Re: [tip:x86/urgent] x86-32: Make sure the stack is set up before weuse it

From: Kees Cook
Date: Sat Feb 05 2011 - 00:37:56 EST


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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