From: "Alexei Starovoitov" <alexei.starovoitov@gmail.com>
To: <bot+bpf-ci@kernel.org>, <yonghong.song@linux.dev>,
<bpf@vger.kernel.org>
Cc: <ast@kernel.org>, <andrii@kernel.org>, <daniel@iogearbox.net>,
<kernel-team@fb.com>, <martin.lau@kernel.org>,
<sashiko-bot@kernel.org>, <eddyz87@gmail.com>, <clm@meta.com>,
<ihor.solodrai@linux.dev>
Subject: Re: [PATCH bpf-next 1/2] bpf: Validate outgoing stack args when btf_prepare_func_args fails
Date: Thu, 14 May 2026 16:53:05 -0700 [thread overview]
Message-ID: <DIISYMB87J47.2N64UTCAGDXFA@gmail.com> (raw)
In-Reply-To: <b3a04daccb7920ec037fa1e814c82d13b626bf24ceed7e03cf54624f9bf477de@mail.kernel.org>
On Thu May 14, 2026 at 12:37 PM PDT, bot+bpf-ci wrote:
>> commit 284cf62e75bd5632d61c528e48fe3f738870b269
>> Author: Yonghong Song <yonghong.song@linux.dev>
>>
>> bpf: Validate outgoing stack args when btf_prepare_func_args fails
>>
>> btf_prepare_func_args() sets sub->arg_cnt before validating arg types.
>> If validation fails (e.g. unsupported pointer type in a static subprog),
>> check_outgoing_stack_args() is skipped because btf_check_func_arg_match()
>> returns early. For static subprogs, check_func_call() ignores non-EFAULT
>> errors and proceeds with the call.
>>
>> This causes the callee to read stack arg slots that the caller never
>> stored or not initialized, potentially dereferencing NULL caller->stack_arg_regs
>> or getting no-initialized value.
>>
>> To fix the issue, when btf_prepare_func_args() fails and the subprog expects
>> stack args, call check_outgoing_stack_args() to verify the caller initialized
>> the slots. Return -EFAULT on failure so the error is not ignored.
>>
>> Reported-by: Sashiko <sashiko-bot@kernel.org>
>> Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
>
> This looks like a bug fix for stack argument handling. Should this include:
>
> Fixes: 3ab5bd317ee2 ("bpf: Set sub->arg_cnt earlier in btf_prepare_func_args()")
fixes tag is necessary indeed, but please drop 'Reported-by: Sashiko'.
If we start doing such things every patch will have it.
next prev parent reply other threads:[~2026-05-14 23:53 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-14 18:48 [PATCH bpf-next 1/2] bpf: Validate outgoing stack args when btf_prepare_func_args fails Yonghong Song
2026-05-14 18:48 ` [PATCH bpf-next 2/2] selftests/bpf: Add test for stack arg read without caller write Yonghong Song
2026-05-14 19:37 ` [PATCH bpf-next 1/2] bpf: Validate outgoing stack args when btf_prepare_func_args fails bot+bpf-ci
2026-05-14 23:53 ` Alexei Starovoitov [this message]
2026-05-15 1:38 ` Yonghong Song
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