bfa142d61571 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -6592,122 +6592,19 @@ int btf_check_type_match(struct bpf_verifier_log *log, const struct bpf_prog *pr
 	return btf_check_func_type_match(log, btf1, t1, btf2, t2);
 }
 
-static u32 *reg2btf_ids[__BPF_REG_TYPE_MAX] = {
-#ifdef CONFIG_NET
-	[PTR_TO_SOCKET] = &btf_sock_ids[BTF_SOCK_TYPE_SOCK],
-	[PTR_TO_SOCK_COMMON] = &btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON],
-	[PTR_TO_TCP_SOCK] = &btf_sock_ids[BTF_SOCK_TYPE_TCP],
-#endif
-};
-
-/* Returns true if struct is composed of scalars, 4 levels of nesting allowed */
-static bool __btf_type_is_scalar_struct(struct bpf_verifier_log *log,
-					const struct btf *btf,
-					const struct btf_type *t, int rec)
-{
-	const struct btf_type *member_type;
-	const struct btf_member *member;
-	u32 i;
-
-	if (!btf_type_is_struct(t))
-		return false;
-
-	for_each_member(i, t, member) {
-		const struct btf_array *array;
-
-		member_type = btf_type_skip_modifiers(btf, member->type, NULL);
-		if (btf_type_is_struct(member_type)) {
-			if (rec >= 3) {
-				bpf_log(log, "max struct nesting depth exceeded\n");
-				return false;
-			}
-			if (!__btf_type_is_scalar_struct(log, btf, member_type, rec + 1))
-				return false;
-			continue;
-		}
-		if (btf_type_is_array(member_type)) {
-			array = btf_type_array(member_type);
-			if (!array->nelems)
-				return false;
-			member_type = btf_type_skip_modifiers(btf, array->type, NULL);
-			if (!btf_type_is_scalar(member_type))
-				return false;
-			continue;
-		}
-		if (!btf_type_is_scalar(member_type))
-			return false;
-	}
-	return true;
-}
-
-static bool is_kfunc_arg_mem_size(const struct btf *btf,
-				  const struct btf_param *arg,
-				  const struct bpf_reg_state *reg)
-{
-	int len, sfx_len = sizeof("__sz") - 1;
-	const struct btf_type *t;
-	const char *param_name;
-
-	t = btf_type_skip_modifiers(btf, arg->type, NULL);
-	if (!btf_type_is_scalar(t) || reg->type != SCALAR_VALUE)
-		return false;
-
-	/* In the future, this can be ported to use BTF tagging */
-	param_name = btf_name_by_offset(btf, arg->name_off);
-	if (str_is_empty(param_name))
-		return false;
-	len = strlen(param_name);
-	if (len < sfx_len)
-		return false;
-	param_name += len - sfx_len;
-	if (strncmp(param_name, "__sz", sfx_len))
-		return false;
-
-	return true;
-}
-
-static bool btf_is_kfunc_arg_mem_size(const struct btf *btf,
-				      const struct btf_param *arg,
-				      const struct bpf_reg_state *reg,
-				      const char *name)
-{
-	int len, target_len = strlen(name);
-	const struct btf_type *t;
-	const char *param_name;
-
-	t = btf_type_skip_modifiers(btf, arg->type, NULL);
-	if (!btf_type_is_scalar(t) || reg->type != SCALAR_VALUE)
-		return false;
-
-	param_name = btf_name_by_offset(btf, arg->name_off);
-	if (str_is_empty(param_name))
-		return false;
-	len = strlen(param_name);
-	if (len != target_len)
-		return false;
-	if (strcmp(param_name, name))
-		return false;
-
-	return true;
-}
-
 static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 				    const struct btf *btf, u32 func_id,
 				    struct bpf_reg_state *regs,
 				    bool ptr_to_mem_ok,
-				    struct bpf_kfunc_arg_meta *kfunc_meta,
 				    bool processing_call)
 {
 	enum bpf_prog_type prog_type = resolve_prog_type(env->prog);
-	bool rel = false, kptr_get = false, trusted_args = false;
-	bool sleepable = false;
 	struct bpf_verifier_log *log = &env->log;
-	u32 i, nargs, ref_id, ref_obj_id = 0;
-	bool is_kfunc = btf_is_kernel(btf);
 	const char *func_name, *ref_tname;
 	const struct btf_type *t, *ref_t;
 	const struct btf_param *args;
-	int ref_regno = 0, ret;
+	u32 i, nargs, ref_id;
+	int ret;
 
 	t = btf_type_by_id(btf, func_id);
 	if (!t || !btf_type_is_func(t)) {
@@ -6733,14 +6630,6 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 		return -EINVAL;
 	}
 
-	if (is_kfunc && kfunc_meta) {
-		/* Only kfunc can be release func */
-		rel = kfunc_meta->flags & KF_RELEASE;
-		kptr_get = kfunc_meta->flags & KF_KPTR_GET;
-		trusted_args = kfunc_meta->flags & KF_TRUSTED_ARGS;
-		sleepable = kfunc_meta->flags & KF_SLEEPABLE;
-	}
-
 	/* check that BTF function arguments match actual types that the
 	 * verifier sees.
 	 */
@@ -6748,42 +6637,9 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 		enum bpf_arg_type arg_type = ARG_DONTCARE;
 		u32 regno = i + 1;
 		struct bpf_reg_state *reg = &regs[regno];
-		bool obj_ptr = false;
 
 		t = btf_type_skip_modifiers(btf, args[i].type, NULL);
 		if (btf_type_is_scalar(t)) {
-			if (is_kfunc && kfunc_meta) {
-				bool is_buf_size = false;
-
-				/* check for any const scalar parameter of name "rdonly_buf_size"
-				 * or "rdwr_buf_size"
-				 */
-				if (btf_is_kfunc_arg_mem_size(btf, &args[i], reg,
-							      "rdonly_buf_size")) {
-					kfunc_meta->r0_rdonly = true;
-					is_buf_size = true;
-				} else if (btf_is_kfunc_arg_mem_size(btf, &args[i], reg,
-								     "rdwr_buf_size"))
-					is_buf_size = true;
-
-				if (is_buf_size) {
-					if (kfunc_meta->r0_size) {
-						bpf_log(log, "2 or more rdonly/rdwr_buf_size parameters for kfunc");
-						return -EINVAL;
-					}
-
-					if (!tnum_is_const(reg->var_off)) {
-						bpf_log(log, "R%d is not a const\n", regno);
-						return -EINVAL;
-					}
-
-					kfunc_meta->r0_size = reg->var_off.value;
-					ret = mark_chain_precision(env, regno);
-					if (ret)
-						return ret;
-				}
-			}
-
 			if (reg->type == SCALAR_VALUE)
 				continue;
 			bpf_log(log, "R%d is not a scalar\n", regno);
@@ -6796,88 +6652,14 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 			return -EINVAL;
 		}
 
-		/* These register types have special constraints wrt ref_obj_id
-		 * and offset checks. The rest of trusted args don't.
-		 */
-		obj_ptr = reg->type == PTR_TO_CTX || reg->type == PTR_TO_BTF_ID ||
-			  reg2btf_ids[base_type(reg->type)];
-
-		/* Check if argument must be a referenced pointer, args + i has
-		 * been verified to be a pointer (after skipping modifiers).
-		 * PTR_TO_CTX is ok without having non-zero ref_obj_id.
-		 */
-		if (is_kfunc && trusted_args && (obj_ptr && reg->type != PTR_TO_CTX) && !reg->ref_obj_id) {
-			bpf_log(log, "R%d must be referenced\n", regno);
-			return -EINVAL;
-		}
-
 		ref_t = btf_type_skip_modifiers(btf, t->type, &ref_id);
 		ref_tname = btf_name_by_offset(btf, ref_t->name_off);
 
-		/* Trusted args have the same offset checks as release arguments */
-		if ((trusted_args && obj_ptr) || (rel && reg->ref_obj_id))
-			arg_type |= OBJ_RELEASE;
 		ret = check_func_arg_reg_off(env, reg, regno, arg_type);
 		if (ret < 0)
 			return ret;
 
-		if (is_kfunc && reg->ref_obj_id) {
-			/* Ensure only one argument is referenced PTR_TO_BTF_ID */
-			if (ref_obj_id) {
-				bpf_log(log, "verifier internal error: more than one arg with ref_obj_id R%d %u %u\n",
-					regno, reg->ref_obj_id, ref_obj_id);
-				return -EFAULT;
-			}
-			ref_regno = regno;
-			ref_obj_id = reg->ref_obj_id;
-		}
-
-		/* kptr_get is only true for kfunc */
-		if (i == 0 && kptr_get) {
-			struct btf_field *kptr_field;
-
-			if (reg->type != PTR_TO_MAP_VALUE) {
-				bpf_log(log, "arg#0 expected pointer to map value\n");
-				return -EINVAL;
-			}
-
-			/* check_func_arg_reg_off allows var_off for
-			 * PTR_TO_MAP_VALUE, but we need fixed offset to find
-			 * off_desc.
-			 */
-			if (!tnum_is_const(reg->var_off)) {
-				bpf_log(log, "arg#0 must have constant offset\n");
-				return -EINVAL;
-			}
-
-			kptr_field = btf_record_find(reg->map_ptr->record, reg->off + reg->var_off.value, BPF_KPTR);
-			if (!kptr_field || kptr_field->type != BPF_KPTR_REF) {
-				bpf_log(log, "arg#0 no referenced kptr at map value offset=%llu\n",
-					reg->off + reg->var_off.value);
-				return -EINVAL;
-			}
-
-			if (!btf_type_is_ptr(ref_t)) {
-				bpf_log(log, "arg#0 BTF type must be a double pointer\n");
-				return -EINVAL;
-			}
-
-			ref_t = btf_type_skip_modifiers(btf, ref_t->type, &ref_id);
-			ref_tname = btf_name_by_offset(btf, ref_t->name_off);
-
-			if (!btf_type_is_struct(ref_t)) {
-				bpf_log(log, "kernel function %s args#%d pointer type %s %s is not supported\n",
-					func_name, i, btf_type_str(ref_t), ref_tname);
-				return -EINVAL;
-			}
-			if (!btf_struct_ids_match(log, btf, ref_id, 0, kptr_field->kptr.btf,
-						  kptr_field->kptr.btf_id, true)) {
-				bpf_log(log, "kernel function %s args#%d expected pointer to %s %s\n",
-					func_name, i, btf_type_str(ref_t), ref_tname);
-				return -EINVAL;
-			}
-			/* rest of the arguments can be anything, like normal kfunc */
-		} else if (btf_get_prog_ctx_type(log, btf, t, prog_type, i)) {
+		if (btf_get_prog_ctx_type(log, btf, t, prog_type, i)) {
 			/* If function expects ctx type in BTF check that caller
 			 * is passing PTR_TO_CTX.
 			 */
@@ -6887,109 +6669,10 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 					i, btf_type_str(t));
 				return -EINVAL;
 			}
-		} else if (is_kfunc && (reg->type == PTR_TO_BTF_ID ||
-			   (reg2btf_ids[base_type(reg->type)] && !type_flag(reg->type)))) {
-			const struct btf_type *reg_ref_t;
-			const struct btf *reg_btf;
-			const char *reg_ref_tname;
-			u32 reg_ref_id;
-
-			if (!btf_type_is_struct(ref_t)) {
-				bpf_log(log, "kernel function %s args#%d pointer type %s %s is not supported\n",
-					func_name, i, btf_type_str(ref_t),
-					ref_tname);
-				return -EINVAL;
-			}
-
-			if (reg->type == PTR_TO_BTF_ID) {
-				reg_btf = reg->btf;
-				reg_ref_id = reg->btf_id;
-			} else {
-				reg_btf = btf_vmlinux;
-				reg_ref_id = *reg2btf_ids[base_type(reg->type)];
-			}
-
-			reg_ref_t = btf_type_skip_modifiers(reg_btf, reg_ref_id,
-							    &reg_ref_id);
-			reg_ref_tname = btf_name_by_offset(reg_btf,
-							   reg_ref_t->name_off);
-			if (!btf_struct_ids_match(log, reg_btf, reg_ref_id,
-						  reg->off, btf, ref_id,
-						  trusted_args || (rel && reg->ref_obj_id))) {
-				bpf_log(log, "kernel function %s args#%d expected pointer to %s %s but R%d has a pointer to %s %s\n",
-					func_name, i,
-					btf_type_str(ref_t), ref_tname,
-					regno, btf_type_str(reg_ref_t),
-					reg_ref_tname);
-				return -EINVAL;
-			}
 		} else if (ptr_to_mem_ok && processing_call) {
 			const struct btf_type *resolve_ret;
 			u32 type_size;
 
-			if (is_kfunc) {
-				bool arg_mem_size = i + 1 < nargs && is_kfunc_arg_mem_size(btf, &args[i + 1], &regs[regno + 1]);
-				bool arg_dynptr = btf_type_is_struct(ref_t) &&
-						  !strcmp(ref_tname,
-							  stringify_struct(bpf_dynptr_kern));
-
-				/* Permit pointer to mem, but only when argument
-				 * type is pointer to scalar, or struct composed
-				 * (recursively) of scalars.
-				 * When arg_mem_size is true, the pointer can be
-				 * void *.
-				 * Also permit initialized local dynamic pointers.
-				 */
-				if (!btf_type_is_scalar(ref_t) &&
-				    !__btf_type_is_scalar_struct(log, btf, ref_t, 0) &&
-				    !arg_dynptr &&
-				    (arg_mem_size ? !btf_type_is_void(ref_t) : 1)) {
-					bpf_log(log,
-						"arg#%d pointer type %s %s must point to %sscalar, or struct with scalar\n",
-						i, btf_type_str(ref_t), ref_tname, arg_mem_size ? "void, " : "");
-					return -EINVAL;
-				}
-
-				if (arg_dynptr) {
-					if (reg->type != PTR_TO_STACK) {
-						bpf_log(log, "arg#%d pointer type %s %s not to stack\n",
-							i, btf_type_str(ref_t),
-							ref_tname);
-						return -EINVAL;
-					}
-
-					if (!is_dynptr_reg_valid_init(env, reg)) {
-						bpf_log(log,
-							"arg#%d pointer type %s %s must be valid and initialized\n",
-							i, btf_type_str(ref_t),
-							ref_tname);
-						return -EINVAL;
-					}
-
-					if (!is_dynptr_type_expected(env, reg,
-							ARG_PTR_TO_DYNPTR | DYNPTR_TYPE_LOCAL)) {
-						bpf_log(log,
-							"arg#%d pointer type %s %s points to unsupported dynamic pointer type\n",
-							i, btf_type_str(ref_t),
-							ref_tname);
-						return -EINVAL;
-					}
-
-					continue;
-				}
-
-				/* Check for mem, len pair */
-				if (arg_mem_size) {
-					if (check_kfunc_mem_size_reg(env, &regs[regno + 1], regno + 1)) {
-						bpf_log(log, "arg#%d arg#%d memory, len pair leads to invalid memory access\n",
-							i, i + 1);
-						return -EINVAL;
-					}
-					i++;
-					continue;
-				}
-			}
-
 			resolve_ret = btf_resolve_size(btf, ref_t, &type_size);
 			if (IS_ERR(resolve_ret)) {
 				bpf_log(log,
@@ -7002,36 +6685,13 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 			if (check_mem_reg(env, reg, regno, type_size))
 				return -EINVAL;
 		} else {
-			bpf_log(log, "reg type unsupported for arg#%d %sfunction %s#%d\n", i,
-				is_kfunc ? "kernel " : "", func_name, func_id);
+			bpf_log(log, "reg type unsupported for arg#%d function %s#%d\n", i,
+				func_name, func_id);
 			return -EINVAL;
 		}
 	}
 
-	/* Either both are set, or neither */
-	WARN_ON_ONCE((ref_obj_id && !ref_regno) || (!ref_obj_id && ref_regno));
-	/* We already made sure ref_obj_id is set only for one argument. We do
-	 * allow (!rel && ref_obj_id), so that passing such referenced
-	 * PTR_TO_BTF_ID to other kfuncs works. Note that rel is only true when
-	 * is_kfunc is true.
-	 */
-	if (rel && !ref_obj_id) {
-		bpf_log(log, "release kernel function %s expects refcounted PTR_TO_BTF_ID\n",
-			func_name);
-		return -EINVAL;
-	}
-
-	if (sleepable && !env->prog->aux->sleepable) {
-		bpf_log(log, "kernel function %s is sleepable but the program is not\n",
-			func_name);
-		return -EINVAL;
-	}
-
-	if (kfunc_meta && ref_obj_id)
-		kfunc_meta->ref_obj_id = ref_obj_id;
-
-	/* returns argument register number > 0 in case of reference release kfunc */
-	return rel ? ref_regno : 0;
+	return 0;
 }
 
 /* Compare BTF of a function declaration with given bpf_reg_state.
@@ -7061,7 +6721,7 @@ int btf_check_subprog_arg_match(struct bpf_verifier_env *env, int subprog,
 		return -EINVAL;
 
 	is_global = prog->aux->func_info_aux[subprog].linkage == BTF_FUNC_GLOBAL;
-	err = btf_check_func_arg_match(env, btf, btf_id, regs, is_global, NULL, false);
+	err = btf_check_func_arg_match(env, btf, btf_id, regs, is_global, false);
 
 	/* Compiler optimizations can remove arguments from static functions
 	 * or mismatched type can be passed into a global function.
@@ -7104,7 +6764,7 @@ int btf_check_subprog_call(struct bpf_verifier_env *env, int subprog,
 		return -EINVAL;
 
 	is_global = prog->aux->func_info_aux[subprog].linkage == BTF_FUNC_GLOBAL;
-	err = btf_check_func_arg_match(env, btf, btf_id, regs, is_global, NULL, true);
+	err = btf_check_func_arg_match(env, btf, btf_id, regs, is_global, true);
 
 	/* Compiler optimizations can remove arguments from static functions
 	 * or mismatched type can be passed into a global function.
@@ -7115,14 +6775,6 @@ int btf_check_subprog_call(struct bpf_verifier_env *env, int subprog,
 	return err;
 }
 
-int btf_check_kfunc_arg_match(struct bpf_verifier_env *env,
-			      const struct btf *btf, u32 func_id,
-			      struct bpf_reg_state *regs,
-			      struct bpf_kfunc_arg_meta *meta)
-{
-	return btf_check_func_arg_match(env, btf, func_id, regs, true, meta, true);
-}
-
 /* Convert BTF of a function into bpf_reg_state if possible
  * Returns:
  * EFAULT - there is a verifier bug. Abort verification.
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 7e50772f9f08..c315e8448156 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5539,8 +5539,8 @@ int check_mem_reg(struct bpf_verifier_env *env, struct bpf_reg_state *reg,
 	return err;
 }
 
-int check_kfunc_mem_size_reg(struct bpf_verifier_env *env, struct bpf_reg_state *reg,
-			     u32 regno)
+static int check_kfunc_mem_size_reg(struct bpf_verifier_env *env, struct bpf_reg_state *reg,
+				    u32 regno)
 {
 	struct bpf_reg_state *mem_reg = &cur_regs(env)[regno - 1];
 	bool may_be_null = type_may_be_null(mem_reg->type);
-- 
2.38.1

[PATCH bpf-next v5 14/25] bpf: Support constant scalar arguments for kfuncs

[Kumar Kartikeya Dwivedi]

Allow passing known constant scalars as arguments to kfuncs that do not
represent a size parameter. This makes the search pruning optimization
of verifier more conservative for such kfunc calls, and each
non-distinct argument is considered unequivalent.

We will use this support to then expose a global bpf_kptr_alloc function
where it takes the local type ID in program BTF, and returns a
PTR_TO_BTF_ID to the local type. These will be called local kptrs, and
allows programs to allocate their own objects.

However, this is still not completely safe, as mark_chain_precision
logic is buggy without more work when the constant argument is not a
size, but still needs precise marker propagation for pruning checks.
Next patch will fix this problem.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 Documentation/bpf/kfuncs.rst | 30 ++++++++++++++++++
 kernel/bpf/verifier.c        | 59 +++++++++++++++++++++++++++---------
 2 files changed, 75 insertions(+), 14 deletions(-)

diff --git a/Documentation/bpf/kfuncs.rst b/Documentation/bpf/kfuncs.rst
index 0f858156371d..7608b066a8ba 100644
--- a/Documentation/bpf/kfuncs.rst
+++ b/Documentation/bpf/kfuncs.rst
@@ -72,6 +72,36 @@ argument as its size. By default, without __sz annotation, the size of the type
 of the pointer is used. Without __sz annotation, a kfunc cannot accept a void
 pointer.
 
+2.2.1 __k Annotation
+--------------------
+
+This annotation is only understood for scalar arguments, where it indicates that
+the verifier must check the scalar argument to be a known constant, which does
+not indicate a size parameter. This distinction is important, as when the scalar
+argument does not represent a size parameter, verifier is more conservative in
+state search pruning and does not consider two arguments equivalent for safety
+purposes if the already verified value was within range of the new one.
+
+This assumption holds well for sizes (as memory accessed within smaller bounds
+in old verified state will also work for bigger bounds in current to be explored
+state), but not for other constant arguments where each carries a distinct
+semantic effect.
+
+An example is given below::
+
+        void *bpf_obj_new(u32 local_type_id__k, ...)
+        {
+        ...
+        }
+
+Here, bpf_obj_new uses local_type_id argument to find out the size of that
+type ID in program's BTF and return a sized pointer to it. Each type ID will
+have a distinct size, hence it is crucial to treat each such call as distinct
+when values don't match.
+
+Hence, whenever a constant scalar argument is accepted by a kfunc which is not a
+size parameter, __k suffix must be used.
+
 .. _BPF_kfunc_nodef:
 
 2.3 Using an existing kernel function
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index c315e8448156..7515b31d2c40 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -7862,6 +7862,10 @@ struct bpf_kfunc_call_arg_meta {
 	u8 release_regno;
 	bool r0_rdonly;
 	u64 r0_size;
+	struct {
+		u64 value;
+		bool found;
+	} arg_constant;
 };
 
 static bool is_kfunc_acquire(struct bpf_kfunc_call_arg_meta *meta)
@@ -7899,30 +7903,40 @@ static bool is_kfunc_arg_kptr_get(struct bpf_kfunc_call_arg_meta *meta, int arg)
 	return arg == 0 && (meta->kfunc_flags & KF_KPTR_GET);
 }
 
-static bool is_kfunc_arg_mem_size(const struct btf *btf,
-				  const struct btf_param *arg,
-				  const struct bpf_reg_state *reg)
+static bool __kfunc_param_match_suffix(const struct btf *btf,
+				       const struct btf_param *arg,
+				       const char *suffix)
 {
-	int len, sfx_len = sizeof("__sz") - 1;
-	const struct btf_type *t;
+	int suffix_len = strlen(suffix), len;
 	const char *param_name;
 
-	t = btf_type_skip_modifiers(btf, arg->type, NULL);
-	if (!btf_type_is_scalar(t) || reg->type != SCALAR_VALUE)
-		return false;
-
 	/* In the future, this can be ported to use BTF tagging */
 	param_name = btf_name_by_offset(btf, arg->name_off);
 	if (str_is_empty(param_name))
 		return false;
 	len = strlen(param_name);
-	if (len < sfx_len)
+	if (len < suffix_len)
 		return false;
-	param_name += len - sfx_len;
-	if (strncmp(param_name, "__sz", sfx_len))
+	param_name += len - suffix_len;
+	return !strncmp(param_name, suffix, suffix_len);
+}
+
+static bool is_kfunc_arg_mem_size(const struct btf *btf,
+				  const struct btf_param *arg,
+				  const struct bpf_reg_state *reg)
+{
+	const struct btf_type *t;
+
+	t = btf_type_skip_modifiers(btf, arg->type, NULL);
+	if (!btf_type_is_scalar(t) || reg->type != SCALAR_VALUE)
 		return false;
 
-	return true;
+	return __kfunc_param_match_suffix(btf, arg, "__sz");
+}
+
+static bool is_kfunc_arg_sfx_constant(const struct btf *btf, const struct btf_param *arg)
+{
+	return __kfunc_param_match_suffix(btf, arg, "__k");
 }
 
 static bool is_kfunc_arg_ret_buf_size(const struct btf *btf,
@@ -8198,7 +8212,24 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
 				verbose(env, "R%d is not a scalar\n", regno);
 				return -EINVAL;
 			}
-			if (is_kfunc_arg_ret_buf_size(btf, &args[i], reg, "rdonly_buf_size")) {
+			if (is_kfunc_arg_sfx_constant(meta->btf, &args[i])) {
+				/* kfunc is already bpf_capable() only, no need
+				 * to check it here.
+				 */
+				if (meta->arg_constant.found) {
+					verbose(env, "verifier internal error: only one constant argument permitted\n");
+					return -EFAULT;
+				}
+				if (!tnum_is_const(reg->var_off)) {
+					verbose(env, "R%d must be a known constant\n", regno);
+					return -EINVAL;
+				}
+				ret = mark_chain_precision(env, regno);
+				if (ret < 0)
+					return ret;
+				meta->arg_constant.found = true;
+				meta->arg_constant.value = reg->var_off.value;
+			} else if (is_kfunc_arg_ret_buf_size(btf, &args[i], reg, "rdonly_buf_size")) {
 					meta->r0_rdonly = true;
 					is_ret_buf_sz = true;
 			} else if (is_kfunc_arg_ret_buf_size(btf, &args[i], reg, "rdwr_buf_size")) {
-- 
2.38.1

[PATCH bpf-next v5 15/25] bpf: Teach verifier about non-size constant arguments

[Kumar Kartikeya Dwivedi]

Currently, the verifier has support for various arguments that either
describe the size of the memory being passed in to a helper, or describe
the size of the memory being returned. When a constant is passed in like
this, it is assumed for the purposes of precision tracking that if the
value in the already explored safe state is within the value in current
state, it would fine to prune the search.

While this holds well for size arguments, arguments where each value may
denote a distinct meaning and needs to be verified separately needs more
work. Search can only be pruned if both are equivalent values. In all
other cases, it would be incorrect to treat those two precise registers
as equivalent if the new value satisfies the old one (i.e. old <= cur).

Hence, make the register precision marker tri-state. There are now three
values that reg->precise takes: NOT_PRECISE, PRECISE, EXACT.

Both PRECISE and EXACT are 'true' values. EXACT affects how regsafe
decides whether both registers are equivalent for the purposes of
verifier state equivalence. When it sees that old state register has
reg->precise == EXACT, unless both are equivalent, it will return false.
Otherwise, for PRECISE case it falls back to the default check that is
present now (i.e. thinking that we're talking about sizes).

This is required as a future patch introduces a BPF memory allocator
interface, where we take the program BTF's type ID as an argument. Each
distinct type ID may result in the returned pointer obtaining a
different size, hence precision tracking is needed, and pruning cannot
just happen when the old value is within the current value. It must only
happen when the type ID is equal. The type ID will always correspond to
prog->aux->btf hence actual type match is not required.

Finally, change mark_chain_precision precision argument to EXACT for
kfuncs constant non-size scalar arguments (tagged with __k suffix).

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 include/linux/bpf_verifier.h |  10 +++-
 kernel/bpf/verifier.c        | 111 ++++++++++++++++++++++-------------
 2 files changed, 76 insertions(+), 45 deletions(-)

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index f3a601d33fb3..1e246ec2ff37 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -43,6 +43,12 @@ enum bpf_reg_liveness {
 	REG_LIVE_DONE = 0x8, /* liveness won't be updating this register anymore */
 };
 
+enum bpf_reg_precise {
+	NOT_PRECISE,
+	PRECISE,
+	EXACT,
+};
+
 struct bpf_reg_state {
 	/* Ordering of fields matters.  See states_equal() */
 	enum bpf_reg_type type;
@@ -180,7 +186,7 @@ struct bpf_reg_state {
 	s32 subreg_def;
 	enum bpf_reg_liveness live;
 	/* if (!precise && SCALAR_VALUE) min/max/tnum don't affect safety */
-	bool precise;
+	enum bpf_reg_precise precise;
 };
 
 enum bpf_stack_slot_type {
@@ -626,8 +632,6 @@ int bpf_check_attach_target(struct bpf_verifier_log *log,
 			    struct bpf_attach_target_info *tgt_info);
 void bpf_free_kfunc_btf_tab(struct bpf_kfunc_btf_tab *tab);
 
-int mark_chain_precision(struct bpf_verifier_env *env, int regno);
-
 #define BPF_BASE_TYPE_MASK	GENMASK(BPF_BASE_TYPE_BITS - 1, 0)
 
 /* extract base type from bpf_{arg, return, reg}_type. */
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 7515b31d2c40..5bfc151711b9 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -864,7 +864,7 @@ static void print_verifier_state(struct bpf_verifier_env *env,
 		print_liveness(env, reg->live);
 		verbose(env, "=");
 		if (t == SCALAR_VALUE && reg->precise)
-			verbose(env, "P");
+			verbose(env, reg->precise == EXACT ? "E" : "P");
 		if ((t == SCALAR_VALUE || t == PTR_TO_STACK) &&
 		    tnum_is_const(reg->var_off)) {
 			/* reg->off should be 0 for SCALAR_VALUE */
@@ -961,7 +961,7 @@ static void print_verifier_state(struct bpf_verifier_env *env,
 			t = reg->type;
 			verbose(env, "=%s", t == SCALAR_VALUE ? "" : reg_type_str(env, t));
 			if (t == SCALAR_VALUE && reg->precise)
-				verbose(env, "P");
+				verbose(env, reg->precise == EXACT ? "E" : "P");
 			if (t == SCALAR_VALUE && tnum_is_const(reg->var_off))
 				verbose(env, "%lld", reg->var_off.value + reg->off);
 		} else {
@@ -1695,7 +1695,16 @@ static void __mark_reg_unknown(const struct bpf_verifier_env *env,
 	reg->type = SCALAR_VALUE;
 	reg->var_off = tnum_unknown;
 	reg->frameno = 0;
-	reg->precise = !env->bpf_capable;
+	/* Helpers requiring EXACT for constant arguments cannot be called from
+	 * programs without CAP_BPF. This is because we don't propagate
+	 * precision markers when CAP_BPF is missing. If we allowed calling such
+	 * heleprs in those programs, the default would have to be EXACT for
+	 * them, which would be too aggresive, or we'd have to propagate it.
+	 *
+	 * Currently, only bpf_obj_new kfunc requires EXACT precision for its
+	 * scalar argument, which is a kfunc (and thus behind CAP_BPF).
+	 */
+	reg->precise = !env->bpf_capable ? PRECISE : NOT_PRECISE;
 	__mark_reg_unbounded(reg);
 }
 
@@ -2750,7 +2759,8 @@ static int backtrack_insn(struct bpf_verifier_env *env, int idx,
  * For now backtracking falls back into conservative marking.
  */
 static void mark_all_scalars_precise(struct bpf_verifier_env *env,
-				     struct bpf_verifier_state *st)
+				     struct bpf_verifier_state *st,
+				     enum bpf_reg_precise precise)
 {
 	struct bpf_func_state *func;
 	struct bpf_reg_state *reg;
@@ -2769,7 +2779,7 @@ static void mark_all_scalars_precise(struct bpf_verifier_env *env,
 				reg = &func->regs[j];
 				if (reg->type != SCALAR_VALUE)
 					continue;
-				reg->precise = true;
+				reg->precise = precise;
 			}
 			for (j = 0; j < func->allocated_stack / BPF_REG_SIZE; j++) {
 				if (!is_spilled_reg(&func->stack[j]))
@@ -2777,7 +2787,7 @@ static void mark_all_scalars_precise(struct bpf_verifier_env *env,
 				reg = &func->stack[j].spilled_ptr;
 				if (reg->type != SCALAR_VALUE)
 					continue;
-				reg->precise = true;
+				reg->precise = precise;
 			}
 		}
 	}
@@ -2795,7 +2805,7 @@ static void mark_all_scalars_imprecise(struct bpf_verifier_env *env, struct bpf_
 			reg = &func->regs[j];
 			if (reg->type != SCALAR_VALUE)
 				continue;
-			reg->precise = false;
+			reg->precise = NOT_PRECISE;
 		}
 		for (j = 0; j < func->allocated_stack / BPF_REG_SIZE; j++) {
 			if (!is_spilled_reg(&func->stack[j]))
@@ -2803,7 +2813,7 @@ static void mark_all_scalars_imprecise(struct bpf_verifier_env *env, struct bpf_
 			reg = &func->stack[j].spilled_ptr;
 			if (reg->type != SCALAR_VALUE)
 				continue;
-			reg->precise = false;
+			reg->precise = NOT_PRECISE;
 		}
 	}
 }
@@ -2896,7 +2906,7 @@ static void mark_all_scalars_imprecise(struct bpf_verifier_env *env, struct bpf_
  * finalized states which help in short circuiting more future states.
  */
 static int __mark_chain_precision(struct bpf_verifier_env *env, int frame, int regno,
-				  int spi)
+				  int spi, enum bpf_reg_precise precise)
 {
 	struct bpf_verifier_state *st = env->cur_state;
 	int first_idx = st->first_insn_idx;
@@ -2909,8 +2919,11 @@ static int __mark_chain_precision(struct bpf_verifier_env *env, int frame, int r
 	bool new_marks = false;
 	int i, err;
 
-	if (!env->bpf_capable)
+	if (!env->bpf_capable) {
+		/* EXACT precision should only be used with CAP_BPF */
+		WARN_ON_ONCE(precise == EXACT);
 		return 0;
+	}
 
 	/* Do sanity checks against current state of register and/or stack
 	 * slot, but don't set precise flag in current state, as precision
@@ -2969,7 +2982,7 @@ static int __mark_chain_precision(struct bpf_verifier_env *env, int frame, int r
 						reg_mask &= ~(1u << i);
 						continue;
 					}
-					reg->precise = true;
+					reg->precise = precise;
 				}
 				return 0;
 			}
@@ -2988,7 +3001,7 @@ static int __mark_chain_precision(struct bpf_verifier_env *env, int frame, int r
 				err = backtrack_insn(env, i, &reg_mask, &stack_mask);
 			}
 			if (err == -ENOTSUPP) {
-				mark_all_scalars_precise(env, st);
+				mark_all_scalars_precise(env, st, precise);
 				return 0;
 			} else if (err) {
 				return err;
@@ -3029,7 +3042,7 @@ static int __mark_chain_precision(struct bpf_verifier_env *env, int frame, int r
 			}
 			if (!reg->precise)
 				new_marks = true;
-			reg->precise = true;
+			reg->precise = precise;
 		}
 
 		bitmap_from_u64(mask, stack_mask);
@@ -3048,7 +3061,7 @@ static int __mark_chain_precision(struct bpf_verifier_env *env, int frame, int r
 				 * fp-8 and it's "unallocated" stack space.
 				 * In such case fallback to conservative.
 				 */
-				mark_all_scalars_precise(env, st);
+				mark_all_scalars_precise(env, st, precise);
 				return 0;
 			}
 
@@ -3063,7 +3076,7 @@ static int __mark_chain_precision(struct bpf_verifier_env *env, int frame, int r
 			}
 			if (!reg->precise)
 				new_marks = true;
-			reg->precise = true;
+			reg->precise = precise;
 		}
 		if (env->log.level & BPF_LOG_LEVEL2) {
 			verbose(env, "parent %s regs=%x stack=%llx marks:",
@@ -3083,19 +3096,22 @@ static int __mark_chain_precision(struct bpf_verifier_env *env, int frame, int r
 	return 0;
 }
 
-int mark_chain_precision(struct bpf_verifier_env *env, int regno)
+static int mark_chain_precision(struct bpf_verifier_env *env, int regno,
+				enum bpf_reg_precise precise)
 {
-	return __mark_chain_precision(env, env->cur_state->curframe, regno, -1);
+	return __mark_chain_precision(env, env->cur_state->curframe, regno, -1, precise);
 }
 
-static int mark_chain_precision_frame(struct bpf_verifier_env *env, int frame, int regno)
+static int mark_chain_precision_frame(struct bpf_verifier_env *env, int frame, int regno,
+				     enum bpf_reg_precise precise)
 {
-	return __mark_chain_precision(env, frame, regno, -1);
+	return __mark_chain_precision(env, frame, regno, -1, precise);
 }
 
-static int mark_chain_precision_stack_frame(struct bpf_verifier_env *env, int frame, int spi)
+static int mark_chain_precision_stack_frame(struct bpf_verifier_env *env, int frame, int spi,
+					    enum bpf_reg_precise precise)
 {
-	return __mark_chain_precision(env, frame, -1, spi);
+	return __mark_chain_precision(env, frame, -1, spi, precise);
 }
 
 static bool is_spillable_regtype(enum bpf_reg_type type)
@@ -3230,7 +3246,7 @@ static int check_stack_write_fixed_off(struct bpf_verifier_env *env,
 			 * Backtrack from here and mark all registers as precise
 			 * that contributed into 'reg' being a constant.
 			 */
-			err = mark_chain_precision(env, value_regno);
+			err = mark_chain_precision(env, value_regno, PRECISE);
 			if (err)
 				return err;
 		}
@@ -3271,7 +3287,7 @@ static int check_stack_write_fixed_off(struct bpf_verifier_env *env,
 		/* when we zero initialize stack slots mark them as such */
 		if (reg && register_is_null(reg)) {
 			/* backtracking doesn't work for STACK_ZERO yet. */
-			err = mark_chain_precision(env, value_regno);
+			err = mark_chain_precision(env, value_regno, PRECISE);
 			if (err)
 				return err;
 			type = STACK_ZERO;
@@ -3387,7 +3403,7 @@ static int check_stack_write_var_off(struct bpf_verifier_env *env,
 	}
 	if (zero_used) {
 		/* backtracking doesn't work for STACK_ZERO yet. */
-		err = mark_chain_precision(env, value_regno);
+		err = mark_chain_precision(env, value_regno, PRECISE);
 		if (err)
 			return err;
 	}
@@ -3436,7 +3452,7 @@ static void mark_reg_stack_read(struct bpf_verifier_env *env,
 		 * backtracking. Any register that contributed
 		 * to const 0 was marked precise before spill.
 		 */
-		state->regs[dst_regno].precise = true;
+		state->regs[dst_regno].precise = PRECISE;
 	} else {
 		/* have read misc data from the stack */
 		mark_reg_unknown(env, state->regs, dst_regno);
@@ -5503,7 +5519,7 @@ static int check_mem_size_reg(struct bpf_verifier_env *env,
 				      reg->umax_value,
 				      zero_size_allowed, meta);
 	if (!err)
-		err = mark_chain_precision(env, regno);
+		err = mark_chain_precision(env, regno, PRECISE);
 	return err;
 }
 
@@ -6311,7 +6327,7 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 			return -EACCES;
 		}
 		meta->mem_size = reg->var_off.value;
-		err = mark_chain_precision(env, regno);
+		err = mark_chain_precision(env, regno, PRECISE);
 		if (err)
 			return err;
 		break;
@@ -7303,7 +7319,7 @@ record_func_key(struct bpf_verifier_env *env, struct bpf_call_arg_meta *meta,
 		return 0;
 	}
 
-	err = mark_chain_precision(env, BPF_REG_3);
+	err = mark_chain_precision(env, BPF_REG_3, PRECISE);
 	if (err)
 		return err;
 	if (bpf_map_key_unseen(aux))
@@ -7403,7 +7419,7 @@ static bool loop_flag_is_zero(struct bpf_verifier_env *env)
 	bool reg_is_null = register_is_null(reg);
 
 	if (reg_is_null)
-		mark_chain_precision(env, BPF_REG_4);
+		mark_chain_precision(env, BPF_REG_4, PRECISE);
 
 	return reg_is_null;
 }
@@ -8224,7 +8240,7 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
 					verbose(env, "R%d must be a known constant\n", regno);
 					return -EINVAL;
 				}
-				ret = mark_chain_precision(env, regno);
+				ret = mark_chain_precision(env, regno, EXACT);
 				if (ret < 0)
 					return ret;
 				meta->arg_constant.found = true;
@@ -8248,7 +8264,7 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
 				}
 
 				meta->r0_size = reg->var_off.value;
-				ret = mark_chain_precision(env, regno);
+				ret = mark_chain_precision(env, regno, PRECISE);
 				if (ret)
 					return ret;
 			}
@@ -9929,7 +9945,7 @@ static int adjust_reg_min_max_vals(struct bpf_verifier_env *env,
 				 * This is legal, but we have to reverse our
 				 * src/dest handling in computing the range
 				 */
-				err = mark_chain_precision(env, insn->dst_reg);
+				err = mark_chain_precision(env, insn->dst_reg, PRECISE);
 				if (err)
 					return err;
 				return adjust_ptr_min_max_vals(env, insn,
@@ -9937,14 +9953,16 @@ static int adjust_reg_min_max_vals(struct bpf_verifier_env *env,
 			}
 		} else if (ptr_reg) {
 			/* pointer += scalar */
-			err = mark_chain_precision(env, insn->src_reg);
+			err = mark_chain_precision(env, insn->src_reg, PRECISE);
 			if (err)
 				return err;
 			return adjust_ptr_min_max_vals(env, insn,
 						       dst_reg, src_reg);
 		} else if (dst_reg->precise) {
-			/* if dst_reg is precise, src_reg should be precise as well */
-			err = mark_chain_precision(env, insn->src_reg);
+			/* If dst_reg is precise, src_reg should be precise as well.
+			 * Propagate EXACT if it is exact, PRECISE if precise.
+			 */
+			err = mark_chain_precision(env, insn->src_reg, dst_reg->precise);
 			if (err)
 				return err;
 		}
@@ -10938,10 +10956,10 @@ static int check_cond_jmp_op(struct bpf_verifier_env *env,
 		 * above is_branch_taken() special cased the 0 comparison.
 		 */
 		if (!__is_pointer_value(false, dst_reg))
-			err = mark_chain_precision(env, insn->dst_reg);
+			err = mark_chain_precision(env, insn->dst_reg, PRECISE);
 		if (BPF_SRC(insn->code) == BPF_X && !err &&
 		    !__is_pointer_value(false, src_reg))
-			err = mark_chain_precision(env, insn->src_reg);
+			err = mark_chain_precision(env, insn->src_reg, PRECISE);
 		if (err)
 			return err;
 	}
@@ -12262,9 +12280,18 @@ static bool regsafe(struct bpf_verifier_env *env, struct bpf_reg_state *rold,
 		if (rcur->type == SCALAR_VALUE) {
 			if (!rold->precise)
 				return true;
-			/* new val must satisfy old val knowledge */
-			return range_within(rold, rcur) &&
-			       tnum_in(rold->var_off, rcur->var_off);
+			/* For EXACT, we need values to match exactly, so simply
+			 * return false as the memcmp above failed already,
+			 * otherwise current being within the old value
+			 * suffices.
+			 */
+			if (rold->precise == EXACT) {
+				return false;
+			} else /* PRECISE */ {
+				/* new val must satisfy old val knowledge */
+				return range_within(rold, rcur) &&
+				       tnum_in(rold->var_off, rcur->var_off);
+			}
 		} else {
 			/* We're trying to use a pointer in place of a scalar.
 			 * Even if the scalar was unbounded, this could lead to
@@ -12595,7 +12622,7 @@ static int propagate_precision(struct bpf_verifier_env *env,
 				continue;
 			if (env->log.level & BPF_LOG_LEVEL2)
 				verbose(env, "frame %d: propagating r%d\n", i, fr);
-			err = mark_chain_precision_frame(env, fr, i);
+			err = mark_chain_precision_frame(env, fr, i, state_reg->precise);
 			if (err < 0)
 				return err;
 		}
@@ -12610,7 +12637,7 @@ static int propagate_precision(struct bpf_verifier_env *env,
 			if (env->log.level & BPF_LOG_LEVEL2)
 				verbose(env, "frame %d: propagating fp%d\n",
 					(-i - 1) * BPF_REG_SIZE, fr);
-			err = mark_chain_precision_stack_frame(env, fr, i);
+			err = mark_chain_precision_stack_frame(env, fr, i, state_reg->precise);
 			if (err < 0)
 				return err;
 		}
-- 
2.38.1

[PATCH bpf-next v5 16/25] bpf: Introduce bpf_obj_new

[Kumar Kartikeya Dwivedi]

Introduce type safe memory allocator bpf_obj_new for BPF programs. The
kernel side kfunc is named bpf_obj_new_impl, as passing hidden arguments
to kfuncs still requires having them in prototype, unlike BPF helpers
which always take 5 arguments and have them checked using bpf_func_proto
in verifier, ignoring unset argument types.

Introduce __ign suffix to ignore a specific kfunc argument during type
checks, then use this to introduce support for passing type metadata to
the bpf_obj_new_impl kfunc.

The user passes BTF ID of the type it wants to allocates in program BTF,
the verifier then rewrites the first argument as the size of this type,
after performing some sanity checks (to ensure it exists and it is a
struct type).

The second argument is also fixed up and passed by the verifier. This is
the btf_struct_meta for the type being allocated. It would be needed
mostly for the offset array which is required for zero initializing
special fields while leaving the rest of storage in unitialized state.

It would also be needed in the next patch to perform proper destruction
of the object's special fields.

Under the hood, bpf_obj_new will call bpf_mem_alloc and bpf_mem_free,
using the any context BPF memory allocator introduced recently. To this
end, a global instance of the BPF memory allocator is initialized on
boot to be used for this purpose. This 'bpf_global_ma' serves all
allocations for bpf_obj_new. In the future, bpf_obj_new variants will
allow specifying a custom allocator.

Note that now that bpf_obj_new can be used to allocate local kptrs that
can be linked to BPF linked list (when future linked list helpers are
available), we need to also free the elements using bpf_mem_free.
However, since the draining of elements is done outside the
bpf_spin_lock, we need to do migrate_disable around the call since
bpf_list_head_free can be called from map free path where migration is
enabled. Otherwise, when called from BPF programs migration is already
disabled.

A convenience macro is included in the bpf_experimental.h header to hide
over the ugly details of the implementation, leading to user code
looking similar to a language level extension which allocates and
constructs fields of a user type.

struct bar {
	struct bpf_list_node node;
};

struct foo {
	struct bpf_spin_lock lock;
	struct bpf_list_head head __contains(bar, node);
};

void prog(void) {
	struct foo *f;

	f = bpf_obj_new(typeof(*f));
	if (!f)
		return;
	...
}

A key piece of this story is still missing, i.e. the free function,
which will come in the next patch.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 include/linux/bpf.h                           |  21 ++--
 include/linux/bpf_verifier.h                  |   2 +
 kernel/bpf/core.c                             |  16 +++
 kernel/bpf/helpers.c                          |  47 ++++++--
 kernel/bpf/verifier.c                         | 107 ++++++++++++++++--
 .../testing/selftests/bpf/bpf_experimental.h  |  25 ++++
 6 files changed, 195 insertions(+), 23 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/bpf_experimental.h

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 7ccd90fd19ba..9b40e4c7db92 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -54,6 +54,8 @@ struct cgroup;
 extern struct idr btf_idr;
 extern spinlock_t btf_idr_lock;
 extern struct kobject *btf_kobj;
+extern struct bpf_mem_alloc bpf_global_ma;
+extern bool bpf_global_ma_set;
 
 typedef u64 (*bpf_callback_t)(u64, u64, u64, u64, u64);
 typedef int (*bpf_iter_init_seq_priv_t)(void *private_data,
@@ -333,16 +335,19 @@ static inline bool btf_record_has_field(const struct btf_record *rec, enum btf_f
 	return rec->field_mask & type;
 }
 
-static inline void check_and_init_map_value(struct bpf_map *map, void *dst)
+static inline void bpf_obj_init(const struct btf_field_offs *foffs, void *obj)
 {
-	if (!IS_ERR_OR_NULL(map->record)) {
-		struct btf_field *fields = map->record->fields;
-		u32 cnt = map->record->cnt;
-		int i;
+	int i;
 
-		for (i = 0; i < cnt; i++)
-			memset(dst + fields[i].offset, 0, btf_field_type_size(fields[i].type));
-	}
+	if (!foffs)
+		return;
+	for (i = 0; i < foffs->cnt; i++)
+		memset(obj + foffs->field_off[i], 0, foffs->field_sz[i]);
+}
+
+static inline void check_and_init_map_value(struct bpf_map *map, void *dst)
+{
+	bpf_obj_init(map->field_offs, dst);
 }
 
 /* memcpy that is used with 8-byte aligned pointers, power-of-8 size and
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 1e246ec2ff37..a009df64ffab 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -428,6 +428,8 @@ struct bpf_insn_aux_data {
 		 */
 		struct bpf_loop_inline_state loop_inline_state;
 	};
+	u64 obj_new_size; /* remember the size of type passed to bpf_obj_new to rewrite R1 */
+	struct btf_struct_meta *kptr_struct_meta;
 	u64 map_key_state; /* constant (32 bit) key tracking for maps */
 	int ctx_field_size; /* the ctx field size for load insn, maybe 0 */
 	u32 seen; /* this insn was processed by the verifier at env->pass_cnt */
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 9c16338bcbe8..2e57fc839a5c 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -34,6 +34,7 @@
 #include <linux/log2.h>
 #include <linux/bpf_verifier.h>
 #include <linux/nodemask.h>
+#include <linux/bpf_mem_alloc.h>
 
 #include <asm/barrier.h>
 #include <asm/unaligned.h>
@@ -60,6 +61,9 @@
 #define CTX	regs[BPF_REG_CTX]
 #define IMM	insn->imm
 
+struct bpf_mem_alloc bpf_global_ma;
+bool bpf_global_ma_set;
+
 /* No hurry in this branch
  *
  * Exported for the bpf jit load helper.
@@ -2746,6 +2750,18 @@ int __weak bpf_arch_text_invalidate(void *dst, size_t len)
 	return -ENOTSUPP;
 }
 
+#ifdef CONFIG_BPF_SYSCALL
+static int __init bpf_global_ma_init(void)
+{
+	int ret;
+
+	ret = bpf_mem_alloc_init(&bpf_global_ma, 0, false);
+	bpf_global_ma_set = !ret;
+	return ret;
+}
+late_initcall(bpf_global_ma_init);
+#endif
+
 DEFINE_STATIC_KEY_FALSE(bpf_stats_enabled_key);
 EXPORT_SYMBOL(bpf_stats_enabled_key);
 
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 5bc0b9f0f306..c4f1c22cc44c 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -19,6 +19,7 @@
 #include <linux/proc_ns.h>
 #include <linux/security.h>
 #include <linux/btf_ids.h>
+#include <linux/bpf_mem_alloc.h>
 
 #include "../../lib/kstrtox.h"
 
@@ -1735,25 +1736,57 @@ void bpf_list_head_free(const struct btf_field *field, void *list_head,
 
 		obj -= field->list_head.node_offset;
 		head = head->next;
-		/* TODO: Rework later */
-		kfree(obj);
+		/* The contained type can also have resources, including a
+		 * bpf_list_head which needs to be freed.
+		 */
+		bpf_obj_free_fields(field->list_head.value_rec, obj);
+		/* bpf_mem_free requires migrate_disable(), since we can be
+		 * called from map free path as well apart from BPF program (as
+		 * part of map ops doing bpf_obj_free_fields).
+		 */
+		migrate_disable();
+		bpf_mem_free(&bpf_global_ma, obj);
+		migrate_enable();
 	}
 }
 
-BTF_SET8_START(tracing_btf_ids)
+__diag_push();
+__diag_ignore_all("-Wmissing-prototypes",
+		  "Global functions as their definitions will be in vmlinux BTF");
+
+void *bpf_obj_new_impl(u64 local_type_id__k, void *meta__ign)
+{
+	struct btf_struct_meta *meta = meta__ign;
+	u64 size = local_type_id__k;
+	void *p;
+
+	if (unlikely(!bpf_global_ma_set))
+		return NULL;
+	p = bpf_mem_alloc(&bpf_global_ma, size);
+	if (!p)
+		return NULL;
+	if (meta)
+		bpf_obj_init(meta->field_offs, p);
+	return p;
+}
+
+__diag_pop();
+
+BTF_SET8_START(generic_btf_ids)
 #ifdef CONFIG_KEXEC_CORE
 BTF_ID_FLAGS(func, crash_kexec, KF_DESTRUCTIVE)
 #endif
-BTF_SET8_END(tracing_btf_ids)
+BTF_ID_FLAGS(func, bpf_obj_new_impl, KF_ACQUIRE | KF_RET_NULL)
+BTF_SET8_END(generic_btf_ids)
 
-static const struct btf_kfunc_id_set tracing_kfunc_set = {
+static const struct btf_kfunc_id_set generic_kfunc_set = {
 	.owner = THIS_MODULE,
-	.set   = &tracing_btf_ids,
+	.set   = &generic_btf_ids,
 };
 
 static int __init kfunc_init(void)
 {
-	return register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &tracing_kfunc_set);
+	return register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &generic_kfunc_set);
 }
 
 late_initcall(kfunc_init);
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 5bfc151711b9..db658a31d64f 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -7955,6 +7955,11 @@ static bool is_kfunc_arg_sfx_constant(const struct btf *btf, const struct btf_pa
 	return __kfunc_param_match_suffix(btf, arg, "__k");
 }
 
+static bool is_kfunc_arg_sfx_ignore(const struct btf *btf, const struct btf_param *arg)
+{
+	return __kfunc_param_match_suffix(btf, arg, "__ign");
+}
+
 static bool is_kfunc_arg_ret_buf_size(const struct btf *btf,
 				      const struct btf_param *arg,
 				      const struct bpf_reg_state *reg,
@@ -8223,6 +8228,10 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
 		int kf_arg_type;
 
 		t = btf_type_skip_modifiers(btf, args[i].type, NULL);
+
+		if (is_kfunc_arg_sfx_ignore(btf, &args[i]))
+			continue;
+
 		if (btf_type_is_scalar(t)) {
 			if (reg->type != SCALAR_VALUE) {
 				verbose(env, "R%d is not a scalar\n", regno);
@@ -8402,6 +8411,17 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
 	return 0;
 }
 
+enum special_kfunc_type {
+	KF_bpf_obj_new_impl,
+};
+
+BTF_SET_START(special_kfunc_set)
+BTF_ID(func, bpf_obj_new_impl)
+BTF_SET_END(special_kfunc_set)
+
+BTF_ID_LIST(special_kfunc_list)
+BTF_ID(func, bpf_obj_new_impl)
+
 static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 			    int *insn_idx_p)
 {
@@ -8476,17 +8496,64 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 	t = btf_type_skip_modifiers(desc_btf, func_proto->type, NULL);
 
 	if (is_kfunc_acquire(&meta) && !btf_type_is_struct_ptr(meta.btf, t)) {
-		verbose(env, "acquire kernel function does not return PTR_TO_BTF_ID\n");
-		return -EINVAL;
+		/* Only exception is bpf_obj_new_impl */
+		if (meta.btf != btf_vmlinux || meta.func_id != special_kfunc_list[KF_bpf_obj_new_impl]) {
+			verbose(env, "acquire kernel function does not return PTR_TO_BTF_ID\n");
+			return -EINVAL;
+		}
 	}
 
 	if (btf_type_is_scalar(t)) {
 		mark_reg_unknown(env, regs, BPF_REG_0);
 		mark_btf_func_reg_size(env, BPF_REG_0, t->size);
 	} else if (btf_type_is_ptr(t)) {
-		ptr_type = btf_type_skip_modifiers(desc_btf, t->type,
-						   &ptr_type_id);
-		if (!btf_type_is_struct(ptr_type)) {
+		ptr_type = btf_type_skip_modifiers(desc_btf, t->type, &ptr_type_id);
+
+		if (meta.btf == btf_vmlinux && btf_id_set_contains(&special_kfunc_set, meta.func_id)) {
+			if (!btf_type_is_void(ptr_type)) {
+				verbose(env, "kernel function %s must have void * return type\n",
+					meta.func_name);
+				return -EINVAL;
+			}
+			if (meta.func_id == special_kfunc_list[KF_bpf_obj_new_impl]) {
+				const struct btf_type *ret_t;
+				struct btf *ret_btf;
+				u32 ret_btf_id;
+
+				if (((u64)(u32)meta.arg_constant.value) != meta.arg_constant.value) {
+					verbose(env, "local type ID argument must be in range [0, U32_MAX]\n");
+					return -EINVAL;
+				}
+
+				ret_btf = env->prog->aux->btf;
+				ret_btf_id = meta.arg_constant.value;
+
+				/* This may be NULL due to user not supplying a BTF */
+				if (!ret_btf) {
+					verbose(env, "bpf_obj_new requires prog BTF\n");
+					return -EINVAL;
+				}
+
+				ret_t = btf_type_by_id(ret_btf, ret_btf_id);
+				if (!ret_t || !__btf_type_is_struct(ret_t)) {
+					verbose(env, "bpf_obj_new type ID argument must be of a struct\n");
+					return -EINVAL;
+				}
+
+				mark_reg_known_zero(env, regs, BPF_REG_0);
+				regs[BPF_REG_0].type = PTR_TO_BTF_ID | MEM_ALLOC;
+				regs[BPF_REG_0].btf = ret_btf;
+				regs[BPF_REG_0].btf_id = ret_btf_id;
+
+				env->insn_aux_data[insn_idx].obj_new_size = ret_t->size;
+				env->insn_aux_data[insn_idx].kptr_struct_meta =
+					btf_find_struct_meta(ret_btf, ret_btf_id);
+			} else {
+				verbose(env, "kernel function %s unhandled dynamic return type\n",
+					meta.func_name);
+				return -EFAULT;
+			}
+		} else if (!__btf_type_is_struct(ptr_type)) {
 			if (!meta.r0_size) {
 				ptr_type_name = btf_name_by_offset(desc_btf,
 								   ptr_type->name_off);
@@ -8514,6 +8581,7 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 			regs[BPF_REG_0].type = PTR_TO_BTF_ID;
 			regs[BPF_REG_0].btf_id = ptr_type_id;
 		}
+
 		if (is_kfunc_ret_null(&meta)) {
 			regs[BPF_REG_0].type |= PTR_MAYBE_NULL;
 			/* For mark_ptr_or_null_reg, see 93c230e3f5bd6 */
@@ -14662,8 +14730,8 @@ static int fixup_call_args(struct bpf_verifier_env *env)
 	return err;
 }
 
-static int fixup_kfunc_call(struct bpf_verifier_env *env,
-			    struct bpf_insn *insn)
+static int fixup_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
+			    struct bpf_insn *insn_buf, int insn_idx, int *cnt)
 {
 	const struct bpf_kfunc_desc *desc;
 
@@ -14682,8 +14750,21 @@ static int fixup_kfunc_call(struct bpf_verifier_env *env,
 		return -EFAULT;
 	}
 
+	*cnt = 0;
 	insn->imm = desc->imm;
+	if (insn->off)
+		return 0;
+	if (desc->func_id == special_kfunc_list[KF_bpf_obj_new_impl]) {
+		struct btf_struct_meta *kptr_struct_meta = env->insn_aux_data[insn_idx].kptr_struct_meta;
+		struct bpf_insn addr[2] = { BPF_LD_IMM64(BPF_REG_2, (long)kptr_struct_meta) };
+		u64 obj_new_size = env->insn_aux_data[insn_idx].obj_new_size;
 
+		insn_buf[0] = BPF_MOV64_IMM(BPF_REG_1, obj_new_size);
+		insn_buf[1] = addr[0];
+		insn_buf[2] = addr[1];
+		insn_buf[3] = *insn;
+		*cnt = 4;
+	}
 	return 0;
 }
 
@@ -14825,9 +14906,19 @@ static int do_misc_fixups(struct bpf_verifier_env *env)
 		if (insn->src_reg == BPF_PSEUDO_CALL)
 			continue;
 		if (insn->src_reg == BPF_PSEUDO_KFUNC_CALL) {
-			ret = fixup_kfunc_call(env, insn);
+			ret = fixup_kfunc_call(env, insn, insn_buf, i + delta, &cnt);
 			if (ret)
 				return ret;
+			if (cnt == 0)
+				continue;
+
+			new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt);
+			if (!new_prog)
+				return -ENOMEM;
+
+			delta	 += cnt - 1;
+			env->prog = prog = new_prog;
+			insn	  = new_prog->insnsi + i + delta;
 			continue;
 		}
 
diff --git a/tools/testing/selftests/bpf/bpf_experimental.h b/tools/testing/selftests/bpf/bpf_experimental.h
new file mode 100644
index 000000000000..3588fe89890c
--- /dev/null
+++ b/tools/testing/selftests/bpf/bpf_experimental.h
@@ -0,0 +1,25 @@
+#ifndef __BPF_EXPERIMENTAL__
+#define __BPF_EXPERIMENTAL__
+
+#include <vmlinux.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_core_read.h>
+
+/* Description
+ *	Allocates a local kptr of type represented by 'local_type_id' in program
+ *	BTF. User may use the bpf_core_type_id_local macro to pass the type ID
+ *	of a struct in program BTF.
+ *
+ *	The 'local_type_id' parameter must be a known constant.
+ *	The 'meta' parameter is a hidden argument that is ignored.
+ * Returns
+ *	A local kptr corresponding to passed in 'local_type_id', or NULL on
+ *	failure.
+ */
+extern void *bpf_obj_new_impl(__u64 local_type_id, void *meta) __ksym;
+
+/* Convenience macro to wrap over bpf_obj_new_impl */
+#define bpf_obj_new(type) ((type *)bpf_obj_new_impl(bpf_core_type_id_local(type), NULL))
+
+#endif
-- 
2.38.1

[PATCH bpf-next v5 17/25] bpf: Introduce bpf_obj_drop

[Kumar Kartikeya Dwivedi]

Introduce bpf_obj_drop, which is the kfunc used to free local kptrs
allocated using bpf_obj_new. Similar to bpf_obj_new, it implicitly
destructs the fields part of the local kptr automatically without user
intervention.

Just like the previous patch, btf_struct_meta that is needed to free up
the special fields is passed as a hidden argument to the kfunc.

For the user, a convenience macro hides over the kernel side kfunc which
is named bpf_obj_drop_impl.

Continuing the previous example:

void prog(void) {
	struct foo *f;

	f = bpf_obj_new(typeof(*f));
	if (!f)
		return;
	bpf_obj_drop(f);
}

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 kernel/bpf/helpers.c                          | 11 ++++
 kernel/bpf/verifier.c                         | 66 +++++++++++++++----
 .../testing/selftests/bpf/bpf_experimental.h  | 13 ++++
 3 files changed, 79 insertions(+), 11 deletions(-)

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index c4f1c22cc44c..02045f6a6ad5 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -1770,6 +1770,16 @@ void *bpf_obj_new_impl(u64 local_type_id__k, void *meta__ign)
 	return p;
 }
 
+void bpf_obj_drop_impl(void *p__lkptr, void *meta__ign)
+{
+	struct btf_struct_meta *meta = meta__ign;
+	void *p = p__lkptr;
+
+	if (meta)
+		bpf_obj_free_fields(meta->record, p);
+	bpf_mem_free(&bpf_global_ma, p);
+}
+
 __diag_pop();
 
 BTF_SET8_START(generic_btf_ids)
@@ -1777,6 +1787,7 @@ BTF_SET8_START(generic_btf_ids)
 BTF_ID_FLAGS(func, crash_kexec, KF_DESTRUCTIVE)
 #endif
 BTF_ID_FLAGS(func, bpf_obj_new_impl, KF_ACQUIRE | KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_obj_drop_impl, KF_RELEASE)
 BTF_SET8_END(generic_btf_ids)
 
 static const struct btf_kfunc_id_set generic_kfunc_set = {
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index db658a31d64f..7c5d9e933d97 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -7882,6 +7882,10 @@ struct bpf_kfunc_call_arg_meta {
 		u64 value;
 		bool found;
 	} arg_constant;
+	struct {
+		struct btf *btf;
+		u32 btf_id;
+	} arg_obj_drop;
 };
 
 static bool is_kfunc_acquire(struct bpf_kfunc_call_arg_meta *meta)
@@ -7960,6 +7964,11 @@ static bool is_kfunc_arg_sfx_ignore(const struct btf *btf, const struct btf_para
 	return __kfunc_param_match_suffix(btf, arg, "__ign");
 }
 
+static bool is_kfunc_arg_local_kptr(const struct btf *btf, const struct btf_param *arg)
+{
+	return __kfunc_param_match_suffix(btf, arg, "__lkptr");
+}
+
 static bool is_kfunc_arg_ret_buf_size(const struct btf *btf,
 				      const struct btf_param *arg,
 				      const struct bpf_reg_state *reg,
@@ -8060,6 +8069,7 @@ static u32 *reg2btf_ids[__BPF_REG_TYPE_MAX] = {
 
 enum kfunc_ptr_arg_type {
 	KF_ARG_PTR_TO_CTX,
+	KF_ARG_PTR_TO_LOCAL_BTF_ID,  /* Local kptr */
 	KF_ARG_PTR_TO_KPTR_STRONG,   /* PTR_TO_KPTR but type specific */
 	KF_ARG_PTR_TO_DYNPTR,
 	KF_ARG_PTR_TO_BTF_ID,	     /* Also covers reg2btf_ids conversions */
@@ -8067,6 +8077,20 @@ enum kfunc_ptr_arg_type {
 	KF_ARG_PTR_TO_MEM_SIZE,	     /* Size derived from next argument, skip it */
 };
 
+enum special_kfunc_type {
+	KF_bpf_obj_new_impl,
+	KF_bpf_obj_drop_impl,
+};
+
+BTF_SET_START(special_kfunc_set)
+BTF_ID(func, bpf_obj_new_impl)
+BTF_ID(func, bpf_obj_drop_impl)
+BTF_SET_END(special_kfunc_set)
+
+BTF_ID_LIST(special_kfunc_list)
+BTF_ID(func, bpf_obj_new_impl)
+BTF_ID(func, bpf_obj_drop_impl)
+
 static enum kfunc_ptr_arg_type
 get_kfunc_ptr_arg_type(struct bpf_verifier_env *env,
 		       struct bpf_kfunc_call_arg_meta *meta,
@@ -8087,6 +8111,9 @@ get_kfunc_ptr_arg_type(struct bpf_verifier_env *env,
 	if (btf_get_prog_ctx_type(&env->log, meta->btf, t, resolve_prog_type(env->prog), argno))
 		return KF_ARG_PTR_TO_CTX;
 
+	if (is_kfunc_arg_local_kptr(meta->btf, &args[argno]))
+		return KF_ARG_PTR_TO_LOCAL_BTF_ID;
+
 	if (is_kfunc_arg_kptr_get(meta, argno)) {
 		if (!btf_type_is_ptr(ref_t)) {
 			verbose(env, "arg#0 BTF type must be a double pointer for kptr_get kfunc\n");
@@ -8305,6 +8332,7 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
 			return kf_arg_type;
 
 		switch (kf_arg_type) {
+		case KF_ARG_PTR_TO_LOCAL_BTF_ID:
 		case KF_ARG_PTR_TO_BTF_ID:
 			if (!is_kfunc_trusted_args(meta))
 				break;
@@ -8341,6 +8369,21 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
 				return -EINVAL;
 			}
 			break;
+		case KF_ARG_PTR_TO_LOCAL_BTF_ID:
+			if (reg->type != (PTR_TO_BTF_ID | MEM_ALLOC)) {
+				verbose(env, "arg#%d expected pointer to local kptr\n", i);
+				return -EINVAL;
+			}
+			if (!reg->ref_obj_id) {
+				verbose(env, "local kptr must be referenced\n");
+				return -EINVAL;
+			}
+			if (meta->btf == btf_vmlinux &&
+			    meta->func_id == special_kfunc_list[KF_bpf_obj_drop_impl]) {
+				meta->arg_obj_drop.btf = reg->btf;
+				meta->arg_obj_drop.btf_id = reg->btf_id;
+			}
+			break;
 		case KF_ARG_PTR_TO_KPTR_STRONG:
 			if (reg->type != PTR_TO_MAP_VALUE) {
 				verbose(env, "arg#0 expected pointer to map value\n");
@@ -8411,17 +8454,6 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
 	return 0;
 }
 
-enum special_kfunc_type {
-	KF_bpf_obj_new_impl,
-};
-
-BTF_SET_START(special_kfunc_set)
-BTF_ID(func, bpf_obj_new_impl)
-BTF_SET_END(special_kfunc_set)
-
-BTF_ID_LIST(special_kfunc_list)
-BTF_ID(func, bpf_obj_new_impl)
-
 static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 			    int *insn_idx_p)
 {
@@ -8548,6 +8580,10 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 				env->insn_aux_data[insn_idx].obj_new_size = ret_t->size;
 				env->insn_aux_data[insn_idx].kptr_struct_meta =
 					btf_find_struct_meta(ret_btf, ret_btf_id);
+			} else if (meta.func_id == special_kfunc_list[KF_bpf_obj_drop_impl]) {
+				env->insn_aux_data[insn_idx].kptr_struct_meta =
+					btf_find_struct_meta(meta.arg_obj_drop.btf,
+							     meta.arg_obj_drop.btf_id);
 			} else {
 				verbose(env, "kernel function %s unhandled dynamic return type\n",
 					meta.func_name);
@@ -14764,6 +14800,14 @@ static int fixup_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 		insn_buf[2] = addr[1];
 		insn_buf[3] = *insn;
 		*cnt = 4;
+	} else if (desc->func_id == special_kfunc_list[KF_bpf_obj_drop_impl]) {
+		struct btf_struct_meta *kptr_struct_meta = env->insn_aux_data[insn_idx].kptr_struct_meta;
+		struct bpf_insn addr[2] = { BPF_LD_IMM64(BPF_REG_2, (long)kptr_struct_meta) };
+
+		insn_buf[0] = addr[0];
+		insn_buf[1] = addr[1];
+		insn_buf[2] = *insn;
+		*cnt = 3;
 	}
 	return 0;
 }
diff --git a/tools/testing/selftests/bpf/bpf_experimental.h b/tools/testing/selftests/bpf/bpf_experimental.h
index 3588fe89890c..d145c93ea663 100644
--- a/tools/testing/selftests/bpf/bpf_experimental.h
+++ b/tools/testing/selftests/bpf/bpf_experimental.h
@@ -22,4 +22,17 @@ extern void *bpf_obj_new_impl(__u64 local_type_id, void *meta) __ksym;
 /* Convenience macro to wrap over bpf_obj_new_impl */
 #define bpf_obj_new(type) ((type *)bpf_obj_new_impl(bpf_core_type_id_local(type), NULL))
 
+/* Description
+ *	Free a local kptr. All fields of local kptr that require destruction
+ *	will be destructed before the storage is freed.
+ *
+ *	The 'meta' parameter is a hidden argument that is ignored.
+ * Returns
+ *	Void.
+ */
+extern void bpf_obj_drop_impl(void *kptr, void *meta) __ksym;
+
+/* Convenience macro to wrap over bpf_obj_drop_impl */
+#define bpf_obj_drop(kptr) bpf_obj_drop_impl(kptr, NULL)
+
 #endif
-- 
2.38.1

[PATCH bpf-next v5 18/25] bpf: Permit NULL checking pointer with non-zero fixed offset

[Kumar Kartikeya Dwivedi]

Pointer increment on seeing PTR_MAYBE_NULL is already protected against,
hence make an exception for local kptrs while still keeping the warning
for other unintended cases that might creep in.

bpf_list_pop_{front,_back} helpers planned to be introduced in next
commit will return a local kptr with incremented offset pointing to
bpf_list_node field. The user is supposed to then obtain the pointer to
the entry using container_of after NULL checking it. The current
restrictions trigger a warning when doing the NULL checking. Revisiting
the reason, it is meant as an assertion which seems to actually work and
catch the bad case.

Hence, under no other circumstances can reg->off be non-zero for a
register that has the PTR_MAYBE_NULL type flag set.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 kernel/bpf/verifier.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 7c5d9e933d97..abcb23a4c6fc 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -10809,15 +10809,20 @@ static void mark_ptr_or_null_reg(struct bpf_func_state *state,
 {
 	if (type_may_be_null(reg->type) && reg->id == id &&
 	    !WARN_ON_ONCE(!reg->id)) {
-		if (WARN_ON_ONCE(reg->smin_value || reg->smax_value ||
-				 !tnum_equals_const(reg->var_off, 0) ||
-				 reg->off)) {
+		if (reg->smin_value || reg->smax_value || !tnum_equals_const(reg->var_off, 0) || reg->off) {
 			/* Old offset (both fixed and variable parts) should
 			 * have been known-zero, because we don't allow pointer
 			 * arithmetic on pointers that might be NULL. If we
 			 * see this happening, don't convert the register.
+			 *
+			 * But in some cases, some helpers that return local
+			 * kptrs advance offset for the returned pointer.
+			 * In those cases, it is fine to expect to see reg->off.
 			 */
-			return;
+			if (WARN_ON_ONCE(reg->type != (PTR_TO_BTF_ID | MEM_ALLOC | PTR_MAYBE_NULL)))
+				return;
+			if (WARN_ON_ONCE(reg->smin_value || reg->smax_value || !tnum_equals_const(reg->var_off, 0)))
+				return;
 		}
 		if (is_null) {
 			reg->type = SCALAR_VALUE;
-- 
2.38.1

[PATCH bpf-next v5 19/25] bpf: Introduce single ownership BPF linked list API

[Kumar Kartikeya Dwivedi]

Add a linked list API for use in BPF programs, where it expects
protection from the bpf_spin_lock in the same allocation as the
bpf_list_head. For now, only one bpf_spin_lock can be present hence that
is assumed to be the one protecting the bpf_list_head.

The following functions are added to kick things off:

// Add node to beginning of list
void bpf_list_push_front(struct bpf_list_head *head, struct bpf_list_node *node);

// Add node to end of list
void bpf_list_push_back(struct bpf_list_head *head, struct bpf_list_node *node);

// Remove node at beginning of list and return it
struct bpf_list_node *bpf_list_pop_front(struct bpf_list_head *head);

// Remove node at end of list and return it
struct bpf_list_node *bpf_list_pop_back(struct bpf_list_head *head);

The lock protecting the bpf_list_head needs to be taken for all
operations. The verifier ensures that the lock that needs to be taken is
always held, and only the correct lock is taken for these operations.
These checks are made statically by relying on the reg->id preserved for
registers pointing into regions having both bpf_spin_lock and the
objects protected by it. The comment over check_reg_allocation_locked in
this change describes the logic in detail.

Note that bpf_list_push_front and bpf_list_push_back are meant to
consume the object containing the node in the 1st argument, however that
specific mechanism is intended to not release the ref_obj_id directly
until the bpf_spin_unlock is called. In this commit, nothing is done,
but the next commit will be introducing logic to handle this case, so it
has been left as is for now.

bpf_list_pop_front and bpf_list_pop_back delete the first or last item
of the list respectively, and return pointer to the element at the
list_node offset. The user can then use container_of style macro to get
the actual entry type. The verifier however statically knows the actual
type, so the safety properties are still preserved.

With these additions, programs can now manage their own linked lists and
store their objects in them.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 kernel/bpf/helpers.c                          |  55 +++-
 kernel/bpf/verifier.c                         | 292 +++++++++++++++++-
 .../testing/selftests/bpf/bpf_experimental.h  |  28 ++
 3 files changed, 361 insertions(+), 14 deletions(-)

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 02045f6a6ad5..461e0c3174c6 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -1780,6 +1780,50 @@ void bpf_obj_drop_impl(void *p__lkptr, void *meta__ign)
 	bpf_mem_free(&bpf_global_ma, p);
 }
 
+static void __bpf_list_add(struct bpf_list_node *node, struct bpf_list_head *head, bool tail)
+{
+	struct list_head *n = (void *)node, *h = (void *)head;
+
+	if (unlikely(!h->next))
+		INIT_LIST_HEAD(h);
+	if (unlikely(!n->next))
+		INIT_LIST_HEAD(n);
+	tail ? list_add_tail(n, h) : list_add(n, h);
+}
+
+void bpf_list_push_front(struct bpf_list_head *head, struct bpf_list_node *node)
+{
+	return __bpf_list_add(node, head, false);
+}
+
+void bpf_list_push_back(struct bpf_list_head *head, struct bpf_list_node *node)
+{
+	return __bpf_list_add(node, head, true);
+}
+
+static struct bpf_list_node *__bpf_list_del(struct bpf_list_head *head, bool tail)
+{
+	struct list_head *n, *h = (void *)head;
+
+	if (unlikely(!h->next))
+		INIT_LIST_HEAD(h);
+	if (list_empty(h))
+		return NULL;
+	n = tail ? h->prev : h->next;
+	list_del_init(n);
+	return (struct bpf_list_node *)n;
+}
+
+struct bpf_list_node *bpf_list_pop_front(struct bpf_list_head *head)
+{
+	return __bpf_list_del(head, false);
+}
+
+struct bpf_list_node *bpf_list_pop_back(struct bpf_list_head *head)
+{
+	return __bpf_list_del(head, true);
+}
+
 __diag_pop();
 
 BTF_SET8_START(generic_btf_ids)
@@ -1788,6 +1832,10 @@ BTF_ID_FLAGS(func, crash_kexec, KF_DESTRUCTIVE)
 #endif
 BTF_ID_FLAGS(func, bpf_obj_new_impl, KF_ACQUIRE | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_obj_drop_impl, KF_RELEASE)
+BTF_ID_FLAGS(func, bpf_list_push_front)
+BTF_ID_FLAGS(func, bpf_list_push_back)
+BTF_ID_FLAGS(func, bpf_list_pop_front, KF_ACQUIRE | KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_list_pop_back, KF_ACQUIRE | KF_RET_NULL)
 BTF_SET8_END(generic_btf_ids)
 
 static const struct btf_kfunc_id_set generic_kfunc_set = {
@@ -1797,7 +1845,12 @@ static const struct btf_kfunc_id_set generic_kfunc_set = {
 
 static int __init kfunc_init(void)
 {
-	return register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &generic_kfunc_set);
+	int ret;
+
+	ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &generic_kfunc_set);
+	if (ret)
+		return ret;
+	return register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_CLS, &generic_kfunc_set);
 }
 
 late_initcall(kfunc_init);
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index abcb23a4c6fc..5b87ef859046 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -7886,6 +7886,9 @@ struct bpf_kfunc_call_arg_meta {
 		struct btf *btf;
 		u32 btf_id;
 	} arg_obj_drop;
+	struct {
+		struct btf_field *field;
+	} arg_list_head;
 };
 
 static bool is_kfunc_acquire(struct bpf_kfunc_call_arg_meta *meta)
@@ -7996,13 +7999,17 @@ static bool is_kfunc_arg_ret_buf_size(const struct btf *btf,
 
 enum {
 	KF_ARG_DYNPTR_ID,
+	KF_ARG_LIST_HEAD_ID,
+	KF_ARG_LIST_NODE_ID,
 };
 
 BTF_ID_LIST(kf_arg_btf_ids)
 BTF_ID(struct, bpf_dynptr_kern)
+BTF_ID(struct, bpf_list_head)
+BTF_ID(struct, bpf_list_node)
 
-static bool is_kfunc_arg_dynptr(const struct btf *btf,
-				const struct btf_param *arg)
+static bool __is_kfunc_ptr_arg_type(const struct btf *btf,
+				    const struct btf_param *arg, int type)
 {
 	const struct btf_type *t;
 	u32 res_id;
@@ -8015,7 +8022,22 @@ static bool is_kfunc_arg_dynptr(const struct btf *btf,
 	t = btf_type_skip_modifiers(btf, t->type, &res_id);
 	if (!t)
 		return false;
-	return btf_types_are_same(btf, res_id, btf_vmlinux, kf_arg_btf_ids[KF_ARG_DYNPTR_ID]);
+	return btf_types_are_same(btf, res_id, btf_vmlinux, kf_arg_btf_ids[type]);
+}
+
+static bool is_kfunc_arg_dynptr(const struct btf *btf, const struct btf_param *arg)
+{
+	return __is_kfunc_ptr_arg_type(btf, arg, KF_ARG_DYNPTR_ID);
+}
+
+static bool is_kfunc_arg_list_head(const struct btf *btf, const struct btf_param *arg)
+{
+	return __is_kfunc_ptr_arg_type(btf, arg, KF_ARG_LIST_HEAD_ID);
+}
+
+static bool is_kfunc_arg_list_node(const struct btf *btf, const struct btf_param *arg)
+{
+	return __is_kfunc_ptr_arg_type(btf, arg, KF_ARG_LIST_NODE_ID);
 }
 
 /* Returns true if struct is composed of scalars, 4 levels of nesting allowed */
@@ -8072,6 +8094,8 @@ enum kfunc_ptr_arg_type {
 	KF_ARG_PTR_TO_LOCAL_BTF_ID,  /* Local kptr */
 	KF_ARG_PTR_TO_KPTR_STRONG,   /* PTR_TO_KPTR but type specific */
 	KF_ARG_PTR_TO_DYNPTR,
+	KF_ARG_PTR_TO_LIST_HEAD,
+	KF_ARG_PTR_TO_LIST_NODE,
 	KF_ARG_PTR_TO_BTF_ID,	     /* Also covers reg2btf_ids conversions */
 	KF_ARG_PTR_TO_MEM,
 	KF_ARG_PTR_TO_MEM_SIZE,	     /* Size derived from next argument, skip it */
@@ -8080,16 +8104,28 @@ enum kfunc_ptr_arg_type {
 enum special_kfunc_type {
 	KF_bpf_obj_new_impl,
 	KF_bpf_obj_drop_impl,
+	KF_bpf_list_push_front,
+	KF_bpf_list_push_back,
+	KF_bpf_list_pop_front,
+	KF_bpf_list_pop_back,
 };
 
 BTF_SET_START(special_kfunc_set)
 BTF_ID(func, bpf_obj_new_impl)
 BTF_ID(func, bpf_obj_drop_impl)
+BTF_ID(func, bpf_list_push_front)
+BTF_ID(func, bpf_list_push_back)
+BTF_ID(func, bpf_list_pop_front)
+BTF_ID(func, bpf_list_pop_back)
 BTF_SET_END(special_kfunc_set)
 
 BTF_ID_LIST(special_kfunc_list)
 BTF_ID(func, bpf_obj_new_impl)
 BTF_ID(func, bpf_obj_drop_impl)
+BTF_ID(func, bpf_list_push_front)
+BTF_ID(func, bpf_list_push_back)
+BTF_ID(func, bpf_list_pop_front)
+BTF_ID(func, bpf_list_pop_back)
 
 static enum kfunc_ptr_arg_type
 get_kfunc_ptr_arg_type(struct bpf_verifier_env *env,
@@ -8132,6 +8168,12 @@ get_kfunc_ptr_arg_type(struct bpf_verifier_env *env,
 	if (is_kfunc_arg_dynptr(meta->btf, &args[argno]))
 		return KF_ARG_PTR_TO_DYNPTR;
 
+	if (is_kfunc_arg_list_head(meta->btf, &args[argno]))
+		return KF_ARG_PTR_TO_LIST_HEAD;
+
+	if (is_kfunc_arg_list_node(meta->btf, &args[argno]))
+		return KF_ARG_PTR_TO_LIST_NODE;
+
 	if ((base_type(reg->type) == PTR_TO_BTF_ID || reg2btf_ids[base_type(reg->type)])) {
 		if (!btf_type_is_struct(ref_t)) {
 			verbose(env, "kernel function %s args#%d pointer type %s %s is not supported\n",
@@ -8227,6 +8269,194 @@ static int process_kf_arg_ptr_to_kptr_strong(struct bpf_verifier_env *env,
 	return 0;
 }
 
+/* Implementation details:
+ *
+ * Each register points to some region of memory, which we define as an
+ * allocation. Each allocation may embed a bpf_spin_lock which protects any
+ * special BPF objects (bpf_list_head, bpf_rb_root, etc.) part of the same
+ * allocation. The lock and the data it protects are colocated in the same
+ * memory region.
+ *
+ * Hence, everytime a register holds a pointer value pointing to such
+ * allocation, the verifier preserves a unique reg->id for it.
+ *
+ * The verifier remembers the lock 'ptr' and the lock 'id' whenever
+ * bpf_spin_lock is called.
+ *
+ * To enable this, lock state in the verifier captures two values:
+ *	active_lock.ptr = Register's type specific pointer
+ *	active_lock.id  = A unique ID for each register pointer value
+ *
+ * Currently, PTR_TO_MAP_VALUE and PTR_TO_BTF_ID | MEM_ALLOC are the two
+ * supported register types.
+ *
+ * The active_lock.ptr in case of map values is the reg->map_ptr, and in case of
+ * local kptrs is the reg->btf pointer.
+ *
+ * The active_lock.id is non-unique for maps supporting direct_value_addr, as we
+ * can establish the provenance of the map value statically for each distinct
+ * lookup into such maps. They always contain a single map value hence unique
+ * IDs for each pseudo load pessimizes the algorithm and rejects valid programs.
+ *
+ * So, in case of global variables, they use array maps with max_entries = 1,
+ * hence their active_lock.ptr becomes map_ptr and id = 0 (since they all point
+ * into the same map value as max_entries is 1, as described above).
+ *
+ * In case of inner map lookups, the inner map pointer has same map_ptr as the
+ * outer map pointer (in verifier context), but each lookup into an inner map
+ * assigns a fresh reg->id to the lookup, so while lookups into distinct inner
+ * maps from the same outer map share the same map_ptr as active_lock.ptr, they
+ * will get different reg->id assigned to each lookup, hence different
+ * active_lock.id.
+ *
+ * In case of local kptrs, active_lock.ptr is the reg->btf, and the reg->id is a
+ * unique ID preserved after the NULL pointer check on the local kptr after its
+ * allocation using bpf_obj_new. Each allocation receives a new reg->id.
+ */
+static int check_reg_allocation_locked(struct bpf_verifier_env *env, struct bpf_reg_state *reg)
+{
+	void *ptr;
+	u32 id;
+
+	switch ((int)reg->type) {
+	case PTR_TO_MAP_VALUE:
+		ptr = reg->map_ptr;
+		break;
+	case PTR_TO_BTF_ID | MEM_ALLOC:
+		ptr = reg->btf;
+		break;
+	default:
+		verbose(env, "verifier internal error: unknown reg type for lock check\n");
+		return -EFAULT;
+	}
+	id = reg->id;
+
+	if (!env->cur_state->active_lock.ptr)
+		return -EINVAL;
+	if (env->cur_state->active_lock.ptr != ptr ||
+	    env->cur_state->active_lock.id != id) {
+		verbose(env, "held lock and object are not in the same allocation\n");
+		return -EINVAL;
+	}
+	return 0;
+}
+
+static bool is_bpf_list_api_kfunc(u32 btf_id)
+{
+	return btf_id == special_kfunc_list[KF_bpf_list_push_front] ||
+	       btf_id == special_kfunc_list[KF_bpf_list_push_back] ||
+	       btf_id == special_kfunc_list[KF_bpf_list_pop_front] ||
+	       btf_id == special_kfunc_list[KF_bpf_list_pop_back];
+}
+
+static int process_kf_arg_ptr_to_list_head(struct bpf_verifier_env *env,
+					   struct bpf_reg_state *reg, u32 regno,
+					   struct bpf_kfunc_call_arg_meta *meta)
+{
+	struct btf_record *rec = NULL;
+	struct btf_field *field;
+	u32 list_head_off;
+
+	if (meta->btf != btf_vmlinux || !is_bpf_list_api_kfunc(meta->func_id)) {
+		verbose(env, "verifier internal error: bpf_list_head argument for unknown kfunc\n");
+		return -EFAULT;
+	}
+
+	if (reg->type == PTR_TO_MAP_VALUE) {
+		rec = reg->map_ptr->record;
+	} else /* PTR_TO_BTF_ID | MEM_ALLOC */ {
+		struct btf_struct_meta *meta;
+
+		meta = btf_find_struct_meta(reg->btf, reg->btf_id);
+		if (!meta) {
+			verbose(env, "bpf_list_head not found for local kptr\n");
+			return -EINVAL;
+		}
+		rec = meta->record;
+	}
+
+	if (!tnum_is_const(reg->var_off)) {
+		verbose(env,
+			"R%d doesn't have constant offset. bpf_list_head has to be at the constant offset\n",
+			regno);
+		return -EINVAL;
+	}
+
+	list_head_off = reg->off + reg->var_off.value;
+	field = btf_record_find(rec, list_head_off, BPF_LIST_HEAD);
+	if (!field) {
+		verbose(env, "bpf_list_head not found at offset=%u\n", list_head_off);
+		return -EINVAL;
+	}
+
+	/* All functions require bpf_list_head to be protected using a bpf_spin_lock */
+	if (check_reg_allocation_locked(env, reg)) {
+		verbose(env, "bpf_spin_lock at off=%d must be held for bpf_list_head\n",
+			rec->spin_lock_off);
+		return -EINVAL;
+	}
+
+	if (meta->arg_list_head.field) {
+		verbose(env, "verifier internal error: repeating bpf_list_head arg\n");
+		return -EFAULT;
+	}
+	meta->arg_list_head.field = field;
+	return 0;
+}
+
+static int process_kf_arg_ptr_to_list_node(struct bpf_verifier_env *env,
+					   struct bpf_reg_state *reg, u32 regno,
+					   struct bpf_kfunc_call_arg_meta *meta)
+{
+	struct btf_struct_meta *struct_meta;
+	struct btf_field *field;
+	struct btf_record *rec;
+	u32 list_node_off;
+
+	if (meta->btf != btf_vmlinux ||
+	    (meta->func_id != special_kfunc_list[KF_bpf_list_push_front] &&
+	     meta->func_id != special_kfunc_list[KF_bpf_list_push_back])) {
+		verbose(env, "verifier internal error: bpf_list_head argument for unknown kfunc\n");
+		return -EFAULT;
+	}
+
+	if (!tnum_is_const(reg->var_off)) {
+		verbose(env,
+			"R%d doesn't have constant offset. bpf_list_head has to be at the constant offset\n",
+			regno);
+		return -EINVAL;
+	}
+
+	struct_meta = btf_find_struct_meta(reg->btf, reg->btf_id);
+	if (!struct_meta) {
+		verbose(env, "bpf_list_node not found for local kptr\n");
+		return -EINVAL;
+	}
+	rec = struct_meta->record;
+
+	list_node_off = reg->off + reg->var_off.value;
+	field = btf_record_find(rec, list_node_off, BPF_LIST_NODE);
+	if (!field || field->offset != list_node_off) {
+		verbose(env, "bpf_list_node not found at offset=%u\n", list_node_off);
+		return -EINVAL;
+	}
+
+	field = meta->arg_list_head.field;
+
+	if (!btf_struct_ids_match(&env->log, reg->btf, reg->btf_id, 0, field->list_head.btf,
+				  field->list_head.value_btf_id, true)) {
+		verbose(env, "bpf_list_head value type does not match arg#1\n");
+		return -EINVAL;
+	}
+
+	if (list_node_off != field->list_head.node_offset) {
+		verbose(env, "arg#1 offset must be for bpf_list_node at off=%d\n",
+			field->list_head.node_offset);
+		return -EINVAL;
+	}
+	return 0;
+}
+
 static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_arg_meta *meta)
 {
 	const char *func_name = meta->func_name, *ref_tname;
@@ -8347,6 +8577,8 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
 			break;
 		case KF_ARG_PTR_TO_KPTR_STRONG:
 		case KF_ARG_PTR_TO_DYNPTR:
+		case KF_ARG_PTR_TO_LIST_HEAD:
+		case KF_ARG_PTR_TO_LIST_NODE:
 		case KF_ARG_PTR_TO_MEM:
 		case KF_ARG_PTR_TO_MEM_SIZE:
 			/* Trusted by default */
@@ -8411,6 +8643,33 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
 				return -EINVAL;
 			}
 			break;
+		case KF_ARG_PTR_TO_LIST_HEAD:
+			if (reg->type != PTR_TO_MAP_VALUE &&
+			    reg->type != (PTR_TO_BTF_ID | MEM_ALLOC)) {
+				verbose(env, "arg#%d expected pointer to map value or local kptr\n", i);
+				return -EINVAL;
+			}
+			if (reg->type == (PTR_TO_BTF_ID | MEM_ALLOC) && !reg->ref_obj_id) {
+				verbose(env, "local kptr must be referenced\n");
+				return -EINVAL;
+			}
+			ret = process_kf_arg_ptr_to_list_head(env, reg, regno, meta);
+			if (ret < 0)
+				return ret;
+			break;
+		case KF_ARG_PTR_TO_LIST_NODE:
+			if (reg->type != (PTR_TO_BTF_ID | MEM_ALLOC)) {
+				verbose(env, "arg#%d expected pointer to local kptr\n", i);
+				return -EINVAL;
+			}
+			if (!reg->ref_obj_id) {
+				verbose(env, "local kptr must be referenced\n");
+				return -EINVAL;
+			}
+			ret = process_kf_arg_ptr_to_list_node(env, reg, regno, meta);
+			if (ret < 0)
+				return ret;
+			break;
 		case KF_ARG_PTR_TO_BTF_ID:
 			/* Only base_type is checked, further checks are done here */
 			if (reg->type != PTR_TO_BTF_ID &&
@@ -8542,11 +8801,6 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 		ptr_type = btf_type_skip_modifiers(desc_btf, t->type, &ptr_type_id);
 
 		if (meta.btf == btf_vmlinux && btf_id_set_contains(&special_kfunc_set, meta.func_id)) {
-			if (!btf_type_is_void(ptr_type)) {
-				verbose(env, "kernel function %s must have void * return type\n",
-					meta.func_name);
-				return -EINVAL;
-			}
 			if (meta.func_id == special_kfunc_list[KF_bpf_obj_new_impl]) {
 				const struct btf_type *ret_t;
 				struct btf *ret_btf;
@@ -8584,6 +8838,15 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 				env->insn_aux_data[insn_idx].kptr_struct_meta =
 					btf_find_struct_meta(meta.arg_obj_drop.btf,
 							     meta.arg_obj_drop.btf_id);
+			} else if (meta.func_id == special_kfunc_list[KF_bpf_list_pop_front] ||
+				   meta.func_id == special_kfunc_list[KF_bpf_list_pop_back]) {
+				struct btf_field *field = meta.arg_list_head.field;
+
+				mark_reg_known_zero(env, regs, BPF_REG_0);
+				regs[BPF_REG_0].type = PTR_TO_BTF_ID | MEM_ALLOC;
+				regs[BPF_REG_0].btf = field->list_head.btf;
+				regs[BPF_REG_0].btf_id = field->list_head.value_btf_id;
+				regs[BPF_REG_0].off = field->list_head.node_offset;
 			} else {
 				verbose(env, "kernel function %s unhandled dynamic return type\n",
 					meta.func_name);
@@ -13262,11 +13525,14 @@ static int do_check(struct bpf_verifier_env *env)
 					return -EINVAL;
 				}
 
-				if (env->cur_state->active_lock.ptr &&
-				    (insn->src_reg == BPF_PSEUDO_CALL ||
-				     insn->imm != BPF_FUNC_spin_unlock)) {
-					verbose(env, "function calls are not allowed while holding a lock\n");
-					return -EINVAL;
+				if (env->cur_state->active_lock.ptr) {
+					if ((insn->src_reg == BPF_REG_0 && insn->imm != BPF_FUNC_spin_unlock) ||
+					    (insn->src_reg == BPF_PSEUDO_CALL) ||
+					    (insn->src_reg == BPF_PSEUDO_KFUNC_CALL &&
+					     (insn->off != 0 || !is_bpf_list_api_kfunc(insn->imm)))) {
+						verbose(env, "function calls are not allowed while holding a lock\n");
+						return -EINVAL;
+					}
 				}
 				if (insn->src_reg == BPF_PSEUDO_CALL)
 					err = check_func_call(env, insn, &env->insn_idx);
diff --git a/tools/testing/selftests/bpf/bpf_experimental.h b/tools/testing/selftests/bpf/bpf_experimental.h
index d145c93ea663..828dd868b658 100644
--- a/tools/testing/selftests/bpf/bpf_experimental.h
+++ b/tools/testing/selftests/bpf/bpf_experimental.h
@@ -35,4 +35,32 @@ extern void bpf_obj_drop_impl(void *kptr, void *meta) __ksym;
 /* Convenience macro to wrap over bpf_obj_drop_impl */
 #define bpf_obj_drop(kptr) bpf_obj_drop_impl(kptr, NULL)
 
+/* Description
+ *	Add a new entry to the beginning of the BPF linked list.
+ * Returns
+ *	Void.
+ */
+extern void bpf_list_push_front(struct bpf_list_head *head, struct bpf_list_node *node) __ksym;
+
+/* Description
+ *	Add a new entry to the end of the BPF linked list.
+ * Returns
+ *	Void.
+ */
+extern void bpf_list_push_back(struct bpf_list_head *head, struct bpf_list_node *node) __ksym;
+
+/* Description
+ *	Remove the entry at the beginning of the BPF linked list.
+ * Returns
+ *	Pointer to bpf_list_node of deleted entry, or NULL if list is empty.
+ */
+extern struct bpf_list_node *bpf_list_pop_front(struct bpf_list_head *head) __ksym;
+
+/* Description
+ *	Remove the entry at the end of the BPF linked list.
+ * Returns
+ *	Pointer to bpf_list_node of deleted entry, or NULL if list is empty.
+ */
+extern struct bpf_list_node *bpf_list_pop_back(struct bpf_list_head *head) __ksym;
+
 #endif
-- 
2.38.1

[PATCH bpf-next v5 20/25] bpf: Add 'release on unlock' logic for bpf_list_push_{front,back}

[Kumar Kartikeya Dwivedi]

This commit implements the delayed release logic for bpf_list_push_front
and bpf_list_push_back.

Once a node has been added to the list, it's pointer changes to
PTR_UNTRUSTED. However, it is only released once the lock protecting the
list is unlocked. For such local kptrs with PTR_UNTRUSTED set but an
active ref_obj_id, it is still permitted to read them as long as the
lock is held. Writing to them is not allowed.

This allows having read access to push items we no longer own until we
release the lock guarding the list, allowing a little more flexibility
when working with these APIs.

Note that enabling write support has fairly tricky interactions with
what happens inside the critical section. Just as an example, currently,
bpf_obj_drop is not permitted, but if it were, being able to write to
the PTR_UNTRUSTED pointer while the object gets released back to the
memory allocator would violate safety properties we wish to guarantee
(i.e. not crashing the kernel). The memory could be reused for a
different type in the BPF program or even in the kernel as it gets
eventually kfree'd.

Not enabling bpf_obj_drop inside the critical section would appear to
prevent all of the above, but that is more of an artifical limitation
right now. Since the write support is tangled with how we handle
potential aliasing of nodes inside the critical section that may or may
not be part of the list anymore, it has been deferred to a future patch.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 include/linux/bpf_verifier.h |  5 ++++
 kernel/bpf/verifier.c        | 48 +++++++++++++++++++++++++++++++++++-
 2 files changed, 52 insertions(+), 1 deletion(-)

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index a009df64ffab..c3b202559b87 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -229,6 +229,11 @@ struct bpf_reference_state {
 	 * exiting a callback function.
 	 */
 	int callback_ref;
+	/* Mark the reference state to release the registers sharing the same id
+	 * on bpf_spin_unlock (for nodes that we will lose ownership to but are
+	 * safe to access inside the critical section).
+	 */
+	bool release_on_unlock;
 };
 
 /* state of the program:
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 5b87ef859046..1900af72df94 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5659,7 +5659,9 @@ static int process_spin_lock(struct bpf_verifier_env *env, int regno,
 			cur->active_lock.ptr = btf;
 		cur->active_lock.id = reg->id;
 	} else {
+		struct bpf_func_state *fstate = cur_func(env);
 		void *ptr;
+		int i;
 
 		if (map)
 			ptr = map;
@@ -5677,6 +5679,16 @@ static int process_spin_lock(struct bpf_verifier_env *env, int regno,
 		}
 		cur->active_lock.ptr = NULL;
 		cur->active_lock.id = 0;
+
+		for (i = 0; i < fstate->acquired_refs; i++) {
+			/* WARN because this reference state cannot be freed
+			 * before this point, as bpf_spin_lock CS does not
+			 * allow functions that release the local kptr
+			 * immediately.
+			 */
+			if (fstate->refs[i].release_on_unlock)
+				WARN_ON_ONCE(release_reference(env, fstate->refs[i].id));
+		}
 	}
 	return 0;
 }
@@ -8269,6 +8281,39 @@ static int process_kf_arg_ptr_to_kptr_strong(struct bpf_verifier_env *env,
 	return 0;
 }
 
+static int ref_set_release_on_unlock(struct bpf_verifier_env *env, u32 ref_obj_id)
+{
+	struct bpf_func_state *state = cur_func(env);
+	struct bpf_reg_state *reg;
+	int i;
+
+	/* bpf_spin_lock only allows calling list_push and list_pop, no BPF
+	 * subprogs, no global functions. This means that the references would
+	 * not be released inside the critical section but they may be added to
+	 * the reference state, and the acquired_refs are never copied out for a
+	 * different frame as BPF to BPF calls don't work in bpf_spin_lock
+	 * critical sections.
+	 */
+	if (!ref_obj_id) {
+		verbose(env, "verifier internal error: ref_obj_id is zero for release_on_unlock\n");
+		return -EFAULT;
+	}
+	for (i = 0; i < state->acquired_refs; i++) {
+		if (state->refs[i].id == ref_obj_id) {
+			WARN_ON_ONCE(state->refs[i].release_on_unlock);
+			state->refs[i].release_on_unlock = true;
+			/* Now mark everyone sharing same ref_obj_id as untrusted */
+			bpf_for_each_reg_in_vstate(env->cur_state, state, reg, ({
+				if (reg->ref_obj_id == ref_obj_id)
+					reg->type |= PTR_UNTRUSTED;
+			}));
+			return 0;
+		}
+	}
+	verbose(env, "verifier internal error: ref state missing for ref_obj_id\n");
+	return -EFAULT;
+}
+
 /* Implementation details:
  *
  * Each register points to some region of memory, which we define as an
@@ -8454,7 +8499,8 @@ static int process_kf_arg_ptr_to_list_node(struct bpf_verifier_env *env,
 			field->list_head.node_offset);
 		return -EINVAL;
 	}
-	return 0;
+	/* Set arg#1 for expiration after unlock */
+	return ref_set_release_on_unlock(env, reg->ref_obj_id);
 }
 
 static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_arg_meta *meta)
-- 
2.38.1

[PATCH bpf-next v5 21/25] selftests/bpf: Add __contains macro to bpf_experimental.h

[Kumar Kartikeya Dwivedi]

Add user facing __contains macro which provides a convenient wrapper
over the verbose kernel specific BTF declaration tag required to
annotate BPF list head structs in user types.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 tools/testing/selftests/bpf/bpf_experimental.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tools/testing/selftests/bpf/bpf_experimental.h b/tools/testing/selftests/bpf/bpf_experimental.h
index 828dd868b658..c5103587b6df 100644
--- a/tools/testing/selftests/bpf/bpf_experimental.h
+++ b/tools/testing/selftests/bpf/bpf_experimental.h
@@ -6,6 +6,8 @@
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_core_read.h>
 
+#define __contains(name, node) __attribute__((btf_decl_tag("contains:" #name ":" #node)))
+
 /* Description
  *	Allocates a local kptr of type represented by 'local_type_id' in program
  *	BTF. User may use the bpf_core_type_id_local macro to pass the type ID
-- 
2.38.1

[PATCH bpf-next v5 22/25] selftests/bpf: Update spinlock selftest

[Kumar Kartikeya Dwivedi]

Make updates in preparation for adding more test cases to this selftest:
- Convert from CHECK_ to ASSERT macros.
- Use BPF skeleton
- Fix typo sping -> spin
- Rename spinlock.c -> spin_lock.c

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 .../selftests/bpf/prog_tests/spin_lock.c      | 46 +++++++++++++++++++
 .../selftests/bpf/prog_tests/spinlock.c       | 45 ------------------
 .../selftests/bpf/progs/test_spin_lock.c      |  4 +-
 3 files changed, 48 insertions(+), 47 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/spin_lock.c
 delete mode 100644 tools/testing/selftests/bpf/prog_tests/spinlock.c

diff --git a/tools/testing/selftests/bpf/prog_tests/spin_lock.c b/tools/testing/selftests/bpf/prog_tests/spin_lock.c
new file mode 100644
index 000000000000..1f720002fe56
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/spin_lock.c
@@ -0,0 +1,46 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <test_progs.h>
+#include <network_helpers.h>
+
+#include "test_spin_lock.skel.h"
+
+static void *spin_lock_thread(void *arg)
+{
+	int err, prog_fd = *(u32 *) arg;
+	LIBBPF_OPTS(bpf_test_run_opts, topts,
+		.data_in = &pkt_v4,
+		.data_size_in = sizeof(pkt_v4),
+		.repeat = 10000,
+	);
+
+	err = bpf_prog_test_run_opts(prog_fd, &topts);
+	ASSERT_OK(err, "test_run");
+	ASSERT_OK(topts.retval, "test_run retval");
+	pthread_exit(arg);
+}
+
+void test_spinlock(void)
+{
+	struct test_spin_lock *skel;
+	pthread_t thread_id[4];
+	int prog_fd, i;
+	void *ret;
+
+	skel = test_spin_lock__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "test_spin_lock__open_and_load"))
+		return;
+	prog_fd = bpf_program__fd(skel->progs.bpf_spin_lock_test);
+	for (i = 0; i < 4; i++)
+		if (!ASSERT_OK(pthread_create(&thread_id[i], NULL,
+					      &spin_lock_thread, &prog_fd), "pthread_create"))
+			goto end;
+
+	for (i = 0; i < 4; i++) {
+		if (!ASSERT_OK(pthread_join(thread_id[i], &ret), "pthread_join"))
+			goto end;
+		if (!ASSERT_EQ(ret, &prog_fd, "ret == prog_fd"))
+			goto end;
+	}
+end:
+	test_spin_lock__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/prog_tests/spinlock.c b/tools/testing/selftests/bpf/prog_tests/spinlock.c
deleted file mode 100644
index 15eb1372d771..000000000000
--- a/tools/testing/selftests/bpf/prog_tests/spinlock.c
+++ /dev/null
@@ -1,45 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-#include <test_progs.h>
-#include <network_helpers.h>
-
-static void *spin_lock_thread(void *arg)
-{
-	int err, prog_fd = *(u32 *) arg;
-	LIBBPF_OPTS(bpf_test_run_opts, topts,
-		.data_in = &pkt_v4,
-		.data_size_in = sizeof(pkt_v4),
-		.repeat = 10000,
-	);
-
-	err = bpf_prog_test_run_opts(prog_fd, &topts);
-	ASSERT_OK(err, "test_run");
-	ASSERT_OK(topts.retval, "test_run retval");
-	pthread_exit(arg);
-}
-
-void test_spinlock(void)
-{
-	const char *file = "./test_spin_lock.bpf.o";
-	pthread_t thread_id[4];
-	struct bpf_object *obj = NULL;
-	int prog_fd;
-	int err = 0, i;
-	void *ret;
-
-	err = bpf_prog_test_load(file, BPF_PROG_TYPE_CGROUP_SKB, &obj, &prog_fd);
-	if (CHECK_FAIL(err)) {
-		printf("test_spin_lock:bpf_prog_test_load errno %d\n", errno);
-		goto close_prog;
-	}
-	for (i = 0; i < 4; i++)
-		if (CHECK_FAIL(pthread_create(&thread_id[i], NULL,
-					      &spin_lock_thread, &prog_fd)))
-			goto close_prog;
-
-	for (i = 0; i < 4; i++)
-		if (CHECK_FAIL(pthread_join(thread_id[i], &ret) ||
-			       ret != (void *)&prog_fd))
-			goto close_prog;
-close_prog:
-	bpf_object__close(obj);
-}
diff --git a/tools/testing/selftests/bpf/progs/test_spin_lock.c b/tools/testing/selftests/bpf/progs/test_spin_lock.c
index 7e88309d3229..5bd10409285b 100644
--- a/tools/testing/selftests/bpf/progs/test_spin_lock.c
+++ b/tools/testing/selftests/bpf/progs/test_spin_lock.c
@@ -45,8 +45,8 @@ struct {
 
 #define CREDIT_PER_NS(delta, rate) (((delta) * rate) >> 20)
 
-SEC("tc")
-int bpf_sping_lock_test(struct __sk_buff *skb)
+SEC("cgroup_skb/ingress")
+int bpf_spin_lock_test(struct __sk_buff *skb)
 {
 	volatile int credit = 0, max_credit = 100, pkt_len = 64;
 	struct hmap_elem zero = {}, *val;
-- 
2.38.1

[PATCH bpf-next v5 23/25] selftests/bpf: Add failure test cases for spin lock pairing

[Kumar Kartikeya Dwivedi]

First, ensure that whenever a bpf_spin_lock is present in an allocation,
the reg->id is preserved. This won't be true for global variables
however, since they have a single map value per map, hence the verifier
harcodes it to 0 (so that multiple pseudo ldimm64 insns can yield the
same lock object per map at a given offset).

Next, add test cases for all possible combinations (kptr, global, map
value, inner map value). Since we lifted restriction on locking in inner
maps, also add test cases for them. Currently, each lookup into an inner
map gets a fresh reg->id, so even if the reg->map_ptr is same, they will
be treated as separate allocations and the incorrect unlock pairing will
be rejected.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 .../selftests/bpf/prog_tests/spin_lock.c      |  89 +++++++-
 .../selftests/bpf/progs/test_spin_lock_fail.c | 204 ++++++++++++++++++
 2 files changed, 292 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/bpf/progs/test_spin_lock_fail.c

diff --git a/tools/testing/selftests/bpf/prog_tests/spin_lock.c b/tools/testing/selftests/bpf/prog_tests/spin_lock.c
index 1f720002fe56..5df959c78fee 100644
--- a/tools/testing/selftests/bpf/prog_tests/spin_lock.c
+++ b/tools/testing/selftests/bpf/prog_tests/spin_lock.c
@@ -3,6 +3,79 @@
 #include <network_helpers.h>
 
 #include "test_spin_lock.skel.h"
+#include "test_spin_lock_fail.skel.h"
+
+static char log_buf[1024 * 1024];
+
+static struct {
+	const char *prog_name;
+	const char *err_msg;
+} spin_lock_fail_tests[] = {
+	{ "lock_id_kptr_preserve",
+	  "5: (bf) r1 = r0                       ; R0_w=ptr_foo(id=2,ref_obj_id=2,off=0,imm=0) "
+	  "R1_w=ptr_foo(id=2,ref_obj_id=2,off=0,imm=0) refs=2\n6: (85) call bpf_this_cpu_ptr#154\n"
+	  "R1 type=ptr_ expected=percpu_ptr_" },
+	{ "lock_id_global_zero",
+	  "; R1_w=map_value(off=0,ks=4,vs=4,imm=0)\n2: (85) call bpf_this_cpu_ptr#154\n"
+	  "R1 type=map_value expected=percpu_ptr_" },
+	{ "lock_id_mapval_preserve",
+	  "8: (bf) r1 = r0                       ; R0_w=map_value(id=1,off=0,ks=4,vs=8,imm=0) "
+	  "R1_w=map_value(id=1,off=0,ks=4,vs=8,imm=0)\n9: (85) call bpf_this_cpu_ptr#154\n"
+	  "R1 type=map_value expected=percpu_ptr_" },
+	{ "lock_id_innermapval_preserve",
+	  "13: (bf) r1 = r0                      ; R0=map_value(id=2,off=0,ks=4,vs=8,imm=0) "
+	  "R1_w=map_value(id=2,off=0,ks=4,vs=8,imm=0)\n14: (85) call bpf_this_cpu_ptr#154\n"
+	  "R1 type=map_value expected=percpu_ptr_" },
+	{ "lock_id_mismatch_kptr_kptr", "bpf_spin_unlock of different lock" },
+	{ "lock_id_mismatch_kptr_global", "bpf_spin_unlock of different lock" },
+	{ "lock_id_mismatch_kptr_mapval", "bpf_spin_unlock of different lock" },
+	{ "lock_id_mismatch_kptr_innermapval", "bpf_spin_unlock of different lock" },
+	{ "lock_id_mismatch_global_global", "bpf_spin_unlock of different lock" },
+	{ "lock_id_mismatch_global_kptr", "bpf_spin_unlock of different lock" },
+	{ "lock_id_mismatch_global_mapval", "bpf_spin_unlock of different lock" },
+	{ "lock_id_mismatch_global_innermapval", "bpf_spin_unlock of different lock" },
+	{ "lock_id_mismatch_mapval_mapval", "bpf_spin_unlock of different lock" },
+	{ "lock_id_mismatch_mapval_kptr", "bpf_spin_unlock of different lock" },
+	{ "lock_id_mismatch_mapval_global", "bpf_spin_unlock of different lock" },
+	{ "lock_id_mismatch_mapval_innermapval", "bpf_spin_unlock of different lock" },
+	{ "lock_id_mismatch_innermapval_innermapval1", "bpf_spin_unlock of different lock" },
+	{ "lock_id_mismatch_innermapval_innermapval2", "bpf_spin_unlock of different lock" },
+	{ "lock_id_mismatch_innermapval_kptr", "bpf_spin_unlock of different lock" },
+	{ "lock_id_mismatch_innermapval_global", "bpf_spin_unlock of different lock" },
+	{ "lock_id_mismatch_innermapval_mapval", "bpf_spin_unlock of different lock" },
+};
+
+static void test_spin_lock_fail_prog(const char *prog_name, const char *err_msg)
+{
+	LIBBPF_OPTS(bpf_object_open_opts, opts, .kernel_log_buf = log_buf,
+						.kernel_log_size = sizeof(log_buf),
+						.kernel_log_level = 1);
+	struct test_spin_lock_fail *skel;
+	struct bpf_program *prog;
+	int ret;
+
+	skel = test_spin_lock_fail__open_opts(&opts);
+	if (!ASSERT_OK_PTR(skel, "test_spin_lock_fail__open_opts"))
+		return;
+
+	prog = bpf_object__find_program_by_name(skel->obj, prog_name);
+	if (!ASSERT_OK_PTR(prog, "bpf_object__find_program_by_name"))
+		goto end;
+
+	bpf_program__set_autoload(prog, true);
+
+	ret = test_spin_lock_fail__load(skel);
+	if (!ASSERT_ERR(ret, "test_spin_lock_fail__load must fail"))
+		goto end;
+
+	if (!ASSERT_OK_PTR(strstr(log_buf, err_msg), "expected error message")) {
+		fprintf(stderr, "Expected: %s\n", err_msg);
+		fprintf(stderr, "Verifier: %s\n", log_buf);
+	}
+
+end:
+	test_spin_lock_fail__destroy(skel);
+}
 
 static void *spin_lock_thread(void *arg)
 {
@@ -19,7 +92,7 @@ static void *spin_lock_thread(void *arg)
 	pthread_exit(arg);
 }
 
-void test_spinlock(void)
+void test_spin_lock_success(void)
 {
 	struct test_spin_lock *skel;
 	pthread_t thread_id[4];
@@ -44,3 +117,17 @@ void test_spinlock(void)
 end:
 	test_spin_lock__destroy(skel);
 }
+
+void test_spin_lock(void)
+{
+	int i;
+
+	test_spin_lock_success();
+
+	for (i = 0; i < ARRAY_SIZE(spin_lock_fail_tests); i++) {
+		if (!test__start_subtest(spin_lock_fail_tests[i].prog_name))
+			continue;
+		test_spin_lock_fail_prog(spin_lock_fail_tests[i].prog_name,
+					 spin_lock_fail_tests[i].err_msg);
+	}
+}
diff --git a/tools/testing/selftests/bpf/progs/test_spin_lock_fail.c b/tools/testing/selftests/bpf/progs/test_spin_lock_fail.c
new file mode 100644
index 000000000000..86cd183ef6dc
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_spin_lock_fail.c
@@ -0,0 +1,204 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <vmlinux.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_experimental.h"
+
+struct foo {
+	struct bpf_spin_lock lock;
+	int data;
+};
+
+struct array_map {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__type(key, int);
+	__type(value, struct foo);
+	__uint(max_entries, 1);
+} array_map SEC(".maps");
+
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY_OF_MAPS);
+	__uint(max_entries, 1);
+	__type(key, int);
+	__type(value, int);
+	__array(values, struct array_map);
+} map_of_maps SEC(".maps") = {
+	.values = {
+		[0] = &array_map,
+	},
+};
+
+SEC(".data.A") struct bpf_spin_lock lockA;
+SEC(".data.B") struct bpf_spin_lock lockB;
+
+SEC("?tc")
+int lock_id_kptr_preserve(void *ctx)
+{
+	struct foo *f;
+
+	f = bpf_obj_new(typeof(*f));
+	if (!f)
+		return 0;
+	bpf_this_cpu_ptr(f);
+	return 0;
+}
+
+SEC("?tc")
+int lock_id_global_zero(void *ctx)
+{
+	bpf_this_cpu_ptr(&lockA);
+	return 0;
+}
+
+SEC("?tc")
+int lock_id_mapval_preserve(void *ctx)
+{
+	struct foo *f;
+	int key = 0;
+
+	f = bpf_map_lookup_elem(&array_map, &key);
+	if (!f)
+		return 0;
+	bpf_this_cpu_ptr(f);
+	return 0;
+}
+
+SEC("?tc")
+int lock_id_innermapval_preserve(void *ctx)
+{
+	struct foo *f;
+	int key = 0;
+	void *map;
+
+	map = bpf_map_lookup_elem(&map_of_maps, &key);
+	if (!map)
+		return 0;
+	f = bpf_map_lookup_elem(map, &key);
+	if (!f)
+		return 0;
+	bpf_this_cpu_ptr(f);
+	return 0;
+}
+
+#define CHECK(test, A, B)                                      \
+	SEC("?tc")                                             \
+	int lock_id_mismatch_##test(void *ctx)                 \
+	{                                                      \
+		struct foo *f1, *f2, *v, *iv;                  \
+		int key = 0;                                   \
+		void *map;                                     \
+                                                               \
+		map = bpf_map_lookup_elem(&map_of_maps, &key); \
+		if (!map)                                      \
+			return 0;                              \
+		iv = bpf_map_lookup_elem(map, &key);           \
+		if (!iv)                                       \
+			return 0;                              \
+		v = bpf_map_lookup_elem(&array_map, &key);     \
+		if (!v)                                        \
+			return 0;                              \
+		f1 = bpf_obj_new(typeof(*f1));                 \
+		if (!f1)                                       \
+			return 0;                              \
+		f2 = bpf_obj_new(typeof(*f2));                 \
+		if (!f2) {                                     \
+			bpf_obj_drop(f1);                      \
+			return 0;                              \
+		}                                              \
+		bpf_spin_lock(A);                              \
+		bpf_spin_unlock(B);                            \
+		return 0;                                      \
+	}
+
+CHECK(kptr_kptr, &f1->lock, &f2->lock);
+CHECK(kptr_global, &f1->lock, &lockA);
+CHECK(kptr_mapval, &f1->lock, &v->lock);
+CHECK(kptr_innermapval, &f1->lock, &iv->lock);
+
+CHECK(global_global, &lockA, &lockB);
+CHECK(global_kptr, &lockA, &f1->lock);
+CHECK(global_mapval, &lockA, &v->lock);
+CHECK(global_innermapval, &lockA, &iv->lock);
+
+SEC("?tc")
+int lock_id_mismatch_mapval_mapval(void *ctx)
+{
+	struct foo *f1, *f2;
+	int key = 0;
+
+	f1 = bpf_map_lookup_elem(&array_map, &key);
+	if (!f1)
+		return 0;
+	f2 = bpf_map_lookup_elem(&array_map, &key);
+	if (!f2)
+		return 0;
+
+	bpf_spin_lock(&f1->lock);
+	f1->data = 42;
+	bpf_spin_unlock(&f2->lock);
+
+	return 0;
+}
+
+CHECK(mapval_kptr, &v->lock, &f1->lock);
+CHECK(mapval_global, &v->lock, &lockB);
+CHECK(mapval_innermapval, &v->lock, &iv->lock);
+
+SEC("?tc")
+int lock_id_mismatch_innermapval_innermapval1(void *ctx)
+{
+	struct foo *f1, *f2;
+	int key = 0;
+	void *map;
+
+	map = bpf_map_lookup_elem(&map_of_maps, &key);
+	if (!map)
+		return 0;
+	f1 = bpf_map_lookup_elem(map, &key);
+	if (!f1)
+		return 0;
+	f2 = bpf_map_lookup_elem(map, &key);
+	if (!f2)
+		return 0;
+
+	bpf_spin_lock(&f1->lock);
+	f1->data = 42;
+	bpf_spin_unlock(&f2->lock);
+
+	return 0;
+}
+
+SEC("?tc")
+int lock_id_mismatch_innermapval_innermapval2(void *ctx)
+{
+	struct foo *f1, *f2;
+	int key = 0;
+	void *map;
+
+	map = bpf_map_lookup_elem(&map_of_maps, &key);
+	if (!map)
+		return 0;
+	f1 = bpf_map_lookup_elem(map, &key);
+	if (!f1)
+		return 0;
+	map = bpf_map_lookup_elem(&map_of_maps, &key);
+	if (!map)
+		return 0;
+	f2 = bpf_map_lookup_elem(map, &key);
+	if (!f2)
+		return 0;
+
+	bpf_spin_lock(&f1->lock);
+	f1->data = 42;
+	bpf_spin_unlock(&f2->lock);
+
+	return 0;
+}
+
+CHECK(innermapval_kptr, &iv->lock, &f1->lock);
+CHECK(innermapval_global, &iv->lock, &lockA);
+CHECK(innermapval_mapval, &iv->lock, &v->lock);
+
+#undef CHECK
+
+char _license[] SEC("license") = "GPL";
-- 
2.38.1

[PATCH bpf-next v5 24/25] selftests/bpf: Add BPF linked list API tests

[Kumar Kartikeya Dwivedi]

Include various tests covering the success and failure cases. Also, run
the success cases at runtime to verify correctness of linked list
manipulation routines, in addition to ensuring successful verification.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 tools/testing/selftests/bpf/DENYLIST.s390x    |   1 +
 .../selftests/bpf/prog_tests/linked_list.c    | 253 ++++++++
 .../testing/selftests/bpf/progs/linked_list.c | 370 +++++++++++
 .../testing/selftests/bpf/progs/linked_list.h |  56 ++
 .../selftests/bpf/progs/linked_list_fail.c    | 581 ++++++++++++++++++
 5 files changed, 1261 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/linked_list.c
 create mode 100644 tools/testing/selftests/bpf/progs/linked_list.c
 create mode 100644 tools/testing/selftests/bpf/progs/linked_list.h
 create mode 100644 tools/testing/selftests/bpf/progs/linked_list_fail.c

diff --git a/tools/testing/selftests/bpf/DENYLIST.s390x b/tools/testing/selftests/bpf/DENYLIST.s390x
index be4e3d47ea3e..072243af93b0 100644
--- a/tools/testing/selftests/bpf/DENYLIST.s390x
+++ b/tools/testing/selftests/bpf/DENYLIST.s390x
@@ -33,6 +33,7 @@ ksyms_module                             # test_ksyms_module__open_and_load unex
 ksyms_module_libbpf                      # JIT does not support calling kernel function                                (kfunc)
 ksyms_module_lskel                       # test_ksyms_module_lskel__open_and_load unexpected error: -9                 (?)
 libbpf_get_fd_by_id_opts                 # failed to attach: ERROR: strerror_r(-524)=22                                (trampoline)
+linked_list				 # JIT does not support calling kernel function                                (kfunc)
 lookup_key                               # JIT does not support calling kernel function                                (kfunc)
 lru_bug                                  # prog 'printk': failed to auto-attach: -524
 map_kptr                                 # failed to open_and_load program: -524 (trampoline)
diff --git a/tools/testing/selftests/bpf/prog_tests/linked_list.c b/tools/testing/selftests/bpf/prog_tests/linked_list.c
new file mode 100644
index 000000000000..669ef4bb9b87
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/linked_list.c
@@ -0,0 +1,253 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <test_progs.h>
+#include <network_helpers.h>
+
+#include "linked_list.skel.h"
+#include "linked_list_fail.skel.h"
+
+static char log_buf[1024 * 1024];
+
+static struct {
+	const char *prog_name;
+	const char *err_msg;
+} linked_list_fail_tests[] = {
+#define TEST(test, off) \
+	{ #test "_missing_lock_push_front", \
+	  "bpf_spin_lock at off=" #off " must be held for bpf_list_head" }, \
+	{ #test "_missing_lock_push_back", \
+	  "bpf_spin_lock at off=" #off " must be held for bpf_list_head" }, \
+	{ #test "_missing_lock_pop_front", \
+	  "bpf_spin_lock at off=" #off " must be held for bpf_list_head" }, \
+	{ #test "_missing_lock_pop_back", \
+	  "bpf_spin_lock at off=" #off " must be held for bpf_list_head" },
+	TEST(kptr, 32)
+	TEST(global, 16)
+	TEST(map, 0)
+	TEST(inner_map, 0)
+#undef TEST
+#define TEST(test, op) \
+	{ #test "_kptr_incorrect_lock_" #op, \
+	  "held lock and object are not in the same allocation\n" \
+	  "bpf_spin_lock at off=32 must be held for bpf_list_head" }, \
+	{ #test "_global_incorrect_lock_" #op, \
+	  "held lock and object are not in the same allocation\n" \
+	  "bpf_spin_lock at off=16 must be held for bpf_list_head" }, \
+	{ #test "_map_incorrect_lock_" #op, \
+	  "held lock and object are not in the same allocation\n" \
+	  "bpf_spin_lock at off=0 must be held for bpf_list_head" }, \
+	{ #test "_inner_map_incorrect_lock_" #op, \
+	  "held lock and object are not in the same allocation\n" \
+	  "bpf_spin_lock at off=0 must be held for bpf_list_head" },
+	TEST(kptr, push_front)
+	TEST(kptr, push_back)
+	TEST(kptr, pop_front)
+	TEST(kptr, pop_back)
+	TEST(global, push_front)
+	TEST(global, push_back)
+	TEST(global, pop_front)
+	TEST(global, pop_back)
+	TEST(map, push_front)
+	TEST(map, push_back)
+	TEST(map, pop_front)
+	TEST(map, pop_back)
+	TEST(inner_map, push_front)
+	TEST(inner_map, push_back)
+	TEST(inner_map, pop_front)
+	TEST(inner_map, pop_back)
+#undef TEST
+	{ "map_compat_kprobe", "tracing progs cannot use bpf_list_head yet" },
+	{ "map_compat_kretprobe", "tracing progs cannot use bpf_list_head yet" },
+	{ "map_compat_tp", "tracing progs cannot use bpf_list_head yet" },
+	{ "map_compat_perf", "tracing progs cannot use bpf_list_head yet" },
+	{ "map_compat_raw_tp", "tracing progs cannot use bpf_list_head yet" },
+	{ "map_compat_raw_tp_w", "tracing progs cannot use bpf_list_head yet" },
+	{ "obj_type_id_oor", "local type ID argument must be in range [0, U32_MAX]" },
+	{ "obj_new_no_composite", "bpf_obj_new type ID argument must be of a struct" },
+	{ "obj_new_no_struct", "bpf_obj_new type ID argument must be of a struct" },
+	{ "obj_drop_non_zero_off", "R1 must have zero offset when passed to release func" },
+	{ "new_null_ret", "R0 invalid mem access 'ptr_or_null_'" },
+	{ "obj_new_acq", "Unreleased reference id=" },
+	{ "use_after_drop", "invalid mem access 'scalar'" },
+	{ "ptr_walk_scalar", "type=scalar expected=percpu_ptr_" },
+	{ "direct_read_lock", "direct access to bpf_spin_lock is disallowed" },
+	{ "direct_write_lock", "direct access to bpf_spin_lock is disallowed" },
+	{ "direct_read_head", "direct access to bpf_list_head is disallowed" },
+	{ "direct_write_head", "direct access to bpf_list_head is disallowed" },
+	{ "direct_read_node", "direct access to bpf_list_node is disallowed" },
+	{ "direct_write_node", "direct access to bpf_list_node is disallowed" },
+	{ "write_after_push_front", "only read is supported" },
+	{ "write_after_push_back", "only read is supported" },
+	{ "use_after_unlock_push_front", "invalid mem access 'scalar'" },
+	{ "use_after_unlock_push_back", "invalid mem access 'scalar'" },
+	{ "double_push_front", "arg#1 expected pointer to local kptr" },
+	{ "double_push_back", "arg#1 expected pointer to local kptr" },
+	{ "no_node_value_type", "bpf_list_node not found for local kptr\n" },
+	{ "incorrect_value_type", "bpf_list_head value type does not match arg#1" },
+	{ "incorrect_node_var_off", "variable ptr_ access var_off=(0x0; 0xffffffff) disallowed" },
+	{ "incorrect_node_off1", "bpf_list_node not found at offset=1" },
+	{ "incorrect_node_off2", "arg#1 offset must be for bpf_list_node at off=0" },
+	{ "no_head_type", "bpf_list_head not found for local kptr" },
+	{ "incorrect_head_var_off1", "R1 doesn't have constant offset" },
+	{ "incorrect_head_var_off2", "variable ptr_ access var_off=(0x0; 0xffffffff) disallowed" },
+	{ "incorrect_head_off1", "bpf_list_head not found at offset=17" },
+	{ "incorrect_head_off2", "bpf_list_head not found at offset=1" },
+	{ "pop_front_off",
+	  "15: (bf) r1 = r6                      ; R1_w=ptr_or_null_foo(id=4,ref_obj_id=4,off=40,imm=0) "
+	  "R6_w=ptr_or_null_foo(id=4,ref_obj_id=4,off=40,imm=0) refs=2,4\n"
+	  "16: (85) call bpf_this_cpu_ptr#154\nR1 type=ptr_or_null_ expected=percpu_ptr_" },
+	{ "pop_back_off",
+	  "15: (bf) r1 = r6                      ; R1_w=ptr_or_null_foo(id=4,ref_obj_id=4,off=40,imm=0) "
+	  "R6_w=ptr_or_null_foo(id=4,ref_obj_id=4,off=40,imm=0) refs=2,4\n"
+	  "16: (85) call bpf_this_cpu_ptr#154\nR1 type=ptr_or_null_ expected=percpu_ptr_" },
+};
+
+static void test_linked_list_fail_prog(const char *prog_name, const char *err_msg)
+{
+	LIBBPF_OPTS(bpf_object_open_opts, opts, .kernel_log_buf = log_buf,
+						.kernel_log_size = sizeof(log_buf),
+						.kernel_log_level = 1);
+	struct linked_list_fail *skel;
+	struct bpf_program *prog;
+	int ret;
+
+	skel = linked_list_fail__open_opts(&opts);
+	if (!ASSERT_OK_PTR(skel, "linked_list_fail__open_opts"))
+		return;
+
+	prog = bpf_object__find_program_by_name(skel->obj, prog_name);
+	if (!ASSERT_OK_PTR(prog, "bpf_object__find_program_by_name"))
+		goto end;
+
+	bpf_program__set_autoload(prog, true);
+
+	ret = linked_list_fail__load(skel);
+	if (!ASSERT_ERR(ret, "linked_list_fail__load must fail"))
+		goto end;
+
+	if (!ASSERT_OK_PTR(strstr(log_buf, err_msg), "expected error message")) {
+		fprintf(stderr, "Expected: %s\n", err_msg);
+		fprintf(stderr, "Verifier: %s\n", log_buf);
+	}
+
+end:
+	linked_list_fail__destroy(skel);
+}
+
+static void clear_fields(struct bpf_map *map)
+{
+	char buf[24];
+	int key = 0;
+
+	memset(buf, 0xff, sizeof(buf));
+	ASSERT_OK(bpf_map__update_elem(map, &key, sizeof(key), buf, sizeof(buf), 0), "check_and_free_fields");
+}
+
+enum {
+	TEST_ALL,
+	PUSH_POP,
+	PUSH_POP_MULT,
+	LIST_IN_LIST,
+};
+
+static void test_linked_list_success(int mode, bool leave_in_map)
+{
+	LIBBPF_OPTS(bpf_test_run_opts, opts,
+		.data_in = &pkt_v4,
+		.data_size_in = sizeof(pkt_v4),
+		.repeat = 1,
+	);
+	struct linked_list *skel;
+	int ret;
+
+	skel = linked_list__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "linked_list__open_and_load"))
+		return;
+
+	if (mode == LIST_IN_LIST)
+		goto lil;
+	if (mode == PUSH_POP_MULT)
+		goto ppm;
+
+	ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.map_list_push_pop), &opts);
+	ASSERT_OK(ret, "map_list_push_pop");
+	ASSERT_OK(opts.retval, "map_list_push_pop retval");
+	if (!leave_in_map)
+		clear_fields(skel->maps.array_map);
+
+	ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.inner_map_list_push_pop), &opts);
+	ASSERT_OK(ret, "inner_map_list_push_pop");
+	ASSERT_OK(opts.retval, "inner_map_list_push_pop retval");
+	if (!leave_in_map)
+		clear_fields(skel->maps.inner_map);
+
+	ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.global_list_push_pop), &opts);
+	ASSERT_OK(ret, "global_list_push_pop");
+	ASSERT_OK(opts.retval, "global_list_push_pop retval");
+	if (!leave_in_map)
+		clear_fields(skel->maps.data_A);
+
+	if (mode == PUSH_POP)
+		goto end;
+
+ppm:
+	ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.map_list_push_pop_multiple), &opts);
+	ASSERT_OK(ret, "map_list_push_pop_multiple");
+	ASSERT_OK(opts.retval, "map_list_push_pop_multiple retval");
+	if (!leave_in_map)
+		clear_fields(skel->maps.array_map);
+
+	ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.inner_map_list_push_pop_multiple), &opts);
+	ASSERT_OK(ret, "inner_map_list_push_pop_multiple");
+	ASSERT_OK(opts.retval, "inner_map_list_push_pop_multiple retval");
+	if (!leave_in_map)
+		clear_fields(skel->maps.inner_map);
+
+	ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.global_list_push_pop_multiple), &opts);
+	ASSERT_OK(ret, "global_list_push_pop_multiple");
+	ASSERT_OK(opts.retval, "global_list_push_pop_multiple retval");
+	if (!leave_in_map)
+		clear_fields(skel->maps.data_A);
+
+	if (mode == PUSH_POP_MULT)
+		goto end;
+
+lil:
+	ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.map_list_in_list), &opts);
+	ASSERT_OK(ret, "map_list_in_list");
+	ASSERT_OK(opts.retval, "map_list_in_list retval");
+	if (!leave_in_map)
+		clear_fields(skel->maps.array_map);
+
+	ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.inner_map_list_in_list), &opts);
+	ASSERT_OK(ret, "inner_map_list_in_list");
+	ASSERT_OK(opts.retval, "inner_map_list_in_list retval");
+	if (!leave_in_map)
+		clear_fields(skel->maps.inner_map);
+
+	ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.global_list_in_list), &opts);
+	ASSERT_OK(ret, "global_list_in_list");
+	ASSERT_OK(opts.retval, "global_list_in_list retval");
+	if (!leave_in_map)
+		clear_fields(skel->maps.data_A);
+end:
+	linked_list__destroy(skel);
+}
+
+void test_linked_list(void)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(linked_list_fail_tests); i++) {
+		if (!test__start_subtest(linked_list_fail_tests[i].prog_name))
+			continue;
+		test_linked_list_fail_prog(linked_list_fail_tests[i].prog_name,
+					   linked_list_fail_tests[i].err_msg);
+	}
+	test_linked_list_success(PUSH_POP, false);
+	test_linked_list_success(PUSH_POP, true);
+	test_linked_list_success(PUSH_POP_MULT, false);
+	test_linked_list_success(PUSH_POP_MULT, true);
+	test_linked_list_success(LIST_IN_LIST, false);
+	test_linked_list_success(LIST_IN_LIST, true);
+	test_linked_list_success(TEST_ALL, false);
+}
diff --git a/tools/testing/selftests/bpf/progs/linked_list.c b/tools/testing/selftests/bpf/progs/linked_list.c
new file mode 100644
index 000000000000..2c7b615c6d41
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/linked_list.c
@@ -0,0 +1,370 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <vmlinux.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_core_read.h>
+#include "bpf_experimental.h"
+
+#ifndef ARRAY_SIZE
+#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
+#endif
+
+#include "linked_list.h"
+
+static __always_inline
+int list_push_pop(struct bpf_spin_lock *lock, struct bpf_list_head *head, bool leave_in_map)
+{
+	struct bpf_list_node *n;
+	struct foo *f;
+
+	f = bpf_obj_new(typeof(*f));
+	if (!f)
+		return 2;
+
+	bpf_spin_lock(lock);
+	n = bpf_list_pop_front(head);
+	bpf_spin_unlock(lock);
+	if (n) {
+		bpf_obj_drop(container_of(n, struct foo, node));
+		bpf_obj_drop(f);
+		return 3;
+	}
+
+	bpf_spin_lock(lock);
+	n = bpf_list_pop_back(head);
+	bpf_spin_unlock(lock);
+	if (n) {
+		bpf_obj_drop(container_of(n, struct foo, node));
+		bpf_obj_drop(f);
+		return 4;
+	}
+
+
+	bpf_spin_lock(lock);
+	f->data = 42;
+	bpf_list_push_front(head, &f->node);
+	bpf_spin_unlock(lock);
+	if (leave_in_map)
+		return 0;
+	bpf_spin_lock(lock);
+	n = bpf_list_pop_back(head);
+	bpf_spin_unlock(lock);
+	if (!n)
+		return 5;
+	f = container_of(n, struct foo, node);
+	if (f->data != 42) {
+		bpf_obj_drop(f);
+		return 6;
+	}
+
+	bpf_spin_lock(lock);
+	f->data = 13;
+	bpf_list_push_front(head, &f->node);
+	bpf_spin_unlock(lock);
+	bpf_spin_lock(lock);
+	n = bpf_list_pop_front(head);
+	bpf_spin_unlock(lock);
+	if (!n)
+		return 7;
+	f = container_of(n, struct foo, node);
+	if (f->data != 13) {
+		bpf_obj_drop(f);
+		return 8;
+	}
+	bpf_obj_drop(f);
+
+	bpf_spin_lock(lock);
+	n = bpf_list_pop_front(head);
+	bpf_spin_unlock(lock);
+	if (n) {
+		bpf_obj_drop(container_of(n, struct foo, node));
+		return 9;
+	}
+
+	bpf_spin_lock(lock);
+	n = bpf_list_pop_back(head);
+	bpf_spin_unlock(lock);
+	if (n) {
+		bpf_obj_drop(container_of(n, struct foo, node));
+		return 10;
+	}
+	return 0;
+}
+
+
+static __always_inline
+int list_push_pop_multiple(struct bpf_spin_lock *lock, struct bpf_list_head *head, bool leave_in_map)
+{
+	struct bpf_list_node *n;
+	struct foo *f[8], *pf;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(f); i++) {
+		f[i] = bpf_obj_new(typeof(**f));
+		if (!f[i])
+			return 2;
+		f[i]->data = i;
+		bpf_spin_lock(lock);
+		bpf_list_push_front(head, &f[i]->node);
+		bpf_spin_unlock(lock);
+	}
+
+	for (i = 0; i < ARRAY_SIZE(f); i++) {
+		bpf_spin_lock(lock);
+		n = bpf_list_pop_front(head);
+		bpf_spin_unlock(lock);
+		if (!n)
+			return 3;
+		pf = container_of(n, struct foo, node);
+		if (pf->data != (ARRAY_SIZE(f) - i - 1)) {
+			bpf_obj_drop(pf);
+			return 4;
+		}
+		bpf_spin_lock(lock);
+		bpf_list_push_back(head, &pf->node);
+		bpf_spin_unlock(lock);
+	}
+
+	if (leave_in_map)
+		return 0;
+
+	for (i = 0; i < ARRAY_SIZE(f); i++) {
+		bpf_spin_lock(lock);
+		n = bpf_list_pop_back(head);
+		bpf_spin_unlock(lock);
+		if (!n)
+			return 5;
+		pf = container_of(n, struct foo, node);
+		if (pf->data != i) {
+			bpf_obj_drop(pf);
+			return 6;
+		}
+		bpf_obj_drop(pf);
+	}
+	bpf_spin_lock(lock);
+	n = bpf_list_pop_back(head);
+	bpf_spin_unlock(lock);
+	if (n) {
+		bpf_obj_drop(container_of(n, struct foo, node));
+		return 7;
+	}
+
+	bpf_spin_lock(lock);
+	n = bpf_list_pop_front(head);
+	bpf_spin_unlock(lock);
+	if (n) {
+		bpf_obj_drop(container_of(n, struct foo, node));
+		return 8;
+	}
+	return 0;
+}
+
+static __always_inline
+int list_in_list(struct bpf_spin_lock *lock, struct bpf_list_head *head, bool leave_in_map)
+{
+	struct bpf_list_node *n;
+	struct bar *ba[8], *b;
+	struct foo *f;
+	int i;
+
+	f = bpf_obj_new(typeof(*f));
+	if (!f)
+		return 2;
+	for (i = 0; i < ARRAY_SIZE(ba); i++) {
+		b = bpf_obj_new(typeof(*b));
+		if (!b) {
+			bpf_obj_drop(f);
+			return 3;
+		}
+		b->data = i;
+		bpf_spin_lock(&f->lock);
+		bpf_list_push_back(&f->head, &b->node);
+		bpf_spin_unlock(&f->lock);
+	}
+
+	bpf_spin_lock(lock);
+	f->data = 42;
+	bpf_list_push_front(head, &f->node);
+	bpf_spin_unlock(lock);
+
+	if (leave_in_map)
+		return 0;
+
+	bpf_spin_lock(lock);
+	n = bpf_list_pop_front(head);
+	bpf_spin_unlock(lock);
+	if (!n)
+		return 4;
+	f = container_of(n, struct foo, node);
+	if (f->data != 42) {
+		bpf_obj_drop(f);
+		return 5;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(ba); i++) {
+		bpf_spin_lock(&f->lock);
+		n = bpf_list_pop_front(&f->head);
+		bpf_spin_unlock(&f->lock);
+		if (!n) {
+			bpf_obj_drop(f);
+			return 6;
+		}
+		b = container_of(n, struct bar, node);
+		if (b->data != i) {
+			bpf_obj_drop(f);
+			bpf_obj_drop(b);
+			return 7;
+		}
+		bpf_obj_drop(b);
+	}
+	bpf_spin_lock(&f->lock);
+	n = bpf_list_pop_front(&f->head);
+	bpf_spin_unlock(&f->lock);
+	if (n) {
+		bpf_obj_drop(f);
+		bpf_obj_drop(container_of(n, struct bar, node));
+		return 8;
+	}
+	bpf_obj_drop(f);
+	return 0;
+}
+
+static __always_inline
+int test_list_push_pop(struct bpf_spin_lock *lock, struct bpf_list_head *head)
+{
+	int ret;
+
+	ret = list_push_pop(lock, head, false);
+	if (ret)
+		return ret;
+	return list_push_pop(lock, head, true);
+}
+
+static __always_inline
+int test_list_push_pop_multiple(struct bpf_spin_lock *lock, struct bpf_list_head *head)
+{
+	int ret;
+
+	ret = list_push_pop_multiple(lock ,head, false);
+	if (ret)
+		return ret;
+	return list_push_pop_multiple(lock, head, true);
+}
+
+static __always_inline
+int test_list_in_list(struct bpf_spin_lock *lock, struct bpf_list_head *head)
+{
+	int ret;
+
+	ret = list_in_list(lock, head, false);
+	if (ret)
+		return ret;
+	return list_in_list(lock, head, true);
+}
+
+SEC("tc")
+int map_list_push_pop(void *ctx)
+{
+	struct map_value *v;
+
+	v = bpf_map_lookup_elem(&array_map, &(int){0});
+	if (!v)
+		return 1;
+	return test_list_push_pop(&v->lock, &v->head);
+}
+
+SEC("tc")
+int inner_map_list_push_pop(void *ctx)
+{
+	struct map_value *v;
+	void *map;
+
+	map = bpf_map_lookup_elem(&map_of_maps, &(int){0});
+	if (!map)
+		return 1;
+	v = bpf_map_lookup_elem(map, &(int){0});
+	if (!v)
+		return 1;
+	return test_list_push_pop(&v->lock, &v->head);
+}
+
+SEC("tc")
+int global_list_push_pop(void *ctx)
+{
+	return test_list_push_pop(&glock, &ghead);
+}
+
+SEC("tc")
+int map_list_push_pop_multiple(void *ctx)
+{
+	struct map_value *v;
+	int ret;
+
+	v = bpf_map_lookup_elem(&array_map, &(int){0});
+	if (!v)
+		return 1;
+	return test_list_push_pop_multiple(&v->lock, &v->head);
+}
+
+SEC("tc")
+int inner_map_list_push_pop_multiple(void *ctx)
+{
+	struct map_value *v;
+	void *map;
+	int ret;
+
+	map = bpf_map_lookup_elem(&map_of_maps, &(int){0});
+	if (!map)
+		return 1;
+	v = bpf_map_lookup_elem(map, &(int){0});
+	if (!v)
+		return 1;
+	return test_list_push_pop_multiple(&v->lock, &v->head);
+}
+
+SEC("tc")
+int global_list_push_pop_multiple(void *ctx)
+{
+	int ret;
+
+	ret = list_push_pop_multiple(&glock, &ghead, false);
+	if (ret)
+		return ret;
+	return list_push_pop_multiple(&glock, &ghead, true);
+}
+
+SEC("tc")
+int map_list_in_list(void *ctx)
+{
+	struct map_value *v;
+	int ret;
+
+	v = bpf_map_lookup_elem(&array_map, &(int){0});
+	if (!v)
+		return 1;
+	return test_list_in_list(&v->lock, &v->head);
+}
+
+SEC("tc")
+int inner_map_list_in_list(void *ctx)
+{
+	struct map_value *v;
+	void *map;
+	int ret;
+
+	map = bpf_map_lookup_elem(&map_of_maps, &(int){0});
+	if (!map)
+		return 1;
+	v = bpf_map_lookup_elem(map, &(int){0});
+	if (!v)
+		return 1;
+	return test_list_in_list(&v->lock, &v->head);
+}
+
+SEC("tc")
+int global_list_in_list(void *ctx)
+{
+	return test_list_in_list(&glock, &ghead);
+}
+
+char _license[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/progs/linked_list.h b/tools/testing/selftests/bpf/progs/linked_list.h
new file mode 100644
index 000000000000..8db80ed64db1
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/linked_list.h
@@ -0,0 +1,56 @@
+// SPDX-License-Identifier: GPL-2.0
+#ifndef LINKED_LIST_H
+#define LINKED_LIST_H
+
+#include <vmlinux.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_experimental.h"
+
+struct bar {
+	struct bpf_list_node node;
+	int data;
+};
+
+struct foo {
+	struct bpf_list_node node;
+	struct bpf_list_head head __contains(bar, node);
+	struct bpf_spin_lock lock;
+	int data;
+	struct bpf_list_node node2;
+};
+
+struct map_value {
+	struct bpf_spin_lock lock;
+	int data;
+	struct bpf_list_head head __contains(foo, node);
+};
+
+struct array_map {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__type(key, int);
+	__type(value, struct map_value);
+	__uint(max_entries, 1);
+};
+
+struct array_map array_map SEC(".maps");
+struct array_map inner_map SEC(".maps");
+
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY_OF_MAPS);
+	__uint(max_entries, 1);
+	__type(key, int);
+	__type(value, int);
+	__array(values, struct array_map);
+} map_of_maps SEC(".maps") = {
+	.values = {
+		[0] = &inner_map,
+	},
+};
+
+#define private(name) SEC(".data." #name) __hidden __attribute__((aligned(8)))
+
+private(A) struct bpf_spin_lock glock;
+private(A) struct bpf_list_head ghead __contains(foo, node);
+private(B) struct bpf_spin_lock glock2;
+
+#endif
diff --git a/tools/testing/selftests/bpf/progs/linked_list_fail.c b/tools/testing/selftests/bpf/progs/linked_list_fail.c
new file mode 100644
index 000000000000..1d9017240e19
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/linked_list_fail.c
@@ -0,0 +1,581 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <vmlinux.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_core_read.h>
+#include "bpf_experimental.h"
+
+#include "linked_list.h"
+
+#define INIT                                                  \
+	struct map_value *v, *v2, *iv, *iv2;                  \
+	struct foo *f, *f1, *f2;                              \
+	struct bar *b;                                        \
+	void *map;                                            \
+                                                              \
+	map = bpf_map_lookup_elem(&map_of_maps, &(int){ 0 }); \
+	if (!map)                                             \
+		return 0;                                     \
+	v = bpf_map_lookup_elem(&array_map, &(int){ 0 });     \
+	if (!v)                                               \
+		return 0;                                     \
+	v2 = bpf_map_lookup_elem(&array_map, &(int){ 0 });    \
+	if (!v2)                                              \
+		return 0;                                     \
+	iv = bpf_map_lookup_elem(map, &(int){ 0 });           \
+	if (!iv)                                              \
+		return 0;                                     \
+	iv2 = bpf_map_lookup_elem(map, &(int){ 0 });          \
+	if (!iv2)                                             \
+		return 0;                                     \
+	f = bpf_obj_new(typeof(*f));                          \
+	if (!f)                                               \
+		return 0;                                     \
+	f1 = f;                                               \
+	f2 = bpf_obj_new(typeof(*f2));                        \
+	if (!f2) {                                            \
+		bpf_obj_drop(f1);                             \
+		return 0;                                     \
+	}                                                     \
+	b = bpf_obj_new(typeof(*b));                          \
+	if (!b) {                                             \
+		bpf_obj_drop(f2);                             \
+		bpf_obj_drop(f1);                             \
+		return 0;                                     \
+	}
+
+#define CHECK(test, op, hexpr)                              \
+	SEC("?tc")                                          \
+	int test##_missing_lock_##op(void *ctx)             \
+	{                                                   \
+		INIT;                                       \
+		void (*p)(void *) = (void *)&bpf_list_##op; \
+		p(hexpr);                                   \
+		return 0;                                   \
+	}
+
+CHECK(kptr, push_front, &f->head);
+CHECK(kptr, push_back, &f->head);
+CHECK(kptr, pop_front, &f->head);
+CHECK(kptr, pop_back, &f->head);
+
+CHECK(global, push_front, &ghead);
+CHECK(global, push_back, &ghead);
+CHECK(global, pop_front, &ghead);
+CHECK(global, pop_back, &ghead);
+
+CHECK(map, push_front, &v->head);
+CHECK(map, push_back, &v->head);
+CHECK(map, pop_front, &v->head);
+CHECK(map, pop_back, &v->head);
+
+CHECK(inner_map, push_front, &iv->head);
+CHECK(inner_map, push_back, &iv->head);
+CHECK(inner_map, pop_front, &iv->head);
+CHECK(inner_map, pop_back, &iv->head);
+
+#undef CHECK
+
+#define CHECK(test, op, lexpr, hexpr)                       \
+	SEC("?tc")                                          \
+	int test##_incorrect_lock_##op(void *ctx)           \
+	{                                                   \
+		INIT;                                       \
+		void (*p)(void *) = (void *)&bpf_list_##op; \
+		bpf_spin_lock(lexpr);                       \
+		p(hexpr);                                   \
+		return 0;                                   \
+	}
+
+#define CHECK_OP(op)                                           \
+	CHECK(kptr_kptr, op, &f1->lock, &f2->head);            \
+	CHECK(kptr_global, op, &f1->lock, &ghead);             \
+	CHECK(kptr_map, op, &f1->lock, &v->head);              \
+	CHECK(kptr_inner_map, op, &f1->lock, &iv->head);       \
+                                                               \
+	CHECK(global_global, op, &glock2, &ghead);             \
+	CHECK(global_kptr, op, &glock, &f1->head);             \
+	CHECK(global_map, op, &glock, &v->head);               \
+	CHECK(global_inner_map, op, &glock, &iv->head);        \
+                                                               \
+	CHECK(map_map, op, &v->lock, &v2->head);               \
+	CHECK(map_kptr, op, &v->lock, &f2->head);              \
+	CHECK(map_global, op, &v->lock, &ghead);               \
+	CHECK(map_inner_map, op, &v->lock, &iv->head);         \
+                                                               \
+	CHECK(inner_map_inner_map, op, &iv->lock, &iv2->head); \
+	CHECK(inner_map_kptr, op, &iv->lock, &f2->head);       \
+	CHECK(inner_map_global, op, &iv->lock, &ghead);        \
+	CHECK(inner_map_map, op, &iv->lock, &v->head);
+
+CHECK_OP(push_front);
+CHECK_OP(push_back);
+CHECK_OP(pop_front);
+CHECK_OP(pop_back);
+
+#undef CHECK
+#undef CHECK_OP
+#undef INIT
+
+SEC("?kprobe/xyz")
+int map_compat_kprobe(void *ctx)
+{
+	bpf_list_push_front(&ghead, NULL);
+	return 0;
+}
+
+SEC("?kretprobe/xyz")
+int map_compat_kretprobe(void *ctx)
+{
+	bpf_list_push_front(&ghead, NULL);
+	return 0;
+}
+
+SEC("?tracepoint/xyz")
+int map_compat_tp(void *ctx)
+{
+	bpf_list_push_front(&ghead, NULL);
+	return 0;
+}
+
+SEC("?perf_event")
+int map_compat_perf(void *ctx)
+{
+	bpf_list_push_front(&ghead, NULL);
+	return 0;
+}
+
+SEC("?raw_tp/xyz")
+int map_compat_raw_tp(void *ctx)
+{
+	bpf_list_push_front(&ghead, NULL);
+	return 0;
+}
+
+SEC("?raw_tp.w/xyz")
+int map_compat_raw_tp_w(void *ctx)
+{
+	bpf_list_push_front(&ghead, NULL);
+	return 0;
+}
+
+SEC("?tc")
+int obj_type_id_oor(void *ctx)
+{
+	bpf_obj_new_impl(~0UL, NULL);
+	return 0;
+}
+
+SEC("?tc")
+int obj_new_no_composite(void *ctx)
+{
+	bpf_obj_new_impl(bpf_core_type_id_local(int), (void *)42);
+	return 0;
+}
+
+SEC("?tc")
+int obj_new_no_struct(void *ctx)
+{
+
+	bpf_obj_new(union { int data; unsigned udata; });
+	return 0;
+}
+
+SEC("?tc")
+int obj_drop_non_zero_off(void *ctx)
+{
+	void *f;
+
+	f = bpf_obj_new(struct foo);
+	if (!f)
+		return 0;
+	bpf_obj_drop(f+1);
+	return 0;
+}
+
+SEC("?tc")
+int new_null_ret(void *ctx)
+{
+	return bpf_obj_new(struct foo)->data;
+}
+
+SEC("?tc")
+int obj_new_acq(void *ctx)
+{
+	bpf_obj_new(struct foo);
+	return 0;
+}
+
+SEC("?tc")
+int use_after_drop(void *ctx)
+{
+	struct foo *f;
+
+	f = bpf_obj_new(typeof(*f));
+	if (!f)
+		return 0;
+	bpf_obj_drop(f);
+	return f->data;
+}
+
+SEC("?tc")
+int ptr_walk_scalar(void *ctx)
+{
+	struct test1 {
+		struct test2 {
+			struct test2 *next;
+		} *ptr;
+	} *p;
+
+	p = bpf_obj_new(typeof(*p));
+	if (!p)
+		return 0;
+	bpf_this_cpu_ptr(p->ptr);
+	return 0;
+}
+
+SEC("?tc")
+int direct_read_lock(void *ctx)
+{
+	struct foo *f;
+
+	f = bpf_obj_new(typeof(*f));
+	if (!f)
+		return 0;
+	return *(int *)&f->lock;
+}
+
+SEC("?tc")
+int direct_write_lock(void *ctx)
+{
+	struct foo *f;
+
+	f = bpf_obj_new(typeof(*f));
+	if (!f)
+		return 0;
+	*(int *)&f->lock = 0;
+	return 0;
+}
+
+SEC("?tc")
+int direct_read_head(void *ctx)
+{
+	struct foo *f;
+
+	f = bpf_obj_new(typeof(*f));
+	if (!f)
+		return 0;
+	return *(int *)&f->head;
+}
+
+SEC("?tc")
+int direct_write_head(void *ctx)
+{
+	struct foo *f;
+
+	f = bpf_obj_new(typeof(*f));
+	if (!f)
+		return 0;
+	*(int *)&f->head = 0;
+	return 0;
+}
+
+SEC("?tc")
+int direct_read_node(void *ctx)
+{
+	struct foo *f;
+
+	f = bpf_obj_new(typeof(*f));
+	if (!f)
+		return 0;
+	return *(int *)&f->node;
+}
+
+SEC("?tc")
+int direct_write_node(void *ctx)
+{
+	struct foo *f;
+
+	f = bpf_obj_new(typeof(*f));
+	if (!f)
+		return 0;
+	*(int *)&f->node = 0;
+	return 0;
+}
+
+static __always_inline
+int write_after_op(void (*push_op)(void *head, void *node))
+{
+	struct foo *f;
+
+	f = bpf_obj_new(typeof(*f));
+	if (!f)
+		return 0;
+	bpf_spin_lock(&glock);
+	push_op(&ghead, &f->node);
+	f->data = 42;
+	bpf_spin_unlock(&glock);
+
+	return 0;
+}
+
+SEC("?tc")
+int write_after_push_front(void *ctx)
+{
+	return write_after_op((void *)bpf_list_push_front);
+}
+
+SEC("?tc")
+int write_after_push_back(void *ctx)
+{
+	return write_after_op((void *)bpf_list_push_back);
+}
+
+static __always_inline
+int use_after_unlock(void (*op)(void *head, void *node))
+{
+	struct foo *f;
+
+	f = bpf_obj_new(typeof(*f));
+	if (!f)
+		return 0;
+	bpf_spin_lock(&glock);
+	f->data = 42;
+	op(&ghead, &f->node);
+	bpf_spin_unlock(&glock);
+
+	return f->data;
+}
+
+SEC("?tc")
+int use_after_unlock_push_front(void *ctx)
+{
+	return use_after_unlock((void *)bpf_list_push_front);
+}
+
+SEC("?tc")
+int use_after_unlock_push_back(void *ctx)
+{
+	return use_after_unlock((void *)bpf_list_push_back);
+}
+
+static __always_inline
+int list_double_add(void (*op)(void *head, void *node))
+{
+	struct foo *f;
+
+	f = bpf_obj_new(typeof(*f));
+	if (!f)
+		return 0;
+	bpf_spin_lock(&glock);
+	op(&ghead, &f->node);
+	op(&ghead, &f->node);
+	bpf_spin_unlock(&glock);
+
+	return 0;
+}
+
+SEC("?tc")
+int double_push_front(void *ctx)
+{
+	return list_double_add((void *)bpf_list_push_front);
+}
+
+SEC("?tc")
+int double_push_back(void *ctx)
+{
+	return list_double_add((void *)bpf_list_push_back);
+}
+
+SEC("?tc")
+int no_node_value_type(void *ctx)
+{
+	void *p;
+
+	p = bpf_obj_new(struct { int data; });
+	if (!p)
+		return 0;
+	bpf_spin_lock(&glock);
+	bpf_list_push_front(&ghead, p);
+	bpf_spin_unlock(&glock);
+
+	return 0;
+}
+
+SEC("?tc")
+int incorrect_value_type(void *ctx)
+{
+	struct bar *b;
+
+	b = bpf_obj_new(typeof(*b));
+	if (!b)
+		return 0;
+	bpf_spin_lock(&glock);
+	bpf_list_push_front(&ghead, &b->node);
+	bpf_spin_unlock(&glock);
+
+	return 0;
+}
+
+SEC("?tc")
+int incorrect_node_var_off(struct __sk_buff *ctx)
+{
+	struct foo *f;
+
+	f = bpf_obj_new(typeof(*f));
+	if (!f)
+		return 0;
+	bpf_spin_lock(&glock);
+	bpf_list_push_front(&ghead, (void *)&f->node + ctx->protocol);
+	bpf_spin_unlock(&glock);
+
+	return 0;
+}
+
+SEC("?tc")
+int incorrect_node_off1(void *ctx)
+{
+	struct foo *f;
+
+	f = bpf_obj_new(typeof(*f));
+	if (!f)
+		return 0;
+	bpf_spin_lock(&glock);
+	bpf_list_push_front(&ghead, (void *)&f->node + 1);
+	bpf_spin_unlock(&glock);
+
+	return 0;
+}
+
+SEC("?tc")
+int incorrect_node_off2(void *ctx)
+{
+	struct foo *f;
+
+	f = bpf_obj_new(typeof(*f));
+	if (!f)
+		return 0;
+	bpf_spin_lock(&glock);
+	bpf_list_push_front(&ghead, &f->node2);
+	bpf_spin_unlock(&glock);
+
+	return 0;
+}
+
+SEC("?tc")
+int no_head_type(void *ctx)
+{
+	void *p;
+
+	p = bpf_obj_new(typeof(struct { int data; }));
+	if (!p)
+		return 0;
+	bpf_spin_lock(&glock);
+	bpf_list_push_front(p, NULL);
+	bpf_spin_lock(&glock);
+
+	return 0;
+}
+
+SEC("?tc")
+int incorrect_head_var_off1(struct __sk_buff *ctx)
+{
+	struct foo *f;
+
+	f = bpf_obj_new(typeof(*f));
+	if (!f)
+		return 0;
+	bpf_spin_lock(&glock);
+	bpf_list_push_front((void *)&ghead + ctx->protocol, &f->node);
+	bpf_spin_unlock(&glock);
+
+	return 0;
+}
+
+SEC("?tc")
+int incorrect_head_var_off2(struct __sk_buff *ctx)
+{
+	struct foo *f;
+
+	f = bpf_obj_new(typeof(*f));
+	if (!f)
+		return 0;
+	bpf_spin_lock(&glock);
+	bpf_list_push_front((void *)&f->head + ctx->protocol, &f->node);
+	bpf_spin_unlock(&glock);
+
+	return 0;
+}
+
+SEC("?tc")
+int incorrect_head_off1(void *ctx)
+{
+	struct foo *f;
+	struct bar *b;
+
+	f = bpf_obj_new(typeof(*f));
+	if (!f)
+		return 0;
+	b = bpf_obj_new(typeof(*b));
+	if (!b) {
+		bpf_obj_drop(f);
+		return 0;
+	}
+
+	bpf_spin_lock(&f->lock);
+	bpf_list_push_front((void *)&f->head + 1, &b->node);
+	bpf_spin_unlock(&f->lock);
+
+	return 0;
+}
+
+SEC("?tc")
+int incorrect_head_off2(void *ctx)
+{
+	struct foo *f;
+	struct bar *b;
+
+	f = bpf_obj_new(typeof(*f));
+	if (!f)
+		return 0;
+
+	bpf_spin_lock(&glock);
+	bpf_list_push_front((void *)&ghead + 1, &f->node);
+	bpf_spin_unlock(&glock);
+
+	return 0;
+}
+
+static __always_inline
+int pop_ptr_off(void *(*op)(void *head))
+{
+	struct {
+		struct bpf_list_head head __contains(foo, node2);
+		struct bpf_spin_lock lock;
+	} *p;
+	struct bpf_list_node *n;
+
+	p = bpf_obj_new(typeof(*p));
+	if (!p)
+		return 0;
+	bpf_spin_lock(&p->lock);
+	n = op(&p->head);
+	bpf_spin_unlock(&p->lock);
+
+	bpf_this_cpu_ptr(n);
+	return 0;
+}
+
+SEC("?tc")
+int pop_front_off(void *ctx)
+{
+	return pop_ptr_off((void *)bpf_list_pop_front);
+}
+
+SEC("?tc")
+int pop_back_off(void *ctx)
+{
+	return pop_ptr_off((void *)bpf_list_pop_back);
+}
+
+char _license[] SEC("license") = "GPL";
-- 
2.38.1

[PATCH bpf-next v5 25/25] selftests/bpf: Add BTF sanity tests

[Kumar Kartikeya Dwivedi]

Preparing the metadata for bpf_list_head involves a complicated parsing
step and type resolution for the contained value. Ensure that corner
cases are tested against and invalid specifications in source are duly
rejected. Also include tests for incorrect ownership relationships in
the BTF.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 .../selftests/bpf/prog_tests/linked_list.c    | 271 ++++++++++++++++++
 1 file changed, 271 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/linked_list.c b/tools/testing/selftests/bpf/prog_tests/linked_list.c
index 669ef4bb9b87..40070e2d22f2 100644
--- a/tools/testing/selftests/bpf/prog_tests/linked_list.c
+++ b/tools/testing/selftests/bpf/prog_tests/linked_list.c
@@ -1,4 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
+#include <bpf/btf.h>
+#include <test_btf.h>
+#include <linux/btf.h>
 #include <test_progs.h>
 #include <network_helpers.h>
 
@@ -233,6 +236,273 @@ static void test_linked_list_success(int mode, bool leave_in_map)
 	linked_list__destroy(skel);
 }
 
+/* struct bpf_spin_lock {
+ *   int foo;
+ * };
+ * struct bpf_list_head {
+ *   __u64 :64;
+ *   __u64 :64;
+ * } __attribute__((aligned(8)));
+ * struct bpf_list_node {
+ *   __u64 :64;
+ *   __u64 :64;
+ * } __attribute__((aligned(8)));
+ */
+static const char btf_str_sec[] = "\0bpf_spin_lock\0bpf_list_head\0bpf_list_node\0foo\0bar\0baz"
+				  "\0contains:foo:foo\0contains:bar:bar\0contains:baz:baz\0bam"
+				  "\0contains:bam:bam";
+
+#define INIT_BTF_TILL_4							\
+	/* int */							\
+	BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),  /* [1] */	\
+	/* struct bpf_spin_lock */                      /* [2] */	\
+	BTF_TYPE_ENC(1, BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 1), 4),	\
+	BTF_MEMBER_ENC(43, 1, 0),					\
+	/* struct bpf_list_head */                      /* [3] */	\
+	BTF_TYPE_ENC(15, BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 0), 16),	\
+	/* struct bpf_list_node */                      /* [4] */	\
+	BTF_TYPE_ENC(29, BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 0), 16),
+
+static void check_btf(u32 *types, u32 types_len, int error)
+{
+	LIBBPF_OPTS(bpf_btf_load_opts, opts,
+		    .log_buf = log_buf,
+		    .log_size = sizeof(log_buf),
+	);
+	struct btf_header hdr = {
+		.magic = BTF_MAGIC,
+		.version = BTF_VERSION,
+		.hdr_len = sizeof(struct btf_header),
+		.type_len = types_len,
+		.str_off = types_len,
+		.str_len = sizeof(btf_str_sec),
+	};
+	void *ptr, *raw_btf;
+	int fd, ret;
+
+	raw_btf = malloc(sizeof(hdr) + hdr.type_len + hdr.str_len);
+	if (!ASSERT_OK_PTR(raw_btf, "malloc(raw_btf)"))
+		return;
+
+	ptr = raw_btf;
+	memcpy(ptr, &hdr, sizeof(hdr));
+	ptr += sizeof(hdr);
+	memcpy(ptr, types, hdr.type_len);
+	ptr += hdr.type_len;
+	memcpy(ptr, btf_str_sec, hdr.str_len);
+	ptr += hdr.str_len;
+
+	fd = bpf_btf_load(raw_btf, ptr - raw_btf, &opts);
+	ret = fd < 0 ? -errno : 0;
+	if (fd >= 0)
+		close(fd);
+	if (error)
+		ASSERT_LT(fd, 0, "bpf_btf_load");
+	else
+		ASSERT_GE(fd, 0, "bpf_btf_load");
+	if (!ASSERT_EQ(ret, error, "-errno == error"))
+		printf("BTF Log:\n%s\n", log_buf);
+	free(raw_btf);
+	return;
+}
+
+#define SPIN_LOCK 2
+#define LIST_HEAD 3
+#define LIST_NODE 4
+#define FOO 43
+#define BAR 47
+#define BAZ 51
+#define BAM 106
+#define CONT_FOO_FOO 55
+#define CONT_BAR_BAR 72
+#define CONT_BAZ_BAZ 89
+#define CONT_BAM_BAM 110
+
+static void test_btf(void)
+{
+	if (test__start_subtest("btf: too many locks")) {
+		u32 types[] = {
+			INIT_BTF_TILL_4
+			BTF_TYPE_ENC(FOO, BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 3), 24), /* [5] */
+			BTF_MEMBER_ENC(BAZ, SPIN_LOCK, 0),
+			BTF_MEMBER_ENC(FOO, SPIN_LOCK, 32),
+			BTF_MEMBER_ENC(BAR, LIST_HEAD, 64),
+		};
+		check_btf(types, sizeof(types), -E2BIG);
+	}
+	if (test__start_subtest("btf: missing lock")) {
+		u32 types[] = {
+			INIT_BTF_TILL_4
+			BTF_TYPE_ENC(FOO, BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 1), 16), /* [5] */
+			BTF_MEMBER_ENC(BAR, LIST_HEAD, 0),
+			BTF_DECL_TAG_ENC(CONT_BAZ_BAZ, 5, 0),
+			BTF_TYPE_ENC(BAZ, BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 1), 16),
+			BTF_MEMBER_ENC(BAZ, LIST_NODE, 0),
+		};
+		check_btf(types, sizeof(types), -EINVAL);
+	}
+	if (test__start_subtest("btf: bad offset")) {
+		u32 types[] = {
+			INIT_BTF_TILL_4
+			BTF_TYPE_ENC(FOO, BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 3), 36), /* [5] */
+			BTF_MEMBER_ENC(BAR, LIST_HEAD, 0),
+			BTF_MEMBER_ENC(FOO, LIST_NODE, 0),
+			BTF_MEMBER_ENC(BAZ, SPIN_LOCK, 0),
+			BTF_DECL_TAG_ENC(CONT_FOO_FOO, 5, 0),
+		};
+		check_btf(types, sizeof(types), -EFAULT);
+	}
+	if (test__start_subtest("btf: missing contains:")) {
+		u32 types[] = {
+			INIT_BTF_TILL_4
+			BTF_TYPE_ENC(FOO, BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 2), 24), /* [5] */
+			BTF_MEMBER_ENC(BAZ, SPIN_LOCK, 0),
+			BTF_MEMBER_ENC(BAR, LIST_HEAD, 64),
+		};
+		check_btf(types, sizeof(types), -EINVAL);
+	}
+	if (test__start_subtest("btf: missing struct")) {
+		u32 types[] = {
+			INIT_BTF_TILL_4
+			BTF_TYPE_ENC(FOO, BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 2), 24), /* [5] */
+			BTF_MEMBER_ENC(BAZ, SPIN_LOCK, 0),
+			BTF_MEMBER_ENC(BAR, LIST_HEAD, 64),
+			BTF_DECL_TAG_ENC(CONT_BAR_BAR, 5, 1),
+		};
+		check_btf(types, sizeof(types), -ENOENT);
+	}
+	if (test__start_subtest("btf: missing node")) {
+		u32 types[] = {
+			INIT_BTF_TILL_4
+			BTF_TYPE_ENC(FOO, BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 2), 24), /* [5] */
+			BTF_MEMBER_ENC(BAZ, SPIN_LOCK, 0),
+			BTF_MEMBER_ENC(BAR, LIST_HEAD, 64),
+			BTF_DECL_TAG_ENC(CONT_FOO_FOO, 5, 1),
+		};
+		check_btf(types, sizeof(types), -ENOENT);
+	}
+	if (test__start_subtest("btf: node incorrect type")) {
+		u32 types[] = {
+			INIT_BTF_TILL_4
+			BTF_TYPE_ENC(FOO, BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 2), 20), /* [5] */
+			BTF_MEMBER_ENC(BAR, LIST_HEAD, 0),
+			BTF_MEMBER_ENC(BAR, SPIN_LOCK, 128),
+			BTF_DECL_TAG_ENC(CONT_BAZ_BAZ, 5, 0),
+			BTF_TYPE_ENC(BAZ, BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 1), 4),
+			BTF_MEMBER_ENC(BAZ, SPIN_LOCK, 0),
+		};
+		check_btf(types, sizeof(types), -EINVAL);
+	}
+	if (test__start_subtest("btf: multiple bpf_list_node with name foo")) {
+		u32 types[] = {
+			INIT_BTF_TILL_4
+			BTF_TYPE_ENC(FOO, BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 3), 52), /* [5] */
+			BTF_MEMBER_ENC(BAR, LIST_HEAD, 0),
+			BTF_MEMBER_ENC(FOO, LIST_NODE, 128),
+			BTF_MEMBER_ENC(FOO, LIST_NODE, 256),
+			BTF_MEMBER_ENC(BAZ, SPIN_LOCK, 384),
+			BTF_DECL_TAG_ENC(CONT_FOO_FOO, 5, 0),
+		};
+		check_btf(types, sizeof(types), -EINVAL);
+	}
+	if (test__start_subtest("btf: owning | owned AA cycle")) {
+		u32 types[] = {
+			INIT_BTF_TILL_4
+			BTF_TYPE_ENC(FOO, BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 3), 36), /* [5] */
+			BTF_MEMBER_ENC(BAR, LIST_HEAD, 0),
+			BTF_MEMBER_ENC(FOO, LIST_NODE, 128),
+			BTF_MEMBER_ENC(BAZ, SPIN_LOCK, 256),
+			BTF_DECL_TAG_ENC(CONT_FOO_FOO, 5, 0),
+		};
+		check_btf(types, sizeof(types), -ELOOP);
+	}
+	if (test__start_subtest("btf: owning | owned ABA cycle")) {
+		u32 types[] = {
+			INIT_BTF_TILL_4
+			BTF_TYPE_ENC(FOO, BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 3), 36), /* [5] */
+			BTF_MEMBER_ENC(BAR, LIST_HEAD, 0),
+			BTF_MEMBER_ENC(FOO, LIST_NODE, 128),
+			BTF_MEMBER_ENC(BAZ, SPIN_LOCK, 256),
+			BTF_DECL_TAG_ENC(CONT_BAR_BAR, 5, 0),			    /* [6] */
+			BTF_TYPE_ENC(BAR, BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 3), 36), /* [7] */
+			BTF_MEMBER_ENC(FOO, LIST_HEAD, 0),
+			BTF_MEMBER_ENC(BAR, LIST_NODE, 128),
+			BTF_MEMBER_ENC(BAZ, SPIN_LOCK, 256),
+			BTF_DECL_TAG_ENC(CONT_FOO_FOO, 7, 0),
+		};
+		check_btf(types, sizeof(types), -ELOOP);
+	}
+	if (test__start_subtest("btf: owning -> owned")) {
+		u32 types[] = {
+			INIT_BTF_TILL_4
+			BTF_TYPE_ENC(FOO, BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 2), 20), /* [5] */
+			BTF_MEMBER_ENC(BAR, LIST_HEAD, 0),
+			BTF_MEMBER_ENC(BAR, SPIN_LOCK, 128),
+			BTF_DECL_TAG_ENC(CONT_BAZ_BAZ, 5, 0),
+			BTF_TYPE_ENC(BAZ, BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 1), 16),
+			BTF_MEMBER_ENC(BAZ, LIST_NODE, 0),
+		};
+		check_btf(types, sizeof(types), 0);
+	}
+	if (test__start_subtest("btf: owning -> owning | owned -> owned")) {
+		u32 types[] = {
+			INIT_BTF_TILL_4
+			BTF_TYPE_ENC(FOO, BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 2), 20), /* [5] */
+			BTF_MEMBER_ENC(BAR, LIST_HEAD, 0),
+			BTF_MEMBER_ENC(BAZ, SPIN_LOCK, 128),
+			BTF_DECL_TAG_ENC(CONT_BAR_BAR, 5, 0),			    /* [6] */
+			BTF_TYPE_ENC(BAR, BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 3), 36), /* [7] */
+			BTF_MEMBER_ENC(FOO, LIST_HEAD, 0),
+			BTF_MEMBER_ENC(BAR, LIST_NODE, 128),
+			BTF_MEMBER_ENC(BAZ, SPIN_LOCK, 256),
+			BTF_DECL_TAG_ENC(CONT_BAZ_BAZ, 7, 0),
+			BTF_TYPE_ENC(BAZ, BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 1), 16),
+			BTF_MEMBER_ENC(BAZ, LIST_NODE, 0),
+		};
+		check_btf(types, sizeof(types), 0);
+	}
+	if (test__start_subtest("btf: owning | owned -> owning | owned -> owned")) {
+		u32 types[] = {
+			INIT_BTF_TILL_4
+			BTF_TYPE_ENC(FOO, BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 3), 36), /* [5] */
+			BTF_MEMBER_ENC(BAR, LIST_HEAD, 0),
+			BTF_MEMBER_ENC(FOO, LIST_NODE, 128),
+			BTF_MEMBER_ENC(BAZ, SPIN_LOCK, 256),
+			BTF_DECL_TAG_ENC(CONT_BAR_BAR, 5, 0),			    /* [6] */
+			BTF_TYPE_ENC(BAR, BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 3), 36), /* [7] */
+			BTF_MEMBER_ENC(FOO, LIST_HEAD, 0),
+			BTF_MEMBER_ENC(BAR, LIST_NODE, 128),
+			BTF_MEMBER_ENC(BAZ, SPIN_LOCK, 256),
+			BTF_DECL_TAG_ENC(CONT_BAZ_BAZ, 7, 0),
+			BTF_TYPE_ENC(BAZ, BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 1), 16),
+			BTF_MEMBER_ENC(BAZ, LIST_NODE, 0),
+		};
+		check_btf(types, sizeof(types), -ELOOP);
+	}
+	if (test__start_subtest("btf: owning -> owning | owned -> owning | owned -> owned")) {
+		u32 types[] = {
+			INIT_BTF_TILL_4
+			BTF_TYPE_ENC(FOO, BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 2), 20), /* [5] */
+			BTF_MEMBER_ENC(BAR, LIST_HEAD, 0),
+			BTF_MEMBER_ENC(BAZ, SPIN_LOCK, 128),
+			BTF_DECL_TAG_ENC(CONT_BAR_BAR, 5, 0),			    /* [6] */
+			BTF_TYPE_ENC(BAR, BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 3), 36), /* [7] */
+			BTF_MEMBER_ENC(FOO, LIST_HEAD, 0),
+			BTF_MEMBER_ENC(BAR, LIST_NODE, 128),
+			BTF_MEMBER_ENC(BAZ, SPIN_LOCK, 256),
+			BTF_DECL_TAG_ENC(CONT_BAZ_BAZ, 7, 0),
+			BTF_TYPE_ENC(BAZ, BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 3), 36), /* [9] */
+			BTF_MEMBER_ENC(BAR, LIST_HEAD, 0),
+			BTF_MEMBER_ENC(BAZ, LIST_NODE, 128),
+			BTF_MEMBER_ENC(FOO, SPIN_LOCK, 256),
+			BTF_DECL_TAG_ENC(CONT_BAM_BAM, 9, 0),
+			BTF_TYPE_ENC(BAM, BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 1), 16),
+			BTF_MEMBER_ENC(BAM, LIST_NODE, 0),
+		};
+		check_btf(types, sizeof(types), -ELOOP);
+	}
+}
+
 void test_linked_list(void)
 {
 	int i;
@@ -243,6 +513,7 @@ void test_linked_list(void)
 		test_linked_list_fail_prog(linked_list_fail_tests[i].prog_name,
 					   linked_list_fail_tests[i].err_msg);
 	}
+	test_btf();
 	test_linked_list_success(PUSH_POP, false);
 	test_linked_list_success(PUSH_POP, true);
 	test_linked_list_success(PUSH_POP_MULT, false);
-- 
2.38.1

Re: [PATCH bpf-next v5 03/25] bpf: Support bpf_list_head in map values

[Andrii Nakryiko]

On Mon, Nov 7, 2022 at 3:10 PM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
>
> Add the support on the map side to parse, recognize, verify, and build
> metadata table for a new special field of the type struct bpf_list_head.
> To parameterize the bpf_list_head for a certain value type and the
> list_node member it will accept in that value type, we use BTF
> declaration tags.
>
> The definition of bpf_list_head in a map value will be done as follows:
>
> struct foo {
>         struct bpf_list_node node;
>         int data;
> };
>
> struct map_value {
>         struct bpf_list_head head __contains(foo, node);
> };
>
> Then, the bpf_list_head only allows adding to the list 'head' using the
> bpf_list_node 'node' for the type struct foo.
>
> The 'contains' annotation is a BTF declaration tag composed of four
> parts, "contains:name:node" where the name is then used to look up the
> type in the map BTF, with its kind hardcoded to BTF_KIND_STRUCT during
> the lookup. The node defines name of the member in this type that has
> the type struct bpf_list_node, which is actually used for linking into
> the linked list. For now, 'kind' part is hardcoded as struct.
>
> This allows building intrusive linked lists in BPF, using container_of
> to obtain pointer to entry, while being completely type safe from the
> perspective of the verifier. The verifier knows exactly the type of the
> nodes, and knows that list helpers return that type at some fixed offset
> where the bpf_list_node member used for this list exists. The verifier
> also uses this information to disallow adding types that are not
> accepted by a certain list.
>
> For now, no elements can be added to such lists. Support for that is
> coming in future patches, hence draining and freeing items is done with
> a TODO that will be resolved in a future patch.
>
> Note that the bpf_list_head_free function moves the list out to a local
> variable under the lock and releases it, doing the actual draining of
> the list items outside the lock. While this helps with not holding the
> lock for too long pessimizing other concurrent list operations, it is
> also necessary for deadlock prevention: unless every function called in
> the critical section would be notrace, a fentry/fexit program could
> attach and call bpf_map_update_elem again on the map, leading to the
> same lock being acquired if the key matches and lead to a deadlock.
> While this requires some special effort on part of the BPF programmer to
> trigger and is highly unlikely to occur in practice, it is always better
> if we can avoid such a condition.
>
> While notrace would prevent this, doing the draining outside the lock
> has advantages of its own, hence it is used to also fix the deadlock
> related problem.
>
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> ---
>  include/linux/bpf.h            |  17 ++++
>  include/uapi/linux/bpf.h       |  10 +++
>  kernel/bpf/btf.c               | 143 ++++++++++++++++++++++++++++++++-
>  kernel/bpf/helpers.c           |  32 ++++++++
>  kernel/bpf/syscall.c           |  22 ++++-
>  kernel/bpf/verifier.c          |   7 ++
>  tools/include/uapi/linux/bpf.h |  10 +++
>  7 files changed, 237 insertions(+), 4 deletions(-)
>

[...]

>  struct bpf_offload_dev;
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 94659f6b3395..dd381086bad9 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -6887,6 +6887,16 @@ struct bpf_dynptr {
>         __u64 :64;
>  } __attribute__((aligned(8)));
>
> +struct bpf_list_head {
> +       __u64 :64;
> +       __u64 :64;
> +} __attribute__((aligned(8)));
> +
> +struct bpf_list_node {
> +       __u64 :64;
> +       __u64 :64;
> +} __attribute__((aligned(8)));

Dave mentioned that this `__u64 :64` trick makes vmlinux.h lose the
alignment information, as the struct itself is empty, and so there is
nothing indicating that it has to be 8-byte aligned.

So what if we have

struct bpf_list_node {
    __u64 __opaque[2];
} __attribute__((aligned(8)));

?

> +
>  struct bpf_sysctl {
>         __u32   write;          /* Sysctl is being read (= 0) or written (= 1).
>                                  * Allows 1,2,4-byte read, but no write.
> diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c

[...]

> @@ -3284,6 +3347,12 @@ static int btf_get_field_type(const char *name, u32 field_mask, u32 *seen_mask,
>                         goto end;
>                 }
>         }
> +       if (field_mask & BPF_LIST_HEAD) {
> +               if (!strcmp(name, "bpf_list_head")) {
> +                       type = BPF_LIST_HEAD;
> +                       goto end;
> +               }
> +       }
>         /* Only return BPF_KPTR when all other types with matchable names fail */
>         if (field_mask & BPF_KPTR) {
>                 type = BPF_KPTR_REF;
> @@ -3317,6 +3386,8 @@ static int btf_find_struct_field(const struct btf *btf,
>                         return field_type;
>
>                 off = __btf_member_bit_offset(t, member);
> +               if (i && !off)
> +                       return -EFAULT;

why? why can't my struct has zero-sized field in the beginning? This
seems like a very incomplete and unnecessary check to me.

>                 if (off % 8)
>                         /* valid C code cannot generate such BTF */
>                         return -EINVAL;
> @@ -3339,6 +3410,12 @@ static int btf_find_struct_field(const struct btf *btf,
>                         if (ret < 0)
>                                 return ret;
>                         break;
> +               case BPF_LIST_HEAD:
> +                       ret = btf_find_list_head(btf, t, member_type, i, off, sz,
> +                                                idx < info_cnt ? &info[idx] : &tmp);
> +                       if (ret < 0)
> +                               return ret;
> +                       break;
>                 default:
>                         return -EFAULT;
>                 }
> @@ -3373,6 +3450,8 @@ static int btf_find_datasec_var(const struct btf *btf, const struct btf_type *t,
>                         return field_type;
>
>                 off = vsi->offset;
> +               if (i && !off)
> +                       return -EFAULT;

similarly, I'd say that either we'd need to calculate the exact
expected offset, or just not do anything here?

>                 if (vsi->size != sz)
>                         continue;
>                 if (off % align)
> @@ -3393,6 +3472,12 @@ static int btf_find_datasec_var(const struct btf *btf, const struct btf_type *t,
>                         if (ret < 0)
>                                 return ret;
>                         break;
> +               case BPF_LIST_HEAD:
> +                       ret = btf_find_list_head(btf, var, var_type, -1, off, sz,
> +                                                idx < info_cnt ? &info[idx] : &tmp);
> +                       if (ret < 0)
> +                               return ret;
> +                       break;
>                 default:
>                         return -EFAULT;
>                 }

[...]

Re: [PATCH bpf-next v5 04/25] bpf: Rename RET_PTR_TO_ALLOC_MEM

[Andrii Nakryiko]

On Mon, Nov 7, 2022 at 3:10 PM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
>
> Currently, the verifier has two return types, RET_PTR_TO_ALLOC_MEM, and
> RET_PTR_TO_ALLOC_MEM_OR_NULL, however the former is confusingly named to
> imply that it carries MEM_ALLOC, while only the latter does. This causes
> confusion during code review leading to conclusions like that the return
> value of RET_PTR_TO_DYNPTR_MEM_OR_NULL (which is RET_PTR_TO_ALLOC_MEM |
> PTR_MAYBE_NULL) may be consumable by bpf_ringbuf_{submit,commit}.
>
> Rename it to make it clear MEM_ALLOC needs to be tacked on top of
> RET_PTR_TO_MEM.
>
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> ---

The whole MEM_ALLOC as related to ringbuf is so confusing. Why can't
be just call it for what it is: RET_PTR_TO_RINGBUF_MEM_OR_NULL,
ARG_PTR_TO_RINGBUF_MEM, PTR_TO_RINGBUF_MEM ?

It would be also much easier to make sure (by looking at the code)
that ringbuf invariants are properly checked.

>  include/linux/bpf.h   | 6 +++---
>  kernel/bpf/verifier.c | 2 +-
>  2 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 05f98e9e5c48..2fe3ec620d54 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -607,7 +607,7 @@ enum bpf_return_type {
>         RET_PTR_TO_SOCKET,              /* returns a pointer to a socket */
>         RET_PTR_TO_TCP_SOCK,            /* returns a pointer to a tcp_sock */
>         RET_PTR_TO_SOCK_COMMON,         /* returns a pointer to a sock_common */
> -       RET_PTR_TO_ALLOC_MEM,           /* returns a pointer to dynamically allocated memory */
> +       RET_PTR_TO_MEM,                 /* returns a pointer to memory */
>         RET_PTR_TO_MEM_OR_BTF_ID,       /* returns a pointer to a valid memory or a btf_id */
>         RET_PTR_TO_BTF_ID,              /* returns a pointer to a btf_id */
>         __BPF_RET_TYPE_MAX,
> @@ -617,8 +617,8 @@ enum bpf_return_type {
>         RET_PTR_TO_SOCKET_OR_NULL       = PTR_MAYBE_NULL | RET_PTR_TO_SOCKET,
>         RET_PTR_TO_TCP_SOCK_OR_NULL     = PTR_MAYBE_NULL | RET_PTR_TO_TCP_SOCK,
>         RET_PTR_TO_SOCK_COMMON_OR_NULL  = PTR_MAYBE_NULL | RET_PTR_TO_SOCK_COMMON,
> -       RET_PTR_TO_ALLOC_MEM_OR_NULL    = PTR_MAYBE_NULL | MEM_ALLOC | RET_PTR_TO_ALLOC_MEM,
> -       RET_PTR_TO_DYNPTR_MEM_OR_NULL   = PTR_MAYBE_NULL | RET_PTR_TO_ALLOC_MEM,
> +       RET_PTR_TO_ALLOC_MEM_OR_NULL    = PTR_MAYBE_NULL | MEM_ALLOC | RET_PTR_TO_MEM,
> +       RET_PTR_TO_DYNPTR_MEM_OR_NULL   = PTR_MAYBE_NULL | RET_PTR_TO_MEM,
>         RET_PTR_TO_BTF_ID_OR_NULL       = PTR_MAYBE_NULL | RET_PTR_TO_BTF_ID,
>
>         /* This must be the last entry. Its purpose is to ensure the enum is
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 0374f03d1f56..2407e3b179ec 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -7621,7 +7621,7 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
>                 mark_reg_known_zero(env, regs, BPF_REG_0);
>                 regs[BPF_REG_0].type = PTR_TO_TCP_SOCK | ret_flag;
>                 break;
> -       case RET_PTR_TO_ALLOC_MEM:
> +       case RET_PTR_TO_MEM:
>                 mark_reg_known_zero(env, regs, BPF_REG_0);
>                 regs[BPF_REG_0].type = PTR_TO_MEM | ret_flag;
>                 regs[BPF_REG_0].mem_size = meta.mem_size;
> --
> 2.38.1
>

Re: [PATCH bpf-next v5 05/25] bpf: Rename MEM_ALLOC to MEM_RINGBUF

[Andrii Nakryiko]

On Mon, Nov 7, 2022 at 3:10 PM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
>
> Currently, verifier uses MEM_ALLOC type tag to specially tag memory
> returned from bpf_ringbuf_reserve helper. However, this is currently
> only used for this purpose and there is an implicit assumption that it
> only refers to ringbuf memory (e.g. the check for ARG_PTR_TO_ALLOC_MEM
> in check_func_arg_reg_off).
>
> Hence, rename MEM_ALLOC to MEM_RINGBUF to indicate this special
> relationship and instead open the use of MEM_ALLOC for more generic
> allocations made for user types.
>
> Also, since ARG_PTR_TO_ALLOC_MEM_OR_NULL is unused, simply drop it.
>
> Finally, update selftests using 'alloc_' verifier string to 'ringbuf_'.
>
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> ---

Ok, so you are doing what I asked in the previous patch, nice :)

>  include/linux/bpf.h                               | 11 ++++-------
>  kernel/bpf/ringbuf.c                              |  6 +++---
>  kernel/bpf/verifier.c                             | 14 +++++++-------
>  tools/testing/selftests/bpf/prog_tests/dynptr.c   |  2 +-
>  tools/testing/selftests/bpf/verifier/ringbuf.c    |  2 +-
>  tools/testing/selftests/bpf/verifier/spill_fill.c |  2 +-
>  6 files changed, 17 insertions(+), 20 deletions(-)
>
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 2fe3ec620d54..afc1c51b59ff 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -488,10 +488,8 @@ enum bpf_type_flag {
>          */
>         MEM_RDONLY              = BIT(1 + BPF_BASE_TYPE_BITS),
>
> -       /* MEM was "allocated" from a different helper, and cannot be mixed
> -        * with regular non-MEM_ALLOC'ed MEM types.
> -        */
> -       MEM_ALLOC               = BIT(2 + BPF_BASE_TYPE_BITS),
> +       /* MEM points to BPF ring buffer reservation. */
> +       MEM_RINGBUF             = BIT(2 + BPF_BASE_TYPE_BITS),

What do we gain by having ringbuf memory as additional modified flag
instead of its own type like PTR_TO_MAP_VALUE or PTR_TO_PACKET? It
feels like here separate register type is more justified and is less
error prone overall.

>
>         /* MEM is in user address space. */
>         MEM_USER                = BIT(3 + BPF_BASE_TYPE_BITS),
> @@ -565,7 +563,7 @@ enum bpf_arg_type {
>         ARG_PTR_TO_LONG,        /* pointer to long */
>         ARG_PTR_TO_SOCKET,      /* pointer to bpf_sock (fullsock) */
>         ARG_PTR_TO_BTF_ID,      /* pointer to in-kernel struct */
> -       ARG_PTR_TO_ALLOC_MEM,   /* pointer to dynamically allocated memory */
> +       ARG_PTR_TO_RINGBUF_MEM, /* pointer to dynamically reserved ringbuf memory */
>         ARG_CONST_ALLOC_SIZE_OR_ZERO,   /* number of allocated bytes requested */
>         ARG_PTR_TO_BTF_ID_SOCK_COMMON,  /* pointer to in-kernel sock_common or bpf-mirrored bpf_sock */
>         ARG_PTR_TO_PERCPU_BTF_ID,       /* pointer to in-kernel percpu type */

[...]

Re: [PATCH bpf-next v5 06/25] bpf: Introduce local kptrs

[Andrii Nakryiko]

On Mon, Nov 7, 2022 at 3:10 PM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
>
> Introduce local kptrs, i.e. PTR_TO_BTF_ID that point to a type in
> program BTF. This is indicated by the presence of MEM_ALLOC type flag in
> reg->type to avoid having to check btf_is_kernel when trying to match
> argument types in helpers.
>
> Refactor btf_struct_access callback to just take bpf_reg_state instead
> of btf and btf_type paramters. Note that the call site in
> check_map_access now simulates access to a PTR_TO_BTF_ID by creating a
> dummy reg on stack. Since only the type, btf, and btf_id of the register
> matter for the checks, it can be done so without complicating the usual
> cases elsewhere in the verifier where reg->btf and reg->btf_id is used
> verbatim.
>
> Whenever walking such types, any pointers being walked will always yield
> a SCALAR instead of pointer. In the future we might permit kptr inside
> local kptr (either kernel or local), and it would be permitted only in
> that case.
>
> For now, these local kptrs will always be referenced in verifier
> context, hence ref_obj_id == 0 for them is a bug. It is allowed to write
> to such objects, as long fields that are special are not touched
> (support for which will be added in subsequent patches). Note that once
> such a local kptr is marked PTR_UNTRUSTED, it is no longer allowed to
> write to it.
>
> No PROBE_MEM handling is therefore done for loads into this type unless
> PTR_UNTRUSTED is part of the register type, since they can never be in
> an undefined state, and their lifetime will always be valid.
>
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> ---
>  include/linux/bpf.h              | 28 ++++++++++++++++--------
>  include/linux/filter.h           |  8 +++----
>  kernel/bpf/btf.c                 | 16 ++++++++++----
>  kernel/bpf/verifier.c            | 37 ++++++++++++++++++++++++++------
>  net/bpf/bpf_dummy_struct_ops.c   | 14 ++++++------
>  net/core/filter.c                | 34 ++++++++++++-----------------
>  net/ipv4/bpf_tcp_ca.c            | 13 ++++++-----
>  net/netfilter/nf_conntrack_bpf.c | 17 ++++++---------
>  8 files changed, 99 insertions(+), 68 deletions(-)
>
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index afc1c51b59ff..75dbd2ecf80a 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -524,6 +524,11 @@ enum bpf_type_flag {
>         /* Size is known at compile time. */
>         MEM_FIXED_SIZE          = BIT(10 + BPF_BASE_TYPE_BITS),
>
> +       /* MEM is of a type from program BTF, not kernel BTF. This is used to
> +        * tag PTR_TO_BTF_ID allocated using bpf_obj_new.
> +        */
> +       MEM_ALLOC               = BIT(11 + BPF_BASE_TYPE_BITS),
> +

you fixed one naming confusion with RINGBUF and basically are creating
a new one, where "ALLOC" means "local kptr"... If we are stuck with
"local kptr" (which I find very confusing as well, but that's beside
the point), why not stick to the whole "local" terminology here?
MEM_LOCAL?

>         __BPF_TYPE_FLAG_MAX,
>         __BPF_TYPE_LAST_FLAG    = __BPF_TYPE_FLAG_MAX - 1,
>  };
> @@ -771,6 +776,7 @@ struct bpf_prog_ops {
>                         union bpf_attr __user *uattr);
>  };
>

[...]

> -int btf_struct_access(struct bpf_verifier_log *log, const struct btf *btf,
> -                     const struct btf_type *t, int off, int size,
> -                     enum bpf_access_type atype __maybe_unused,
> +int btf_struct_access(struct bpf_verifier_log *log,
> +                     const struct bpf_reg_state *reg,
> +                     int off, int size, enum bpf_access_type atype __maybe_unused,
>                       u32 *next_btf_id, enum bpf_type_flag *flag)
>  {
> +       const struct btf *btf = reg->btf;
>         enum bpf_type_flag tmp_flag = 0;
> +       const struct btf_type *t;
> +       u32 id = reg->btf_id;
>         int err;
> -       u32 id;
>
> +       t = btf_type_by_id(btf, id);
>         do {
>                 err = btf_struct_walk(log, btf, t, off, size, &id, &tmp_flag);
>
>                 switch (err) {
>                 case WALK_PTR:
> +                       /* For local types, the destination register cannot
> +                        * become a pointer again.
> +                        */
> +                       if (type_is_local_kptr(reg->type))
> +                               return SCALAR_VALUE;

passing the entire bpf_reg_state just to differentiate between local
vs kernel pointer seems like a huge overkill. bpf_reg_state is quite a
complicated and extensive amount of state, and it seems cleaner to
just pass it as a flag whether to allow pointer chasing or not. At
least then we know we only care about that specific aspect, not about
dozens of other possible fields of bpf_reg_state.


>                         /* If we found the pointer or scalar on t+off,
>                          * we're done.
>                          */

[...]

Re: [PATCH bpf-next v5 10/25] bpf: Allow locking bpf_spin_lock global variables

[Andrii Nakryiko]

On Mon, Nov 7, 2022 at 3:10 PM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
>
> Global variables reside in maps accessible using direct_value_addr
> callbacks, so giving each load instruction's rewrite a unique reg->id
> disallows us from holding locks which are global.
>
> The reason for preserving reg->id as a unique value for registers that
> may point to spin lock is that two separate lookups are treated as two
> separate memory regions, and any possible aliasing is ignored for the
> purposes of spin lock correctness.
>
> This is not great especially for the global variable case, which are
> served from maps that have max_entries == 1, i.e. they always lead to
> map values pointing into the same map value.
>
> So refactor the active_spin_lock into a 'active_lock' structure which
> represents the lock identity, and instead of the reg->id, remember two
> fields, a pointer and the reg->id. The pointer will store reg->map_ptr
> or reg->btf. It's only necessary to distinguish for the id == 0 case of
> global variables, but always setting the pointer to a non-NULL value and
> using the pointer to check whether the lock is held simplifies code in
> the verifier.
>
> This is generic enough to allow it for global variables, map lookups,
> and local kptr registers at the same time.
>
> Note that while whether a lock is held can be answered by just comparing
> active_lock.ptr to NULL, to determine whether the register is pointing
> to the same held lock requires comparing _both_ ptr and id.
>
> Finally, as a result of this refactoring, pseudo load instructions are
> not given a unique reg->id, as they are doing lookup for the same map
> value (max_entries is never greater than 1).
>
> Essentially, we consider that the tuple of (ptr, id) will always be
> unique for any kind of argument to bpf_spin_{lock,unlock}.
>
> Note that this can be extended in the future to also remember offset
> used for locking, so that we can introduce multiple bpf_spin_lock fields
> in the same allocation.
>
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> ---
>  include/linux/bpf_verifier.h |  5 ++++-
>  kernel/bpf/verifier.c        | 41 ++++++++++++++++++++++++------------
>  2 files changed, 32 insertions(+), 14 deletions(-)
>
> diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
> index 1a32baa78ce2..70cccac62a15 100644
> --- a/include/linux/bpf_verifier.h
> +++ b/include/linux/bpf_verifier.h
> @@ -323,7 +323,10 @@ struct bpf_verifier_state {
>         u32 branches;
>         u32 insn_idx;
>         u32 curframe;
> -       u32 active_spin_lock;
> +       struct {
> +               void *ptr;

document that this could be either struct bpf_map or struct btf
pointer, at least?

> +               u32 id;
> +       } active_lock;
>         bool speculative;
>
>         /* first and last insn idx of this verifier state */

[...]

Re: [PATCH bpf-next v5 03/25] bpf: Support bpf_list_head in map values

[Kumar Kartikeya Dwivedi]

On Wed, Nov 09, 2022 at 04:31:52AM IST, Andrii Nakryiko wrote:
> On Mon, Nov 7, 2022 at 3:10 PM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
> >
> > Add the support on the map side to parse, recognize, verify, and build
> > metadata table for a new special field of the type struct bpf_list_head.
> > To parameterize the bpf_list_head for a certain value type and the
> > list_node member it will accept in that value type, we use BTF
> > declaration tags.
> >
> > The definition of bpf_list_head in a map value will be done as follows:
> >
> > struct foo {
> >         struct bpf_list_node node;
> >         int data;
> > };
> >
> > struct map_value {
> >         struct bpf_list_head head __contains(foo, node);
> > };
> >
> > Then, the bpf_list_head only allows adding to the list 'head' using the
> > bpf_list_node 'node' for the type struct foo.
> >
> > The 'contains' annotation is a BTF declaration tag composed of four
> > parts, "contains:name:node" where the name is then used to look up the
> > type in the map BTF, with its kind hardcoded to BTF_KIND_STRUCT during
> > the lookup. The node defines name of the member in this type that has
> > the type struct bpf_list_node, which is actually used for linking into
> > the linked list. For now, 'kind' part is hardcoded as struct.
> >
> > This allows building intrusive linked lists in BPF, using container_of
> > to obtain pointer to entry, while being completely type safe from the
> > perspective of the verifier. The verifier knows exactly the type of the
> > nodes, and knows that list helpers return that type at some fixed offset
> > where the bpf_list_node member used for this list exists. The verifier
> > also uses this information to disallow adding types that are not
> > accepted by a certain list.
> >
> > For now, no elements can be added to such lists. Support for that is
> > coming in future patches, hence draining and freeing items is done with
> > a TODO that will be resolved in a future patch.
> >
> > Note that the bpf_list_head_free function moves the list out to a local
> > variable under the lock and releases it, doing the actual draining of
> > the list items outside the lock. While this helps with not holding the
> > lock for too long pessimizing other concurrent list operations, it is
> > also necessary for deadlock prevention: unless every function called in
> > the critical section would be notrace, a fentry/fexit program could
> > attach and call bpf_map_update_elem again on the map, leading to the
> > same lock being acquired if the key matches and lead to a deadlock.
> > While this requires some special effort on part of the BPF programmer to
> > trigger and is highly unlikely to occur in practice, it is always better
> > if we can avoid such a condition.
> >
> > While notrace would prevent this, doing the draining outside the lock
> > has advantages of its own, hence it is used to also fix the deadlock
> > related problem.
> >
> > Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> > ---
> >  include/linux/bpf.h            |  17 ++++
> >  include/uapi/linux/bpf.h       |  10 +++
> >  kernel/bpf/btf.c               | 143 ++++++++++++++++++++++++++++++++-
> >  kernel/bpf/helpers.c           |  32 ++++++++
> >  kernel/bpf/syscall.c           |  22 ++++-
> >  kernel/bpf/verifier.c          |   7 ++
> >  tools/include/uapi/linux/bpf.h |  10 +++
> >  7 files changed, 237 insertions(+), 4 deletions(-)
> >
>
> [...]
>
> >  struct bpf_offload_dev;
> > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > index 94659f6b3395..dd381086bad9 100644
> > --- a/include/uapi/linux/bpf.h
> > +++ b/include/uapi/linux/bpf.h
> > @@ -6887,6 +6887,16 @@ struct bpf_dynptr {
> >         __u64 :64;
> >  } __attribute__((aligned(8)));
> >
> > +struct bpf_list_head {
> > +       __u64 :64;
> > +       __u64 :64;
> > +} __attribute__((aligned(8)));
> > +
> > +struct bpf_list_node {
> > +       __u64 :64;
> > +       __u64 :64;
> > +} __attribute__((aligned(8)));
>
> Dave mentioned that this `__u64 :64` trick makes vmlinux.h lose the
> alignment information, as the struct itself is empty, and so there is
> nothing indicating that it has to be 8-byte aligned.
>
> So what if we have
>
> struct bpf_list_node {
>     __u64 __opaque[2];
> } __attribute__((aligned(8)));
>
> ?
>

Yep, can do that. Note that it's also potentially an issue for existing cases,
like bpf_spin_lock, bpf_timer, bpf_dynptr, etc. Not completely sure if changing
things now is possible, but if it is, we should probably make it for all of
them?

> > +
> >  struct bpf_sysctl {
> >         __u32   write;          /* Sysctl is being read (= 0) or written (= 1).
> >                                  * Allows 1,2,4-byte read, but no write.
> > diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
>
> [...]
>
> > @@ -3284,6 +3347,12 @@ static int btf_get_field_type(const char *name, u32 field_mask, u32 *seen_mask,
> >                         goto end;
> >                 }
> >         }
> > +       if (field_mask & BPF_LIST_HEAD) {
> > +               if (!strcmp(name, "bpf_list_head")) {
> > +                       type = BPF_LIST_HEAD;
> > +                       goto end;
> > +               }
> > +       }
> >         /* Only return BPF_KPTR when all other types with matchable names fail */
> >         if (field_mask & BPF_KPTR) {
> >                 type = BPF_KPTR_REF;
> > @@ -3317,6 +3386,8 @@ static int btf_find_struct_field(const struct btf *btf,
> >                         return field_type;
> >
> >                 off = __btf_member_bit_offset(t, member);
> > +               if (i && !off)
> > +                       return -EFAULT;
>
> why? why can't my struct has zero-sized field in the beginning? This
> seems like a very incomplete and unnecessary check to me.
>

Right, I will drop it for the struct case.

> >                 if (off % 8)
> >                         /* valid C code cannot generate such BTF */
> >                         return -EINVAL;
> > @@ -3339,6 +3410,12 @@ static int btf_find_struct_field(const struct btf *btf,
> >                         if (ret < 0)
> >                                 return ret;
> >                         break;
> > +               case BPF_LIST_HEAD:
> > +                       ret = btf_find_list_head(btf, t, member_type, i, off, sz,
> > +                                                idx < info_cnt ? &info[idx] : &tmp);
> > +                       if (ret < 0)
> > +                               return ret;
> > +                       break;
> >                 default:
> >                         return -EFAULT;
> >                 }
> > @@ -3373,6 +3450,8 @@ static int btf_find_datasec_var(const struct btf *btf, const struct btf_type *t,
> >                         return field_type;
> >
> >                 off = vsi->offset;
> > +               if (i && !off)
> > +                       return -EFAULT;
>
> similarly, I'd say that either we'd need to calculate the exact
> expected offset, or just not do anything here?
>

This thread is actually what prompted this check:
https://lore.kernel.org/bpf/CAEf4Bza7ga2hEQ4J7EtgRHz49p1vZtaT4d2RDiyGOKGK41Nt=Q@mail.gmail.com

Unless loaded using libbpf all offsets are zero. So I think we need to reject it
here, but I think the same zero sized field might be an issue for this as well,
so maybe we remember the last field size and check whether it was zero or not?

I'll also include some more tests for these cases.

Re: [PATCH bpf-next v5 05/25] bpf: Rename MEM_ALLOC to MEM_RINGBUF

[Kumar Kartikeya Dwivedi]

On Wed, Nov 09, 2022 at 04:44:16AM IST, Andrii Nakryiko wrote:
> On Mon, Nov 7, 2022 at 3:10 PM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
> >
> > Currently, verifier uses MEM_ALLOC type tag to specially tag memory
> > returned from bpf_ringbuf_reserve helper. However, this is currently
> > only used for this purpose and there is an implicit assumption that it
> > only refers to ringbuf memory (e.g. the check for ARG_PTR_TO_ALLOC_MEM
> > in check_func_arg_reg_off).
> >
> > Hence, rename MEM_ALLOC to MEM_RINGBUF to indicate this special
> > relationship and instead open the use of MEM_ALLOC for more generic
> > allocations made for user types.
> >
> > Also, since ARG_PTR_TO_ALLOC_MEM_OR_NULL is unused, simply drop it.
> >
> > Finally, update selftests using 'alloc_' verifier string to 'ringbuf_'.
> >
> > Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> > ---
>
> Ok, so you are doing what I asked in the previous patch, nice :)
>
> >  include/linux/bpf.h                               | 11 ++++-------
> >  kernel/bpf/ringbuf.c                              |  6 +++---
> >  kernel/bpf/verifier.c                             | 14 +++++++-------
> >  tools/testing/selftests/bpf/prog_tests/dynptr.c   |  2 +-
> >  tools/testing/selftests/bpf/verifier/ringbuf.c    |  2 +-
> >  tools/testing/selftests/bpf/verifier/spill_fill.c |  2 +-
> >  6 files changed, 17 insertions(+), 20 deletions(-)
> >
> > diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> > index 2fe3ec620d54..afc1c51b59ff 100644
> > --- a/include/linux/bpf.h
> > +++ b/include/linux/bpf.h
> > @@ -488,10 +488,8 @@ enum bpf_type_flag {
> >          */
> >         MEM_RDONLY              = BIT(1 + BPF_BASE_TYPE_BITS),
> >
> > -       /* MEM was "allocated" from a different helper, and cannot be mixed
> > -        * with regular non-MEM_ALLOC'ed MEM types.
> > -        */
> > -       MEM_ALLOC               = BIT(2 + BPF_BASE_TYPE_BITS),
> > +       /* MEM points to BPF ring buffer reservation. */
> > +       MEM_RINGBUF             = BIT(2 + BPF_BASE_TYPE_BITS),
>
> What do we gain by having ringbuf memory as additional modified flag
> instead of its own type like PTR_TO_MAP_VALUE or PTR_TO_PACKET? It
> feels like here separate register type is more justified and is less
> error prone overall.
>

I'm not sure it's all that different. It only matters when checking argument
during release. We want to ensure it came from ringbuf_reserve. That's all,
apart from that it's no different from PTR_TO_MEM. In all other places it's
folded and code for PTR_TO_MEM is used. Same idea as PTR_TO_BTF_ID | MEM_ALLOC.

But I don't feel too strongly, so if you still think it's better I can make the
switch.

Re: [PATCH bpf-next v5 06/25] bpf: Introduce local kptrs

[Kumar Kartikeya Dwivedi]

On Wed, Nov 09, 2022 at 04:59:41AM IST, Andrii Nakryiko wrote:
> On Mon, Nov 7, 2022 at 3:10 PM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
> >
> > Introduce local kptrs, i.e. PTR_TO_BTF_ID that point to a type in
> > program BTF. This is indicated by the presence of MEM_ALLOC type flag in
> > reg->type to avoid having to check btf_is_kernel when trying to match
> > argument types in helpers.
> >
> > Refactor btf_struct_access callback to just take bpf_reg_state instead
> > of btf and btf_type paramters. Note that the call site in
> > check_map_access now simulates access to a PTR_TO_BTF_ID by creating a
> > dummy reg on stack. Since only the type, btf, and btf_id of the register
> > matter for the checks, it can be done so without complicating the usual
> > cases elsewhere in the verifier where reg->btf and reg->btf_id is used
> > verbatim.
> >
> > Whenever walking such types, any pointers being walked will always yield
> > a SCALAR instead of pointer. In the future we might permit kptr inside
> > local kptr (either kernel or local), and it would be permitted only in
> > that case.
> >
> > For now, these local kptrs will always be referenced in verifier
> > context, hence ref_obj_id == 0 for them is a bug. It is allowed to write
> > to such objects, as long fields that are special are not touched
> > (support for which will be added in subsequent patches). Note that once
> > such a local kptr is marked PTR_UNTRUSTED, it is no longer allowed to
> > write to it.
> >
> > No PROBE_MEM handling is therefore done for loads into this type unless
> > PTR_UNTRUSTED is part of the register type, since they can never be in
> > an undefined state, and their lifetime will always be valid.
> >
> > Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> > ---
> >  include/linux/bpf.h              | 28 ++++++++++++++++--------
> >  include/linux/filter.h           |  8 +++----
> >  kernel/bpf/btf.c                 | 16 ++++++++++----
> >  kernel/bpf/verifier.c            | 37 ++++++++++++++++++++++++++------
> >  net/bpf/bpf_dummy_struct_ops.c   | 14 ++++++------
> >  net/core/filter.c                | 34 ++++++++++++-----------------
> >  net/ipv4/bpf_tcp_ca.c            | 13 ++++++-----
> >  net/netfilter/nf_conntrack_bpf.c | 17 ++++++---------
> >  8 files changed, 99 insertions(+), 68 deletions(-)
> >
> > diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> > index afc1c51b59ff..75dbd2ecf80a 100644
> > --- a/include/linux/bpf.h
> > +++ b/include/linux/bpf.h
> > @@ -524,6 +524,11 @@ enum bpf_type_flag {
> >         /* Size is known at compile time. */
> >         MEM_FIXED_SIZE          = BIT(10 + BPF_BASE_TYPE_BITS),
> >
> > +       /* MEM is of a type from program BTF, not kernel BTF. This is used to
> > +        * tag PTR_TO_BTF_ID allocated using bpf_obj_new.
> > +        */
> > +       MEM_ALLOC               = BIT(11 + BPF_BASE_TYPE_BITS),
> > +
>
> you fixed one naming confusion with RINGBUF and basically are creating
> a new one, where "ALLOC" means "local kptr"... If we are stuck with
> "local kptr" (which I find very confusing as well, but that's beside
> the point), why not stick to the whole "local" terminology here?
> MEM_LOCAL?
>

See the discussion about this in v4:
https://lore.kernel.org/bpf/20221104075113.5ighwdvero4mugu7@apollo

It was MEM_TYPE_LOCAL before. Also, better naming suggestions are always
welcome, I asked the same in that message as well.

> >         __BPF_TYPE_FLAG_MAX,
> >         __BPF_TYPE_LAST_FLAG    = __BPF_TYPE_FLAG_MAX - 1,
> >  };
> > @@ -771,6 +776,7 @@ struct bpf_prog_ops {
> >                         union bpf_attr __user *uattr);
> >  };
> >
>
> [...]
>
> > -int btf_struct_access(struct bpf_verifier_log *log, const struct btf *btf,
> > -                     const struct btf_type *t, int off, int size,
> > -                     enum bpf_access_type atype __maybe_unused,
> > +int btf_struct_access(struct bpf_verifier_log *log,
> > +                     const struct bpf_reg_state *reg,
> > +                     int off, int size, enum bpf_access_type atype __maybe_unused,
> >                       u32 *next_btf_id, enum bpf_type_flag *flag)
> >  {
> > +       const struct btf *btf = reg->btf;
> >         enum bpf_type_flag tmp_flag = 0;
> > +       const struct btf_type *t;
> > +       u32 id = reg->btf_id;
> >         int err;
> > -       u32 id;
> >
> > +       t = btf_type_by_id(btf, id);
> >         do {
> >                 err = btf_struct_walk(log, btf, t, off, size, &id, &tmp_flag);
> >
> >                 switch (err) {
> >                 case WALK_PTR:
> > +                       /* For local types, the destination register cannot
> > +                        * become a pointer again.
> > +                        */
> > +                       if (type_is_local_kptr(reg->type))
> > +                               return SCALAR_VALUE;
>
> passing the entire bpf_reg_state just to differentiate between local
> vs kernel pointer seems like a huge overkill. bpf_reg_state is quite a
> complicated and extensive amount of state, and it seems cleaner to
> just pass it as a flag whether to allow pointer chasing or not. At
> least then we know we only care about that specific aspect, not about
> dozens of other possible fields of bpf_reg_state.
>

I agree that the separation is usually better, especially because this is also a
callback. I don't feel too strong about this though, we certainly do pass the
whole reg to functions which only work on a specific type of pointer. Though the
concern in this case is justified as it's not only an internal function but also
a callback.

It was just a bool in the RFC.
But in https://lore.kernel.org/bpf/20220907233023.x3uclwlnjuhftvtb@macbook-pro-4.dhcp.thefacebook.com
Alexei suggested passing reg instead.
From the link:
> imo it's cleaner to pass 'reg' instead of 'reg->btf',
> so we don't have to pass another boolean.
> And check type_is_local(reg) inside btf_struct_access().

Re: [PATCH bpf-next v5 10/25] bpf: Allow locking bpf_spin_lock global variables

[Kumar Kartikeya Dwivedi]

On Wed, Nov 09, 2022 at 05:07:44AM IST, Andrii Nakryiko wrote:
> On Mon, Nov 7, 2022 at 3:10 PM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
> >
> > Global variables reside in maps accessible using direct_value_addr
> > callbacks, so giving each load instruction's rewrite a unique reg->id
> > disallows us from holding locks which are global.
> >
> > The reason for preserving reg->id as a unique value for registers that
> > may point to spin lock is that two separate lookups are treated as two
> > separate memory regions, and any possible aliasing is ignored for the
> > purposes of spin lock correctness.
> >
> > This is not great especially for the global variable case, which are
> > served from maps that have max_entries == 1, i.e. they always lead to
> > map values pointing into the same map value.
> >
> > So refactor the active_spin_lock into a 'active_lock' structure which
> > represents the lock identity, and instead of the reg->id, remember two
> > fields, a pointer and the reg->id. The pointer will store reg->map_ptr
> > or reg->btf. It's only necessary to distinguish for the id == 0 case of
> > global variables, but always setting the pointer to a non-NULL value and
> > using the pointer to check whether the lock is held simplifies code in
> > the verifier.
> >
> > This is generic enough to allow it for global variables, map lookups,
> > and local kptr registers at the same time.
> >
> > Note that while whether a lock is held can be answered by just comparing
> > active_lock.ptr to NULL, to determine whether the register is pointing
> > to the same held lock requires comparing _both_ ptr and id.
> >
> > Finally, as a result of this refactoring, pseudo load instructions are
> > not given a unique reg->id, as they are doing lookup for the same map
> > value (max_entries is never greater than 1).
> >
> > Essentially, we consider that the tuple of (ptr, id) will always be
> > unique for any kind of argument to bpf_spin_{lock,unlock}.
> >
> > Note that this can be extended in the future to also remember offset
> > used for locking, so that we can introduce multiple bpf_spin_lock fields
> > in the same allocation.
> >
> > Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> > ---
> >  include/linux/bpf_verifier.h |  5 ++++-
> >  kernel/bpf/verifier.c        | 41 ++++++++++++++++++++++++------------
> >  2 files changed, 32 insertions(+), 14 deletions(-)
> >
> > diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
> > index 1a32baa78ce2..70cccac62a15 100644
> > --- a/include/linux/bpf_verifier.h
> > +++ b/include/linux/bpf_verifier.h
> > @@ -323,7 +323,10 @@ struct bpf_verifier_state {
> >         u32 branches;
> >         u32 insn_idx;
> >         u32 curframe;
> > -       u32 active_spin_lock;
> > +       struct {
> > +               void *ptr;
>
> document that this could be either struct bpf_map or struct btf
> pointer, at least?
>
Ack, I'll add a comment.

Though it's not really meant to be used (i.e. turned back into a pointer to
them), it's just an 'identity' pointer.

Re: [PATCH bpf-next v5 15/25] bpf: Teach verifier about non-size constant arguments

[Andrii Nakryiko]

On Mon, Nov 7, 2022 at 3:10 PM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
>
> Currently, the verifier has support for various arguments that either
> describe the size of the memory being passed in to a helper, or describe
> the size of the memory being returned. When a constant is passed in like
> this, it is assumed for the purposes of precision tracking that if the
> value in the already explored safe state is within the value in current
> state, it would fine to prune the search.
>
> While this holds well for size arguments, arguments where each value may
> denote a distinct meaning and needs to be verified separately needs more
> work. Search can only be pruned if both are equivalent values. In all
> other cases, it would be incorrect to treat those two precise registers
> as equivalent if the new value satisfies the old one (i.e. old <= cur).
>
> Hence, make the register precision marker tri-state. There are now three
> values that reg->precise takes: NOT_PRECISE, PRECISE, EXACT.
>
> Both PRECISE and EXACT are 'true' values. EXACT affects how regsafe
> decides whether both registers are equivalent for the purposes of
> verifier state equivalence. When it sees that old state register has
> reg->precise == EXACT, unless both are equivalent, it will return false.
> Otherwise, for PRECISE case it falls back to the default check that is
> present now (i.e. thinking that we're talking about sizes).
>
> This is required as a future patch introduces a BPF memory allocator
> interface, where we take the program BTF's type ID as an argument. Each
> distinct type ID may result in the returned pointer obtaining a
> different size, hence precision tracking is needed, and pruning cannot
> just happen when the old value is within the current value. It must only
> happen when the type ID is equal. The type ID will always correspond to
> prog->aux->btf hence actual type match is not required.
>
> Finally, change mark_chain_precision precision argument to EXACT for
> kfuncs constant non-size scalar arguments (tagged with __k suffix).
>
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> ---

I think this needs a bit more thinking, tbh. First, with my recent
changes we don't even set precision marks in current state, everything
stays imprecise. And then under CAP_BPF we also aggressively reset
precision. This might work for EXACT, but needs careful consideration.

But, taking a step back. I'm trying to understand why this whole EXACT
mode is necessary. SCALAR has min/max values which regsafe() does
check. So for those special ___k arguments, if we correctly set
min/max values to be *exactly* the btf_id passed in, why would
regsafe()'s logic not work?

>  include/linux/bpf_verifier.h |  10 +++-
>  kernel/bpf/verifier.c        | 111 ++++++++++++++++++++++-------------
>  2 files changed, 76 insertions(+), 45 deletions(-)
>
> diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
> index f3a601d33fb3..1e246ec2ff37 100644
> --- a/include/linux/bpf_verifier.h
> +++ b/include/linux/bpf_verifier.h
> @@ -43,6 +43,12 @@ enum bpf_reg_liveness {
>         REG_LIVE_DONE = 0x8, /* liveness won't be updating this register anymore */
>  };
>
> +enum bpf_reg_precise {
> +       NOT_PRECISE,

IMPRECISE?

> +       PRECISE,
> +       EXACT,
> +};
> +
>  struct bpf_reg_state {
>         /* Ordering of fields matters.  See states_equal() */
>         enum bpf_reg_type type;
> @@ -180,7 +186,7 @@ struct bpf_reg_state {
>         s32 subreg_def;
>         enum bpf_reg_liveness live;
>         /* if (!precise && SCALAR_VALUE) min/max/tnum don't affect safety */
> -       bool precise;
> +       enum bpf_reg_precise precise;
>  };
>
>  enum bpf_stack_slot_type {
> @@ -626,8 +632,6 @@ int bpf_check_attach_target(struct bpf_verifier_log *log,
>                             struct bpf_attach_target_info *tgt_info);
>  void bpf_free_kfunc_btf_tab(struct bpf_kfunc_btf_tab *tab);
>
> -int mark_chain_precision(struct bpf_verifier_env *env, int regno);
> -
>  #define BPF_BASE_TYPE_MASK     GENMASK(BPF_BASE_TYPE_BITS - 1, 0)
>
>  /* extract base type from bpf_{arg, return, reg}_type. */
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 7515b31d2c40..5bfc151711b9 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -864,7 +864,7 @@ static void print_verifier_state(struct bpf_verifier_env *env,
>                 print_liveness(env, reg->live);
>                 verbose(env, "=");
>                 if (t == SCALAR_VALUE && reg->precise)
> -                       verbose(env, "P");
> +                       verbose(env, reg->precise == EXACT ? "E" : "P");
>                 if ((t == SCALAR_VALUE || t == PTR_TO_STACK) &&
>                     tnum_is_const(reg->var_off)) {
>                         /* reg->off should be 0 for SCALAR_VALUE */
> @@ -961,7 +961,7 @@ static void print_verifier_state(struct bpf_verifier_env *env,
>                         t = reg->type;
>                         verbose(env, "=%s", t == SCALAR_VALUE ? "" : reg_type_str(env, t));
>                         if (t == SCALAR_VALUE && reg->precise)
> -                               verbose(env, "P");
> +                               verbose(env, reg->precise == EXACT ? "E" : "P");
>                         if (t == SCALAR_VALUE && tnum_is_const(reg->var_off))
>                                 verbose(env, "%lld", reg->var_off.value + reg->off);
>                 } else {
> @@ -1695,7 +1695,16 @@ static void __mark_reg_unknown(const struct bpf_verifier_env *env,
>         reg->type = SCALAR_VALUE;
>         reg->var_off = tnum_unknown;
>         reg->frameno = 0;
> -       reg->precise = !env->bpf_capable;
> +       /* Helpers requiring EXACT for constant arguments cannot be called from
> +        * programs without CAP_BPF. This is because we don't propagate
> +        * precision markers when CAP_BPF is missing. If we allowed calling such
> +        * heleprs in those programs, the default would have to be EXACT for
> +        * them, which would be too aggresive, or we'd have to propagate it.

typos: helpers, aggressive

> +        *
> +        * Currently, only bpf_obj_new kfunc requires EXACT precision for its
> +        * scalar argument, which is a kfunc (and thus behind CAP_BPF).
> +        */
> +       reg->precise = !env->bpf_capable ? PRECISE : NOT_PRECISE;
>         __mark_reg_unbounded(reg);
>  }
>

[...]

>         /* Do sanity checks against current state of register and/or stack
>          * slot, but don't set precise flag in current state, as precision
> @@ -2969,7 +2982,7 @@ static int __mark_chain_precision(struct bpf_verifier_env *env, int frame, int r
>                                                 reg_mask &= ~(1u << i);
>                                                 continue;
>                                         }
> -                                       reg->precise = true;
> +                                       reg->precise = precise;
>                                 }
>                                 return 0;
>                         }
> @@ -2988,7 +3001,7 @@ static int __mark_chain_precision(struct bpf_verifier_env *env, int frame, int r
>                                 err = backtrack_insn(env, i, &reg_mask, &stack_mask);
>                         }
>                         if (err == -ENOTSUPP) {
> -                               mark_all_scalars_precise(env, st);
> +                               mark_all_scalars_precise(env, st, precise);

well... do you really intend to remark everything as EXACT, even
registers that have no business of being EXACT? Seems a bit too blunt.

>                                 return 0;
>                         } else if (err) {
>                                 return err;
> @@ -3029,7 +3042,7 @@ static int __mark_chain_precision(struct bpf_verifier_env *env, int frame, int r
>                         }
>                         if (!reg->precise)
>                                 new_marks = true;
> -                       reg->precise = true;
> +                       reg->precise = precise;
>                 }
>
>                 bitmap_from_u64(mask, stack_mask);

[...]

Re: [PATCH bpf-next v5 22/25] selftests/bpf: Update spinlock selftest

[Andrii Nakryiko]

On Mon, Nov 7, 2022 at 3:11 PM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
>
> Make updates in preparation for adding more test cases to this selftest:
> - Convert from CHECK_ to ASSERT macros.
> - Use BPF skeleton
> - Fix typo sping -> spin
> - Rename spinlock.c -> spin_lock.c
>
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> ---
>  .../selftests/bpf/prog_tests/spin_lock.c      | 46 +++++++++++++++++++
>  .../selftests/bpf/prog_tests/spinlock.c       | 45 ------------------
>  .../selftests/bpf/progs/test_spin_lock.c      |  4 +-
>  3 files changed, 48 insertions(+), 47 deletions(-)
>  create mode 100644 tools/testing/selftests/bpf/prog_tests/spin_lock.c
>  delete mode 100644 tools/testing/selftests/bpf/prog_tests/spinlock.c
>

[...]

> +void test_spinlock(void)
> +{
> +       struct test_spin_lock *skel;
> +       pthread_t thread_id[4];
> +       int prog_fd, i;
> +       void *ret;
> +
> +       skel = test_spin_lock__open_and_load();
> +       if (!ASSERT_OK_PTR(skel, "test_spin_lock__open_and_load"))
> +               return;
> +       prog_fd = bpf_program__fd(skel->progs.bpf_spin_lock_test);
> +       for (i = 0; i < 4; i++)
> +               if (!ASSERT_OK(pthread_create(&thread_id[i], NULL,
> +                                             &spin_lock_thread, &prog_fd), "pthread_create"))

I mean... does that pthread_create() call have to happen inside ASSERT_OK?

err = pthread_create(...)
if (!ASSERT_OK(err, "pthread_create"))
    goto end;

> +                       goto end;
> +
> +       for (i = 0; i < 4; i++) {
> +               if (!ASSERT_OK(pthread_join(thread_id[i], &ret), "pthread_join"))
> +                       goto end;
> +               if (!ASSERT_EQ(ret, &prog_fd, "ret == prog_fd"))
> +                       goto end;
> +       }
> +end:
> +       test_spin_lock__destroy(skel);
> +}

[...]

Re: [PATCH bpf-next v5 25/25] selftests/bpf: Add BTF sanity tests

[Andrii Nakryiko]

On Mon, Nov 7, 2022 at 3:11 PM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
>
> Preparing the metadata for bpf_list_head involves a complicated parsing
> step and type resolution for the contained value. Ensure that corner
> cases are tested against and invalid specifications in source are duly
> rejected. Also include tests for incorrect ownership relationships in
> the BTF.
>
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> ---
>  .../selftests/bpf/prog_tests/linked_list.c    | 271 ++++++++++++++++++
>  1 file changed, 271 insertions(+)
>

Have you considered using BTW write API to construct BTFs?
btf__new_empty() + btf__add_xxx()?

> diff --git a/tools/testing/selftests/bpf/prog_tests/linked_list.c b/tools/testing/selftests/bpf/prog_tests/linked_list.c
> index 669ef4bb9b87..40070e2d22f2 100644
> --- a/tools/testing/selftests/bpf/prog_tests/linked_list.c
> +++ b/tools/testing/selftests/bpf/prog_tests/linked_list.c
> @@ -1,4 +1,7 @@
>  // SPDX-License-Identifier: GPL-2.0
> +#include <bpf/btf.h>
> +#include <test_btf.h>
> +#include <linux/btf.h>
>  #include <test_progs.h>
>  #include <network_helpers.h>
>

[...]

Re: [PATCH bpf-next v5 03/25] bpf: Support bpf_list_head in map values

[Andrii Nakryiko]

On Tue, Nov 8, 2022 at 3:39 PM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
>
> On Wed, Nov 09, 2022 at 04:31:52AM IST, Andrii Nakryiko wrote:
> > On Mon, Nov 7, 2022 at 3:10 PM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
> > >
> > > Add the support on the map side to parse, recognize, verify, and build
> > > metadata table for a new special field of the type struct bpf_list_head.
> > > To parameterize the bpf_list_head for a certain value type and the
> > > list_node member it will accept in that value type, we use BTF
> > > declaration tags.
> > >
> > > The definition of bpf_list_head in a map value will be done as follows:
> > >
> > > struct foo {
> > >         struct bpf_list_node node;
> > >         int data;
> > > };
> > >
> > > struct map_value {
> > >         struct bpf_list_head head __contains(foo, node);
> > > };
> > >
> > > Then, the bpf_list_head only allows adding to the list 'head' using the
> > > bpf_list_node 'node' for the type struct foo.
> > >
> > > The 'contains' annotation is a BTF declaration tag composed of four
> > > parts, "contains:name:node" where the name is then used to look up the
> > > type in the map BTF, with its kind hardcoded to BTF_KIND_STRUCT during
> > > the lookup. The node defines name of the member in this type that has
> > > the type struct bpf_list_node, which is actually used for linking into
> > > the linked list. For now, 'kind' part is hardcoded as struct.
> > >
> > > This allows building intrusive linked lists in BPF, using container_of
> > > to obtain pointer to entry, while being completely type safe from the
> > > perspective of the verifier. The verifier knows exactly the type of the
> > > nodes, and knows that list helpers return that type at some fixed offset
> > > where the bpf_list_node member used for this list exists. The verifier
> > > also uses this information to disallow adding types that are not
> > > accepted by a certain list.
> > >
> > > For now, no elements can be added to such lists. Support for that is
> > > coming in future patches, hence draining and freeing items is done with
> > > a TODO that will be resolved in a future patch.
> > >
> > > Note that the bpf_list_head_free function moves the list out to a local
> > > variable under the lock and releases it, doing the actual draining of
> > > the list items outside the lock. While this helps with not holding the
> > > lock for too long pessimizing other concurrent list operations, it is
> > > also necessary for deadlock prevention: unless every function called in
> > > the critical section would be notrace, a fentry/fexit program could
> > > attach and call bpf_map_update_elem again on the map, leading to the
> > > same lock being acquired if the key matches and lead to a deadlock.
> > > While this requires some special effort on part of the BPF programmer to
> > > trigger and is highly unlikely to occur in practice, it is always better
> > > if we can avoid such a condition.
> > >
> > > While notrace would prevent this, doing the draining outside the lock
> > > has advantages of its own, hence it is used to also fix the deadlock
> > > related problem.
> > >
> > > Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> > > ---
> > >  include/linux/bpf.h            |  17 ++++
> > >  include/uapi/linux/bpf.h       |  10 +++
> > >  kernel/bpf/btf.c               | 143 ++++++++++++++++++++++++++++++++-
> > >  kernel/bpf/helpers.c           |  32 ++++++++
> > >  kernel/bpf/syscall.c           |  22 ++++-
> > >  kernel/bpf/verifier.c          |   7 ++
> > >  tools/include/uapi/linux/bpf.h |  10 +++
> > >  7 files changed, 237 insertions(+), 4 deletions(-)
> > >
> >
> > [...]
> >
> > >  struct bpf_offload_dev;
> > > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > > index 94659f6b3395..dd381086bad9 100644
> > > --- a/include/uapi/linux/bpf.h
> > > +++ b/include/uapi/linux/bpf.h
> > > @@ -6887,6 +6887,16 @@ struct bpf_dynptr {
> > >         __u64 :64;
> > >  } __attribute__((aligned(8)));
> > >
> > > +struct bpf_list_head {
> > > +       __u64 :64;
> > > +       __u64 :64;
> > > +} __attribute__((aligned(8)));
> > > +
> > > +struct bpf_list_node {
> > > +       __u64 :64;
> > > +       __u64 :64;
> > > +} __attribute__((aligned(8)));
> >
> > Dave mentioned that this `__u64 :64` trick makes vmlinux.h lose the
> > alignment information, as the struct itself is empty, and so there is
> > nothing indicating that it has to be 8-byte aligned.
> >
> > So what if we have
> >
> > struct bpf_list_node {
> >     __u64 __opaque[2];
> > } __attribute__((aligned(8)));
> >
> > ?
> >
>
> Yep, can do that. Note that it's also potentially an issue for existing cases,
> like bpf_spin_lock, bpf_timer, bpf_dynptr, etc. Not completely sure if changing
> things now is possible, but if it is, we should probably make it for all of
> them?

Why not? We are not removing anything or changing sizes, so it's
backwards compatible. But I have a suspicion Alexei might not like
this __opaque field, so let's see what he says.

>
> > > +
> > >  struct bpf_sysctl {
> > >         __u32   write;          /* Sysctl is being read (= 0) or written (= 1).
> > >                                  * Allows 1,2,4-byte read, but no write.
> > > diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
> >
> > [...]
> >
> > > @@ -3284,6 +3347,12 @@ static int btf_get_field_type(const char *name, u32 field_mask, u32 *seen_mask,
> > >                         goto end;
> > >                 }
> > >         }
> > > +       if (field_mask & BPF_LIST_HEAD) {
> > > +               if (!strcmp(name, "bpf_list_head")) {
> > > +                       type = BPF_LIST_HEAD;
> > > +                       goto end;
> > > +               }
> > > +       }
> > >         /* Only return BPF_KPTR when all other types with matchable names fail */
> > >         if (field_mask & BPF_KPTR) {
> > >                 type = BPF_KPTR_REF;
> > > @@ -3317,6 +3386,8 @@ static int btf_find_struct_field(const struct btf *btf,
> > >                         return field_type;
> > >
> > >                 off = __btf_member_bit_offset(t, member);
> > > +               if (i && !off)
> > > +                       return -EFAULT;
> >
> > why? why can't my struct has zero-sized field in the beginning? This
> > seems like a very incomplete and unnecessary check to me.
> >
>
> Right, I will drop it for the struct case.
>
> > >                 if (off % 8)
> > >                         /* valid C code cannot generate such BTF */
> > >                         return -EINVAL;
> > > @@ -3339,6 +3410,12 @@ static int btf_find_struct_field(const struct btf *btf,
> > >                         if (ret < 0)
> > >                                 return ret;
> > >                         break;
> > > +               case BPF_LIST_HEAD:
> > > +                       ret = btf_find_list_head(btf, t, member_type, i, off, sz,
> > > +                                                idx < info_cnt ? &info[idx] : &tmp);
> > > +                       if (ret < 0)
> > > +                               return ret;
> > > +                       break;
> > >                 default:
> > >                         return -EFAULT;
> > >                 }
> > > @@ -3373,6 +3450,8 @@ static int btf_find_datasec_var(const struct btf *btf, const struct btf_type *t,
> > >                         return field_type;
> > >
> > >                 off = vsi->offset;
> > > +               if (i && !off)
> > > +                       return -EFAULT;
> >
> > similarly, I'd say that either we'd need to calculate the exact
> > expected offset, or just not do anything here?
> >
>
> This thread is actually what prompted this check:
> https://lore.kernel.org/bpf/CAEf4Bza7ga2hEQ4J7EtgRHz49p1vZtaT4d2RDiyGOKGK41Nt=Q@mail.gmail.com
>
> Unless loaded using libbpf all offsets are zero. So I think we need to reject it
> here, but I think the same zero sized field might be an issue for this as well,
> so maybe we remember the last field size and check whether it was zero or not?
>
> I'll also include some more tests for these cases.

The question is whether this affects correctness from the verifier
standpoint? If it does, there must be some other place where this will
cause problem and should be caught and reported.

My main objection is that it's half a check, we check that it's
non-zero, but we don't check that it is correct in stricter sense. So
I'd rather drop it altogether, or go all the way to check that it is
correct offset (taking into account sizes of previous vars).

Re: [PATCH bpf-next v5 05/25] bpf: Rename MEM_ALLOC to MEM_RINGBUF

[Andrii Nakryiko]

On Tue, Nov 8, 2022 at 3:49 PM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
>
> On Wed, Nov 09, 2022 at 04:44:16AM IST, Andrii Nakryiko wrote:
> > On Mon, Nov 7, 2022 at 3:10 PM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
> > >
> > > Currently, verifier uses MEM_ALLOC type tag to specially tag memory
> > > returned from bpf_ringbuf_reserve helper. However, this is currently
> > > only used for this purpose and there is an implicit assumption that it
> > > only refers to ringbuf memory (e.g. the check for ARG_PTR_TO_ALLOC_MEM
> > > in check_func_arg_reg_off).
> > >
> > > Hence, rename MEM_ALLOC to MEM_RINGBUF to indicate this special
> > > relationship and instead open the use of MEM_ALLOC for more generic
> > > allocations made for user types.
> > >
> > > Also, since ARG_PTR_TO_ALLOC_MEM_OR_NULL is unused, simply drop it.
> > >
> > > Finally, update selftests using 'alloc_' verifier string to 'ringbuf_'.
> > >
> > > Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> > > ---
> >
> > Ok, so you are doing what I asked in the previous patch, nice :)
> >
> > >  include/linux/bpf.h                               | 11 ++++-------
> > >  kernel/bpf/ringbuf.c                              |  6 +++---
> > >  kernel/bpf/verifier.c                             | 14 +++++++-------
> > >  tools/testing/selftests/bpf/prog_tests/dynptr.c   |  2 +-
> > >  tools/testing/selftests/bpf/verifier/ringbuf.c    |  2 +-
> > >  tools/testing/selftests/bpf/verifier/spill_fill.c |  2 +-
> > >  6 files changed, 17 insertions(+), 20 deletions(-)
> > >
> > > diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> > > index 2fe3ec620d54..afc1c51b59ff 100644
> > > --- a/include/linux/bpf.h
> > > +++ b/include/linux/bpf.h
> > > @@ -488,10 +488,8 @@ enum bpf_type_flag {
> > >          */
> > >         MEM_RDONLY              = BIT(1 + BPF_BASE_TYPE_BITS),
> > >
> > > -       /* MEM was "allocated" from a different helper, and cannot be mixed
> > > -        * with regular non-MEM_ALLOC'ed MEM types.
> > > -        */
> > > -       MEM_ALLOC               = BIT(2 + BPF_BASE_TYPE_BITS),
> > > +       /* MEM points to BPF ring buffer reservation. */
> > > +       MEM_RINGBUF             = BIT(2 + BPF_BASE_TYPE_BITS),
> >
> > What do we gain by having ringbuf memory as additional modified flag
> > instead of its own type like PTR_TO_MAP_VALUE or PTR_TO_PACKET? It
> > feels like here separate register type is more justified and is less
> > error prone overall.
> >
>
> I'm not sure it's all that different. It only matters when checking argument
> during release. We want to ensure it came from ringbuf_reserve. That's all,
> apart from that it's no different from PTR_TO_MEM. In all other places it's
> folded and code for PTR_TO_MEM is used. Same idea as PTR_TO_BTF_ID | MEM_ALLOC.
>
> But I don't feel too strongly, so if you still think it's better I can make the
> switch.

Not strongly, but I think having this as a flag is more error prone.
For cases where ringbuf memory should be treated just as memory, we
should use the same mechanism we have for MAP_VALUE. But I haven't
checked how we deal with MAP_VALUE, if that's a special case
everywhere, in addition to generic PTR_TO_MEM, then fine. But if
having PTR_TO_RINGBUF_MEM is converted to PTR_TO_MEM generically where
needed, I'd have dedicated PTR_TO_RINGBUF_MEM.

Re: [PATCH bpf-next v5 06/25] bpf: Introduce local kptrs

[Andrii Nakryiko]

On Tue, Nov 8, 2022 at 4:00 PM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
>
> On Wed, Nov 09, 2022 at 04:59:41AM IST, Andrii Nakryiko wrote:
> > On Mon, Nov 7, 2022 at 3:10 PM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
> > >
> > > Introduce local kptrs, i.e. PTR_TO_BTF_ID that point to a type in
> > > program BTF. This is indicated by the presence of MEM_ALLOC type flag in
> > > reg->type to avoid having to check btf_is_kernel when trying to match
> > > argument types in helpers.
> > >
> > > Refactor btf_struct_access callback to just take bpf_reg_state instead
> > > of btf and btf_type paramters. Note that the call site in
> > > check_map_access now simulates access to a PTR_TO_BTF_ID by creating a
> > > dummy reg on stack. Since only the type, btf, and btf_id of the register
> > > matter for the checks, it can be done so without complicating the usual
> > > cases elsewhere in the verifier where reg->btf and reg->btf_id is used
> > > verbatim.
> > >
> > > Whenever walking such types, any pointers being walked will always yield
> > > a SCALAR instead of pointer. In the future we might permit kptr inside
> > > local kptr (either kernel or local), and it would be permitted only in
> > > that case.
> > >
> > > For now, these local kptrs will always be referenced in verifier
> > > context, hence ref_obj_id == 0 for them is a bug. It is allowed to write
> > > to such objects, as long fields that are special are not touched
> > > (support for which will be added in subsequent patches). Note that once
> > > such a local kptr is marked PTR_UNTRUSTED, it is no longer allowed to
> > > write to it.
> > >
> > > No PROBE_MEM handling is therefore done for loads into this type unless
> > > PTR_UNTRUSTED is part of the register type, since they can never be in
> > > an undefined state, and their lifetime will always be valid.
> > >
> > > Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> > > ---
> > >  include/linux/bpf.h              | 28 ++++++++++++++++--------
> > >  include/linux/filter.h           |  8 +++----
> > >  kernel/bpf/btf.c                 | 16 ++++++++++----
> > >  kernel/bpf/verifier.c            | 37 ++++++++++++++++++++++++++------
> > >  net/bpf/bpf_dummy_struct_ops.c   | 14 ++++++------
> > >  net/core/filter.c                | 34 ++++++++++++-----------------
> > >  net/ipv4/bpf_tcp_ca.c            | 13 ++++++-----
> > >  net/netfilter/nf_conntrack_bpf.c | 17 ++++++---------
> > >  8 files changed, 99 insertions(+), 68 deletions(-)
> > >
> > > diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> > > index afc1c51b59ff..75dbd2ecf80a 100644
> > > --- a/include/linux/bpf.h
> > > +++ b/include/linux/bpf.h
> > > @@ -524,6 +524,11 @@ enum bpf_type_flag {
> > >         /* Size is known at compile time. */
> > >         MEM_FIXED_SIZE          = BIT(10 + BPF_BASE_TYPE_BITS),
> > >
> > > +       /* MEM is of a type from program BTF, not kernel BTF. This is used to
> > > +        * tag PTR_TO_BTF_ID allocated using bpf_obj_new.
> > > +        */
> > > +       MEM_ALLOC               = BIT(11 + BPF_BASE_TYPE_BITS),
> > > +
> >
> > you fixed one naming confusion with RINGBUF and basically are creating
> > a new one, where "ALLOC" means "local kptr"... If we are stuck with
> > "local kptr" (which I find very confusing as well, but that's beside
> > the point), why not stick to the whole "local" terminology here?
> > MEM_LOCAL?
> >
>
> See the discussion about this in v4:
> https://lore.kernel.org/bpf/20221104075113.5ighwdvero4mugu7@apollo
>
> It was MEM_TYPE_LOCAL before. Also, better naming suggestions are always
> welcome, I asked the same in that message as well.

Sorry, I haven't followed <v5. Don't have perfect name, but logically
this is BPF program memory. So "prog_kptr" would be something to
convert this, but I'm not super happy with such a name. "user_kptr"
would be too confusing, drawing incorrect "kernel space vs user space"
comparison, while both are kernel memory. It's BPF-side kptr, so
"bpf_kptr", but also not great.

So that's why didn't suggest anything specific, but at least as far as
MEM_xxx flag goes, MEM_LOCAL_KPTR is better than MEM_ALLOC, IMO. It's
at least consistent with the official name of the concept it
represents.

>
> > >         __BPF_TYPE_FLAG_MAX,
> > >         __BPF_TYPE_LAST_FLAG    = __BPF_TYPE_FLAG_MAX - 1,
> > >  };
> > > @@ -771,6 +776,7 @@ struct bpf_prog_ops {
> > >                         union bpf_attr __user *uattr);
> > >  };
> > >
> >
> > [...]
> >
> > > -int btf_struct_access(struct bpf_verifier_log *log, const struct btf *btf,
> > > -                     const struct btf_type *t, int off, int size,
> > > -                     enum bpf_access_type atype __maybe_unused,
> > > +int btf_struct_access(struct bpf_verifier_log *log,
> > > +                     const struct bpf_reg_state *reg,
> > > +                     int off, int size, enum bpf_access_type atype __maybe_unused,
> > >                       u32 *next_btf_id, enum bpf_type_flag *flag)
> > >  {
> > > +       const struct btf *btf = reg->btf;
> > >         enum bpf_type_flag tmp_flag = 0;
> > > +       const struct btf_type *t;
> > > +       u32 id = reg->btf_id;
> > >         int err;
> > > -       u32 id;
> > >
> > > +       t = btf_type_by_id(btf, id);
> > >         do {
> > >                 err = btf_struct_walk(log, btf, t, off, size, &id, &tmp_flag);
> > >
> > >                 switch (err) {
> > >                 case WALK_PTR:
> > > +                       /* For local types, the destination register cannot
> > > +                        * become a pointer again.
> > > +                        */
> > > +                       if (type_is_local_kptr(reg->type))
> > > +                               return SCALAR_VALUE;
> >
> > passing the entire bpf_reg_state just to differentiate between local
> > vs kernel pointer seems like a huge overkill. bpf_reg_state is quite a
> > complicated and extensive amount of state, and it seems cleaner to
> > just pass it as a flag whether to allow pointer chasing or not. At
> > least then we know we only care about that specific aspect, not about
> > dozens of other possible fields of bpf_reg_state.
> >
>
> I agree that the separation is usually better, especially because this is also a
> callback. I don't feel too strong about this though, we certainly do pass the
> whole reg to functions which only work on a specific type of pointer. Though the

Yeah, and then it takes a lot of grepping and jumping around the code
to verify that only one simple field out of the entire bpf_reg_state
is actually used. I'd say this is actually bad that we do pass it
around so willy-nilly. Verifier code is already a hot complex mess,
let's not actively make it harder than necessary.

> concern in this case is justified as it's not only an internal function but also
> a callback.
>
> It was just a bool in the RFC.
> But in https://lore.kernel.org/bpf/20220907233023.x3uclwlnjuhftvtb@macbook-pro-4.dhcp.thefacebook.com
> Alexei suggested passing reg instead.
> From the link:
> > imo it's cleaner to pass 'reg' instead of 'reg->btf',
> > so we don't have to pass another boolean.
> > And check type_is_local(reg) inside btf_struct_access().

I sympathize with "too many input args" (especially if it's a bunch of
bools) argument, but see above, I find it increasingly harder to know
what parts of complex internal register state is used by helper
functions and which are not.

And the fact that we have to construct a fake register state in some
case is a red flag to me. Pass enum bpf_reg_type type to avoid passing
true/false. Or let's invent a new enum. Or extend enum bpf_access_type
to have READ_NOPTR/WRITE_NOPTR or something like that. Don't know.

This isn't a major issue, I can live with this just fine, but this
definitely doesn't feel like a clean approach.

Re: [PATCH bpf-next v5 03/25] bpf: Support bpf_list_head in map values

[Alexei Starovoitov]

On Tue, Nov 8, 2022 at 4:23 PM Andrii Nakryiko
<andrii.nakryiko@gmail.com> wrote:
> > > >  struct bpf_offload_dev;
> > > > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > > > index 94659f6b3395..dd381086bad9 100644
> > > > --- a/include/uapi/linux/bpf.h
> > > > +++ b/include/uapi/linux/bpf.h
> > > > @@ -6887,6 +6887,16 @@ struct bpf_dynptr {
> > > >         __u64 :64;
> > > >  } __attribute__((aligned(8)));
> > > >
> > > > +struct bpf_list_head {
> > > > +       __u64 :64;
> > > > +       __u64 :64;
> > > > +} __attribute__((aligned(8)));
> > > > +
> > > > +struct bpf_list_node {
> > > > +       __u64 :64;
> > > > +       __u64 :64;
> > > > +} __attribute__((aligned(8)));
> > >
> > > Dave mentioned that this `__u64 :64` trick makes vmlinux.h lose the
> > > alignment information, as the struct itself is empty, and so there is
> > > nothing indicating that it has to be 8-byte aligned.

Since it's not a new issue let's fix it for all.
Whether it's a combination of pahole + bpftool or just pahole.

> > >
> > > So what if we have
> > >
> > > struct bpf_list_node {
> > >     __u64 __opaque[2];
> > > } __attribute__((aligned(8)));
> > >
> > > ?
> > >
> >
> > Yep, can do that. Note that it's also potentially an issue for existing cases,
> > like bpf_spin_lock, bpf_timer, bpf_dynptr, etc. Not completely sure if changing
> > things now is possible, but if it is, we should probably make it for all of
> > them?
>
> Why not? We are not removing anything or changing sizes, so it's
> backwards compatible.
> But I have a suspicion Alexei might not like
> this __opaque field, so let's see what he says.

I prefer to fix them all at once without adding a name.

>
> > > >                 off = vsi->offset;
> > > > +               if (i && !off)
> > > > +                       return -EFAULT;
> > >
> > > similarly, I'd say that either we'd need to calculate the exact
> > > expected offset, or just not do anything here?
> > >
> >
> > This thread is actually what prompted this check:
> > https://lore.kernel.org/bpf/CAEf4Bza7ga2hEQ4J7EtgRHz49p1vZtaT4d2RDiyGOKGK41Nt=Q@mail.gmail.com
> >
> > Unless loaded using libbpf all offsets are zero. So I think we need to reject it
> > here, but I think the same zero sized field might be an issue for this as well,
> > so maybe we remember the last field size and check whether it was zero or not?
> >
> > I'll also include some more tests for these cases.
>
> The question is whether this affects correctness from the verifier
> standpoint? If it does, there must be some other place where this will
> cause problem and should be caught and reported.

If it's an issue with BTF then we should probably check it
during generic datasec verification.
Here it's kinda late to warn.

> My main objection is that it's half a check, we check that it's
> non-zero, but we don't check that it is correct in stricter sense. So
> I'd rather drop it altogether, or go all the way to check that it is
> correct offset (taking into account sizes of previous vars).

Re: [PATCH bpf-next v5 05/25] bpf: Rename MEM_ALLOC to MEM_RINGBUF

[Alexei Starovoitov]

On Tue, Nov 8, 2022 at 4:26 PM Andrii Nakryiko
<andrii.nakryiko@gmail.com> wrote:
>
> On Tue, Nov 8, 2022 at 3:49 PM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
> >
> > On Wed, Nov 09, 2022 at 04:44:16AM IST, Andrii Nakryiko wrote:
> > > On Mon, Nov 7, 2022 at 3:10 PM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
> > > >
> > > > Currently, verifier uses MEM_ALLOC type tag to specially tag memory
> > > > returned from bpf_ringbuf_reserve helper. However, this is currently
> > > > only used for this purpose and there is an implicit assumption that it
> > > > only refers to ringbuf memory (e.g. the check for ARG_PTR_TO_ALLOC_MEM
> > > > in check_func_arg_reg_off).
> > > >
> > > > Hence, rename MEM_ALLOC to MEM_RINGBUF to indicate this special
> > > > relationship and instead open the use of MEM_ALLOC for more generic
> > > > allocations made for user types.
> > > >
> > > > Also, since ARG_PTR_TO_ALLOC_MEM_OR_NULL is unused, simply drop it.
> > > >
> > > > Finally, update selftests using 'alloc_' verifier string to 'ringbuf_'.
> > > >
> > > > Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> > > > ---
> > >
> > > Ok, so you are doing what I asked in the previous patch, nice :)
> > >
> > > >  include/linux/bpf.h                               | 11 ++++-------
> > > >  kernel/bpf/ringbuf.c                              |  6 +++---
> > > >  kernel/bpf/verifier.c                             | 14 +++++++-------
> > > >  tools/testing/selftests/bpf/prog_tests/dynptr.c   |  2 +-
> > > >  tools/testing/selftests/bpf/verifier/ringbuf.c    |  2 +-
> > > >  tools/testing/selftests/bpf/verifier/spill_fill.c |  2 +-
> > > >  6 files changed, 17 insertions(+), 20 deletions(-)
> > > >
> > > > diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> > > > index 2fe3ec620d54..afc1c51b59ff 100644
> > > > --- a/include/linux/bpf.h
> > > > +++ b/include/linux/bpf.h
> > > > @@ -488,10 +488,8 @@ enum bpf_type_flag {
> > > >          */
> > > >         MEM_RDONLY              = BIT(1 + BPF_BASE_TYPE_BITS),
> > > >
> > > > -       /* MEM was "allocated" from a different helper, and cannot be mixed
> > > > -        * with regular non-MEM_ALLOC'ed MEM types.
> > > > -        */
> > > > -       MEM_ALLOC               = BIT(2 + BPF_BASE_TYPE_BITS),
> > > > +       /* MEM points to BPF ring buffer reservation. */
> > > > +       MEM_RINGBUF             = BIT(2 + BPF_BASE_TYPE_BITS),
> > >
> > > What do we gain by having ringbuf memory as additional modified flag
> > > instead of its own type like PTR_TO_MAP_VALUE or PTR_TO_PACKET? It
> > > feels like here separate register type is more justified and is less
> > > error prone overall.
> > >
> >
> > I'm not sure it's all that different. It only matters when checking argument
> > during release. We want to ensure it came from ringbuf_reserve. That's all,
> > apart from that it's no different from PTR_TO_MEM. In all other places it's
> > folded and code for PTR_TO_MEM is used. Same idea as PTR_TO_BTF_ID | MEM_ALLOC.
> >
> > But I don't feel too strongly, so if you still think it's better I can make the
> > switch.
>
> Not strongly, but I think having this as a flag is more error prone.
> For cases where ringbuf memory should be treated just as memory, we
> should use the same mechanism we have for MAP_VALUE. But I haven't
> checked how we deal with MAP_VALUE, if that's a special case
> everywhere, in addition to generic PTR_TO_MEM, then fine. But if
> having PTR_TO_RINGBUF_MEM is converted to PTR_TO_MEM generically where
> needed, I'd have dedicated PTR_TO_RINGBUF_MEM.

I don't think we can or at least it's not as easy to generalize
ringbuf mem as map_value.
iirc MEM_ALLOC was there to make sure reserver->commit is the same mem.
That's what MEM_RINGBUF will doing after this patch.

Re: [PATCH bpf-next v5 06/25] bpf: Introduce local kptrs

[Alexei Starovoitov]

On Tue, Nov 8, 2022 at 4:36 PM Andrii Nakryiko
<andrii.nakryiko@gmail.com> wrote:
>
> On Tue, Nov 8, 2022 at 4:00 PM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
> >
> > On Wed, Nov 09, 2022 at 04:59:41AM IST, Andrii Nakryiko wrote:
> > > On Mon, Nov 7, 2022 at 3:10 PM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
> > > >
> > > > Introduce local kptrs, i.e. PTR_TO_BTF_ID that point to a type in
> > > > program BTF. This is indicated by the presence of MEM_ALLOC type flag in
> > > > reg->type to avoid having to check btf_is_kernel when trying to match
> > > > argument types in helpers.
> > > >
> > > > Refactor btf_struct_access callback to just take bpf_reg_state instead
> > > > of btf and btf_type paramters. Note that the call site in
> > > > check_map_access now simulates access to a PTR_TO_BTF_ID by creating a
> > > > dummy reg on stack. Since only the type, btf, and btf_id of the register
> > > > matter for the checks, it can be done so without complicating the usual
> > > > cases elsewhere in the verifier where reg->btf and reg->btf_id is used
> > > > verbatim.
> > > >
> > > > Whenever walking such types, any pointers being walked will always yield
> > > > a SCALAR instead of pointer. In the future we might permit kptr inside
> > > > local kptr (either kernel or local), and it would be permitted only in
> > > > that case.
> > > >
> > > > For now, these local kptrs will always be referenced in verifier
> > > > context, hence ref_obj_id == 0 for them is a bug. It is allowed to write
> > > > to such objects, as long fields that are special are not touched
> > > > (support for which will be added in subsequent patches). Note that once
> > > > such a local kptr is marked PTR_UNTRUSTED, it is no longer allowed to
> > > > write to it.
> > > >
> > > > No PROBE_MEM handling is therefore done for loads into this type unless
> > > > PTR_UNTRUSTED is part of the register type, since they can never be in
> > > > an undefined state, and their lifetime will always be valid.
> > > >
> > > > Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> > > > ---
> > > >  include/linux/bpf.h              | 28 ++++++++++++++++--------
> > > >  include/linux/filter.h           |  8 +++----
> > > >  kernel/bpf/btf.c                 | 16 ++++++++++----
> > > >  kernel/bpf/verifier.c            | 37 ++++++++++++++++++++++++++------
> > > >  net/bpf/bpf_dummy_struct_ops.c   | 14 ++++++------
> > > >  net/core/filter.c                | 34 ++++++++++++-----------------
> > > >  net/ipv4/bpf_tcp_ca.c            | 13 ++++++-----
> > > >  net/netfilter/nf_conntrack_bpf.c | 17 ++++++---------
> > > >  8 files changed, 99 insertions(+), 68 deletions(-)
> > > >
> > > > diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> > > > index afc1c51b59ff..75dbd2ecf80a 100644
> > > > --- a/include/linux/bpf.h
> > > > +++ b/include/linux/bpf.h
> > > > @@ -524,6 +524,11 @@ enum bpf_type_flag {
> > > >         /* Size is known at compile time. */
> > > >         MEM_FIXED_SIZE          = BIT(10 + BPF_BASE_TYPE_BITS),
> > > >
> > > > +       /* MEM is of a type from program BTF, not kernel BTF. This is used to
> > > > +        * tag PTR_TO_BTF_ID allocated using bpf_obj_new.
> > > > +        */
> > > > +       MEM_ALLOC               = BIT(11 + BPF_BASE_TYPE_BITS),
> > > > +
> > >
> > > you fixed one naming confusion with RINGBUF and basically are creating
> > > a new one, where "ALLOC" means "local kptr"... If we are stuck with
> > > "local kptr" (which I find very confusing as well, but that's beside
> > > the point), why not stick to the whole "local" terminology here?
> > > MEM_LOCAL?
> > >
> >
> > See the discussion about this in v4:
> > https://lore.kernel.org/bpf/20221104075113.5ighwdvero4mugu7@apollo
> >
> > It was MEM_TYPE_LOCAL before. Also, better naming suggestions are always
> > welcome, I asked the same in that message as well.
>
> Sorry, I haven't followed <v5. Don't have perfect name, but logically
> this is BPF program memory. So "prog_kptr" would be something to
> convert this, but I'm not super happy with such a name. "user_kptr"
> would be too confusing, drawing incorrect "kernel space vs user space"
> comparison, while both are kernel memory. It's BPF-side kptr, so
> "bpf_kptr", but also not great.

yep. I went through the same thinking process.

> So that's why didn't suggest anything specific, but at least as far as
> MEM_xxx flag goes, MEM_LOCAL_KPTR is better than MEM_ALLOC, IMO. It's
> at least consistent with the official name of the concept it
> represents.

"local kptr" doesn't fit here.
In libbpf, "local" is equally badly named.
If "local" was a good name we wouldn't have had this discussion.
So we need to fix it libbpf, but we should start with a proper
name in the kernel.
And "local kptr" is not it.

We must avoid exhausting bikeshedding too.
MEM_ALLOC is something we can use right now and
as long as "local kptr" doesn't appear in docs, comments and
commit logs we're good.
We can rename MEM_ALLOC to something else later.

In commit logs we can just say that this is
a pointer to an object allocated by the bpf program.
It's crystal clear definition whereas "local kptr" is nonsensical.

Going back to the kptr definition.
kptr was supposed to mean a pointer to a kernel object.
In that light "pointer to an object allocated by the bpf prog"
is something else.
Maybe "bptr" ?
In some ways bpf is a layer different from kernel space and user space.
Some people joked that there is ring-0 for kernel, ring-3 for user space
while bpf runs in ring-B.
Two new btf_tags __bptr and __bptr_ref (or may be just one?)
might be necessary as well to make it easier to distinguish
kernel and bpf prog allocated objects.

> >
> > It was just a bool in the RFC.
> > But in https://lore.kernel.org/bpf/20220907233023.x3uclwlnjuhftvtb@macbook-pro-4.dhcp.thefacebook.com
> > Alexei suggested passing reg instead.
> > From the link:
> > > imo it's cleaner to pass 'reg' instead of 'reg->btf',
> > > so we don't have to pass another boolean.
> > > And check type_is_local(reg) inside btf_struct_access().
>
> I sympathize with "too many input args" (especially if it's a bunch of
> bools) argument, but see above, I find it increasingly harder to know
> what parts of complex internal register state is used by helper
> functions and which are not.
>
> And the fact that we have to construct a fake register state in some
> case is a red flag to me. Pass enum bpf_reg_type type to avoid passing
> true/false. Or let's invent a new enum. Or extend enum bpf_access_type
> to have READ_NOPTR/WRITE_NOPTR or something like that. Don't know.
>
> This isn't a major issue, I can live with this just fine, but this
> definitely doesn't feel like a clean approach.

I think passing bpf_reg_state is a lesser evil _right_now_ and
I prefer we proceed this way, since other works are blocked on
this patch set.
We did plenty of refactoring of the verifier in the past.
There will be more in the future.

Re: [PATCH bpf-next v5 15/25] bpf: Teach verifier about non-size constant arguments

[Kumar Kartikeya Dwivedi]

On Wed, Nov 09, 2022 at 05:35:26AM IST, Andrii Nakryiko wrote:
> On Mon, Nov 7, 2022 at 3:10 PM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
> >
> > Currently, the verifier has support for various arguments that either
> > describe the size of the memory being passed in to a helper, or describe
> > the size of the memory being returned. When a constant is passed in like
> > this, it is assumed for the purposes of precision tracking that if the
> > value in the already explored safe state is within the value in current
> > state, it would fine to prune the search.
> >
> > While this holds well for size arguments, arguments where each value may
> > denote a distinct meaning and needs to be verified separately needs more
> > work. Search can only be pruned if both are equivalent values. In all
> > other cases, it would be incorrect to treat those two precise registers
> > as equivalent if the new value satisfies the old one (i.e. old <= cur).
> >
> > Hence, make the register precision marker tri-state. There are now three
> > values that reg->precise takes: NOT_PRECISE, PRECISE, EXACT.
> >
> > Both PRECISE and EXACT are 'true' values. EXACT affects how regsafe
> > decides whether both registers are equivalent for the purposes of
> > verifier state equivalence. When it sees that old state register has
> > reg->precise == EXACT, unless both are equivalent, it will return false.
> > Otherwise, for PRECISE case it falls back to the default check that is
> > present now (i.e. thinking that we're talking about sizes).
> >
> > This is required as a future patch introduces a BPF memory allocator
> > interface, where we take the program BTF's type ID as an argument. Each
> > distinct type ID may result in the returned pointer obtaining a
> > different size, hence precision tracking is needed, and pruning cannot
> > just happen when the old value is within the current value. It must only
> > happen when the type ID is equal. The type ID will always correspond to
> > prog->aux->btf hence actual type match is not required.
> >
> > Finally, change mark_chain_precision precision argument to EXACT for
> > kfuncs constant non-size scalar arguments (tagged with __k suffix).
> >
> > Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> > ---
>
> I think this needs a bit more thinking, tbh. First, with my recent
> changes we don't even set precision marks in current state, everything
> stays imprecise. And then under CAP_BPF we also aggressively reset
> precision. This might work for EXACT, but needs careful consideration.
>

I'm sorry, I didn't have the time to look at the series, but I spent the whole
day going over it today, and it makes a lot of sense to me. I think I also
misunderstood some things and going through it brought some clarity.

I think resetting precision is fine here too. As you've stated in that series,
the verifier while simulating execution in current state already checks
everything.

> But, taking a step back. I'm trying to understand why this whole EXACT
> mode is necessary. SCALAR has min/max values which regsafe() does
> check. So for those special ___k arguments, if we correctly set
> min/max values to be *exactly* the btf_id passed in, why would
> regsafe()'s logic not work?
>

Yes, when you have tnum_is_const var_off, regsafe will return false (when
reg->precise is true). So EXACT is unnecessary in that case.

I think you're probably right. The range_within will fail for k1 != k2,
but I was more concerned for cases where it's not a constant made a concrete
value later.

rX = ...; [X1, Y1];
if (cond) // unknown
  rX = ...; [X2, Y2];
p:
...

p is a pruning point, so states will be compared there. I spent a fair amount of
time today trying to break this in different ways but failed so far. Also,
thinking about if it still lies within that range, things should still be ok
since it's in the same admissible set of values for the scalar that was later
refined and used as a constant for bpf_obj_new. So it's probably unncessary to
make things more pessimistic. The verifier will ensure the current value is
always a subset of the old value.

I guess I'll hold on for this patch and work towards getting the rest in first
(since Alexei mentioned others are waiting on this), and circle back to this if
I am able to construct a real test case that breaks. bpf_obj_new is already
behind CAP_BPF.

Re: [PATCH bpf-next v5 22/25] selftests/bpf: Update spinlock selftest

[Kumar Kartikeya Dwivedi]

On Wed, Nov 09, 2022 at 05:43:34AM IST, Andrii Nakryiko wrote:
> On Mon, Nov 7, 2022 at 3:11 PM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
> >
> > Make updates in preparation for adding more test cases to this selftest:
> > - Convert from CHECK_ to ASSERT macros.
> > - Use BPF skeleton
> > - Fix typo sping -> spin
> > - Rename spinlock.c -> spin_lock.c
> >
> > Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> > ---
> >  .../selftests/bpf/prog_tests/spin_lock.c      | 46 +++++++++++++++++++
> >  .../selftests/bpf/prog_tests/spinlock.c       | 45 ------------------
> >  .../selftests/bpf/progs/test_spin_lock.c      |  4 +-
> >  3 files changed, 48 insertions(+), 47 deletions(-)
> >  create mode 100644 tools/testing/selftests/bpf/prog_tests/spin_lock.c
> >  delete mode 100644 tools/testing/selftests/bpf/prog_tests/spinlock.c
> >
>
> [...]
>
> > +void test_spinlock(void)
> > +{
> > +       struct test_spin_lock *skel;
> > +       pthread_t thread_id[4];
> > +       int prog_fd, i;
> > +       void *ret;
> > +
> > +       skel = test_spin_lock__open_and_load();
> > +       if (!ASSERT_OK_PTR(skel, "test_spin_lock__open_and_load"))
> > +               return;
> > +       prog_fd = bpf_program__fd(skel->progs.bpf_spin_lock_test);
> > +       for (i = 0; i < 4; i++)
> > +               if (!ASSERT_OK(pthread_create(&thread_id[i], NULL,
> > +                                             &spin_lock_thread, &prog_fd), "pthread_create"))
>
> I mean... does that pthread_create() call have to happen inside ASSERT_OK?
>
> err = pthread_create(...)
> if (!ASSERT_OK(err, "pthread_create"))
>     goto end;
>

Ack, I'll rewrite it like this.

Re: [PATCH bpf-next v5 25/25] selftests/bpf: Add BTF sanity tests

[Kumar Kartikeya Dwivedi]

On Wed, Nov 09, 2022 at 05:48:00AM IST, Andrii Nakryiko wrote:
> On Mon, Nov 7, 2022 at 3:11 PM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
> >
> > Preparing the metadata for bpf_list_head involves a complicated parsing
> > step and type resolution for the contained value. Ensure that corner
> > cases are tested against and invalid specifications in source are duly
> > rejected. Also include tests for incorrect ownership relationships in
> > the BTF.
> >
> > Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> > ---
> >  .../selftests/bpf/prog_tests/linked_list.c    | 271 ++++++++++++++++++
> >  1 file changed, 271 insertions(+)
> >
>
> Have you considered using BTW write API to construct BTFs?
> btf__new_empty() + btf__add_xxx()?
>

I didn't know about these. Let me give them a shot!

Re: [PATCH bpf-next v5 03/25] bpf: Support bpf_list_head in map values

[Kumar Kartikeya Dwivedi]

On Wed, Nov 09, 2022 at 06:33:25AM IST, Alexei Starovoitov wrote:
> On Tue, Nov 8, 2022 at 4:23 PM Andrii Nakryiko
> <andrii.nakryiko@gmail.com> wrote:
> > > > >  struct bpf_offload_dev;
> > > > > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > > > > index 94659f6b3395..dd381086bad9 100644
> > > > > --- a/include/uapi/linux/bpf.h
> > > > > +++ b/include/uapi/linux/bpf.h
> > > > > @@ -6887,6 +6887,16 @@ struct bpf_dynptr {
> > > > >         __u64 :64;
> > > > >  } __attribute__((aligned(8)));
> > > > >
> > > > > +struct bpf_list_head {
> > > > > +       __u64 :64;
> > > > > +       __u64 :64;
> > > > > +} __attribute__((aligned(8)));
> > > > > +
> > > > > +struct bpf_list_node {
> > > > > +       __u64 :64;
> > > > > +       __u64 :64;
> > > > > +} __attribute__((aligned(8)));
> > > >
> > > > Dave mentioned that this `__u64 :64` trick makes vmlinux.h lose the
> > > > alignment information, as the struct itself is empty, and so there is
> > > > nothing indicating that it has to be 8-byte aligned.
>
> Since it's not a new issue let's fix it for all.
> Whether it's a combination of pahole + bpftool or just pahole.
>

Would it make sense to do that as a follow up? The selftest does work right now
because I specified __attribute__((aligned(8))) manually for the variables.

> > > >
> > > > So what if we have
> > > >
> > > > struct bpf_list_node {
> > > >     __u64 __opaque[2];
> > > > } __attribute__((aligned(8)));
> > > >
> > > > ?
> > > >
> > >
> > > Yep, can do that. Note that it's also potentially an issue for existing cases,
> > > like bpf_spin_lock, bpf_timer, bpf_dynptr, etc. Not completely sure if changing
> > > things now is possible, but if it is, we should probably make it for all of
> > > them?
> >
> > Why not? We are not removing anything or changing sizes, so it's
> > backwards compatible.
> > But I have a suspicion Alexei might not like
> > this __opaque field, so let's see what he says.
>
> I prefer to fix them all at once without adding a name.
>
> >
> > > > >                 off = vsi->offset;
> > > > > +               if (i && !off)
> > > > > +                       return -EFAULT;
> > > >
> > > > similarly, I'd say that either we'd need to calculate the exact
> > > > expected offset, or just not do anything here?
> > > >
> > >
> > > This thread is actually what prompted this check:
> > > https://lore.kernel.org/bpf/CAEf4Bza7ga2hEQ4J7EtgRHz49p1vZtaT4d2RDiyGOKGK41Nt=Q@mail.gmail.com
> > >
> > > Unless loaded using libbpf all offsets are zero. So I think we need to reject it
> > > here, but I think the same zero sized field might be an issue for this as well,
> > > so maybe we remember the last field size and check whether it was zero or not?
> > >
> > > I'll also include some more tests for these cases.
> >
> > The question is whether this affects correctness from the verifier
> > standpoint? If it does, there must be some other place where this will
> > cause problem and should be caught and reported.

The problem here is that if the BTF is incorrect like this, where you have same
off for multiple items (bpf_spin_lock, bpf_list_head, etc.) like off=0 here,
they essentially get the same offset in our btf_record array.

I can check for it when appending items to the array (i.e. next offset must be
atleast prev_off + prev_sz at the very minimum).

>
> If it's an issue with BTF then we should probably check it
> during generic datasec verification.
> Here it's kinda late to warn.
>

There's also a concern that clang produces this BTF by default. If you're not
using libbpf as a loader, BTF that loaded previously will fail now (since
DATASEC var offs are always 0 and we will complain during validation and return
an error). Not sure what the impact will be, but just putting it out there.

Let me know what should be better. In either case I'll add a test case.

Re: [PATCH bpf-next v5 06/25] bpf: Introduce local kptrs

[Kumar Kartikeya Dwivedi]

On Wed, Nov 09, 2022 at 07:02:11AM IST, Alexei Starovoitov wrote:
> On Tue, Nov 8, 2022 at 4:36 PM Andrii Nakryiko
> <andrii.nakryiko@gmail.com> wrote:
> >
> > On Tue, Nov 8, 2022 at 4:00 PM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
> > >
> > > On Wed, Nov 09, 2022 at 04:59:41AM IST, Andrii Nakryiko wrote:
> > > > On Mon, Nov 7, 2022 at 3:10 PM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
> > > > >
> > > > > Introduce local kptrs, i.e. PTR_TO_BTF_ID that point to a type in
> > > > > program BTF. This is indicated by the presence of MEM_ALLOC type flag in
> > > > > reg->type to avoid having to check btf_is_kernel when trying to match
> > > > > argument types in helpers.
> > > > >
> > > > > Refactor btf_struct_access callback to just take bpf_reg_state instead
> > > > > of btf and btf_type paramters. Note that the call site in
> > > > > check_map_access now simulates access to a PTR_TO_BTF_ID by creating a
> > > > > dummy reg on stack. Since only the type, btf, and btf_id of the register
> > > > > matter for the checks, it can be done so without complicating the usual
> > > > > cases elsewhere in the verifier where reg->btf and reg->btf_id is used
> > > > > verbatim.
> > > > >
> > > > > Whenever walking such types, any pointers being walked will always yield
> > > > > a SCALAR instead of pointer. In the future we might permit kptr inside
> > > > > local kptr (either kernel or local), and it would be permitted only in
> > > > > that case.
> > > > >
> > > > > For now, these local kptrs will always be referenced in verifier
> > > > > context, hence ref_obj_id == 0 for them is a bug. It is allowed to write
> > > > > to such objects, as long fields that are special are not touched
> > > > > (support for which will be added in subsequent patches). Note that once
> > > > > such a local kptr is marked PTR_UNTRUSTED, it is no longer allowed to
> > > > > write to it.
> > > > >
> > > > > No PROBE_MEM handling is therefore done for loads into this type unless
> > > > > PTR_UNTRUSTED is part of the register type, since they can never be in
> > > > > an undefined state, and their lifetime will always be valid.
> > > > >
> > > > > Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> > > > > ---
> > > > >  include/linux/bpf.h              | 28 ++++++++++++++++--------
> > > > >  include/linux/filter.h           |  8 +++----
> > > > >  kernel/bpf/btf.c                 | 16 ++++++++++----
> > > > >  kernel/bpf/verifier.c            | 37 ++++++++++++++++++++++++++------
> > > > >  net/bpf/bpf_dummy_struct_ops.c   | 14 ++++++------
> > > > >  net/core/filter.c                | 34 ++++++++++++-----------------
> > > > >  net/ipv4/bpf_tcp_ca.c            | 13 ++++++-----
> > > > >  net/netfilter/nf_conntrack_bpf.c | 17 ++++++---------
> > > > >  8 files changed, 99 insertions(+), 68 deletions(-)
> > > > >
> > > > > diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> > > > > index afc1c51b59ff..75dbd2ecf80a 100644
> > > > > --- a/include/linux/bpf.h
> > > > > +++ b/include/linux/bpf.h
> > > > > @@ -524,6 +524,11 @@ enum bpf_type_flag {
> > > > >         /* Size is known at compile time. */
> > > > >         MEM_FIXED_SIZE          = BIT(10 + BPF_BASE_TYPE_BITS),
> > > > >
> > > > > +       /* MEM is of a type from program BTF, not kernel BTF. This is used to
> > > > > +        * tag PTR_TO_BTF_ID allocated using bpf_obj_new.
> > > > > +        */
> > > > > +       MEM_ALLOC               = BIT(11 + BPF_BASE_TYPE_BITS),
> > > > > +
> > > >
> > > > you fixed one naming confusion with RINGBUF and basically are creating
> > > > a new one, where "ALLOC" means "local kptr"... If we are stuck with
> > > > "local kptr" (which I find very confusing as well, but that's beside
> > > > the point), why not stick to the whole "local" terminology here?
> > > > MEM_LOCAL?
> > > >
> > >
> > > See the discussion about this in v4:
> > > https://lore.kernel.org/bpf/20221104075113.5ighwdvero4mugu7@apollo
> > >
> > > It was MEM_TYPE_LOCAL before. Also, better naming suggestions are always
> > > welcome, I asked the same in that message as well.
> >
> > Sorry, I haven't followed <v5. Don't have perfect name, but logically
> > this is BPF program memory. So "prog_kptr" would be something to
> > convert this, but I'm not super happy with such a name. "user_kptr"
> > would be too confusing, drawing incorrect "kernel space vs user space"
> > comparison, while both are kernel memory. It's BPF-side kptr, so
> > "bpf_kptr", but also not great.
>
> yep. I went through the same thinking process.
>
> > So that's why didn't suggest anything specific, but at least as far as
> > MEM_xxx flag goes, MEM_LOCAL_KPTR is better than MEM_ALLOC, IMO. It's
> > at least consistent with the official name of the concept it
> > represents.
>
> "local kptr" doesn't fit here.
> In libbpf, "local" is equally badly named.
> If "local" was a good name we wouldn't have had this discussion.
> So we need to fix it libbpf, but we should start with a proper
> name in the kernel.
> And "local kptr" is not it.
>
> We must avoid exhausting bikeshedding too.
> MEM_ALLOC is something we can use right now and
> as long as "local kptr" doesn't appear in docs, comments and
> commit logs we're good.
> We can rename MEM_ALLOC to something else later.
>
> In commit logs we can just say that this is
> a pointer to an object allocated by the bpf program.
> It's crystal clear definition whereas "local kptr" is nonsensical.
>

Ok, I'll drop the naming everywhere.

> Going back to the kptr definition.
> kptr was supposed to mean a pointer to a kernel object.
> In that light "pointer to an object allocated by the bpf prog"
> is something else.
> Maybe "bptr" ?
> In some ways bpf is a layer different from kernel space and user space.
> Some people joked that there is ring-0 for kernel, ring-3 for user space
> while bpf runs in ring-B.
> Two new btf_tags __bptr and __bptr_ref (or may be just one?)
> might be necessary as well to make it easier to distinguish
> kernel and bpf prog allocated objects.
>

There's also the option of simply using __kptr and __kptr_ref for these (without
__local tag in BPF maps) and doing two stage name lookup for the types. Kernel
BTF takes precedence, if not found there, then it searches program BTF for a
local type. It would probably the simplest for users.

struct map_value {
	struct nf_conn __kptr_ref *ct; // kernel
	struct foo __kptr_ref *f; // local
	struct task_struct __kptr_ref *t; // kernel
	struct bar __kptr_ref *b; // local
}

We can revisit this again once the post the follow up to store them in maps.

Re: [PATCH bpf-next v5 05/25] bpf: Rename MEM_ALLOC to MEM_RINGBUF

[Andrii Nakryiko]

On Tue, Nov 8, 2022 at 5:05 PM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> On Tue, Nov 8, 2022 at 4:26 PM Andrii Nakryiko
> <andrii.nakryiko@gmail.com> wrote:
> >
> > On Tue, Nov 8, 2022 at 3:49 PM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
> > >
> > > On Wed, Nov 09, 2022 at 04:44:16AM IST, Andrii Nakryiko wrote:
> > > > On Mon, Nov 7, 2022 at 3:10 PM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
> > > > >
> > > > > Currently, verifier uses MEM_ALLOC type tag to specially tag memory
> > > > > returned from bpf_ringbuf_reserve helper. However, this is currently
> > > > > only used for this purpose and there is an implicit assumption that it
> > > > > only refers to ringbuf memory (e.g. the check for ARG_PTR_TO_ALLOC_MEM
> > > > > in check_func_arg_reg_off).
> > > > >
> > > > > Hence, rename MEM_ALLOC to MEM_RINGBUF to indicate this special
> > > > > relationship and instead open the use of MEM_ALLOC for more generic
> > > > > allocations made for user types.
> > > > >
> > > > > Also, since ARG_PTR_TO_ALLOC_MEM_OR_NULL is unused, simply drop it.
> > > > >
> > > > > Finally, update selftests using 'alloc_' verifier string to 'ringbuf_'.
> > > > >
> > > > > Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> > > > > ---
> > > >
> > > > Ok, so you are doing what I asked in the previous patch, nice :)
> > > >
> > > > >  include/linux/bpf.h                               | 11 ++++-------
> > > > >  kernel/bpf/ringbuf.c                              |  6 +++---
> > > > >  kernel/bpf/verifier.c                             | 14 +++++++-------
> > > > >  tools/testing/selftests/bpf/prog_tests/dynptr.c   |  2 +-
> > > > >  tools/testing/selftests/bpf/verifier/ringbuf.c    |  2 +-
> > > > >  tools/testing/selftests/bpf/verifier/spill_fill.c |  2 +-
> > > > >  6 files changed, 17 insertions(+), 20 deletions(-)
> > > > >
> > > > > diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> > > > > index 2fe3ec620d54..afc1c51b59ff 100644
> > > > > --- a/include/linux/bpf.h
> > > > > +++ b/include/linux/bpf.h
> > > > > @@ -488,10 +488,8 @@ enum bpf_type_flag {
> > > > >          */
> > > > >         MEM_RDONLY              = BIT(1 + BPF_BASE_TYPE_BITS),
> > > > >
> > > > > -       /* MEM was "allocated" from a different helper, and cannot be mixed
> > > > > -        * with regular non-MEM_ALLOC'ed MEM types.
> > > > > -        */
> > > > > -       MEM_ALLOC               = BIT(2 + BPF_BASE_TYPE_BITS),
> > > > > +       /* MEM points to BPF ring buffer reservation. */
> > > > > +       MEM_RINGBUF             = BIT(2 + BPF_BASE_TYPE_BITS),
> > > >
> > > > What do we gain by having ringbuf memory as additional modified flag
> > > > instead of its own type like PTR_TO_MAP_VALUE or PTR_TO_PACKET? It
> > > > feels like here separate register type is more justified and is less
> > > > error prone overall.
> > > >
> > >
> > > I'm not sure it's all that different. It only matters when checking argument
> > > during release. We want to ensure it came from ringbuf_reserve. That's all,
> > > apart from that it's no different from PTR_TO_MEM. In all other places it's
> > > folded and code for PTR_TO_MEM is used. Same idea as PTR_TO_BTF_ID | MEM_ALLOC.
> > >
> > > But I don't feel too strongly, so if you still think it's better I can make the
> > > switch.
> >
> > Not strongly, but I think having this as a flag is more error prone.
> > For cases where ringbuf memory should be treated just as memory, we
> > should use the same mechanism we have for MAP_VALUE. But I haven't
> > checked how we deal with MAP_VALUE, if that's a special case
> > everywhere, in addition to generic PTR_TO_MEM, then fine. But if
> > having PTR_TO_RINGBUF_MEM is converted to PTR_TO_MEM generically where
> > needed, I'd have dedicated PTR_TO_RINGBUF_MEM.
>
> I don't think we can or at least it's not as easy to generalize
> ringbuf mem as map_value.
> iirc MEM_ALLOC was there to make sure reserver->commit is the same mem.
> That's what MEM_RINGBUF will doing after this patch.

I'm not sure we are talking about the same thing. My only point was to
have RINGBUF_MEM as *base type* instead of as an *add-on flag*.
MAP_VALUE was an example of another special register type that is base
type but behaves like PTR_TO_MEM for helpers that don't care about
where specifically memory is coming from. I didn't mean to unify
RINGBUF_MEM and MAP_VALUE in any way (if that's what you are
proposing, I'm actually not sure exactly).

But as I said, no big deal with a flag, we can always change that in
the future as well.

Re: [PATCH bpf-next v5 03/25] bpf: Support bpf_list_head in map values

[Andrii Nakryiko]

On Tue, Nov 8, 2022 at 5:03 PM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> On Tue, Nov 8, 2022 at 4:23 PM Andrii Nakryiko
> <andrii.nakryiko@gmail.com> wrote:
> > > > >  struct bpf_offload_dev;
> > > > > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > > > > index 94659f6b3395..dd381086bad9 100644
> > > > > --- a/include/uapi/linux/bpf.h
> > > > > +++ b/include/uapi/linux/bpf.h
> > > > > @@ -6887,6 +6887,16 @@ struct bpf_dynptr {
> > > > >         __u64 :64;
> > > > >  } __attribute__((aligned(8)));
> > > > >
> > > > > +struct bpf_list_head {
> > > > > +       __u64 :64;
> > > > > +       __u64 :64;
> > > > > +} __attribute__((aligned(8)));
> > > > > +
> > > > > +struct bpf_list_node {
> > > > > +       __u64 :64;
> > > > > +       __u64 :64;
> > > > > +} __attribute__((aligned(8)));
> > > >
> > > > Dave mentioned that this `__u64 :64` trick makes vmlinux.h lose the
> > > > alignment information, as the struct itself is empty, and so there is
> > > > nothing indicating that it has to be 8-byte aligned.
>
> Since it's not a new issue let's fix it for all.
> Whether it's a combination of pahole + bpftool or just pahole.

So yeah, I was expecting if we do this, we'd do this for all opaque
BPF UAPI structs like this (bpf_spin_lock and others), of course.

>
> > > >
> > > > So what if we have
> > > >
> > > > struct bpf_list_node {
> > > >     __u64 __opaque[2];
> > > > } __attribute__((aligned(8)));
> > > >
> > > > ?
> > > >
> > >
> > > Yep, can do that. Note that it's also potentially an issue for existing cases,
> > > like bpf_spin_lock, bpf_timer, bpf_dynptr, etc. Not completely sure if changing
> > > things now is possible, but if it is, we should probably make it for all of
> > > them?
> >
> > Why not? We are not removing anything or changing sizes, so it's
> > backwards compatible.
> > But I have a suspicion Alexei might not like
> > this __opaque field, so let's see what he says.
>
> I prefer to fix them all at once without adding a name.
>

This is not an issue with BTF per se.

struct blah {
  u64: 64
};

is just an empty struct blah with 8-byte size. Both BTF and DWARF will
record it as just

struct blah {
}

and record it's size as 8 bytes.

With that, there is nothing to suggest that this struct has to have
8-byte alignment.

If we mark explicitly __attribute__((aligned(8))) then DWARF will
additionally record alignment=8 for such struct. BTF doesn't record
alignment, though.

adding u64 fields internally will make libbpf recognize that struct
needs at least 8-byte alignment, which is what I propose as a simple
solution.

Alternatives are:
 - extend BTF to record struct/union alignments in BTF_KIND_{STRUCT,UNION}
 - record __attribute__((aligned(8))) as a new KIND (BTF_KIND_ATTRIBUTE)

Both seem like a bit of an overkill, given the work around is to have
u64 __opaque[] fields, which we won't have to remove or rename ever
(because those fields are not used).

> >
> > > > >                 off = vsi->offset;
> > > > > +               if (i && !off)
> > > > > +                       return -EFAULT;
> > > >
> > > > similarly, I'd say that either we'd need to calculate the exact
> > > > expected offset, or just not do anything here?
> > > >
> > >
> > > This thread is actually what prompted this check:
> > > https://lore.kernel.org/bpf/CAEf4Bza7ga2hEQ4J7EtgRHz49p1vZtaT4d2RDiyGOKGK41Nt=Q@mail.gmail.com
> > >
> > > Unless loaded using libbpf all offsets are zero. So I think we need to reject it
> > > here, but I think the same zero sized field might be an issue for this as well,
> > > so maybe we remember the last field size and check whether it was zero or not?
> > >
> > > I'll also include some more tests for these cases.
> >
> > The question is whether this affects correctness from the verifier
> > standpoint? If it does, there must be some other place where this will
> > cause problem and should be caught and reported.
>
> If it's an issue with BTF then we should probably check it
> during generic datasec verification.
> Here it's kinda late to warn.

+1 and do it more properly than forcing it to be non-zero

>
> > My main objection is that it's half a check, we check that it's
> > non-zero, but we don't check that it is correct in stricter sense. So
> > I'd rather drop it altogether, or go all the way to check that it is
> > correct offset (taking into account sizes of previous vars).

Re: [PATCH bpf-next v5 03/25] bpf: Support bpf_list_head in map values

[Andrii Nakryiko]

On Wed, Nov 9, 2022 at 8:41 AM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
>
> On Wed, Nov 09, 2022 at 06:33:25AM IST, Alexei Starovoitov wrote:
> > On Tue, Nov 8, 2022 at 4:23 PM Andrii Nakryiko
> > <andrii.nakryiko@gmail.com> wrote:
> > > > > >  struct bpf_offload_dev;
> > > > > > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > > > > > index 94659f6b3395..dd381086bad9 100644
> > > > > > --- a/include/uapi/linux/bpf.h
> > > > > > +++ b/include/uapi/linux/bpf.h
> > > > > > @@ -6887,6 +6887,16 @@ struct bpf_dynptr {
> > > > > >         __u64 :64;
> > > > > >  } __attribute__((aligned(8)));
> > > > > >
> > > > > > +struct bpf_list_head {
> > > > > > +       __u64 :64;
> > > > > > +       __u64 :64;
> > > > > > +} __attribute__((aligned(8)));
> > > > > > +
> > > > > > +struct bpf_list_node {
> > > > > > +       __u64 :64;
> > > > > > +       __u64 :64;
> > > > > > +} __attribute__((aligned(8)));
> > > > >
> > > > > Dave mentioned that this `__u64 :64` trick makes vmlinux.h lose the
> > > > > alignment information, as the struct itself is empty, and so there is
> > > > > nothing indicating that it has to be 8-byte aligned.
> >
> > Since it's not a new issue let's fix it for all.
> > Whether it's a combination of pahole + bpftool or just pahole.
> >
>
> Would it make sense to do that as a follow up? The selftest does work right now
> because I specified __attribute__((aligned(8))) manually for the variables.
>
> > > > >
> > > > > So what if we have
> > > > >
> > > > > struct bpf_list_node {
> > > > >     __u64 __opaque[2];
> > > > > } __attribute__((aligned(8)));
> > > > >
> > > > > ?
> > > > >
> > > >
> > > > Yep, can do that. Note that it's also potentially an issue for existing cases,
> > > > like bpf_spin_lock, bpf_timer, bpf_dynptr, etc. Not completely sure if changing
> > > > things now is possible, but if it is, we should probably make it for all of
> > > > them?
> > >
> > > Why not? We are not removing anything or changing sizes, so it's
> > > backwards compatible.
> > > But I have a suspicion Alexei might not like
> > > this __opaque field, so let's see what he says.
> >
> > I prefer to fix them all at once without adding a name.
> >
> > >
> > > > > >                 off = vsi->offset;
> > > > > > +               if (i && !off)
> > > > > > +                       return -EFAULT;
> > > > >
> > > > > similarly, I'd say that either we'd need to calculate the exact
> > > > > expected offset, or just not do anything here?
> > > > >
> > > >
> > > > This thread is actually what prompted this check:
> > > > https://lore.kernel.org/bpf/CAEf4Bza7ga2hEQ4J7EtgRHz49p1vZtaT4d2RDiyGOKGK41Nt=Q@mail.gmail.com
> > > >
> > > > Unless loaded using libbpf all offsets are zero. So I think we need to reject it
> > > > here, but I think the same zero sized field might be an issue for this as well,
> > > > so maybe we remember the last field size and check whether it was zero or not?
> > > >
> > > > I'll also include some more tests for these cases.
> > >
> > > The question is whether this affects correctness from the verifier
> > > standpoint? If it does, there must be some other place where this will
> > > cause problem and should be caught and reported.
>
> The problem here is that if the BTF is incorrect like this, where you have same
> off for multiple items (bpf_spin_lock, bpf_list_head, etc.) like off=0 here,
> they essentially get the same offset in our btf_record array.
>
> I can check for it when appending items to the array (i.e. next offset must be
> atleast prev_off + prev_sz at the very minimum).

yes, that would be more correct, because you can still generate bad
BTF where you have different non-zero offsets, but overlapping
variables. Such a situation should be prevented anyways, right?

>
> >
> > If it's an issue with BTF then we should probably check it
> > during generic datasec verification.
> > Here it's kinda late to warn.
> >
>
> There's also a concern that clang produces this BTF by default. If you're not
> using libbpf as a loader, BTF that loaded previously will fail now (since
> DATASEC var offs are always 0 and we will complain during validation and return
> an error). Not sure what the impact will be, but just putting it out there.
>
> Let me know what should be better. In either case I'll add a test case.

So on one hand all BPF loaders like libbpf should be adjusting and
fixing such incomplete BTFs coming from Clang. On the other hand, we
can add such enforcements only if such special global variables are
present. I.e., if we care about DATASEC layout for correctness.

Re: [PATCH bpf-next v5 06/25] bpf: Introduce local kptrs

[Andrii Nakryiko]

On Tue, Nov 8, 2022 at 5:32 PM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> On Tue, Nov 8, 2022 at 4:36 PM Andrii Nakryiko
> <andrii.nakryiko@gmail.com> wrote:
> >
> > On Tue, Nov 8, 2022 at 4:00 PM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
> > >
> > > On Wed, Nov 09, 2022 at 04:59:41AM IST, Andrii Nakryiko wrote:
> > > > On Mon, Nov 7, 2022 at 3:10 PM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
> > > > >
> > > > > Introduce local kptrs, i.e. PTR_TO_BTF_ID that point to a type in
> > > > > program BTF. This is indicated by the presence of MEM_ALLOC type flag in
> > > > > reg->type to avoid having to check btf_is_kernel when trying to match
> > > > > argument types in helpers.
> > > > >
> > > > > Refactor btf_struct_access callback to just take bpf_reg_state instead
> > > > > of btf and btf_type paramters. Note that the call site in
> > > > > check_map_access now simulates access to a PTR_TO_BTF_ID by creating a
> > > > > dummy reg on stack. Since only the type, btf, and btf_id of the register
> > > > > matter for the checks, it can be done so without complicating the usual
> > > > > cases elsewhere in the verifier where reg->btf and reg->btf_id is used
> > > > > verbatim.
> > > > >
> > > > > Whenever walking such types, any pointers being walked will always yield
> > > > > a SCALAR instead of pointer. In the future we might permit kptr inside
> > > > > local kptr (either kernel or local), and it would be permitted only in
> > > > > that case.
> > > > >
> > > > > For now, these local kptrs will always be referenced in verifier
> > > > > context, hence ref_obj_id == 0 for them is a bug. It is allowed to write
> > > > > to such objects, as long fields that are special are not touched
> > > > > (support for which will be added in subsequent patches). Note that once
> > > > > such a local kptr is marked PTR_UNTRUSTED, it is no longer allowed to
> > > > > write to it.
> > > > >
> > > > > No PROBE_MEM handling is therefore done for loads into this type unless
> > > > > PTR_UNTRUSTED is part of the register type, since they can never be in
> > > > > an undefined state, and their lifetime will always be valid.
> > > > >
> > > > > Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> > > > > ---
> > > > >  include/linux/bpf.h              | 28 ++++++++++++++++--------
> > > > >  include/linux/filter.h           |  8 +++----
> > > > >  kernel/bpf/btf.c                 | 16 ++++++++++----
> > > > >  kernel/bpf/verifier.c            | 37 ++++++++++++++++++++++++++------
> > > > >  net/bpf/bpf_dummy_struct_ops.c   | 14 ++++++------
> > > > >  net/core/filter.c                | 34 ++++++++++++-----------------
> > > > >  net/ipv4/bpf_tcp_ca.c            | 13 ++++++-----
> > > > >  net/netfilter/nf_conntrack_bpf.c | 17 ++++++---------
> > > > >  8 files changed, 99 insertions(+), 68 deletions(-)
> > > > >
> > > > > diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> > > > > index afc1c51b59ff..75dbd2ecf80a 100644
> > > > > --- a/include/linux/bpf.h
> > > > > +++ b/include/linux/bpf.h
> > > > > @@ -524,6 +524,11 @@ enum bpf_type_flag {
> > > > >         /* Size is known at compile time. */
> > > > >         MEM_FIXED_SIZE          = BIT(10 + BPF_BASE_TYPE_BITS),
> > > > >
> > > > > +       /* MEM is of a type from program BTF, not kernel BTF. This is used to
> > > > > +        * tag PTR_TO_BTF_ID allocated using bpf_obj_new.
> > > > > +        */
> > > > > +       MEM_ALLOC               = BIT(11 + BPF_BASE_TYPE_BITS),
> > > > > +
> > > >
> > > > you fixed one naming confusion with RINGBUF and basically are creating
> > > > a new one, where "ALLOC" means "local kptr"... If we are stuck with
> > > > "local kptr" (which I find very confusing as well, but that's beside
> > > > the point), why not stick to the whole "local" terminology here?
> > > > MEM_LOCAL?
> > > >
> > >
> > > See the discussion about this in v4:
> > > https://lore.kernel.org/bpf/20221104075113.5ighwdvero4mugu7@apollo
> > >
> > > It was MEM_TYPE_LOCAL before. Also, better naming suggestions are always
> > > welcome, I asked the same in that message as well.
> >
> > Sorry, I haven't followed <v5. Don't have perfect name, but logically
> > this is BPF program memory. So "prog_kptr" would be something to
> > convert this, but I'm not super happy with such a name. "user_kptr"
> > would be too confusing, drawing incorrect "kernel space vs user space"
> > comparison, while both are kernel memory. It's BPF-side kptr, so
> > "bpf_kptr", but also not great.
>
> yep. I went through the same thinking process.
>
> > So that's why didn't suggest anything specific, but at least as far as
> > MEM_xxx flag goes, MEM_LOCAL_KPTR is better than MEM_ALLOC, IMO. It's
> > at least consistent with the official name of the concept it
> > represents.
>
> "local kptr" doesn't fit here.
> In libbpf, "local" is equally badly named.
> If "local" was a good name we wouldn't have had this discussion.
> So we need to fix it libbpf, but we should start with a proper
> name in the kernel.
> And "local kptr" is not it.
>
> We must avoid exhausting bikeshedding too.
> MEM_ALLOC is something we can use right now and
> as long as "local kptr" doesn't appear in docs, comments and
> commit logs we're good.
> We can rename MEM_ALLOC to something else later.

agreed

>
> In commit logs we can just say that this is
> a pointer to an object allocated by the bpf program.
> It's crystal clear definition whereas "local kptr" is nonsensical.
>
> Going back to the kptr definition.
> kptr was supposed to mean a pointer to a kernel object.
> In that light "pointer to an object allocated by the bpf prog"
> is something else.
> Maybe "bptr" ?
> In some ways bpf is a layer different from kernel space and user space.
> Some people joked that there is ring-0 for kernel, ring-3 for user space
> while bpf runs in ring-B.
> Two new btf_tags __bptr and __bptr_ref (or may be just one?)
> might be necessary as well to make it easier to distinguish
> kernel and bpf prog allocated objects.

bptr isn't terrific, but I don't have any good suggestions. bptr,
bpfptr, tptr (for "typed pointer" as opposed to untyped dynptr), all
kind of meh. I'm fine with whatever.

>
> > >
> > > It was just a bool in the RFC.
> > > But in https://lore.kernel.org/bpf/20220907233023.x3uclwlnjuhftvtb@macbook-pro-4.dhcp.thefacebook.com
> > > Alexei suggested passing reg instead.
> > > From the link:
> > > > imo it's cleaner to pass 'reg' instead of 'reg->btf',
> > > > so we don't have to pass another boolean.
> > > > And check type_is_local(reg) inside btf_struct_access().
> >
> > I sympathize with "too many input args" (especially if it's a bunch of
> > bools) argument, but see above, I find it increasingly harder to know
> > what parts of complex internal register state is used by helper
> > functions and which are not.
> >
> > And the fact that we have to construct a fake register state in some
> > case is a red flag to me. Pass enum bpf_reg_type type to avoid passing
> > true/false. Or let's invent a new enum. Or extend enum bpf_access_type
> > to have READ_NOPTR/WRITE_NOPTR or something like that. Don't know.
> >
> > This isn't a major issue, I can live with this just fine, but this
> > definitely doesn't feel like a clean approach.
>
> I think passing bpf_reg_state is a lesser evil _right_now_ and
> I prefer we proceed this way, since other works are blocked on
> this patch set.
> We did plenty of refactoring of the verifier in the past.
> There will be more in the future.

sure, not crucial

Re: [PATCH bpf-next v5 06/25] bpf: Introduce local kptrs

[Andrii Nakryiko]

On Wed, Nov 9, 2022 at 9:00 AM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
>
> On Wed, Nov 09, 2022 at 07:02:11AM IST, Alexei Starovoitov wrote:
> > On Tue, Nov 8, 2022 at 4:36 PM Andrii Nakryiko
> > <andrii.nakryiko@gmail.com> wrote:
> > >
> > > On Tue, Nov 8, 2022 at 4:00 PM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
> > > >
> > > > On Wed, Nov 09, 2022 at 04:59:41AM IST, Andrii Nakryiko wrote:
> > > > > On Mon, Nov 7, 2022 at 3:10 PM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
> > > > > >
> > > > > > Introduce local kptrs, i.e. PTR_TO_BTF_ID that point to a type in
> > > > > > program BTF. This is indicated by the presence of MEM_ALLOC type flag in
> > > > > > reg->type to avoid having to check btf_is_kernel when trying to match
> > > > > > argument types in helpers.
> > > > > >
> > > > > > Refactor btf_struct_access callback to just take bpf_reg_state instead
> > > > > > of btf and btf_type paramters. Note that the call site in
> > > > > > check_map_access now simulates access to a PTR_TO_BTF_ID by creating a
> > > > > > dummy reg on stack. Since only the type, btf, and btf_id of the register
> > > > > > matter for the checks, it can be done so without complicating the usual
> > > > > > cases elsewhere in the verifier where reg->btf and reg->btf_id is used
> > > > > > verbatim.
> > > > > >
> > > > > > Whenever walking such types, any pointers being walked will always yield
> > > > > > a SCALAR instead of pointer. In the future we might permit kptr inside
> > > > > > local kptr (either kernel or local), and it would be permitted only in
> > > > > > that case.
> > > > > >
> > > > > > For now, these local kptrs will always be referenced in verifier
> > > > > > context, hence ref_obj_id == 0 for them is a bug. It is allowed to write
> > > > > > to such objects, as long fields that are special are not touched
> > > > > > (support for which will be added in subsequent patches). Note that once
> > > > > > such a local kptr is marked PTR_UNTRUSTED, it is no longer allowed to
> > > > > > write to it.
> > > > > >
> > > > > > No PROBE_MEM handling is therefore done for loads into this type unless
> > > > > > PTR_UNTRUSTED is part of the register type, since they can never be in
> > > > > > an undefined state, and their lifetime will always be valid.
> > > > > >
> > > > > > Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> > > > > > ---
> > > > > >  include/linux/bpf.h              | 28 ++++++++++++++++--------
> > > > > >  include/linux/filter.h           |  8 +++----
> > > > > >  kernel/bpf/btf.c                 | 16 ++++++++++----
> > > > > >  kernel/bpf/verifier.c            | 37 ++++++++++++++++++++++++++------
> > > > > >  net/bpf/bpf_dummy_struct_ops.c   | 14 ++++++------
> > > > > >  net/core/filter.c                | 34 ++++++++++++-----------------
> > > > > >  net/ipv4/bpf_tcp_ca.c            | 13 ++++++-----
> > > > > >  net/netfilter/nf_conntrack_bpf.c | 17 ++++++---------
> > > > > >  8 files changed, 99 insertions(+), 68 deletions(-)
> > > > > >
> > > > > > diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> > > > > > index afc1c51b59ff..75dbd2ecf80a 100644
> > > > > > --- a/include/linux/bpf.h
> > > > > > +++ b/include/linux/bpf.h
> > > > > > @@ -524,6 +524,11 @@ enum bpf_type_flag {
> > > > > >         /* Size is known at compile time. */
> > > > > >         MEM_FIXED_SIZE          = BIT(10 + BPF_BASE_TYPE_BITS),
> > > > > >
> > > > > > +       /* MEM is of a type from program BTF, not kernel BTF. This is used to
> > > > > > +        * tag PTR_TO_BTF_ID allocated using bpf_obj_new.
> > > > > > +        */
> > > > > > +       MEM_ALLOC               = BIT(11 + BPF_BASE_TYPE_BITS),
> > > > > > +
> > > > >
> > > > > you fixed one naming confusion with RINGBUF and basically are creating
> > > > > a new one, where "ALLOC" means "local kptr"... If we are stuck with
> > > > > "local kptr" (which I find very confusing as well, but that's beside
> > > > > the point), why not stick to the whole "local" terminology here?
> > > > > MEM_LOCAL?
> > > > >
> > > >
> > > > See the discussion about this in v4:
> > > > https://lore.kernel.org/bpf/20221104075113.5ighwdvero4mugu7@apollo
> > > >
> > > > It was MEM_TYPE_LOCAL before. Also, better naming suggestions are always
> > > > welcome, I asked the same in that message as well.
> > >
> > > Sorry, I haven't followed <v5. Don't have perfect name, but logically
> > > this is BPF program memory. So "prog_kptr" would be something to
> > > convert this, but I'm not super happy with such a name. "user_kptr"
> > > would be too confusing, drawing incorrect "kernel space vs user space"
> > > comparison, while both are kernel memory. It's BPF-side kptr, so
> > > "bpf_kptr", but also not great.
> >
> > yep. I went through the same thinking process.
> >
> > > So that's why didn't suggest anything specific, but at least as far as
> > > MEM_xxx flag goes, MEM_LOCAL_KPTR is better than MEM_ALLOC, IMO. It's
> > > at least consistent with the official name of the concept it
> > > represents.
> >
> > "local kptr" doesn't fit here.
> > In libbpf, "local" is equally badly named.
> > If "local" was a good name we wouldn't have had this discussion.
> > So we need to fix it libbpf, but we should start with a proper
> > name in the kernel.
> > And "local kptr" is not it.
> >
> > We must avoid exhausting bikeshedding too.
> > MEM_ALLOC is something we can use right now and
> > as long as "local kptr" doesn't appear in docs, comments and
> > commit logs we're good.
> > We can rename MEM_ALLOC to something else later.
> >
> > In commit logs we can just say that this is
> > a pointer to an object allocated by the bpf program.
> > It's crystal clear definition whereas "local kptr" is nonsensical.
> >
>
> Ok, I'll drop the naming everywhere.
>
> > Going back to the kptr definition.
> > kptr was supposed to mean a pointer to a kernel object.
> > In that light "pointer to an object allocated by the bpf prog"
> > is something else.
> > Maybe "bptr" ?
> > In some ways bpf is a layer different from kernel space and user space.
> > Some people joked that there is ring-0 for kernel, ring-3 for user space
> > while bpf runs in ring-B.
> > Two new btf_tags __bptr and __bptr_ref (or may be just one?)
> > might be necessary as well to make it easier to distinguish
> > kernel and bpf prog allocated objects.
> >
>
> There's also the option of simply using __kptr and __kptr_ref for these (without
> __local tag in BPF maps) and doing two stage name lookup for the types. Kernel
> BTF takes precedence, if not found there, then it searches program BTF for a
> local type. It would probably the simplest for users.

Disagree about the simplest for users. It's going to be quite
confusing for anyone reading the code and trying to understand what's
going on. Explicit tag seems better to me. But it's subjective.

>
> struct map_value {
>         struct nf_conn __kptr_ref *ct; // kernel
>         struct foo __kptr_ref *f; // local
>         struct task_struct __kptr_ref *t; // kernel
>         struct bar __kptr_ref *b; // local
> }
>
> We can revisit this again once the post the follow up to store them in maps.

Re: [PATCH bpf-next v5 03/25] bpf: Support bpf_list_head in map values

[Alexei Starovoitov]

On Wed, Nov 9, 2022 at 3:11 PM Andrii Nakryiko
<andrii.nakryiko@gmail.com> wrote:
>
> >
> > > > >
> > > > > So what if we have
> > > > >
> > > > > struct bpf_list_node {
> > > > >     __u64 __opaque[2];
> > > > > } __attribute__((aligned(8)));
> > > > >
> > > > > ?
> > > > >
> > > >
> > > > Yep, can do that. Note that it's also potentially an issue for existing cases,
> > > > like bpf_spin_lock, bpf_timer, bpf_dynptr, etc. Not completely sure if changing
> > > > things now is possible, but if it is, we should probably make it for all of
> > > > them?
> > >
> > > Why not? We are not removing anything or changing sizes, so it's
> > > backwards compatible.
> > > But I have a suspicion Alexei might not like
> > > this __opaque field, so let's see what he says.
> >
> > I prefer to fix them all at once without adding a name.
> >
>
> This is not an issue with BTF per se.
>
> struct blah {
>   u64: 64
> };
>
> is just an empty struct blah with 8-byte size. Both BTF and DWARF will
> record it as just
>
> struct blah {
> }
>
> and record it's size as 8 bytes.
>
> With that, there is nothing to suggest that this struct has to have
> 8-byte alignment.
>
> If we mark explicitly __attribute__((aligned(8))) then DWARF will
> additionally record alignment=8 for such struct. BTF doesn't record
> alignment, though.
>
> adding u64 fields internally will make libbpf recognize that struct
> needs at least 8-byte alignment, which is what I propose as a simple
> solution.
>
> Alternatives are:
>  - extend BTF to record struct/union alignments in BTF_KIND_{STRUCT,UNION}
>  - record __attribute__((aligned(8))) as a new KIND (BTF_KIND_ATTRIBUTE)

imo above two options are way better than adding __opaque which
is nothing but a workaround for a missing feature in BTF.

> Both seem like a bit of an overkill, given the work around is to have
> u64 __opaque[] fields, which we won't have to remove or rename ever
> (because those fields are not used).

There is no rush to do this workaround.
As Kumar says we can land the existing patch as-is
and add BTF_KIND_ATTR (or anything else) in the followup.

Adding __opaque now won't work, since we won't be able
to remove it later due to backward compat.