[PATCH v2 2/2] KVM: Inject #GP on invalid writes to x2APIC registers

From: Venkatesh Srinivas <venkateshs@chromium.org>
To: kvm@vger.kernel.org
Cc: seanjc@google.com, marcorr@google.com, venkateshs@chromium.org
Subject: [PATCH v2 2/2] KVM: Inject #GP on invalid writes to x2APIC registers
Date: Wed, 25 May 2022 17:39:33 +0000	[thread overview]
Message-ID: <20220525173933.1611076-2-venkateshs@chromium.org> (raw)
In-Reply-To: <20220525173933.1611076-1-venkateshs@chromium.org>

From: Marc Orr <marcorr@google.com>

From: Venkatesh Srinivas <venkateshs@chromium.org>

The upper bytes of any x2APIC register are reserved. Inject a #GP
into the guest if any of these reserved bits are set.

Signed-off-by: Marc Orr <marcorr@google.com>
Signed-off-by: Venkatesh Srinivas <venkateshs@chromium.org>
---
 arch/x86/kvm/lapic.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 6f8522e8c492..617e4936c5cc 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -2907,6 +2907,8 @@ int kvm_x2apic_msr_write(struct kvm_vcpu *vcpu, u32 msr, u64 data)
 
 	if (!lapic_in_kernel(vcpu) || !apic_x2apic_mode(apic))
 		return 1;
+	else if (data >> 32)
+		return 1;
 
 	return kvm_lapic_msr_write(apic, reg, data);
 }
-- 
2.36.1.124.g0e6072fb45-goog

