[PATCH v3 1/1] bpf: Ensure correct locking around vulnerable function find_vpid()

* [PATCH v3 1/1] bpf: Ensure correct locking around vulnerable function find_vpid()
@ 2022-09-12 13:38 Lee Jones
  2022-09-12 14:55 ` Yonghong Song
  2022-09-16 16:10 ` patchwork-bot+netdevbpf
  0 siblings, 2 replies; 5+ messages in thread
From: Lee Jones @ 2022-09-12 13:38 UTC (permalink / raw)
  To: lee
  Cc: linux-kernel, Jiri Olsa, Alexei Starovoitov, Daniel Borkmann,
	John Fastabend, Andrii Nakryiko, Martin KaFai Lau, Song Liu,
	Yonghong Song, KP Singh, Stanislav Fomichev, Hao Luo, bpf

The documentation for find_vpid() clearly states:

  "Must be called with the tasklist_lock or rcu_read_lock() held."

Presently we do neither.

Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Martin KaFai Lau <martin.lau@linux.dev>
Cc: Song Liu <song@kernel.org>
Cc: Yonghong Song <yhs@fb.com>
Cc: KP Singh <kpsingh@kernel.org>
Cc: Stanislav Fomichev <sdf@google.com>
Cc: Hao Luo <haoluo@google.com>
Cc: bpf@vger.kernel.org
Fixes: 41bdc4b40ed6f ("bpf: introduce bpf subcommand BPF_TASK_FD_QUERY")
Signed-off-by: Lee Jones <lee@kernel.org>
---

v2 => v3:
  * Changed strategy from find_get_pid() to rcu_read_{un}lock()
  * Removed Jiri's Ack

v1 => v2:
  * Commit log update - no code differences

 kernel/bpf/syscall.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 69be1c612daa5..d5c77c021c043 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -4399,7 +4399,9 @@ static int bpf_task_fd_query(const union bpf_attr *attr,
 	if (attr->task_fd_query.flags != 0)
 		return -EINVAL;
 
+	rcu_read_lock();
 	task = get_pid_task(find_vpid(pid), PIDTYPE_PID);
+	rcu_read_unlock();
 	if (!task)
 		return -ENOENT;
 
-- 
2.37.2.789.g6183377224-goog


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