From: Sean Christopherson <seanjc@google.com>
To: sashiko-reviews@lists.linux.dev
Cc: kvm@vger.kernel.org
Subject: Re: [PATCH v3 3/8] KVM: x86: Manually check DR4/5 write values to fix SVM intercept priority
Date: Fri, 12 Jun 2026 16:51:26 -0700 [thread overview]
Message-ID: <aiybfjQbD4qMRMGi@google.com> (raw)
In-Reply-To: <20260612232829.482311F000E9@smtp.kernel.org>
On Fri, Jun 12, 2026, sashiko-bot@kernel.org wrote:
> > diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> > index 4484c5fa19e33..a1bccab0eefee 100644
> > --- a/arch/x86/kvm/emulate.c
> > +++ b/arch/x86/kvm/emulate.c
> > @@ -3853,15 +3853,23 @@ static int check_dr_read(struct x86_emulate_ctxt *ctxt)
> > static int check_dr_write(struct x86_emulate_ctxt *ctxt)
> > {
> > u64 new_val = ctxt->src.val64;
> > - int dr = ctxt->modrm_reg;
> > int rc;
> >
> > rc = check_dr_read(ctxt);
> > if (rc != X86EMUL_CONTINUE)
> > return rc;
> >
> > - if ((dr == 6 || dr == 7) && (new_val & 0xffffffff00000000ULL))
> > - return emulate_gp(ctxt, 0);
> > + switch (ctxt->modrm_reg) {
> > + case 4:
> > + case 5:
> > + case 6:
> > + case 7:
> > + if (new_val & 0xffffffff00000000ULL)
> > + return emulate_gp(ctxt, 0);
> > + break;
> > + default:
> > + break;
>
> [Severity: Critical]
> This is a pre-existing issue, but does this code need to check for canonical
> addresses on DR0-DR3?
No, MOV DR doesn't do canonical checks on the debug reg value. I double checked
the SDM, and on both AMD and Intel hardware.
next prev parent reply other threads:[~2026-06-12 23:51 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-12 23:01 [PATCH v3 0/8] KVM: x86: Fix emulated MOV DR{4,5} #GP bugs Sean Christopherson
2026-06-12 23:01 ` [PATCH v3 1/8] KVM: x86: Treat any non-zero return from set_dr() as a faulting condition Sean Christopherson
2026-06-12 23:01 ` [PATCH v3 2/8] KVM: x86: Prioritize DR7.GD #DB over #GP due to illegal DR6/7 value Sean Christopherson
2026-06-12 23:01 ` [PATCH v3 3/8] KVM: x86: Manually check DR4/5 write values to fix SVM intercept priority Sean Christopherson
2026-06-12 23:28 ` sashiko-bot
2026-06-12 23:51 ` Sean Christopherson [this message]
2026-06-12 23:01 ` [PATCH v3 4/8] KVM: x86: Prioritize #UD on MOV DR over #GP due to non-zero CPL Sean Christopherson
2026-06-12 23:01 ` [PATCH v3 5/8] KVM: VMX: Prioritize DR7.GD=1 #DB over CPL>0 #GP on Intel Sean Christopherson
2026-06-12 23:01 ` [PATCH v3 6/8] KVM: x86: Use kvm_dr{6,7}_valid() to check DR{4,5,6,7} write values in emulator Sean Christopherson
2026-06-12 23:01 ` [PATCH v3 7/8] KVM: x86: WARN if MOV DR emulation hits a "too late" #GP Sean Christopherson
2026-06-12 23:01 ` [PATCH v3 8/8] KVM: x86: Read CR4.DE in emulator if and only if accessing DR4 or DR5 Sean Christopherson
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