linux-kernel - Re: bpf: incorrect passing infinate loop causing rcu detected stall during bpf_prog

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Date:   Sat, 28 Oct 2023 17:34:56 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Hao Sun <sunhao.th@...il.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        John Fastabend <john.fastabend@...il.com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>,
        Yonghong Song <yonghong.song@...ux.dev>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        Mykola Lysenko <mykolal@...com>, Shuah Khan <shuah@...nel.org>,
        bpf <bpf@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: bpf: incorrect passing infinate loop causing rcu detected stall
 during bpf_prog_run()

On Fri, Oct 27, 2023 at 2:09 AM Hao Sun <sunhao.th@...il.com> wrote:
>
> Hi,
>
> The following C repro contains a bpf program that can cause rcu
> stall/soft lockup during running in bpf_prog_run(). Seems the verifier
> incorrectly passed the program with an infinite loop.
>
> C repro: https://pastebin.com/raw/ymzAxjeU

Thanks for the report.
Did you debug what exactly caused this bug?
Are you planning to work on the fix?

> Verifier's log: https://pastebin.com/raw/thZDTFJc

log is trimmed.