From: Maxim Levitsky mlevitsk@redhat.com

[ upstream commit 0f923e07124df069ba68d8bb12324398f4b6b709 ]

* Invert the mask of bits that we pick from L2 in nested_vmcb02_prepare_control

* Invert and explicitly use VIRQ related bits bitmask in svm_clear_vintr

This fixes a security issue 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.

Fixes: 3d6368ef580a ("KVM: SVM: Add VMRUN handler") Signed-off-by: Maxim Levitsky mlevitsk@redhat.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com --- The above upstream SHA1 is still on its way to Linus

arch/x86/include/asm/svm.h | 2 ++ arch/x86/kvm/svm.c | 15 ++++++++------- 2 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/asm/svm.h b/arch/x86/include/asm/svm.h index 93b462e48067..b6dedf6c835c 100644 --- a/arch/x86/include/asm/svm.h +++ b/arch/x86/include/asm/svm.h @@ -118,6 +118,8 @@ struct __attribute__ ((__packed__)) vmcb_control_area { #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)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index bd463d684237..5ddf63896d01 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -1394,12 +1394,7 @@ static __init int svm_hardware_setup(void) } }

- if (vgif) { - if (!boot_cpu_has(X86_FEATURE_VGIF)) - vgif = false; - else - pr_info("Virtual GIF supported\n"); - } + vgif = false; /* Disabled for CVE-2021-3653 */

return 0;

@@ -3590,7 +3590,13 @@ static void enter_svm_guest_mode(struct vcpu_svm *svm, u64 vmcb_gpa, 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