Re: [PATCH bpf-next v4 10/18] bpf: Fix interaction between stack argument PTR_TO_STACK and dead slot poisoning

Yonghong Song
2026-04-13T16:36:10Z

On 4/11/26 10:43 PM, bot+bpf-ci@kernel.org wrote:
> commit 7570556100592966981ed4784bb775307405e5f0
> Author: Yonghong Song <yonghong.song@linux.dev>
>
> bpf: Fix interaction between stack argument PTR_TO_STACK and dead slot poisoning
>
> This commit fixes a false rejection where the verifier rejects valid
> cross-frame stack reads because the static liveness pass cannot track
> indirect references through stack-argument-passed pointers, causing
> parent frame slots to be incorrectly poisoned.
>
> This patch fixes a bug introduced by an earlier commit in the same
> series but does not include a Fixes: tag. The issue is introduced
> when stack argument support is added, because BPF_REG_STACK_ARG_BASE
> (r12) is not tracked by the liveness pass. Without attribution, it
> is harder to identify the scope of the fix during bisection or
> stable backporting.
>
> Would it make sense to add:
>
> Fixes: 442d7da1edaf ("bpf: Support stack arguments for bpf functions")

I will swap this patch vs. the previous patch to avoid bisection issue.
There is no need to have Fixes tag then.

>
>
> ---
> AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
> See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
>
> CI run summary: https://github.com/kernel-patches/bpf/actions/runs/24299298635