linux-kernel - Re: [PATCH AUTOSEL 4.19 18/21] kprobes: Tell lockdep about kprobe nesting

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Message-ID: <20201114225850.GH403069@sasha-vm>
Date:   Sat, 14 Nov 2020 17:58:50 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        "Steven Rostedt (VMware)" <rostedt@...dmis.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH AUTOSEL 4.19 18/21] kprobes: Tell lockdep about kprobe
 nesting

On Tue, Nov 10, 2020 at 03:44:58PM +0900, Masami Hiramatsu wrote:
>Hi,
>
>On Mon,  9 Nov 2020 22:55:38 -0500
>Sasha Levin <sashal@...nel.org> wrote:
>
>> From: "Steven Rostedt (VMware)" <rostedt@...dmis.org>
>>
>> [ Upstream commit 645f224e7ba2f4200bf163153d384ceb0de5462e ]
>>
>> Since the kprobe handlers have protection that prohibits other handlers from
>> executing in other contexts (like if an NMI comes in while processing a
>> kprobe, and executes the same kprobe, it will get fail with a "busy"
>> return). Lockdep is unaware of this protection. Use lockdep's nesting api to
>> differentiate between locks taken in INT3 context and other context to
>> suppress the false warnings.
>>
>> Link: https://lore.kernel.org/r/20201102160234.fa0ae70915ad9e2b21c08b85@kernel.org
>>
>
>This fixes a lockdep false positive warning comes from commit e03b4a084ea6
>("kprobes: Remove NMI context check"). Does anyone report that happen on the
>stable kernel?
>
>If not, you do not need this patch for stable kernels.

I'll drop it, thanks!

-- 
Thanks,
Sasha