Re: [edk2-devel] [PATCH] OvmfPkg: Harden #VC instruction emulation somewhat (CVE-2024-25742)

["Adam Dunlap via groups.io" <acdunlap=google.com@groups.io>]

On Fri, Apr 19, 2024 at 8:13 AM Tom Lendacky <thomas.lendacky@amd.com> wrote:
>
> On 4/17/24 11:54, Adam Dunlap wrote:
> > +
> > +    case SVM_EXIT_INVD:
> > +      break;
>
> This changes the current behavior today, but I'm ok with that.
>

Whoops, I should've checked that. Should we delete InvdExit() then, if
it's dead code?

> > +
> > +    case SVM_EXIT_MONITOR:
> > +      CcDecodeModRm (Regs, InstructionData);
> > +
> > +      if ((OpCode == 0x01) && (InstructionData->ModRm.Uint8 == 0xc8)) {
>
> This should also handle the MONITORX opcode (hmmm... I need to send a
> patch to the kernel).
>
> > +        return 0;
> > +      }
> > +
> > +      break;
> > +
> > +    case SVM_EXIT_MWAIT:
> > +      CcDecodeModRm (Regs, InstructionData);
> > +
> > +      if ((OpCode == 0x01) && (InstructionData->ModRm.Uint8 == 0xc9)) {
>
> Same here for MWAITX.
>
> Thanks,
> Tom

Got it! I'll send out a new patch shortly if I can figure out how to
use git send-email correctly.


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