UPSTREAM: bpf: Ensure correct locking around vulnerable function find_vpid()

[ Upstream commit 83c10cc362d91c0d8d25e60779ee52fdbbf3894d ]

The documentation for find_vpid() clearly states:

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

Presently we do neither for find_vpid() instance in bpf_task_fd_query().
Add proper rcu_read_lock/unlock() to fix the issue.

Bug: 232939090
Fixes: 41bdc4b4 ("bpf: introduce bpf subcommand BPF_TASK_FD_QUERY")
Signed-off-by: Lee Jones <lee@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20220912133855.1218900-1-lee@kernel.org


Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Lee Jones <joneslee@google.com>
Change-Id: I517b52d97a22b92be1a479279067ddb7b84efbba