From: Lee Jones <lee@kernel.org>
Date: Mon, 12 Sep 2022 13:38:55 +0000 (+0100)
Subject: bpf: Ensure correct locking around vulnerable function find_vpid()
X-Git-Tag: v6.1-rc5~319^2~1^2~2^2~3
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=83c10cc362d91c0d8d25e60779ee52fdbbf3894d;p=platform%2Fkernel%2Flinux-starfive.git

bpf: Ensure correct locking around vulnerable function find_vpid()

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.

Fixes: 41bdc4b40ed6f ("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
---

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 2776062..1bd18af 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -4395,7 +4395,9 @@ 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;