linux-kernel - Re: [PATCH bpf-next v3 1/2] bpf: fix nullness propagation for reg to reg comparisons

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Date:   Fri, 23 Dec 2022 01:30:16 +0000
From:   patchwork-bot+netdevbpf@...nel.org
To:     Hao Sun <sunhao.th@...il.com>
Cc:     bpf@...r.kernel.org, ast@...nel.org, daniel@...earbox.net,
        john.fastabend@...il.com, andrii@...nel.org, martin.lau@...ux.dev,
        song@...nel.org, yhs@...com, kpsingh@...nel.org, sdf@...gle.com,
        haoluo@...gle.com, jolsa@...nel.org, davem@...emloft.net,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH bpf-next v3 1/2] bpf: fix nullness propagation for reg to reg
 comparisons

Hello:

This series was applied to bpf/bpf.git (master)
by Martin KaFai Lau <martin.lau@...nel.org>:

On Thu, 22 Dec 2022 10:44:13 +0800 you wrote:
> After befae75856ab, the verifier would propagate null information after
> JEQ/JNE, e.g., if two pointers, one is maybe_null and the other is not,
> the former would be marked as non-null in eq path. However, as comment
> "PTR_TO_BTF_ID points to a kernel struct that does not need to be null
> checked by the BPF program ... The verifier must keep this in mind and
> can make no assumptions about null or non-null when doing branch ...".
> If one pointer is maybe_null and the other is PTR_TO_BTF, the former is
> incorrectly marked non-null. The following BPF prog can trigger a
> null-ptr-deref, also see this report for more details[1]:
> 
> [...]

Here is the summary with links:
  - [bpf-next,v3,1/2] bpf: fix nullness propagation for reg to reg comparisons
    https://git.kernel.org/bpf/bpf/c/8374bfd5a3c9
  - [bpf-next,v3,2/2] selftests/bpf: check null propagation only neither reg is PTR_TO_BTF_ID
    https://git.kernel.org/bpf/bpf/c/cedebd74cf38

You are awesome, thank you!
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