Re: [Security] [PATCH v3 0/4] x86: clear XD_DISABLED flag on Intelto regain NX

[Kees Cook]

On Tue, Nov 09, 2010 at 06:31:42PM +0000, Alan Cox wrote:
> > In a review[1] of reported hardware being used by Ubuntu bug reporters,
> > almost 10% of systems had an incorrectly configured BIOS, leaving their
> > systems unable to use the NX features of their CPU.
> 
> Ouch

Yeah :(

> > This change will clear the MSR_IA32_MISC_ENABLE_XD_DISABLE bit so that NX
> > cannot be inappropriately controlled by the BIOS on Intel CPUs.  If, under
> > very strange hardware configurations, NX actually needs to be disabled,
> > "noexec=off" can be used to restore the prior behavior.
> 
> Have you done an audit of CPU errata to ensure that none of these cases
> are ones where the BIOS has disabled it to avoid an erratum. I'd hate to
> turn it on and find out the BIOS actually turned it off for good reason !

Where can I find those details?

-Kees

-- 
Kees Cook
Ubuntu Security Team
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/