Patch-mainline: v6.3-rc1
Git-commit: ba5838abb05334e4abfdff1490585c7f365e0424
References: git-fixes
From: Sean Christopherson <seanjc@google.com>
Date: Sat, 7 Jan 2023 01:10:20 +0000
Subject: [PATCH] KVM: x86: Inject #GP if WRMSR sets reserved bits in APIC
 Self-IPI

Inject a #GP if the guest attempts to set reserved bits in the x2APIC-only
Self-IPI register.  Bits 7:0 hold the vector, all other bits are reserved.

Reported-by: Marc Orr <marcorr@google.com>
Cc: Ben Gardon <bgardon@google.com>
Cc: Venkatesh Srinivas <venkateshs@chromium.org>
Cc: stable@vger.kernel.org
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Link: https://lore.kernel.org/r/20230107011025.565472-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
---
 arch/x86/kvm/lapic.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 08450b3e7040..9aca006b2d22 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -2324,10 +2324,14 @@ static int kvm_lapic_reg_write(struct kvm_lapic *apic, u32 reg, u32 val)
 		break;
 
 	case APIC_SELF_IPI:
-		if (apic_x2apic_mode(apic))
-			kvm_apic_send_ipi(apic, APIC_DEST_SELF | (val & APIC_VECTOR_MASK), 0);
-		else
+		/*
+		 * Self-IPI exists only when x2APIC is enabled.  Bits 7:0 hold
+		 * the vector, everything else is reserved.
+		 */
+		if (!apic_x2apic_mode(apic) || (val & ~APIC_VECTOR_MASK))
 			ret = 1;
+		else
+			kvm_apic_send_ipi(apic, APIC_DEST_SELF | val, 0);
 		break;
 	default:
 		ret = 1;
-- 
2.35.3