Messages in this thread | | | From | Jim Mattson <> | Date | Thu, 31 Aug 2023 12:28:27 -0700 | Subject | Re: [PATCH] x86/fpu/xstate: Fix PKRU covert channel |
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On Thu, Aug 31, 2023 at 12:12 PM Dave Hansen <dave.hansen@intel.com> wrote: > > On 8/30/23 21:32, Jim Mattson wrote: > > When XCR0[9] is set, PKRU can be read and written from userspace with > > XSAVE and XRSTOR, even when CR4.PKE is clear. > > > > Clear XCR0[9] when protection keys are disabled. > > > > Reported-by: Tavis Ormandy <taviso@google.com> > > Signed-off-by: Jim Mattson <jmattson@google.com> > > Is there any way to trigger this other than "nopku" on the command-line?
Or by configuration option:
CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS=n
> I'm not sure how scary this particular covert channel is, but it does > make sense to do this even if it's only to avoid wasting XSAVE space on > a feature that nobody can use (for things other than covert channels). > > Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
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