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Date:   Tue, 31 May 2022 00:00:06 +0200
From:   Steven Rostedt <rostedt@goodmis.org>
To:     Daniel Borkmann <daniel@iogearbox.net>,
        "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
CC:     Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@kernel.org>, Yonghong Song <yhs@fb.com>,
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        linux-kernel@vger.kernel.org, stable@vger.kernel.org
Subject: =?US-ASCII?Q?Re=3A_=5BPATCH=5D_tracing/kprobes=3A_Check_whether_get=5Fk?= =?US-ASCII?Q?retprobe=28=29_returns_NULL_in_kretprobe=5Fdispatcher=28=29?=
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On May 30, 2022 9:33:23 PM GMT+02:00, Daniel Borkmann <daniel@iogearbox.net> wrote:
>On 5/27/22 5:55 PM, Masami Hiramatsu (Google) wrote:
>> From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
>> 
>> There is a small chance that get_kretprobe(ri) returns NULL in
>> kretprobe_dispatcher() when another CPU unregisters the kretprobe
>> right after __kretprobe_trampoline_handler().
>> 
>> To avoid this issue, kretprobe_dispatcher() checks the get_kretprobe()
>> return value again. And if it is NULL, it returns soon because that
>> kretprobe is under unregistering process.
>> 
>> This issue has been introduced when the kretprobe is decoupled
>> from the struct kretprobe_instance by commit d741bf41d7c7
>> ("kprobes: Remove kretprobe hash"). Before that commit, the
>> struct kretprob_instance::rp directly points the kretprobe
>> and it is never be NULL.
>> 
>> Reported-by: Yonghong Song <yhs@fb.com>
>> Fixes: d741bf41d7c7 ("kprobes: Remove kretprobe hash")
>> Cc: stable@vger.kernel.org
>> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
>
>Steven, I presume you'll pick this fix up?

I'm currently at Embedded/Kernel Recipes, but yeah, I'll take a look at it. (Just need to finish my slides first ;-)

-- Steve
>
>Thanks,
>Daniel

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