From: Maxim Levitsky <mlevitsk@redhat.com>
Date: Thu, 29 Jul 2021 17:54:04 +0300
Subject: KVM: nSVM: avoid picking up unsupported bits from L2 in
int_ctl
Git-commit: 0f923e07124df069ba68d8bb12324398f4b6b709
Patch-mainline: v5.14-rc7
References: bsc#1189399, CVE-2021-3653
This fixes CVE-2021-3653 that allowed a malicious L1 to run L2 with
AVIC enabled, which allowed the L2 to exploit the uninitialized and enabled
AVIC to read/write the host physical memory at some offsets.
The bug was discovered by Maxim Levitsky.
Fixes: 3d6368ef580a ("KVM: SVM: Add VMRUN handler")
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: Joerg Roedel <jroedel@suse.de>
---
arch/x86/include/asm/svm.h | 2 ++
arch/x86/kvm/svm.c | 10 ++++++++--
2 files changed, 10 insertions(+), 2 deletions(-)
--- a/arch/x86/include/asm/svm.h
+++ b/arch/x86/include/asm/svm.h
@@ -118,6 +118,8 @@ struct __attribute__ ((__packed__)) vmcb
#define V_IGN_TPR_SHIFT 20
#define V_IGN_TPR_MASK (1 << V_IGN_TPR_SHIFT)
+#define V_IRQ_INJECTION_BITS_MASK (V_IRQ_MASK | V_INTR_PRIO_MASK | V_IGN_TPR_MASK)
+
#define V_INTR_MASKING_SHIFT 24
#define V_INTR_MASKING_MASK (1 << V_INTR_MASKING_SHIFT)
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -3409,7 +3409,7 @@ static int nested_svm_vmexit(struct vcpu
nested_vmcb->save.dr6 = vmcb->save.dr6;
nested_vmcb->save.cpl = vmcb->save.cpl;
- nested_vmcb->control.int_ctl = vmcb->control.int_ctl;
+ nested_vmcb->control.int_ctl = vmcb->control.int_ctl & (V_INTR_MASKING_MASK | V_TPR_MASK | V_IRQ_INJECTION_BITS_MASK);
nested_vmcb->control.int_vector = vmcb->control.int_vector;
nested_vmcb->control.int_state = vmcb->control.int_state;
nested_vmcb->control.exit_code = vmcb->control.exit_code;
@@ -3606,7 +3606,13 @@ static void enter_svm_guest_mode(struct
svm->nested.intercept = nested_vmcb->control.intercept;
svm_flush_tlb(&svm->vcpu, true);
- svm->vmcb->control.int_ctl = nested_vmcb->control.int_ctl | V_INTR_MASKING_MASK;
+
+ svm->vmcb->control.int_ctl &=
+ V_INTR_MASKING_MASK | V_GIF_ENABLE_MASK | V_GIF_MASK;
+
+ svm->vmcb->control.int_ctl |= nested_vmcb->control.int_ctl &
+ (V_TPR_MASK | V_IRQ_INJECTION_BITS_MASK);
+
if (nested_vmcb->control.int_ctl & V_INTR_MASKING_MASK)
svm->vcpu.arch.hflags |= HF_VINTR_MASK;
else