linux-kernel - Re: [PATCH bpf-next] kallsyms: Disable preemption for find_kallsyms_symbol

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Date:   Thu, 6 Apr 2023 16:47:49 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     Jiri Olsa <jolsa@...nel.org>
Cc:     Luis Chamberlain <mcgrof@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Artem Savkov <asavkov@...hat.com>, bpf@...r.kernel.org,
        linux-modules@...r.kernel.org, linux-kernel@...r.kernel.org,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>,
        "Leizhen (ThunderTown)" <thunder.leizhen@...wei.com>,
        Viktor Malik <vmalik@...hat.com>
Subject: Re: [PATCH bpf-next] kallsyms: Disable preemption for
 find_kallsyms_symbol_value

On Tue 2023-04-04 00:02:54, Jiri Olsa wrote:
> Artem reported suspicious RCU usage [1]. The reason is that verifier
> calls find_kallsyms_symbol_value with preemption enabled which will
> trigger suspicious RCU usage warning in rcu_dereference_sched call.
> 
> Disabling preemption in find_kallsyms_symbol_value and adding
> __find_kallsyms_symbol_value function.
> 
> Fixes: 31bf1dbccfb0 ("bpf: Fix attaching fentry/fexit/fmod_ret/lsm to modules")
> [1] https://lore.kernel.org/bpf/ZBrPMkv8YVRiWwCR@samus.usersys.redhat.com/
> Reported-by: Artem Savkov <asavkov@...hat.com>
> Signed-off-by: Jiri Olsa <jolsa@...nel.org>

Just for record:

Reviewed-by: Petr Mladek <pmladek@...e.com>

Best Regards,
Petr