Messages in this thread | | | Date | Thu, 31 Aug 2023 12:12:22 -0700 | Subject | Re: [PATCH] x86/fpu/xstate: Fix PKRU covert channel | From | Dave Hansen <> |
| |
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?
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>
| |