[PATCH bpf-next 0/3] bpf: Enable bpf_sk_storage for FENTRY/FEXIT/RAW_TP

[PATCH bpf-next 0/3] bpf: Enable bpf_sk_storage for FENTRY/FEXIT/RAW_TP

[Martin KaFai Lau]

This set is to allow the FENTRY/FEXIT/RAW_TP tracing program to use
bpf_sk_storage.  The first patch is a cleanup.  The last patch is
tests.  The second patch has the required kernel changes to
enable bpf_sk_storage for FENTRY/FEXIT/RAW_TP.

Please see individual patch for details.

Martin KaFai Lau (3):
  bpf: Folding omem_charge() into sk_storage_charge()
  bpf: Allow using bpf_sk_storage in FENTRY/FEXIT/RAW_TP
  bpf: selftest: Use bpf_sk_storage in FENTRY/FEXIT/RAW_TP

 include/net/bpf_sk_storage.h                  |   2 +
 kernel/trace/bpf_trace.c                      |   5 +
 net/core/bpf_sk_storage.c                     |  96 +++++++++++--
 .../bpf/prog_tests/sk_storage_tracing.c       | 135 ++++++++++++++++++
 .../bpf/progs/test_sk_storage_trace_itself.c  |  29 ++++
 .../bpf/progs/test_sk_storage_tracing.c       |  95 ++++++++++++
 6 files changed, 349 insertions(+), 13 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/sk_storage_tracing.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_sk_storage_trace_itself.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_sk_storage_tracing.c

-- 
2.24.1

[PATCH bpf-next 1/3] bpf: Folding omem_charge() into sk_storage_charge()

[Martin KaFai Lau]

sk_storage_charge() is the only user of omem_charge().
This patch simplifies it by folding omem_charge() into
sk_storage_charge().

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
---
 net/core/bpf_sk_storage.c | 23 ++++++++++-------------
 1 file changed, 10 insertions(+), 13 deletions(-)

diff --git a/net/core/bpf_sk_storage.c b/net/core/bpf_sk_storage.c
index c907f0dc7f87..001eac65e40f 100644
--- a/net/core/bpf_sk_storage.c
+++ b/net/core/bpf_sk_storage.c
@@ -15,18 +15,6 @@
 
 DEFINE_BPF_STORAGE_CACHE(sk_cache);
 
-static int omem_charge(struct sock *sk, unsigned int size)
-{
-	/* same check as in sock_kmalloc() */
-	if (size <= sysctl_optmem_max &&
-	    atomic_read(&sk->sk_omem_alloc) + size < sysctl_optmem_max) {
-		atomic_add(size, &sk->sk_omem_alloc);
-		return 0;
-	}
-
-	return -ENOMEM;
-}
-
 static struct bpf_local_storage_data *
 sk_storage_lookup(struct sock *sk, struct bpf_map *map, bool cacheit_lockit)
 {
@@ -316,7 +304,16 @@ BPF_CALL_2(bpf_sk_storage_delete, struct bpf_map *, map, struct sock *, sk)
 static int sk_storage_charge(struct bpf_local_storage_map *smap,
 			     void *owner, u32 size)
 {
-	return omem_charge(owner, size);
+	struct sock *sk = (struct sock *)owner;
+
+	/* same check as in sock_kmalloc() */
+	if (size <= sysctl_optmem_max &&
+	    atomic_read(&sk->sk_omem_alloc) + size < sysctl_optmem_max) {
+		atomic_add(size, &sk->sk_omem_alloc);
+		return 0;
+	}
+
+	return -ENOMEM;
 }
 
 static void sk_storage_uncharge(struct bpf_local_storage_map *smap,
-- 
2.24.1

[PATCH bpf-next 2/3] bpf: Allow using bpf_sk_storage in FENTRY/FEXIT/RAW_TP

[Martin KaFai Lau]

This patch enables the FENTRY/FEXIT/RAW_TP tracing program to use
the bpf_sk_storage_(get|delete) helper, so those tracing programs
can access the sk's bpf_local_storage and the later selftest
will show some examples.

The bpf_sk_storage is currently used in bpf-tcp-cc, tc,
cg sockops...etc which is running either in softirq or
task context.

This patch adds bpf_sk_storage_get_tracing_proto and
bpf_sk_storage_delete_tracing_proto.  They will check
in runtime that the helpers can only be called when serving
softirq or running in a task context.  That should enable
most common tracing use cases on sk.

During the load time, the new tracing_allowed() function
will ensure the tracing prog using the bpf_sk_storage_(get|delete)
helper is not tracing any *sk_storage*() function itself.
The sk is passed as "void *" when calling into bpf_local_storage.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
---
 include/net/bpf_sk_storage.h |  2 +
 kernel/trace/bpf_trace.c     |  5 +++
 net/core/bpf_sk_storage.c    | 73 ++++++++++++++++++++++++++++++++++++
 3 files changed, 80 insertions(+)

diff --git a/include/net/bpf_sk_storage.h b/include/net/bpf_sk_storage.h
index 3c516dd07caf..0e85713f56df 100644
--- a/include/net/bpf_sk_storage.h
+++ b/include/net/bpf_sk_storage.h
@@ -20,6 +20,8 @@ void bpf_sk_storage_free(struct sock *sk);
 
 extern const struct bpf_func_proto bpf_sk_storage_get_proto;
 extern const struct bpf_func_proto bpf_sk_storage_delete_proto;
+extern const struct bpf_func_proto bpf_sk_storage_get_tracing_proto;
+extern const struct bpf_func_proto bpf_sk_storage_delete_tracing_proto;
 
 struct bpf_local_storage_elem;
 struct bpf_sk_storage_diag;
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index e4515b0f62a8..cfce60ad1cb5 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 <net/bpf_sk_storage.h>
 
 #include <uapi/linux/bpf.h>
 #include <uapi/linux/btf.h>
@@ -1735,6 +1736,10 @@ tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return &bpf_skc_to_tcp_request_sock_proto;
 	case BPF_FUNC_skc_to_udp6_sock:
 		return &bpf_skc_to_udp6_sock_proto;
+	case BPF_FUNC_sk_storage_get:
+		return &bpf_sk_storage_get_tracing_proto;
+	case BPF_FUNC_sk_storage_delete:
+		return &bpf_sk_storage_delete_tracing_proto;
 #endif
 	case BPF_FUNC_seq_printf:
 		return prog->expected_attach_type == BPF_TRACE_ITER ?
diff --git a/net/core/bpf_sk_storage.c b/net/core/bpf_sk_storage.c
index 001eac65e40f..1a41c917e08d 100644
--- a/net/core/bpf_sk_storage.c
+++ b/net/core/bpf_sk_storage.c
@@ -6,6 +6,7 @@
 #include <linux/types.h>
 #include <linux/spinlock.h>
 #include <linux/bpf.h>
+#include <linux/btf.h>
 #include <linux/btf_ids.h>
 #include <linux/bpf_local_storage.h>
 #include <net/bpf_sk_storage.h>
@@ -378,6 +379,78 @@ const struct bpf_func_proto bpf_sk_storage_delete_proto = {
 	.arg2_type	= ARG_PTR_TO_BTF_ID_SOCK_COMMON,
 };
 
+static bool bpf_sk_storage_tracing_allowed(const struct bpf_prog *prog)
+{
+	const struct btf *btf_vmlinux;
+	const struct btf_type *t;
+	const char *tname;
+	u32 btf_id;
+
+	if (prog->aux->dst_prog)
+		return false;
+
+	/* Ensure the tracing program is not tracing
+	 * any *sk_storage*() function and also
+	 * use the bpf_sk_storage_(get|delete) helper.
+	 */
+	switch (prog->expected_attach_type) {
+	case BPF_TRACE_RAW_TP:
+		/* bpf_sk_storage has no trace point */
+		return true;
+	case BPF_TRACE_FENTRY:
+	case BPF_TRACE_FEXIT:
+		btf_vmlinux = bpf_get_btf_vmlinux();
+		btf_id = prog->aux->attach_btf_id;
+		t = btf_type_by_id(btf_vmlinux, btf_id);
+		tname = btf_name_by_offset(btf_vmlinux, t->name_off);
+		return !strstr(tname, "sk_storage");
+	default:
+		return false;
+	}
+
+	return false;
+}
+
+BPF_CALL_4(bpf_sk_storage_get_tracing, struct bpf_map *, map, struct sock *, sk,
+	   void *, value, u64, flags)
+{
+	if (!in_serving_softirq() && !in_task())
+		return (unsigned long)NULL;
+
+	return (unsigned long)____bpf_sk_storage_get(map, sk, value, flags);
+}
+
+BPF_CALL_2(bpf_sk_storage_delete_tracing, struct bpf_map *, map,
+	   struct sock *, sk)
+{
+	if (!in_serving_softirq() && !in_task())
+		return -EPERM;
+
+	return ____bpf_sk_storage_delete(map, sk);
+}
+
+const struct bpf_func_proto bpf_sk_storage_get_tracing_proto = {
+	.func		= bpf_sk_storage_get_tracing,
+	.gpl_only	= false,
+	.ret_type	= RET_PTR_TO_MAP_VALUE_OR_NULL,
+	.arg1_type	= ARG_CONST_MAP_PTR,
+	.arg2_type	= ARG_PTR_TO_BTF_ID,
+	.arg2_btf_id	= &btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON],
+	.arg3_type	= ARG_PTR_TO_MAP_VALUE_OR_NULL,
+	.arg4_type	= ARG_ANYTHING,
+	.allowed	= bpf_sk_storage_tracing_allowed,
+};
+
+const struct bpf_func_proto bpf_sk_storage_delete_tracing_proto = {
+	.func		= bpf_sk_storage_delete_tracing,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_CONST_MAP_PTR,
+	.arg2_type	= ARG_PTR_TO_BTF_ID,
+	.arg2_btf_id	= &btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON],
+	.allowed	= bpf_sk_storage_tracing_allowed,
+};
+
 struct bpf_sk_storage_diag {
 	u32 nr_maps;
 	struct bpf_map *maps[];
-- 
2.24.1

[PATCH bpf-next 3/3] bpf: selftest: Use bpf_sk_storage in FENTRY/FEXIT/RAW_TP

[Martin KaFai Lau]

This patch tests storing the task's related info into the
bpf_sk_storage by fentry/fexit tracing at listen, accept,
and connect.  It also tests the raw_tp at inet_sock_set_state.

A negative test is done by tracing the bpf_sk_storage_free()
and using bpf_sk_storage_get() at the same time.  It ensures
this bpf program cannot load.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
---
 .../bpf/prog_tests/sk_storage_tracing.c       | 135 ++++++++++++++++++
 .../bpf/progs/test_sk_storage_trace_itself.c  |  29 ++++
 .../bpf/progs/test_sk_storage_tracing.c       |  95 ++++++++++++
 3 files changed, 259 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/sk_storage_tracing.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_sk_storage_trace_itself.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_sk_storage_tracing.c

diff --git a/tools/testing/selftests/bpf/prog_tests/sk_storage_tracing.c b/tools/testing/selftests/bpf/prog_tests/sk_storage_tracing.c
new file mode 100644
index 000000000000..2b392590e8ca
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/sk_storage_tracing.c
@@ -0,0 +1,135 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020 Facebook */
+
+#include <sys/types.h>
+#include <bpf/bpf.h>
+#include <bpf/libbpf.h>
+#include "test_progs.h"
+#include "network_helpers.h"
+#include "test_sk_storage_trace_itself.skel.h"
+#include "test_sk_storage_tracing.skel.h"
+
+#define LO_ADDR6 "::1"
+#define TEST_COMM "test_progs"
+
+struct sk_stg {
+	__u32 pid;
+	__u32 last_notclose_state;
+	char comm[16];
+};
+
+static struct test_sk_storage_tracing *skel;
+static __u32 duration;
+static pid_t my_pid;
+
+static int check_sk_stg(int sk_fd, __u32 expected_state)
+{
+	struct sk_stg sk_stg;
+	int err;
+
+	err = bpf_map_lookup_elem(bpf_map__fd(skel->maps.sk_stg_map), &sk_fd,
+				  &sk_stg);
+	if (!ASSERT_OK(err, "map_lookup(sk_stg_map)"))
+		return -1;
+
+	if (!ASSERT_EQ(sk_stg.last_notclose_state, expected_state,
+		       "last_notclose_state"))
+		return -1;
+
+	if (!ASSERT_EQ(sk_stg.pid, my_pid, "pid"))
+		return -1;
+
+	if (!ASSERT_STREQ(sk_stg.comm, skel->bss->task_comm, "task_comm"))
+		return -1;
+
+	return 0;
+}
+
+static void do_test(void)
+{
+	int listen_fd = -1, passive_fd = -1, active_fd = -1, value = 1, err;
+	char abyte;
+
+	listen_fd = start_server(AF_INET6, SOCK_STREAM, LO_ADDR6, 0, 0);
+	if (CHECK(listen_fd == -1, "start_server",
+		  "listen_fd:%d errno:%d\n", listen_fd, errno))
+		return;
+
+	active_fd = connect_to_fd(listen_fd, 0);
+	if (CHECK(active_fd == -1, "connect_to_fd", "active_fd:%d errno:%d\n",
+		  active_fd, errno))
+		goto out;
+
+	err = bpf_map_update_elem(bpf_map__fd(skel->maps.del_sk_stg_map),
+				  &active_fd, &value, 0);
+	if (!ASSERT_OK(err, "map_update(del_sk_stg_map)"))
+		goto out;
+
+	passive_fd = accept(listen_fd, NULL, 0);
+	if (CHECK(passive_fd == -1, "accept", "passive_fd:%d errno:%d\n",
+		  passive_fd, errno))
+		goto out;
+
+	shutdown(active_fd, SHUT_WR);
+	err = read(passive_fd, &abyte, 1);
+	if (!ASSERT_OK(err, "read(passive_fd)"))
+		goto out;
+
+	shutdown(passive_fd, SHUT_WR);
+	err = read(active_fd, &abyte, 1);
+	if (!ASSERT_OK(err, "read(active_fd)"))
+		goto out;
+
+	err = bpf_map_lookup_elem(bpf_map__fd(skel->maps.del_sk_stg_map),
+				  &active_fd, &value);
+	if (!ASSERT_ERR(err, "map_lookup(del_sk_stg_map)"))
+		goto out;
+
+	err = check_sk_stg(listen_fd, BPF_TCP_LISTEN);
+	if (!ASSERT_OK(err, "listen_fd sk_stg"))
+		goto out;
+
+	err = check_sk_stg(active_fd, BPF_TCP_FIN_WAIT2);
+	if (!ASSERT_OK(err, "active_fd sk_stg"))
+		goto out;
+
+	err = check_sk_stg(passive_fd, BPF_TCP_LAST_ACK);
+	ASSERT_OK(err, "passive_fd sk_stg");
+
+out:
+	if (active_fd != -1)
+		close(active_fd);
+	if (passive_fd != -1)
+		close(passive_fd);
+	if (listen_fd != -1)
+		close(listen_fd);
+}
+
+void test_sk_storage_tracing(void)
+{
+	struct test_sk_storage_trace_itself *skel_itself;
+	int err;
+
+	my_pid = getpid();
+
+	skel_itself = test_sk_storage_trace_itself__open_and_load();
+
+	if (!ASSERT_NULL(skel_itself, "test_sk_storage_trace_itself")) {
+		test_sk_storage_trace_itself__destroy(skel_itself);
+		return;
+	}
+
+	skel = test_sk_storage_tracing__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "test_sk_storage_tracing"))
+		return;
+
+	err = test_sk_storage_tracing__attach(skel);
+	if (!ASSERT_OK(err, "test_sk_storage_tracing__attach")) {
+		test_sk_storage_tracing__destroy(skel);
+		return;
+	}
+
+	do_test();
+
+	test_sk_storage_tracing__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/test_sk_storage_trace_itself.c b/tools/testing/selftests/bpf/progs/test_sk_storage_trace_itself.c
new file mode 100644
index 000000000000..59ef72d02a61
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_sk_storage_trace_itself.c
@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020 Facebook */
+
+#include <vmlinux.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_helpers.h>
+
+struct {
+	__uint(type, BPF_MAP_TYPE_SK_STORAGE);
+	__uint(map_flags, BPF_F_NO_PREALLOC);
+	__type(key, int);
+	__type(value, int);
+} sk_stg_map SEC(".maps");
+
+SEC("fentry/bpf_sk_storage_free")
+int BPF_PROG(trace_bpf_sk_storage_free, struct sock *sk)
+{
+	int *value;
+
+	value = bpf_sk_storage_get(&sk_stg_map, sk, 0,
+				   BPF_SK_STORAGE_GET_F_CREATE);
+
+	if (value)
+		*value = 1;
+
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/progs/test_sk_storage_tracing.c b/tools/testing/selftests/bpf/progs/test_sk_storage_tracing.c
new file mode 100644
index 000000000000..8e94e5c080aa
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_sk_storage_tracing.c
@@ -0,0 +1,95 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020 Facebook */
+
+#include <vmlinux.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_core_read.h>
+#include <bpf/bpf_helpers.h>
+
+struct sk_stg {
+	__u32 pid;
+	__u32 last_notclose_state;
+	char comm[16];
+};
+
+struct {
+	__uint(type, BPF_MAP_TYPE_SK_STORAGE);
+	__uint(map_flags, BPF_F_NO_PREALLOC);
+	__type(key, int);
+	__type(value, struct sk_stg);
+} sk_stg_map SEC(".maps");
+
+/* Testing delete */
+struct {
+	__uint(type, BPF_MAP_TYPE_SK_STORAGE);
+	__uint(map_flags, BPF_F_NO_PREALLOC);
+	__type(key, int);
+	__type(value, int);
+} del_sk_stg_map SEC(".maps");
+
+char task_comm[16] = "";
+
+SEC("tp_btf/inet_sock_set_state")
+int BPF_PROG(trace_inet_sock_set_state, struct sock *sk, int oldstate,
+	     int newstate)
+{
+	struct sk_stg *stg;
+
+	if (newstate == BPF_TCP_CLOSE)
+		return 0;
+
+	stg = bpf_sk_storage_get(&sk_stg_map, sk, 0,
+				 BPF_SK_STORAGE_GET_F_CREATE);
+	if (!stg)
+		return 0;
+
+	stg->last_notclose_state = newstate;
+
+	bpf_sk_storage_delete(&del_sk_stg_map, sk);
+
+	return 0;
+}
+
+static void set_task_info(struct sock *sk)
+{
+	struct task_struct *task;
+	struct sk_stg *stg;
+
+	stg = bpf_sk_storage_get(&sk_stg_map, sk, 0,
+				 BPF_SK_STORAGE_GET_F_CREATE);
+	if (!stg)
+		return;
+
+	stg->pid = bpf_get_current_pid_tgid();
+
+	task = (struct task_struct *)bpf_get_current_task();
+	bpf_core_read_str(&stg->comm, sizeof(stg->comm), &task->comm);
+	bpf_core_read_str(&task_comm, sizeof(task_comm), &task->comm);
+}
+
+SEC("fentry/inet_csk_listen_start")
+int BPF_PROG(trace_inet_csk_listen_start, struct sock *sk, int backlog)
+{
+	set_task_info(sk);
+
+	return 0;
+}
+
+SEC("fentry/tcp_connect")
+int BPF_PROG(trace_tcp_connect, struct sock *sk)
+{
+	set_task_info(sk);
+
+	return 0;
+}
+
+SEC("fexit/inet_csk_accept")
+int BPF_PROG(inet_csk_accept, struct sock *sk, int flags, int *err, bool kern,
+	     struct sock *accepted_sk)
+{
+	set_task_info(accepted_sk);
+
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";
-- 
2.24.1

Re: [PATCH bpf-next 1/3] bpf: Folding omem_charge() into sk_storage_charge()

[Song Liu]

> On Nov 6, 2020, at 2:07 PM, Martin KaFai Lau <kafai@fb.com> wrote:
> 
> sk_storage_charge() is the only user of omem_charge().
> This patch simplifies it by folding omem_charge() into
> sk_storage_charge().
> 
> Signed-off-by: Martin KaFai Lau <kafai@fb.com>

Acked-by: Song Liu <songliubraving@fb.com>

> ---
> net/core/bpf_sk_storage.c | 23 ++++++++++-------------
> 1 file changed, 10 insertions(+), 13 deletions(-)
> 
> diff --git a/net/core/bpf_sk_storage.c b/net/core/bpf_sk_storage.c
> index c907f0dc7f87..001eac65e40f 100644
> --- a/net/core/bpf_sk_storage.c
> +++ b/net/core/bpf_sk_storage.c
> @@ -15,18 +15,6 @@
> 
> DEFINE_BPF_STORAGE_CACHE(sk_cache);
> 
> -static int omem_charge(struct sock *sk, unsigned int size)
> -{
> -	/* same check as in sock_kmalloc() */
> -	if (size <= sysctl_optmem_max &&
> -	    atomic_read(&sk->sk_omem_alloc) + size < sysctl_optmem_max) {
> -		atomic_add(size, &sk->sk_omem_alloc);
> -		return 0;
> -	}
> -
> -	return -ENOMEM;
> -}
> -
> static struct bpf_local_storage_data *
> sk_storage_lookup(struct sock *sk, struct bpf_map *map, bool cacheit_lockit)
> {
> @@ -316,7 +304,16 @@ BPF_CALL_2(bpf_sk_storage_delete, struct bpf_map *, map, struct sock *, sk)
> static int sk_storage_charge(struct bpf_local_storage_map *smap,
> 			     void *owner, u32 size)
> {
> -	return omem_charge(owner, size);
> +	struct sock *sk = (struct sock *)owner;
> +
> +	/* same check as in sock_kmalloc() */
> +	if (size <= sysctl_optmem_max &&
> +	    atomic_read(&sk->sk_omem_alloc) + size < sysctl_optmem_max) {
> +		atomic_add(size, &sk->sk_omem_alloc);
> +		return 0;
> +	}
> +
> +	return -ENOMEM;
> }
> 
> static void sk_storage_uncharge(struct bpf_local_storage_map *smap,
> -- 
> 2.24.1
> 

Re: [PATCH bpf-next 2/3] bpf: Allow using bpf_sk_storage in FENTRY/FEXIT/RAW_TP

[Song Liu]

> On Nov 6, 2020, at 2:08 PM, Martin KaFai Lau <kafai@fb.com> wrote:
> 
> This patch enables the FENTRY/FEXIT/RAW_TP tracing program to use
> the bpf_sk_storage_(get|delete) helper, so those tracing programs
> can access the sk's bpf_local_storage and the later selftest
> will show some examples.
> 
> The bpf_sk_storage is currently used in bpf-tcp-cc, tc,
> cg sockops...etc which is running either in softirq or
> task context.
> 
> This patch adds bpf_sk_storage_get_tracing_proto and
> bpf_sk_storage_delete_tracing_proto.  They will check
> in runtime that the helpers can only be called when serving
> softirq or running in a task context.  That should enable
> most common tracing use cases on sk.
> 
> During the load time, the new tracing_allowed() function
> will ensure the tracing prog using the bpf_sk_storage_(get|delete)
> helper is not tracing any *sk_storage*() function itself.
> The sk is passed as "void *" when calling into bpf_local_storage.
> 
> Signed-off-by: Martin KaFai Lau <kafai@fb.com>
> ---
> include/net/bpf_sk_storage.h |  2 +
> kernel/trace/bpf_trace.c     |  5 +++
> net/core/bpf_sk_storage.c    | 73 ++++++++++++++++++++++++++++++++++++
> 3 files changed, 80 insertions(+)
> 
> diff --git a/include/net/bpf_sk_storage.h b/include/net/bpf_sk_storage.h
> index 3c516dd07caf..0e85713f56df 100644
> --- a/include/net/bpf_sk_storage.h
> +++ b/include/net/bpf_sk_storage.h
> @@ -20,6 +20,8 @@ void bpf_sk_storage_free(struct sock *sk);
> 
> extern const struct bpf_func_proto bpf_sk_storage_get_proto;
> extern const struct bpf_func_proto bpf_sk_storage_delete_proto;
> +extern const struct bpf_func_proto bpf_sk_storage_get_tracing_proto;
> +extern const struct bpf_func_proto bpf_sk_storage_delete_tracing_proto;
> 
> struct bpf_local_storage_elem;
> struct bpf_sk_storage_diag;
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index e4515b0f62a8..cfce60ad1cb5 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 <net/bpf_sk_storage.h>
> 
> #include <uapi/linux/bpf.h>
> #include <uapi/linux/btf.h>
> @@ -1735,6 +1736,10 @@ tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
> 		return &bpf_skc_to_tcp_request_sock_proto;
> 	case BPF_FUNC_skc_to_udp6_sock:
> 		return &bpf_skc_to_udp6_sock_proto;
> +	case BPF_FUNC_sk_storage_get:
> +		return &bpf_sk_storage_get_tracing_proto;
> +	case BPF_FUNC_sk_storage_delete:
> +		return &bpf_sk_storage_delete_tracing_proto;
> #endif
> 	case BPF_FUNC_seq_printf:
> 		return prog->expected_attach_type == BPF_TRACE_ITER ?
> diff --git a/net/core/bpf_sk_storage.c b/net/core/bpf_sk_storage.c
> index 001eac65e40f..1a41c917e08d 100644
> --- a/net/core/bpf_sk_storage.c
> +++ b/net/core/bpf_sk_storage.c
> @@ -6,6 +6,7 @@
> #include <linux/types.h>
> #include <linux/spinlock.h>
> #include <linux/bpf.h>
> +#include <linux/btf.h>
> #include <linux/btf_ids.h>
> #include <linux/bpf_local_storage.h>
> #include <net/bpf_sk_storage.h>
> @@ -378,6 +379,78 @@ const struct bpf_func_proto bpf_sk_storage_delete_proto = {
> 	.arg2_type	= ARG_PTR_TO_BTF_ID_SOCK_COMMON,
> };
> 
> +static bool bpf_sk_storage_tracing_allowed(const struct bpf_prog *prog)
> +{
> +	const struct btf *btf_vmlinux;
> +	const struct btf_type *t;
> +	const char *tname;
> +	u32 btf_id;
> +
> +	if (prog->aux->dst_prog)
> +		return false;
> +
> +	/* Ensure the tracing program is not tracing
> +	 * any *sk_storage*() function and also
> +	 * use the bpf_sk_storage_(get|delete) helper.
> +	 */
> +	switch (prog->expected_attach_type) {
> +	case BPF_TRACE_RAW_TP:
> +		/* bpf_sk_storage has no trace point */
> +		return true;
> +	case BPF_TRACE_FENTRY:
> +	case BPF_TRACE_FEXIT:
> +		btf_vmlinux = bpf_get_btf_vmlinux();
> +		btf_id = prog->aux->attach_btf_id;
> +		t = btf_type_by_id(btf_vmlinux, btf_id);

What happens to fentry/fexit attach to other BPF programs? I guess
we should check for t == NULL?

Thanks,
Song

> +		tname = btf_name_by_offset(btf_vmlinux, t->name_off);
> +		return !strstr(tname, "sk_storage");
> +	default:
> +		return false;
> +	}
> +
> +	return false;
> +}

[...]

Re: [PATCH bpf-next 2/3] bpf: Allow using bpf_sk_storage in FENTRY/FEXIT/RAW_TP

[Martin KaFai Lau]

On Fri, Nov 06, 2020 at 02:59:14PM -0800, Song Liu wrote:
> 
> 
> > On Nov 6, 2020, at 2:08 PM, Martin KaFai Lau <kafai@fb.com> wrote:
> > 
> > This patch enables the FENTRY/FEXIT/RAW_TP tracing program to use
> > the bpf_sk_storage_(get|delete) helper, so those tracing programs
> > can access the sk's bpf_local_storage and the later selftest
> > will show some examples.
> > 
> > The bpf_sk_storage is currently used in bpf-tcp-cc, tc,
> > cg sockops...etc which is running either in softirq or
> > task context.
> > 
> > This patch adds bpf_sk_storage_get_tracing_proto and
> > bpf_sk_storage_delete_tracing_proto.  They will check
> > in runtime that the helpers can only be called when serving
> > softirq or running in a task context.  That should enable
> > most common tracing use cases on sk.
> > 
> > During the load time, the new tracing_allowed() function
> > will ensure the tracing prog using the bpf_sk_storage_(get|delete)
> > helper is not tracing any *sk_storage*() function itself.
> > The sk is passed as "void *" when calling into bpf_local_storage.
> > 
> > Signed-off-by: Martin KaFai Lau <kafai@fb.com>
> > ---
> > include/net/bpf_sk_storage.h |  2 +
> > kernel/trace/bpf_trace.c     |  5 +++
> > net/core/bpf_sk_storage.c    | 73 ++++++++++++++++++++++++++++++++++++
> > 3 files changed, 80 insertions(+)
> > 
> > diff --git a/include/net/bpf_sk_storage.h b/include/net/bpf_sk_storage.h
> > index 3c516dd07caf..0e85713f56df 100644
> > --- a/include/net/bpf_sk_storage.h
> > +++ b/include/net/bpf_sk_storage.h
> > @@ -20,6 +20,8 @@ void bpf_sk_storage_free(struct sock *sk);
> > 
> > extern const struct bpf_func_proto bpf_sk_storage_get_proto;
> > extern const struct bpf_func_proto bpf_sk_storage_delete_proto;
> > +extern const struct bpf_func_proto bpf_sk_storage_get_tracing_proto;
> > +extern const struct bpf_func_proto bpf_sk_storage_delete_tracing_proto;
> > 
> > struct bpf_local_storage_elem;
> > struct bpf_sk_storage_diag;
> > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> > index e4515b0f62a8..cfce60ad1cb5 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 <net/bpf_sk_storage.h>
> > 
> > #include <uapi/linux/bpf.h>
> > #include <uapi/linux/btf.h>
> > @@ -1735,6 +1736,10 @@ tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
> > 		return &bpf_skc_to_tcp_request_sock_proto;
> > 	case BPF_FUNC_skc_to_udp6_sock:
> > 		return &bpf_skc_to_udp6_sock_proto;
> > +	case BPF_FUNC_sk_storage_get:
> > +		return &bpf_sk_storage_get_tracing_proto;
> > +	case BPF_FUNC_sk_storage_delete:
> > +		return &bpf_sk_storage_delete_tracing_proto;
> > #endif
> > 	case BPF_FUNC_seq_printf:
> > 		return prog->expected_attach_type == BPF_TRACE_ITER ?
> > diff --git a/net/core/bpf_sk_storage.c b/net/core/bpf_sk_storage.c
> > index 001eac65e40f..1a41c917e08d 100644
> > --- a/net/core/bpf_sk_storage.c
> > +++ b/net/core/bpf_sk_storage.c
> > @@ -6,6 +6,7 @@
> > #include <linux/types.h>
> > #include <linux/spinlock.h>
> > #include <linux/bpf.h>
> > +#include <linux/btf.h>
> > #include <linux/btf_ids.h>
> > #include <linux/bpf_local_storage.h>
> > #include <net/bpf_sk_storage.h>
> > @@ -378,6 +379,78 @@ const struct bpf_func_proto bpf_sk_storage_delete_proto = {
> > 	.arg2_type	= ARG_PTR_TO_BTF_ID_SOCK_COMMON,
> > };
> > 
> > +static bool bpf_sk_storage_tracing_allowed(const struct bpf_prog *prog)
> > +{
> > +	const struct btf *btf_vmlinux;
> > +	const struct btf_type *t;
> > +	const char *tname;
> > +	u32 btf_id;
> > +
> > +	if (prog->aux->dst_prog)
> > +		return false;
> > +
> > +	/* Ensure the tracing program is not tracing
> > +	 * any *sk_storage*() function and also
> > +	 * use the bpf_sk_storage_(get|delete) helper.
> > +	 */
> > +	switch (prog->expected_attach_type) {
> > +	case BPF_TRACE_RAW_TP:
> > +		/* bpf_sk_storage has no trace point */
> > +		return true;
> > +	case BPF_TRACE_FENTRY:
> > +	case BPF_TRACE_FEXIT:
> > +		btf_vmlinux = bpf_get_btf_vmlinux();
> > +		btf_id = prog->aux->attach_btf_id;
> > +		t = btf_type_by_id(btf_vmlinux, btf_id);
> 
> What happens to fentry/fexit attach to other BPF programs? I guess
> we should check for t == NULL?
It does not support tracing BPF program and using bpf_sk_storage
at the same time for now, so there is a "if (prog->aux->dst_prog)" test earlier.
It could be extended to do it later as a follow up.
I missed to mention that in the commit message.  

"t" should not be NULL here when tracing a kernel function.
The verifier should have already checked it and ensured "t" is a FUNC.

> > +		tname = btf_name_by_offset(btf_vmlinux, t->name_off);
> > +		return !strstr(tname, "sk_storage");
> > +	default:
> > +		return false;
> > +	}
> > +
> > +	return false;
> > +}
> 
> [...]
> 
> 

Re: [PATCH bpf-next 2/3] bpf: Allow using bpf_sk_storage in FENTRY/FEXIT/RAW_TP

[Song Liu]

> On Nov 6, 2020, at 3:18 PM, Martin Lau <kafai@fb.com> wrote:
> 
> On Fri, Nov 06, 2020 at 02:59:14PM -0800, Song Liu wrote:
>> 
>> 
>>> On Nov 6, 2020, at 2:08 PM, Martin KaFai Lau <kafai@fb.com> wrote:
>>> 

[...]

>>> +static bool bpf_sk_storage_tracing_allowed(const struct bpf_prog *prog)
>>> +{
>>> +	const struct btf *btf_vmlinux;
>>> +	const struct btf_type *t;
>>> +	const char *tname;
>>> +	u32 btf_id;
>>> +
>>> +	if (prog->aux->dst_prog)
>>> +		return false;
>>> +
>>> +	/* Ensure the tracing program is not tracing
>>> +	 * any *sk_storage*() function and also
>>> +	 * use the bpf_sk_storage_(get|delete) helper.
>>> +	 */
>>> +	switch (prog->expected_attach_type) {
>>> +	case BPF_TRACE_RAW_TP:
>>> +		/* bpf_sk_storage has no trace point */
>>> +		return true;
>>> +	case BPF_TRACE_FENTRY:
>>> +	case BPF_TRACE_FEXIT:
>>> +		btf_vmlinux = bpf_get_btf_vmlinux();
>>> +		btf_id = prog->aux->attach_btf_id;
>>> +		t = btf_type_by_id(btf_vmlinux, btf_id);
>> 
>> What happens to fentry/fexit attach to other BPF programs? I guess
>> we should check for t == NULL?
> It does not support tracing BPF program and using bpf_sk_storage
> at the same time for now, so there is a "if (prog->aux->dst_prog)" test earlier.
> It could be extended to do it later as a follow up.
> I missed to mention that in the commit message.  
> 
> "t" should not be NULL here when tracing a kernel function.
> The verifier should have already checked it and ensured "t" is a FUNC.

Ah, I missed the dst_prog check. Thanks for the explanation. 

Acked-by: Song Liu <songliubraving@fb.com>

Re: [PATCH bpf-next 2/3] bpf: Allow using bpf_sk_storage in FENTRY/FEXIT/RAW_TP

[Andrii Nakryiko]

On Fri, Nov 6, 2020 at 2:08 PM Martin KaFai Lau <kafai@fb.com> wrote:
>
> This patch enables the FENTRY/FEXIT/RAW_TP tracing program to use
> the bpf_sk_storage_(get|delete) helper, so those tracing programs
> can access the sk's bpf_local_storage and the later selftest
> will show some examples.
>
> The bpf_sk_storage is currently used in bpf-tcp-cc, tc,
> cg sockops...etc which is running either in softirq or
> task context.
>
> This patch adds bpf_sk_storage_get_tracing_proto and
> bpf_sk_storage_delete_tracing_proto.  They will check
> in runtime that the helpers can only be called when serving
> softirq or running in a task context.  That should enable
> most common tracing use cases on sk.
>
> During the load time, the new tracing_allowed() function
> will ensure the tracing prog using the bpf_sk_storage_(get|delete)
> helper is not tracing any *sk_storage*() function itself.
> The sk is passed as "void *" when calling into bpf_local_storage.
>
> Signed-off-by: Martin KaFai Lau <kafai@fb.com>
> ---
>  include/net/bpf_sk_storage.h |  2 +
>  kernel/trace/bpf_trace.c     |  5 +++
>  net/core/bpf_sk_storage.c    | 73 ++++++++++++++++++++++++++++++++++++
>  3 files changed, 80 insertions(+)
>

[...]

> +       switch (prog->expected_attach_type) {
> +       case BPF_TRACE_RAW_TP:
> +               /* bpf_sk_storage has no trace point */
> +               return true;
> +       case BPF_TRACE_FENTRY:
> +       case BPF_TRACE_FEXIT:
> +               btf_vmlinux = bpf_get_btf_vmlinux();
> +               btf_id = prog->aux->attach_btf_id;
> +               t = btf_type_by_id(btf_vmlinux, btf_id);
> +               tname = btf_name_by_offset(btf_vmlinux, t->name_off);
> +               return !strstr(tname, "sk_storage");

I'm always feeling uneasy about substring checks... Also, KP just
fixed the issue with string-based checks for LSM. Can we use a
BTF_ID_SET of blacklisted functions instead?

> +       default:
> +               return false;
> +       }
> +
> +       return false;
> +}
> +

[...]

Re: [PATCH bpf-next 2/3] bpf: Allow using bpf_sk_storage in FENTRY/FEXIT/RAW_TP

[Martin KaFai Lau]

On Fri, Nov 06, 2020 at 05:14:14PM -0800, Andrii Nakryiko wrote:
> On Fri, Nov 6, 2020 at 2:08 PM Martin KaFai Lau <kafai@fb.com> wrote:
> >
> > This patch enables the FENTRY/FEXIT/RAW_TP tracing program to use
> > the bpf_sk_storage_(get|delete) helper, so those tracing programs
> > can access the sk's bpf_local_storage and the later selftest
> > will show some examples.
> >
> > The bpf_sk_storage is currently used in bpf-tcp-cc, tc,
> > cg sockops...etc which is running either in softirq or
> > task context.
> >
> > This patch adds bpf_sk_storage_get_tracing_proto and
> > bpf_sk_storage_delete_tracing_proto.  They will check
> > in runtime that the helpers can only be called when serving
> > softirq or running in a task context.  That should enable
> > most common tracing use cases on sk.
> >
> > During the load time, the new tracing_allowed() function
> > will ensure the tracing prog using the bpf_sk_storage_(get|delete)
> > helper is not tracing any *sk_storage*() function itself.
> > The sk is passed as "void *" when calling into bpf_local_storage.
> >
> > Signed-off-by: Martin KaFai Lau <kafai@fb.com>
> > ---
> >  include/net/bpf_sk_storage.h |  2 +
> >  kernel/trace/bpf_trace.c     |  5 +++
> >  net/core/bpf_sk_storage.c    | 73 ++++++++++++++++++++++++++++++++++++
> >  3 files changed, 80 insertions(+)
> >
> 
> [...]
> 
> > +       switch (prog->expected_attach_type) {
> > +       case BPF_TRACE_RAW_TP:
> > +               /* bpf_sk_storage has no trace point */
> > +               return true;
> > +       case BPF_TRACE_FENTRY:
> > +       case BPF_TRACE_FEXIT:
> > +               btf_vmlinux = bpf_get_btf_vmlinux();
> > +               btf_id = prog->aux->attach_btf_id;
> > +               t = btf_type_by_id(btf_vmlinux, btf_id);
> > +               tname = btf_name_by_offset(btf_vmlinux, t->name_off);
> > +               return !strstr(tname, "sk_storage");
> 
> I'm always feeling uneasy about substring checks... Also, KP just
> fixed the issue with string-based checks for LSM. Can we use a
> BTF_ID_SET of blacklisted functions instead?
KP one is different.  It accidentally whitelist-ed more than it should.

It is a blacklist here.  It is actually cleaner and safer to blacklist
all functions with "sk_storage" and too pessimistic is fine here.

> 
> > +       default:
> > +               return false;
> > +       }
> > +
> > +       return false;
> > +}
> > +
> 
> [...]

Re: [PATCH bpf-next 2/3] bpf: Allow using bpf_sk_storage in FENTRY/FEXIT/RAW_TP

[Andrii Nakryiko]

On Fri, Nov 6, 2020 at 5:52 PM Martin KaFai Lau <kafai@fb.com> wrote:
>
> On Fri, Nov 06, 2020 at 05:14:14PM -0800, Andrii Nakryiko wrote:
> > On Fri, Nov 6, 2020 at 2:08 PM Martin KaFai Lau <kafai@fb.com> wrote:
> > >
> > > This patch enables the FENTRY/FEXIT/RAW_TP tracing program to use
> > > the bpf_sk_storage_(get|delete) helper, so those tracing programs
> > > can access the sk's bpf_local_storage and the later selftest
> > > will show some examples.
> > >
> > > The bpf_sk_storage is currently used in bpf-tcp-cc, tc,
> > > cg sockops...etc which is running either in softirq or
> > > task context.
> > >
> > > This patch adds bpf_sk_storage_get_tracing_proto and
> > > bpf_sk_storage_delete_tracing_proto.  They will check
> > > in runtime that the helpers can only be called when serving
> > > softirq or running in a task context.  That should enable
> > > most common tracing use cases on sk.
> > >
> > > During the load time, the new tracing_allowed() function
> > > will ensure the tracing prog using the bpf_sk_storage_(get|delete)
> > > helper is not tracing any *sk_storage*() function itself.
> > > The sk is passed as "void *" when calling into bpf_local_storage.
> > >
> > > Signed-off-by: Martin KaFai Lau <kafai@fb.com>
> > > ---
> > >  include/net/bpf_sk_storage.h |  2 +
> > >  kernel/trace/bpf_trace.c     |  5 +++
> > >  net/core/bpf_sk_storage.c    | 73 ++++++++++++++++++++++++++++++++++++
> > >  3 files changed, 80 insertions(+)
> > >
> >
> > [...]
> >
> > > +       switch (prog->expected_attach_type) {
> > > +       case BPF_TRACE_RAW_TP:
> > > +               /* bpf_sk_storage has no trace point */
> > > +               return true;
> > > +       case BPF_TRACE_FENTRY:
> > > +       case BPF_TRACE_FEXIT:
> > > +               btf_vmlinux = bpf_get_btf_vmlinux();
> > > +               btf_id = prog->aux->attach_btf_id;
> > > +               t = btf_type_by_id(btf_vmlinux, btf_id);
> > > +               tname = btf_name_by_offset(btf_vmlinux, t->name_off);
> > > +               return !strstr(tname, "sk_storage");
> >
> > I'm always feeling uneasy about substring checks... Also, KP just
> > fixed the issue with string-based checks for LSM. Can we use a
> > BTF_ID_SET of blacklisted functions instead?
> KP one is different.  It accidentally whitelist-ed more than it should.
>
> It is a blacklist here.  It is actually cleaner and safer to blacklist
> all functions with "sk_storage" and too pessimistic is fine here.

Fine for whom? Prefix check would be half-bad, but substring check is
horrible. Suddenly "task_storage" (and anything related) would be also
blacklisted. Let's do a prefix check at least.

>
> >
> > > +       default:
> > > +               return false;
> > > +       }
> > > +
> > > +       return false;
> > > +}
> > > +
> >
> > [...]

Re: [PATCH bpf-next 2/3] bpf: Allow using bpf_sk_storage in FENTRY/FEXIT/RAW_TP

[John Fastabend]

Andrii Nakryiko wrote:
> On Fri, Nov 6, 2020 at 5:52 PM Martin KaFai Lau <kafai@fb.com> wrote:
> >
> > On Fri, Nov 06, 2020 at 05:14:14PM -0800, Andrii Nakryiko wrote:
> > > On Fri, Nov 6, 2020 at 2:08 PM Martin KaFai Lau <kafai@fb.com> wrote:
> > > >
> > > > This patch enables the FENTRY/FEXIT/RAW_TP tracing program to use
> > > > the bpf_sk_storage_(get|delete) helper, so those tracing programs
> > > > can access the sk's bpf_local_storage and the later selftest
> > > > will show some examples.
> > > >
> > > > The bpf_sk_storage is currently used in bpf-tcp-cc, tc,
> > > > cg sockops...etc which is running either in softirq or
> > > > task context.
> > > >
> > > > This patch adds bpf_sk_storage_get_tracing_proto and
> > > > bpf_sk_storage_delete_tracing_proto.  They will check
> > > > in runtime that the helpers can only be called when serving
> > > > softirq or running in a task context.  That should enable
> > > > most common tracing use cases on sk.
> > > >
> > > > During the load time, the new tracing_allowed() function
> > > > will ensure the tracing prog using the bpf_sk_storage_(get|delete)
> > > > helper is not tracing any *sk_storage*() function itself.
> > > > The sk is passed as "void *" when calling into bpf_local_storage.
> > > >
> > > > Signed-off-by: Martin KaFai Lau <kafai@fb.com>
> > > > ---
> > > >  include/net/bpf_sk_storage.h |  2 +
> > > >  kernel/trace/bpf_trace.c     |  5 +++
> > > >  net/core/bpf_sk_storage.c    | 73 ++++++++++++++++++++++++++++++++++++
> > > >  3 files changed, 80 insertions(+)
> > > >
> > >
> > > [...]
> > >
> > > > +       switch (prog->expected_attach_type) {
> > > > +       case BPF_TRACE_RAW_TP:
> > > > +               /* bpf_sk_storage has no trace point */
> > > > +               return true;
> > > > +       case BPF_TRACE_FENTRY:
> > > > +       case BPF_TRACE_FEXIT:
> > > > +               btf_vmlinux = bpf_get_btf_vmlinux();
> > > > +               btf_id = prog->aux->attach_btf_id;
> > > > +               t = btf_type_by_id(btf_vmlinux, btf_id);
> > > > +               tname = btf_name_by_offset(btf_vmlinux, t->name_off);
> > > > +               return !strstr(tname, "sk_storage");
> > >
> > > I'm always feeling uneasy about substring checks... Also, KP just
> > > fixed the issue with string-based checks for LSM. Can we use a
> > > BTF_ID_SET of blacklisted functions instead?
> > KP one is different.  It accidentally whitelist-ed more than it should.
> >
> > It is a blacklist here.  It is actually cleaner and safer to blacklist
> > all functions with "sk_storage" and too pessimistic is fine here.
> 
> Fine for whom? Prefix check would be half-bad, but substring check is
> horrible. Suddenly "task_storage" (and anything related) would be also
> blacklisted. Let's do a prefix check at least.
> 

Agree, prefix check sounds like a good idea. But, just doing a quick
grep seems like it will need at least bpf_sk_storage and sk_storage to
catch everything.

Re: [PATCH bpf-next 2/3] bpf: Allow using bpf_sk_storage in FENTRY/FEXIT/RAW_TP

[KP Singh]

On Mon, Nov 9, 2020 at 9:32 PM John Fastabend <john.fastabend@gmail.com> wrote:
>
> Andrii Nakryiko wrote:
> > On Fri, Nov 6, 2020 at 5:52 PM Martin KaFai Lau <kafai@fb.com> wrote:
> > >
> > > On Fri, Nov 06, 2020 at 05:14:14PM -0800, Andrii Nakryiko wrote:
> > > > On Fri, Nov 6, 2020 at 2:08 PM Martin KaFai Lau <kafai@fb.com> wrote:
> > > > >
> > > > > This patch enables the FENTRY/FEXIT/RAW_TP tracing program to use
> > > > > the bpf_sk_storage_(get|delete) helper, so those tracing programs
> > > > > can access the sk's bpf_local_storage and the later selftest
> > > > > will show some examples.
> > > > >
> > > > > The bpf_sk_storage is currently used in bpf-tcp-cc, tc,
> > > > > cg sockops...etc which is running either in softirq or
> > > > > task context.
> > > > >
> > > > > This patch adds bpf_sk_storage_get_tracing_proto and
> > > > > bpf_sk_storage_delete_tracing_proto.  They will check
> > > > > in runtime that the helpers can only be called when serving
> > > > > softirq or running in a task context.  That should enable
> > > > > most common tracing use cases on sk.
> > > > >
> > > > > During the load time, the new tracing_allowed() function
> > > > > will ensure the tracing prog using the bpf_sk_storage_(get|delete)
> > > > > helper is not tracing any *sk_storage*() function itself.
> > > > > The sk is passed as "void *" when calling into bpf_local_storage.
> > > > >
> > > > > Signed-off-by: Martin KaFai Lau <kafai@fb.com>
> > > > > ---
> > > > >  include/net/bpf_sk_storage.h |  2 +
> > > > >  kernel/trace/bpf_trace.c     |  5 +++
> > > > >  net/core/bpf_sk_storage.c    | 73 ++++++++++++++++++++++++++++++++++++
> > > > >  3 files changed, 80 insertions(+)
> > > > >
> > > >
> > > > [...]
> > > >
> > > > > +       switch (prog->expected_attach_type) {
> > > > > +       case BPF_TRACE_RAW_TP:
> > > > > +               /* bpf_sk_storage has no trace point */
> > > > > +               return true;
> > > > > +       case BPF_TRACE_FENTRY:
> > > > > +       case BPF_TRACE_FEXIT:
> > > > > +               btf_vmlinux = bpf_get_btf_vmlinux();
> > > > > +               btf_id = prog->aux->attach_btf_id;
> > > > > +               t = btf_type_by_id(btf_vmlinux, btf_id);
> > > > > +               tname = btf_name_by_offset(btf_vmlinux, t->name_off);
> > > > > +               return !strstr(tname, "sk_storage");
> > > >
> > > > I'm always feeling uneasy about substring checks... Also, KP just
> > > > fixed the issue with string-based checks for LSM. Can we use a
> > > > BTF_ID_SET of blacklisted functions instead?
> > > KP one is different.  It accidentally whitelist-ed more than it should.
> > >
> > > It is a blacklist here.  It is actually cleaner and safer to blacklist
> > > all functions with "sk_storage" and too pessimistic is fine here.
> >
> > Fine for whom? Prefix check would be half-bad, but substring check is
> > horrible. Suddenly "task_storage" (and anything related) would be also
> > blacklisted. Let's do a prefix check at least.
> >
>
> Agree, prefix check sounds like a good idea. But, just doing a quick
> grep seems like it will need at least bpf_sk_storage and sk_storage to
> catch everything.

Is there any reason we are not using BTF ID sets and an allow list similar
to bpf_d_path helper? (apart from the obvious inconvenience of
needing to update the set in the kernel)

Re: [PATCH bpf-next 2/3] bpf: Allow using bpf_sk_storage in FENTRY/FEXIT/RAW_TP

[Martin KaFai Lau]

On Tue, Nov 10, 2020 at 11:01:12PM +0100, KP Singh wrote:
> On Mon, Nov 9, 2020 at 9:32 PM John Fastabend <john.fastabend@gmail.com> wrote:
> >
> > Andrii Nakryiko wrote:
> > > On Fri, Nov 6, 2020 at 5:52 PM Martin KaFai Lau <kafai@fb.com> wrote:
> > > >
> > > > On Fri, Nov 06, 2020 at 05:14:14PM -0800, Andrii Nakryiko wrote:
> > > > > On Fri, Nov 6, 2020 at 2:08 PM Martin KaFai Lau <kafai@fb.com> wrote:
> > > > > >
> > > > > > This patch enables the FENTRY/FEXIT/RAW_TP tracing program to use
> > > > > > the bpf_sk_storage_(get|delete) helper, so those tracing programs
> > > > > > can access the sk's bpf_local_storage and the later selftest
> > > > > > will show some examples.
> > > > > >
> > > > > > The bpf_sk_storage is currently used in bpf-tcp-cc, tc,
> > > > > > cg sockops...etc which is running either in softirq or
> > > > > > task context.
> > > > > >
> > > > > > This patch adds bpf_sk_storage_get_tracing_proto and
> > > > > > bpf_sk_storage_delete_tracing_proto.  They will check
> > > > > > in runtime that the helpers can only be called when serving
> > > > > > softirq or running in a task context.  That should enable
> > > > > > most common tracing use cases on sk.
> > > > > >
> > > > > > During the load time, the new tracing_allowed() function
> > > > > > will ensure the tracing prog using the bpf_sk_storage_(get|delete)
> > > > > > helper is not tracing any *sk_storage*() function itself.
> > > > > > The sk is passed as "void *" when calling into bpf_local_storage.
> > > > > >
> > > > > > Signed-off-by: Martin KaFai Lau <kafai@fb.com>
> > > > > > ---
> > > > > >  include/net/bpf_sk_storage.h |  2 +
> > > > > >  kernel/trace/bpf_trace.c     |  5 +++
> > > > > >  net/core/bpf_sk_storage.c    | 73 ++++++++++++++++++++++++++++++++++++
> > > > > >  3 files changed, 80 insertions(+)
> > > > > >
> > > > >
> > > > > [...]
> > > > >
> > > > > > +       switch (prog->expected_attach_type) {
> > > > > > +       case BPF_TRACE_RAW_TP:
> > > > > > +               /* bpf_sk_storage has no trace point */
> > > > > > +               return true;
> > > > > > +       case BPF_TRACE_FENTRY:
> > > > > > +       case BPF_TRACE_FEXIT:
> > > > > > +               btf_vmlinux = bpf_get_btf_vmlinux();
> > > > > > +               btf_id = prog->aux->attach_btf_id;
> > > > > > +               t = btf_type_by_id(btf_vmlinux, btf_id);
> > > > > > +               tname = btf_name_by_offset(btf_vmlinux, t->name_off);
> > > > > > +               return !strstr(tname, "sk_storage");
> > > > >
> > > > > I'm always feeling uneasy about substring checks... Also, KP just
> > > > > fixed the issue with string-based checks for LSM. Can we use a
> > > > > BTF_ID_SET of blacklisted functions instead?
> > > > KP one is different.  It accidentally whitelist-ed more than it should.
> > > >
> > > > It is a blacklist here.  It is actually cleaner and safer to blacklist
> > > > all functions with "sk_storage" and too pessimistic is fine here.
> > >
> > > Fine for whom? Prefix check would be half-bad, but substring check is
> > > horrible. Suddenly "task_storage" (and anything related) would be also
> > > blacklisted. Let's do a prefix check at least.
> > >
> >
> > Agree, prefix check sounds like a good idea. But, just doing a quick
> > grep seems like it will need at least bpf_sk_storage and sk_storage to
> > catch everything.
> 
> Is there any reason we are not using BTF ID sets and an allow list similar
> to bpf_d_path helper? (apart from the obvious inconvenience of
> needing to update the set in the kernel)
It is a blacklist here, a small recap from commit message.

> During the load time, the new tracing_allowed() function
> will ensure the tracing prog using the bpf_sk_storage_(get|delete)
> helper is not tracing any *sk_storage*() function itself.
> The sk is passed as "void *" when calling into bpf_local_storage.

Both BTF_ID and string-based (either prefix/substr) will work.

The intention is to first disallow a tracing program from tracing
any function in bpf_sk_storage.c and also calling the
bpf_sk_storage_(get|delete) helper at the same time.
This blacklist can be revisited later if there would
be a use case in some of the blacklist-ed
functions (which I doubt).

To use BTF_ID, it needs to consider about if the current (and future)
bpf_sk_storage function can be used in BTF_ID or not:
static, global/external, or inlined.

If BTF_ID is the best way for doing all black/white list, I don't mind
either.  I could force some to inline and we need to remember
to revisit the blacklist when the scope of fentry/fexit tracable
function changed, e.g. when static function becomes traceable
later.  The future changes to bpf_sk_storage.c will need to
adjust this list also.

Re: [PATCH bpf-next 2/3] bpf: Allow using bpf_sk_storage in FENTRY/FEXIT/RAW_TP

[Andrii Nakryiko]

On Tue, Nov 10, 2020 at 3:43 PM Martin KaFai Lau <kafai@fb.com> wrote:
>
> On Tue, Nov 10, 2020 at 11:01:12PM +0100, KP Singh wrote:
> > On Mon, Nov 9, 2020 at 9:32 PM John Fastabend <john.fastabend@gmail.com> wrote:
> > >
> > > Andrii Nakryiko wrote:
> > > > On Fri, Nov 6, 2020 at 5:52 PM Martin KaFai Lau <kafai@fb.com> wrote:
> > > > >
> > > > > On Fri, Nov 06, 2020 at 05:14:14PM -0800, Andrii Nakryiko wrote:
> > > > > > On Fri, Nov 6, 2020 at 2:08 PM Martin KaFai Lau <kafai@fb.com> wrote:
> > > > > > >
> > > > > > > This patch enables the FENTRY/FEXIT/RAW_TP tracing program to use
> > > > > > > the bpf_sk_storage_(get|delete) helper, so those tracing programs
> > > > > > > can access the sk's bpf_local_storage and the later selftest
> > > > > > > will show some examples.
> > > > > > >
> > > > > > > The bpf_sk_storage is currently used in bpf-tcp-cc, tc,
> > > > > > > cg sockops...etc which is running either in softirq or
> > > > > > > task context.
> > > > > > >
> > > > > > > This patch adds bpf_sk_storage_get_tracing_proto and
> > > > > > > bpf_sk_storage_delete_tracing_proto.  They will check
> > > > > > > in runtime that the helpers can only be called when serving
> > > > > > > softirq or running in a task context.  That should enable
> > > > > > > most common tracing use cases on sk.
> > > > > > >
> > > > > > > During the load time, the new tracing_allowed() function
> > > > > > > will ensure the tracing prog using the bpf_sk_storage_(get|delete)
> > > > > > > helper is not tracing any *sk_storage*() function itself.
> > > > > > > The sk is passed as "void *" when calling into bpf_local_storage.
> > > > > > >
> > > > > > > Signed-off-by: Martin KaFai Lau <kafai@fb.com>
> > > > > > > ---
> > > > > > >  include/net/bpf_sk_storage.h |  2 +
> > > > > > >  kernel/trace/bpf_trace.c     |  5 +++
> > > > > > >  net/core/bpf_sk_storage.c    | 73 ++++++++++++++++++++++++++++++++++++
> > > > > > >  3 files changed, 80 insertions(+)
> > > > > > >
> > > > > >
> > > > > > [...]
> > > > > >
> > > > > > > +       switch (prog->expected_attach_type) {
> > > > > > > +       case BPF_TRACE_RAW_TP:
> > > > > > > +               /* bpf_sk_storage has no trace point */
> > > > > > > +               return true;
> > > > > > > +       case BPF_TRACE_FENTRY:
> > > > > > > +       case BPF_TRACE_FEXIT:
> > > > > > > +               btf_vmlinux = bpf_get_btf_vmlinux();
> > > > > > > +               btf_id = prog->aux->attach_btf_id;
> > > > > > > +               t = btf_type_by_id(btf_vmlinux, btf_id);
> > > > > > > +               tname = btf_name_by_offset(btf_vmlinux, t->name_off);
> > > > > > > +               return !strstr(tname, "sk_storage");
> > > > > >
> > > > > > I'm always feeling uneasy about substring checks... Also, KP just
> > > > > > fixed the issue with string-based checks for LSM. Can we use a
> > > > > > BTF_ID_SET of blacklisted functions instead?
> > > > > KP one is different.  It accidentally whitelist-ed more than it should.
> > > > >
> > > > > It is a blacklist here.  It is actually cleaner and safer to blacklist
> > > > > all functions with "sk_storage" and too pessimistic is fine here.
> > > >
> > > > Fine for whom? Prefix check would be half-bad, but substring check is
> > > > horrible. Suddenly "task_storage" (and anything related) would be also
> > > > blacklisted. Let's do a prefix check at least.
> > > >
> > >
> > > Agree, prefix check sounds like a good idea. But, just doing a quick
> > > grep seems like it will need at least bpf_sk_storage and sk_storage to
> > > catch everything.
> >
> > Is there any reason we are not using BTF ID sets and an allow list similar
> > to bpf_d_path helper? (apart from the obvious inconvenience of
> > needing to update the set in the kernel)
> It is a blacklist here, a small recap from commit message.
>
> > During the load time, the new tracing_allowed() function
> > will ensure the tracing prog using the bpf_sk_storage_(get|delete)
> > helper is not tracing any *sk_storage*() function itself.
> > The sk is passed as "void *" when calling into bpf_local_storage.
>
> Both BTF_ID and string-based (either prefix/substr) will work.
>
> The intention is to first disallow a tracing program from tracing
> any function in bpf_sk_storage.c and also calling the
> bpf_sk_storage_(get|delete) helper at the same time.
> This blacklist can be revisited later if there would
> be a use case in some of the blacklist-ed
> functions (which I doubt).
>
> To use BTF_ID, it needs to consider about if the current (and future)
> bpf_sk_storage function can be used in BTF_ID or not:
> static, global/external, or inlined.
>
> If BTF_ID is the best way for doing all black/white list, I don't mind
> either.  I could force some to inline and we need to remember
> to revisit the blacklist when the scope of fentry/fexit tracable
> function changed, e.g. when static function becomes traceable

You can consider static functions traceable already. Arnaldo landed a
change a day or so ago in pahole that exposes static functions in BTF
and makes it possible to fentry/fexit attach them.

> later.  The future changes to bpf_sk_storage.c will need to
> adjust this list also.

Re: [PATCH bpf-next 2/3] bpf: Allow using bpf_sk_storage in FENTRY/FEXIT/RAW_TP

[Martin KaFai Lau]

On Tue, Nov 10, 2020 at 03:53:13PM -0800, Andrii Nakryiko wrote:
> On Tue, Nov 10, 2020 at 3:43 PM Martin KaFai Lau <kafai@fb.com> wrote:
> >
> > On Tue, Nov 10, 2020 at 11:01:12PM +0100, KP Singh wrote:
> > > On Mon, Nov 9, 2020 at 9:32 PM John Fastabend <john.fastabend@gmail.com> wrote:
> > > >
> > > > Andrii Nakryiko wrote:
> > > > > On Fri, Nov 6, 2020 at 5:52 PM Martin KaFai Lau <kafai@fb.com> wrote:
> > > > > >
> > > > > > On Fri, Nov 06, 2020 at 05:14:14PM -0800, Andrii Nakryiko wrote:
> > > > > > > On Fri, Nov 6, 2020 at 2:08 PM Martin KaFai Lau <kafai@fb.com> wrote:
> > > > > > > >
> > > > > > > > This patch enables the FENTRY/FEXIT/RAW_TP tracing program to use
> > > > > > > > the bpf_sk_storage_(get|delete) helper, so those tracing programs
> > > > > > > > can access the sk's bpf_local_storage and the later selftest
> > > > > > > > will show some examples.
> > > > > > > >
> > > > > > > > The bpf_sk_storage is currently used in bpf-tcp-cc, tc,
> > > > > > > > cg sockops...etc which is running either in softirq or
> > > > > > > > task context.
> > > > > > > >
> > > > > > > > This patch adds bpf_sk_storage_get_tracing_proto and
> > > > > > > > bpf_sk_storage_delete_tracing_proto.  They will check
> > > > > > > > in runtime that the helpers can only be called when serving
> > > > > > > > softirq or running in a task context.  That should enable
> > > > > > > > most common tracing use cases on sk.
> > > > > > > >
> > > > > > > > During the load time, the new tracing_allowed() function
> > > > > > > > will ensure the tracing prog using the bpf_sk_storage_(get|delete)
> > > > > > > > helper is not tracing any *sk_storage*() function itself.
> > > > > > > > The sk is passed as "void *" when calling into bpf_local_storage.
> > > > > > > >
> > > > > > > > Signed-off-by: Martin KaFai Lau <kafai@fb.com>
> > > > > > > > ---
> > > > > > > >  include/net/bpf_sk_storage.h |  2 +
> > > > > > > >  kernel/trace/bpf_trace.c     |  5 +++
> > > > > > > >  net/core/bpf_sk_storage.c    | 73 ++++++++++++++++++++++++++++++++++++
> > > > > > > >  3 files changed, 80 insertions(+)
> > > > > > > >
> > > > > > >
> > > > > > > [...]
> > > > > > >
> > > > > > > > +       switch (prog->expected_attach_type) {
> > > > > > > > +       case BPF_TRACE_RAW_TP:
> > > > > > > > +               /* bpf_sk_storage has no trace point */
> > > > > > > > +               return true;
> > > > > > > > +       case BPF_TRACE_FENTRY:
> > > > > > > > +       case BPF_TRACE_FEXIT:
> > > > > > > > +               btf_vmlinux = bpf_get_btf_vmlinux();
> > > > > > > > +               btf_id = prog->aux->attach_btf_id;
> > > > > > > > +               t = btf_type_by_id(btf_vmlinux, btf_id);
> > > > > > > > +               tname = btf_name_by_offset(btf_vmlinux, t->name_off);
> > > > > > > > +               return !strstr(tname, "sk_storage");
> > > > > > >
> > > > > > > I'm always feeling uneasy about substring checks... Also, KP just
> > > > > > > fixed the issue with string-based checks for LSM. Can we use a
> > > > > > > BTF_ID_SET of blacklisted functions instead?
> > > > > > KP one is different.  It accidentally whitelist-ed more than it should.
> > > > > >
> > > > > > It is a blacklist here.  It is actually cleaner and safer to blacklist
> > > > > > all functions with "sk_storage" and too pessimistic is fine here.
> > > > >
> > > > > Fine for whom? Prefix check would be half-bad, but substring check is
> > > > > horrible. Suddenly "task_storage" (and anything related) would be also
> > > > > blacklisted. Let's do a prefix check at least.
> > > > >
> > > >
> > > > Agree, prefix check sounds like a good idea. But, just doing a quick
> > > > grep seems like it will need at least bpf_sk_storage and sk_storage to
> > > > catch everything.
> > >
> > > Is there any reason we are not using BTF ID sets and an allow list similar
> > > to bpf_d_path helper? (apart from the obvious inconvenience of
> > > needing to update the set in the kernel)
> > It is a blacklist here, a small recap from commit message.
> >
> > > During the load time, the new tracing_allowed() function
> > > will ensure the tracing prog using the bpf_sk_storage_(get|delete)
> > > helper is not tracing any *sk_storage*() function itself.
> > > The sk is passed as "void *" when calling into bpf_local_storage.
> >
> > Both BTF_ID and string-based (either prefix/substr) will work.
> >
> > The intention is to first disallow a tracing program from tracing
> > any function in bpf_sk_storage.c and also calling the
> > bpf_sk_storage_(get|delete) helper at the same time.
> > This blacklist can be revisited later if there would
> > be a use case in some of the blacklist-ed
> > functions (which I doubt).
> >
> > To use BTF_ID, it needs to consider about if the current (and future)
> > bpf_sk_storage function can be used in BTF_ID or not:
> > static, global/external, or inlined.
> >
> > If BTF_ID is the best way for doing all black/white list, I don't mind
> > either.  I could force some to inline and we need to remember
> > to revisit the blacklist when the scope of fentry/fexit tracable
> > function changed, e.g. when static function becomes traceable
> 
> You can consider static functions traceable already. Arnaldo landed a
> change a day or so ago in pahole that exposes static functions in BTF
> and makes it possible to fentry/fexit attach them.
Good to know.

Is all static traceable (and can be used in BTF_ID)?

Re: [PATCH bpf-next 2/3] bpf: Allow using bpf_sk_storage in FENTRY/FEXIT/RAW_TP

[Andrii Nakryiko]

On Tue, Nov 10, 2020 at 4:07 PM Martin KaFai Lau <kafai@fb.com> wrote:
>
> On Tue, Nov 10, 2020 at 03:53:13PM -0800, Andrii Nakryiko wrote:
> > On Tue, Nov 10, 2020 at 3:43 PM Martin KaFai Lau <kafai@fb.com> wrote:
> > >
> > > On Tue, Nov 10, 2020 at 11:01:12PM +0100, KP Singh wrote:
> > > > On Mon, Nov 9, 2020 at 9:32 PM John Fastabend <john.fastabend@gmail.com> wrote:
> > > > >
> > > > > Andrii Nakryiko wrote:
> > > > > > On Fri, Nov 6, 2020 at 5:52 PM Martin KaFai Lau <kafai@fb.com> wrote:
> > > > > > >
> > > > > > > On Fri, Nov 06, 2020 at 05:14:14PM -0800, Andrii Nakryiko wrote:
> > > > > > > > On Fri, Nov 6, 2020 at 2:08 PM Martin KaFai Lau <kafai@fb.com> wrote:
> > > > > > > > >
> > > > > > > > > This patch enables the FENTRY/FEXIT/RAW_TP tracing program to use
> > > > > > > > > the bpf_sk_storage_(get|delete) helper, so those tracing programs
> > > > > > > > > can access the sk's bpf_local_storage and the later selftest
> > > > > > > > > will show some examples.
> > > > > > > > >
> > > > > > > > > The bpf_sk_storage is currently used in bpf-tcp-cc, tc,
> > > > > > > > > cg sockops...etc which is running either in softirq or
> > > > > > > > > task context.
> > > > > > > > >
> > > > > > > > > This patch adds bpf_sk_storage_get_tracing_proto and
> > > > > > > > > bpf_sk_storage_delete_tracing_proto.  They will check
> > > > > > > > > in runtime that the helpers can only be called when serving
> > > > > > > > > softirq or running in a task context.  That should enable
> > > > > > > > > most common tracing use cases on sk.
> > > > > > > > >
> > > > > > > > > During the load time, the new tracing_allowed() function
> > > > > > > > > will ensure the tracing prog using the bpf_sk_storage_(get|delete)
> > > > > > > > > helper is not tracing any *sk_storage*() function itself.
> > > > > > > > > The sk is passed as "void *" when calling into bpf_local_storage.
> > > > > > > > >
> > > > > > > > > Signed-off-by: Martin KaFai Lau <kafai@fb.com>
> > > > > > > > > ---
> > > > > > > > >  include/net/bpf_sk_storage.h |  2 +
> > > > > > > > >  kernel/trace/bpf_trace.c     |  5 +++
> > > > > > > > >  net/core/bpf_sk_storage.c    | 73 ++++++++++++++++++++++++++++++++++++
> > > > > > > > >  3 files changed, 80 insertions(+)
> > > > > > > > >
> > > > > > > >
> > > > > > > > [...]
> > > > > > > >
> > > > > > > > > +       switch (prog->expected_attach_type) {
> > > > > > > > > +       case BPF_TRACE_RAW_TP:
> > > > > > > > > +               /* bpf_sk_storage has no trace point */
> > > > > > > > > +               return true;
> > > > > > > > > +       case BPF_TRACE_FENTRY:
> > > > > > > > > +       case BPF_TRACE_FEXIT:
> > > > > > > > > +               btf_vmlinux = bpf_get_btf_vmlinux();
> > > > > > > > > +               btf_id = prog->aux->attach_btf_id;
> > > > > > > > > +               t = btf_type_by_id(btf_vmlinux, btf_id);
> > > > > > > > > +               tname = btf_name_by_offset(btf_vmlinux, t->name_off);
> > > > > > > > > +               return !strstr(tname, "sk_storage");
> > > > > > > >
> > > > > > > > I'm always feeling uneasy about substring checks... Also, KP just
> > > > > > > > fixed the issue with string-based checks for LSM. Can we use a
> > > > > > > > BTF_ID_SET of blacklisted functions instead?
> > > > > > > KP one is different.  It accidentally whitelist-ed more than it should.
> > > > > > >
> > > > > > > It is a blacklist here.  It is actually cleaner and safer to blacklist
> > > > > > > all functions with "sk_storage" and too pessimistic is fine here.
> > > > > >
> > > > > > Fine for whom? Prefix check would be half-bad, but substring check is
> > > > > > horrible. Suddenly "task_storage" (and anything related) would be also
> > > > > > blacklisted. Let's do a prefix check at least.
> > > > > >
> > > > >
> > > > > Agree, prefix check sounds like a good idea. But, just doing a quick
> > > > > grep seems like it will need at least bpf_sk_storage and sk_storage to
> > > > > catch everything.
> > > >
> > > > Is there any reason we are not using BTF ID sets and an allow list similar
> > > > to bpf_d_path helper? (apart from the obvious inconvenience of
> > > > needing to update the set in the kernel)
> > > It is a blacklist here, a small recap from commit message.
> > >
> > > > During the load time, the new tracing_allowed() function
> > > > will ensure the tracing prog using the bpf_sk_storage_(get|delete)
> > > > helper is not tracing any *sk_storage*() function itself.
> > > > The sk is passed as "void *" when calling into bpf_local_storage.
> > >
> > > Both BTF_ID and string-based (either prefix/substr) will work.
> > >
> > > The intention is to first disallow a tracing program from tracing
> > > any function in bpf_sk_storage.c and also calling the
> > > bpf_sk_storage_(get|delete) helper at the same time.
> > > This blacklist can be revisited later if there would
> > > be a use case in some of the blacklist-ed
> > > functions (which I doubt).
> > >
> > > To use BTF_ID, it needs to consider about if the current (and future)
> > > bpf_sk_storage function can be used in BTF_ID or not:
> > > static, global/external, or inlined.
> > >
> > > If BTF_ID is the best way for doing all black/white list, I don't mind
> > > either.  I could force some to inline and we need to remember
> > > to revisit the blacklist when the scope of fentry/fexit tracable
> > > function changed, e.g. when static function becomes traceable
> >
> > You can consider static functions traceable already. Arnaldo landed a
> > change a day or so ago in pahole that exposes static functions in BTF
> > and makes it possible to fentry/fexit attach them.
> Good to know.
>
> Is all static traceable (and can be used in BTF_ID)?

Only those that end up not inlined, I think. Similarly as with
kprobes. pahole actually checks mcount section to keep only those that
are attachable with ftrace. See [0] for patches.

  [0] https://patchwork.kernel.org/project/netdevbpf/list/?series=379377&state=*

Re: [PATCH bpf-next 2/3] bpf: Allow using bpf_sk_storage in FENTRY/FEXIT/RAW_TP

[Martin KaFai Lau]

On Tue, Nov 10, 2020 at 04:17:06PM -0800, Andrii Nakryiko wrote:
> On Tue, Nov 10, 2020 at 4:07 PM Martin KaFai Lau <kafai@fb.com> wrote:
> >
> > On Tue, Nov 10, 2020 at 03:53:13PM -0800, Andrii Nakryiko wrote:
> > > On Tue, Nov 10, 2020 at 3:43 PM Martin KaFai Lau <kafai@fb.com> wrote:
> > > >
> > > > On Tue, Nov 10, 2020 at 11:01:12PM +0100, KP Singh wrote:
> > > > > On Mon, Nov 9, 2020 at 9:32 PM John Fastabend <john.fastabend@gmail.com> wrote:
> > > > > >
> > > > > > Andrii Nakryiko wrote:
> > > > > > > On Fri, Nov 6, 2020 at 5:52 PM Martin KaFai Lau <kafai@fb.com> wrote:
> > > > > > > >
> > > > > > > > On Fri, Nov 06, 2020 at 05:14:14PM -0800, Andrii Nakryiko wrote:
> > > > > > > > > On Fri, Nov 6, 2020 at 2:08 PM Martin KaFai Lau <kafai@fb.com> wrote:
> > > > > > > > > >
> > > > > > > > > > This patch enables the FENTRY/FEXIT/RAW_TP tracing program to use
> > > > > > > > > > the bpf_sk_storage_(get|delete) helper, so those tracing programs
> > > > > > > > > > can access the sk's bpf_local_storage and the later selftest
> > > > > > > > > > will show some examples.
> > > > > > > > > >
> > > > > > > > > > The bpf_sk_storage is currently used in bpf-tcp-cc, tc,
> > > > > > > > > > cg sockops...etc which is running either in softirq or
> > > > > > > > > > task context.
> > > > > > > > > >
> > > > > > > > > > This patch adds bpf_sk_storage_get_tracing_proto and
> > > > > > > > > > bpf_sk_storage_delete_tracing_proto.  They will check
> > > > > > > > > > in runtime that the helpers can only be called when serving
> > > > > > > > > > softirq or running in a task context.  That should enable
> > > > > > > > > > most common tracing use cases on sk.
> > > > > > > > > >
> > > > > > > > > > During the load time, the new tracing_allowed() function
> > > > > > > > > > will ensure the tracing prog using the bpf_sk_storage_(get|delete)
> > > > > > > > > > helper is not tracing any *sk_storage*() function itself.
> > > > > > > > > > The sk is passed as "void *" when calling into bpf_local_storage.
> > > > > > > > > >
> > > > > > > > > > Signed-off-by: Martin KaFai Lau <kafai@fb.com>
> > > > > > > > > > ---
> > > > > > > > > >  include/net/bpf_sk_storage.h |  2 +
> > > > > > > > > >  kernel/trace/bpf_trace.c     |  5 +++
> > > > > > > > > >  net/core/bpf_sk_storage.c    | 73 ++++++++++++++++++++++++++++++++++++
> > > > > > > > > >  3 files changed, 80 insertions(+)
> > > > > > > > > >
> > > > > > > > >
> > > > > > > > > [...]
> > > > > > > > >
> > > > > > > > > > +       switch (prog->expected_attach_type) {
> > > > > > > > > > +       case BPF_TRACE_RAW_TP:
> > > > > > > > > > +               /* bpf_sk_storage has no trace point */
> > > > > > > > > > +               return true;
> > > > > > > > > > +       case BPF_TRACE_FENTRY:
> > > > > > > > > > +       case BPF_TRACE_FEXIT:
> > > > > > > > > > +               btf_vmlinux = bpf_get_btf_vmlinux();
> > > > > > > > > > +               btf_id = prog->aux->attach_btf_id;
> > > > > > > > > > +               t = btf_type_by_id(btf_vmlinux, btf_id);
> > > > > > > > > > +               tname = btf_name_by_offset(btf_vmlinux, t->name_off);
> > > > > > > > > > +               return !strstr(tname, "sk_storage");
> > > > > > > > >
> > > > > > > > > I'm always feeling uneasy about substring checks... Also, KP just
> > > > > > > > > fixed the issue with string-based checks for LSM. Can we use a
> > > > > > > > > BTF_ID_SET of blacklisted functions instead?
> > > > > > > > KP one is different.  It accidentally whitelist-ed more than it should.
> > > > > > > >
> > > > > > > > It is a blacklist here.  It is actually cleaner and safer to blacklist
> > > > > > > > all functions with "sk_storage" and too pessimistic is fine here.
> > > > > > >
> > > > > > > Fine for whom? Prefix check would be half-bad, but substring check is
> > > > > > > horrible. Suddenly "task_storage" (and anything related) would be also
> > > > > > > blacklisted. Let's do a prefix check at least.
> > > > > > >
> > > > > >
> > > > > > Agree, prefix check sounds like a good idea. But, just doing a quick
> > > > > > grep seems like it will need at least bpf_sk_storage and sk_storage to
> > > > > > catch everything.
> > > > >
> > > > > Is there any reason we are not using BTF ID sets and an allow list similar
> > > > > to bpf_d_path helper? (apart from the obvious inconvenience of
> > > > > needing to update the set in the kernel)
> > > > It is a blacklist here, a small recap from commit message.
> > > >
> > > > > During the load time, the new tracing_allowed() function
> > > > > will ensure the tracing prog using the bpf_sk_storage_(get|delete)
> > > > > helper is not tracing any *sk_storage*() function itself.
> > > > > The sk is passed as "void *" when calling into bpf_local_storage.
> > > >
> > > > Both BTF_ID and string-based (either prefix/substr) will work.
> > > >
> > > > The intention is to first disallow a tracing program from tracing
> > > > any function in bpf_sk_storage.c and also calling the
> > > > bpf_sk_storage_(get|delete) helper at the same time.
> > > > This blacklist can be revisited later if there would
> > > > be a use case in some of the blacklist-ed
> > > > functions (which I doubt).
> > > >
> > > > To use BTF_ID, it needs to consider about if the current (and future)
> > > > bpf_sk_storage function can be used in BTF_ID or not:
> > > > static, global/external, or inlined.
> > > >
> > > > If BTF_ID is the best way for doing all black/white list, I don't mind
> > > > either.  I could force some to inline and we need to remember
> > > > to revisit the blacklist when the scope of fentry/fexit tracable
> > > > function changed, e.g. when static function becomes traceable
> > >
> > > You can consider static functions traceable already. Arnaldo landed a
> > > change a day or so ago in pahole that exposes static functions in BTF
> > > and makes it possible to fentry/fexit attach them.
> > Good to know.
> >
> > Is all static traceable (and can be used in BTF_ID)?
> 
> Only those that end up not inlined, I think. Similarly as with
> kprobes. pahole actually checks mcount section to keep only those that
> are attachable with ftrace. See [0] for patches.
> 
>   [0] https://patchwork.kernel.org/project/netdevbpf/list/?series=379377&state=*
I will go with the prefix then to avoid tagging functions with
inline/noinline.