linux-kernel - Re: [PATCH] x86: add missing verify

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Message-ID: <20110703121549.GA21127@elf.ucw.cz>
Date:	Sun, 3 Jul 2011 14:15:49 +0200
From:	Pavel Machek <pavel@....cz>
To:	Kees Cook <kees.cook@...onical.com>
Cc:	linux-kernel@...r.kernel.org, Len Brown <len.brown@...el.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Pekka Enberg <penberg@...helsinki.fi>,
	Brian Gerst <brgerst@...il.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: [PATCH] x86: add missing verify_cpu to 32bit wakeup

Hi!

> Some BIOSes will reset the Intel XD_DISABLE MSR bit when resuming from S3,
> which can interact poorly with ebba638ae723d8a8fc2f7abce5ec18b688b791d7.
> In 32bit PAE mode, this can lead to a fault when EFER is restored by
> the kernel wakeup routines, due to it setting the NX bit for a CPU
> that (thanks to the BIOS reset) now incorrectly thinks it lacks the NX
> feature. 64bit wakeup already handled this through its common call path
> that would hit verify_cpu(). 32bit has a separate path for restoring
> CPU state on S3 wakeup, and needed to call verify_cpu() to handle this
> situation.
> 
> Signed-off-by: Kees Cook <kees.cook@...onical.com>
> Cc: stable@...nel.org

Looks ok to me, but I'm not sure it is stable material.
									Pavel
-- 
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