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

From: Yonghong Song
Date: Mon Sep 12 2022 - 12:02:57 EST




On 9/12/22 4:14 PM, Lee Jones wrote:
On Mon, 12 Sep 2022, Yonghong Song wrote:
On 9/12/22 2:38 PM, Lee Jones wrote:
The documentation for find_vpid() clearly states:


No need for the above extra line.

The intentional blank formatting line?

The commit message would look worse without it.

Is this really a blocker?

Not a blocker. Just a suggestion. I won't enforce it
if you do have this extra line.


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

Presently we do neither.

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

I can expand this.

Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Cc: John Fastabend <john.fastabend@xxxxxxxxx>
Cc: Andrii Nakryiko <andrii@xxxxxxxxxx>
Cc: Martin KaFai Lau <martin.lau@xxxxxxxxx>
Cc: Song Liu <song@xxxxxxxxxx>
Cc: Yonghong Song <yhs@xxxxxx>
Cc: KP Singh <kpsingh@xxxxxxxxxx>
Cc: Stanislav Fomichev <sdf@xxxxxxxxxx>
Cc: Hao Luo <haoluo@xxxxxxxxxx>
Cc: bpf@xxxxxxxxxxxxxxx
Fixes: 41bdc4b40ed6f ("bpf: introduce bpf subcommand BPF_TASK_FD_QUERY")
Signed-off-by: Lee Jones <lee@xxxxxxxxxx>

Ack with above a few suggestions for the commit message.

Acked-by: Yonghong Song <yhs@xxxxxx>