linux-kernel - Re: [PATCH] tracing/kprobes: Check whether get_kretprobe() returns NULL in kretprobe

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Date:   Mon, 30 May 2022 21:33:23 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     "Masami Hiramatsu (Google)" <mhiramat@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>, Yonghong Song <yhs@...com>,
        bpf <bpf@...r.kernel.org>, Kernel Team <kernel-team@...com>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] tracing/kprobes: Check whether get_kretprobe() returns
 NULL in kretprobe_dispatcher()

On 5/27/22 5:55 PM, Masami Hiramatsu (Google) wrote:
> From: Masami Hiramatsu (Google) <mhiramat@...nel.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@...com>
> Fixes: d741bf41d7c7 ("kprobes: Remove kretprobe hash")
> Cc: stable@...r.kernel.org
> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>

Steven, I presume you'll pick this fix up?

Thanks,
Daniel