Messages in this thread | | | Date | Tue, 9 Nov 2010 16:43:47 -0800 | From | Kees Cook <> | Subject | Re: [Security] [PATCH v3 0/4] x86: clear XD_DISABLED flag on Intel to regain NX |
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On Wed, Nov 10, 2010 at 12:21:53AM +0000, Alan Cox wrote: > > Only Intel has this problem (it's the only CPU that defines this MSR), so > > that'll reduce it. But Google is of no help to me on this; where can I find > > these documents? > > www.intel.com 8)
Gee, thanks. :P
I looks like there is nothing that actually lists errata directly, so walking the entire site for lists of all processor types, e.g.: http://www.intel.com/products/processors/previousgeneration/index.htm http://www.intel.com/design/celeron/documentation.htm and then checking spec updates is the only way to go.
> > > I'm not specifically aware of any but I do know for example that there > > > are other CPU BIOS disablable features that some systems disable in the > > > BIOS for good reason (an ancient example being the original Pentium > > > REP MOVS optimisation on some steppings) > > > > By definition there should be fewer errata CPUs than those than need their > > BIOS ignored, so I still think this patch makes sense (especially since it > > can trivially be worked around with the noexec=off boot option). > > We need to be sure because the last thing you want is even 1% of your 10% > of users to sudden get magical random memory corruption from overriding > something wrongly ! > > It's definitely worth checking and worth doing because even if there is > one (and I have no idea if there is) it'll tell you which steppings
I will report if I find anything bad.
-Kees
-- Kees Cook Ubuntu Security Team
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