[PATCH bpf-next v3 0/2] Sleepable LSM Hooks

[PATCH bpf-next v3 0/2] Sleepable LSM Hooks

[KP Singh]

From: KP Singh <kpsingh@google.com>

# v2 -> v3

  * Remove the list of non-sleepable hooks, will send a separate patch
    to the lsm list based on the discussion with Daniel.
  * Add Andrii's ack for real

# v1 -> v2

  * Fixed typos and formatting errors.
  * Added Andrii's ack.

KP Singh (2):
  bpf: Augment the set of sleepable LSM hooks
  bpf: Expose bpf_d_path helper to sleepable LSM hooks

 include/linux/bpf_lsm.h  |  7 ++++
 kernel/bpf/bpf_lsm.c     | 81 ++++++++++++++++++++++++++++++++++++++++
 kernel/bpf/verifier.c    | 16 +-------
 kernel/trace/bpf_trace.c |  7 +++-
 4 files changed, 95 insertions(+), 16 deletions(-)

-- 
2.29.2.299.gdc1121823c-goog

[PATCH bpf-next v3 1/2] bpf: Augment the set of sleepable LSM hooks

[KP Singh]

From: KP Singh <kpsingh@google.com>

Update the set of sleepable hooks with the ones that do not trigger
a warning with might_fault() when exercised with the correct kernel
config options enabled, i.e.

	DEBUG_ATOMIC_SLEEP=y
	LOCKDEP=y
	PROVE_LOCKING=y

This means that a sleepable LSM eBPF program can be attached to these
LSM hooks. A new helper method bpf_lsm_is_sleepable_hook is added and
the set is maintained locally in bpf_lsm.c

Signed-off-by: KP Singh <kpsingh@google.com>
---
 include/linux/bpf_lsm.h |  7 ++++
 kernel/bpf/bpf_lsm.c    | 81 +++++++++++++++++++++++++++++++++++++++++
 kernel/bpf/verifier.c   | 16 +-------
 3 files changed, 89 insertions(+), 15 deletions(-)

diff --git a/include/linux/bpf_lsm.h b/include/linux/bpf_lsm.h
index 73226181b744..0d1c33ace398 100644
--- a/include/linux/bpf_lsm.h
+++ b/include/linux/bpf_lsm.h
@@ -27,6 +27,8 @@ extern struct lsm_blob_sizes bpf_lsm_blob_sizes;
 int bpf_lsm_verify_prog(struct bpf_verifier_log *vlog,
 			const struct bpf_prog *prog);
 
+bool bpf_lsm_is_sleepable_hook(u32 btf_id);
+
 static inline struct bpf_storage_blob *bpf_inode(
 	const struct inode *inode)
 {
@@ -54,6 +56,11 @@ void bpf_task_storage_free(struct task_struct *task);
 
 #else /* !CONFIG_BPF_LSM */
 
+static inline bool bpf_lsm_is_sleepable_hook(u32 btf_id)
+{
+	return false;
+}
+
 static inline int bpf_lsm_verify_prog(struct bpf_verifier_log *vlog,
 				      const struct bpf_prog *prog)
 {
diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c
index e92c51bebb47..aed74b853415 100644
--- a/kernel/bpf/bpf_lsm.c
+++ b/kernel/bpf/bpf_lsm.c
@@ -13,6 +13,7 @@
 #include <linux/bpf_verifier.h>
 #include <net/bpf_sk_storage.h>
 #include <linux/bpf_local_storage.h>
+#include <linux/btf_ids.h>
 
 /* For every LSM hook that allows attachment of BPF programs, declare a nop
  * function where a BPF program can be attached.
@@ -72,6 +73,86 @@ bpf_lsm_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 	}
 }
 
+/* The set of hooks which are called without pagefaults disabled and are allowed
+ * to "sleep" and thus can be used for sleeable BPF programs.
+ */
+BTF_SET_START(sleepable_lsm_hooks)
+BTF_ID(func, bpf_lsm_bpf)
+BTF_ID(func, bpf_lsm_bpf_map)
+BTF_ID(func, bpf_lsm_bpf_map_alloc_security)
+BTF_ID(func, bpf_lsm_bpf_map_free_security)
+BTF_ID(func, bpf_lsm_bpf_prog)
+BTF_ID(func, bpf_lsm_bprm_check_security)
+BTF_ID(func, bpf_lsm_bprm_committed_creds)
+BTF_ID(func, bpf_lsm_bprm_committing_creds)
+BTF_ID(func, bpf_lsm_bprm_creds_for_exec)
+BTF_ID(func, bpf_lsm_bprm_creds_from_file)
+BTF_ID(func, bpf_lsm_capget)
+BTF_ID(func, bpf_lsm_capset)
+BTF_ID(func, bpf_lsm_cred_prepare)
+BTF_ID(func, bpf_lsm_file_ioctl)
+BTF_ID(func, bpf_lsm_file_lock)
+BTF_ID(func, bpf_lsm_file_open)
+BTF_ID(func, bpf_lsm_file_receive)
+BTF_ID(func, bpf_lsm_inet_conn_established)
+BTF_ID(func, bpf_lsm_inode_create)
+BTF_ID(func, bpf_lsm_inode_free_security)
+BTF_ID(func, bpf_lsm_inode_getattr)
+BTF_ID(func, bpf_lsm_inode_getxattr)
+BTF_ID(func, bpf_lsm_inode_mknod)
+BTF_ID(func, bpf_lsm_inode_need_killpriv)
+BTF_ID(func, bpf_lsm_inode_post_setxattr)
+BTF_ID(func, bpf_lsm_inode_readlink)
+BTF_ID(func, bpf_lsm_inode_rename)
+BTF_ID(func, bpf_lsm_inode_rmdir)
+BTF_ID(func, bpf_lsm_inode_setattr)
+BTF_ID(func, bpf_lsm_inode_setxattr)
+BTF_ID(func, bpf_lsm_inode_symlink)
+BTF_ID(func, bpf_lsm_inode_unlink)
+BTF_ID(func, bpf_lsm_kernel_module_request)
+BTF_ID(func, bpf_lsm_kernfs_init_security)
+BTF_ID(func, bpf_lsm_key_free)
+BTF_ID(func, bpf_lsm_mmap_file)
+BTF_ID(func, bpf_lsm_netlink_send)
+BTF_ID(func, bpf_lsm_path_notify)
+BTF_ID(func, bpf_lsm_release_secctx)
+BTF_ID(func, bpf_lsm_sb_alloc_security)
+BTF_ID(func, bpf_lsm_sb_eat_lsm_opts)
+BTF_ID(func, bpf_lsm_sb_kern_mount)
+BTF_ID(func, bpf_lsm_sb_mount)
+BTF_ID(func, bpf_lsm_sb_remount)
+BTF_ID(func, bpf_lsm_sb_set_mnt_opts)
+BTF_ID(func, bpf_lsm_sb_show_options)
+BTF_ID(func, bpf_lsm_sb_statfs)
+BTF_ID(func, bpf_lsm_sb_umount)
+BTF_ID(func, bpf_lsm_settime)
+BTF_ID(func, bpf_lsm_socket_accept)
+BTF_ID(func, bpf_lsm_socket_bind)
+BTF_ID(func, bpf_lsm_socket_connect)
+BTF_ID(func, bpf_lsm_socket_create)
+BTF_ID(func, bpf_lsm_socket_getpeername)
+BTF_ID(func, bpf_lsm_socket_getpeersec_dgram)
+BTF_ID(func, bpf_lsm_socket_getsockname)
+BTF_ID(func, bpf_lsm_socket_getsockopt)
+BTF_ID(func, bpf_lsm_socket_listen)
+BTF_ID(func, bpf_lsm_socket_post_create)
+BTF_ID(func, bpf_lsm_socket_recvmsg)
+BTF_ID(func, bpf_lsm_socket_sendmsg)
+BTF_ID(func, bpf_lsm_socket_shutdown)
+BTF_ID(func, bpf_lsm_socket_socketpair)
+BTF_ID(func, bpf_lsm_syslog)
+BTF_ID(func, bpf_lsm_task_alloc)
+BTF_ID(func, bpf_lsm_task_getsecid)
+BTF_ID(func, bpf_lsm_task_prctl)
+BTF_ID(func, bpf_lsm_task_setscheduler)
+BTF_ID(func, bpf_lsm_task_to_inode)
+BTF_SET_END(sleepable_lsm_hooks)
+
+bool bpf_lsm_is_sleepable_hook(u32 btf_id)
+{
+	return btf_id_set_contains(&sleepable_lsm_hooks, btf_id);
+}
+
 const struct bpf_prog_ops lsm_prog_ops = {
 };
 
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 10da26e55130..364ec1958c85 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -11477,20 +11477,6 @@ static int check_attach_modify_return(unsigned long addr, const char *func_name)
 	return -EINVAL;
 }
 
-/* non exhaustive list of sleepable bpf_lsm_*() functions */
-BTF_SET_START(btf_sleepable_lsm_hooks)
-#ifdef CONFIG_BPF_LSM
-BTF_ID(func, bpf_lsm_bprm_committed_creds)
-#else
-BTF_ID_UNUSED
-#endif
-BTF_SET_END(btf_sleepable_lsm_hooks)
-
-static int check_sleepable_lsm_hook(u32 btf_id)
-{
-	return btf_id_set_contains(&btf_sleepable_lsm_hooks, btf_id);
-}
-
 /* list of non-sleepable functions that are otherwise on
  * ALLOW_ERROR_INJECTION list
  */
@@ -11712,7 +11698,7 @@ int bpf_check_attach_target(struct bpf_verifier_log *log,
 				/* LSM progs check that they are attached to bpf_lsm_*() funcs.
 				 * Only some of them are sleepable.
 				 */
-				if (check_sleepable_lsm_hook(btf_id))
+				if (bpf_lsm_is_sleepable_hook(btf_id))
 					ret = 0;
 				break;
 			default:
-- 
2.29.2.299.gdc1121823c-goog

[PATCH bpf-next v3 2/2] bpf: Expose bpf_d_path helper to sleepable LSM hooks

[KP Singh]

From: KP Singh <kpsingh@google.com>

Sleepable hooks are never called from an NMI/interrupt context, so it is
safe to use the bpf_d_path helper in LSM programs attaching to these
hooks.

The helper is not restricted to sleepable programs and merely uses the
list of sleeable hooks as the initial subset of LSM hooks where it can
be used.

Acked-by: Andrii Nakryiko <andrii@kernel.org>

Signed-off-by: KP Singh <kpsingh@google.com>
---
 kernel/trace/bpf_trace.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index e4515b0f62a8..eab1af02c90d 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -16,6 +16,7 @@
 #include <linux/syscalls.h>
 #include <linux/error-injection.h>
 #include <linux/btf_ids.h>
+#include <linux/bpf_lsm.h>
 
 #include <uapi/linux/bpf.h>
 #include <uapi/linux/btf.h>
@@ -1178,7 +1179,11 @@ BTF_SET_END(btf_allowlist_d_path)
 
 static bool bpf_d_path_allowed(const struct bpf_prog *prog)
 {
-	return btf_id_set_contains(&btf_allowlist_d_path, prog->aux->attach_btf_id);
+	if (prog->type == BPF_PROG_TYPE_LSM)
+		return bpf_lsm_is_sleepable_hook(prog->aux->attach_btf_id);
+
+	return btf_id_set_contains(&btf_allowlist_d_path,
+				   prog->aux->attach_btf_id);
 }
 
 BTF_ID_LIST_SINGLE(bpf_d_path_btf_ids, struct, path)
-- 
2.29.2.299.gdc1121823c-goog