Re: [PATCH bpf-next v2 09/23] bpf: Extend liveness analysis to track stack argument slots

[Yonghong Song <yonghong.song@linux.dev>]

On 5/7/26 12:11 AM, bot+bpf-ci@kernel.org wrote:
> commit 66a19f95afbdbdfe3c3c887c8656037ebcca1be1
> Author: Yonghong Song <yonghong.song@linux.dev>
>
> bpf: Extend liveness analysis to track stack argument slots
>
> BPF_REG_PARAMS (R11) is at index MAX_BPF_REG, which is beyond the
> register tracking arrays in const_fold.c and liveness.c. Handle it
> explicitly to avoid out-of-bounds accesses.
>
> Extend the arg tracking dataflow to cover stack arg slots. Otherwise,
> pointers passed through stack args are invisible to liveness, causing
> the pointed-to stack slots to be incorrectly poisoned.

We should be okay since is_stack_arg_{st,stx,ldx} will explicitly
handle the liveness and then return. So there is no out-of-bounds access.

>
> This commit fixes a bug introduced in c364b7a0f7ae ("bpf: Support stack
> arguments for bpf functions"). That earlier commit added support for
> stack arguments but did not extend the liveness analysis to track them,
> resulting in incorrect poisoning of stack slots when pointers are passed
> through stack arguments.
>
> Should this commit include a Fixes tag referencing c364b7a0f7ae? The
> commit message describes fixing out-of-bounds accesses and incorrect
> poisoning that were introduced by the stack argument support.
>
> Suggested: Fixes: c364b7a0f7ae ("bpf: Support stack arguments for bpf functions")
>
>
> ---
> 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/25523765323