linux-kernel - Re: [patch 0/2] x86/alternatives: Prevent crash in NOP optimizer

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Message-ID: <20231215091053.GI36716@noisy.programming.kicks-ass.net>
Date: Fri, 15 Dec 2023 10:10:53 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: LKML <linux-kernel@...r.kernel.org>, paul.gortmaker@...driver.com,
	x86@...nel.org, regressions@...mhuis.info,
	richard.purdie@...uxfoundation.org, regressions@...ts.linux.dev
Subject: Re: [patch 0/2] x86/alternatives: Prevent crash in NOP optimizer

On Thu, Dec 07, 2023 at 08:49:22PM +0100, Thomas Gleixner wrote:
> The following series addresses the regression report from Paul on behalf of
> the yocto project. It turns out that the recent changes to alternatives
> opened a race window where interrupts are enabled and NOPs are optimized in
> place. An interrupt hitting into the modification will observe inconsistent
> text and crash and burn.
> 
> A 32bit QEMU crashes w/o these fixes reliably within about 50 boot
> attempts. With the fix applied it survived close to 600 attempts by
> now.
> 
> Thanks to Paul for providing all the information!

Urgh and D'0h.

Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>