linux-kernel - Re: [tip:x86/urgent] x86-32: Make sure the stack is set up before we use it

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Message-ID: <20110205053716.GR5503@outflux.net>
Date:	Fri, 4 Feb 2011 21:37:16 -0800
From:	Kees Cook <kees.cook@...onical.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	mingo@...hat.com, linux-kernel@...r.kernel.org,
	castet.matthieu@...e.fr, tglx@...utronix.de, hpa@...ux.intel.com
Subject: Re: [tip:x86/urgent] x86-32: Make sure the stack is set up before we
 use it

On Fri, Feb 04, 2011 at 08:37:37PM -0800, H. Peter Anvin wrote:
> On 02/04/2011 06:19 PM, Kees Cook wrote:
> > This works for me doing CPU hotplugging on ia32, but on x86_64 it hangs.
> > (Both boot, though.)
> 
> I can't reproduce the failure here, and it's hard to see how this patch
> would make a significant change on 64 bits.  Could you try reverting
> *only* the head_64.S hunk and try it on your platform again?

With the head_64.S hunk dropped, it runs fine. My highly fine-tuned
test-case is:

  while :; do ls -la / -R >/dev/null 2>/dev/null; done &
  while :; do echo 0 > /sys/devices/system/cpu/cpu1/online ; echo 1 > /sys/devices/system/cpu/cpu1/online ; done &

Looks good from this end. Thanks!

-Kees

-- 
Kees Cook
Ubuntu Security Team
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