linux-kernel - Re: [PATCH -tip] x86/kprobes: Handle removed INT3 in do

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Message-ID: <Y4Bxnw1xev8r7gJY@hirez.programming.kicks-ass.net>
Date:   Fri, 25 Nov 2022 08:41:19 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
Cc:     x86@...nel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>,
        Huacai Chen <chenhuacai@...ngson.cn>,
        Jinyang He <hejinyang@...ngson.cn>,
        Tiezhu Yang <yangtiezhu@...ngson.cn>,
        "Naveen N . Rao" <naveen.n.rao@...ux.ibm.com>
Subject: Re: [PATCH -tip] x86/kprobes: Handle removed INT3 in do_int3()

On Fri, Nov 25, 2022 at 10:09:02AM +0900, Masami Hiramatsu (Google) wrote:
> From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> 
> Since x86 doesn't use stop_machine() to patch the kernel text,
> there is a small chance that the another CPU removes the INT3
> during do_int3(). In this case, if no INT3 notifier callbacks
> handled that, the kernel calls die() because of a stray INT3.

Please clarify; how would that happen? Should not everybody modifying
text take text_mutex ?