diff options
| author | Eric Northup <digitaleric@google.com> | 2015-11-03 18:03:53 +0100 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2015-11-17 15:54:46 +0000 |
| commit | 3553e5d34d72a3aac5d967ec8b4d45a88340d679 (patch) | |
| tree | bd8006da580b44cd8e0f57ea616143569fee0aed /arch | |
| parent | e94e60d82b9fd6c592bfe7b939a991bfe98179ae (diff) | |
KVM: x86: work around infinite loop in microcode when #AC is delivered
commit 54a20552e1eae07aa240fa370a0293e006b5faed upstream.
It was found that a guest can DoS a host by triggering an infinite
stream of "alignment check" (#AC) exceptions. This causes the
microcode to enter an infinite loop where the core never receives
another interrupt. The host kernel panics pretty quickly due to the
effects (CVE-2015-5307).
Signed-off-by: Eric Northup <digitaleric@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
[bwh: Backported to 3.2:
- Add definition of AC_VECTOR
- Adjust filename, context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/include/asm/kvm_host.h | 1 | ||||
| -rw-r--r-- | arch/x86/kvm/svm.c | 8 | ||||
| -rw-r--r-- | arch/x86/kvm/trace.h | 1 | ||||
| -rw-r--r-- | arch/x86/kvm/vmx.c | 5 |
4 files changed, 14 insertions, 1 deletions
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 93ce7e44eb12..51f85fc08cf1 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -83,6 +83,7 @@ #define GP_VECTOR 13 #define PF_VECTOR 14 #define MF_VECTOR 16 +#define AC_VECTOR 17 #define MC_VECTOR 18 #define SELECTOR_TI_MASK (1 << 2) diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index 7a2d9d6d521b..0de6783b42a3 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -1014,6 +1014,7 @@ static void init_vmcb(struct vcpu_svm *svm) set_exception_intercept(svm, PF_VECTOR); set_exception_intercept(svm, UD_VECTOR); set_exception_intercept(svm, MC_VECTOR); + set_exception_intercept(svm, AC_VECTOR); set_intercept(svm, INTERCEPT_INTR); set_intercept(svm, INTERCEPT_NMI); @@ -1689,6 +1690,12 @@ static int ud_interception(struct vcpu_svm *svm) return 1; } +static int ac_interception(struct vcpu_svm *svm) +{ + kvm_queue_exception_e(&svm->vcpu, AC_VECTOR, 0); + return 1; +} + static void svm_fpu_activate(struct kvm_vcpu *vcpu) { struct vcpu_svm *svm = to_svm(vcpu); @@ -3188,6 +3195,7 @@ static int (*svm_exit_handlers[])(struct vcpu_svm *svm) = { [SVM_EXIT_EXCP_BASE + PF_VECTOR] = pf_interception, [SVM_EXIT_EXCP_BASE + NM_VECTOR] = nm_interception, [SVM_EXIT_EXCP_BASE + MC_VECTOR] = mc_interception, + [SVM_EXIT_EXCP_BASE + AC_VECTOR] = ac_interception, [SVM_EXIT_INTR] = intr_interception, [SVM_EXIT_NMI] = nmi_interception, [SVM_EXIT_SMI] = nop_on_interception, diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h index 911d2641f14c..7216916a522e 100644 --- a/arch/x86/kvm/trace.h +++ b/arch/x86/kvm/trace.h @@ -244,6 +244,7 @@ TRACE_EVENT(kvm_apic, { SVM_EXIT_EXCP_BASE + UD_VECTOR, "UD excp" }, \ { SVM_EXIT_EXCP_BASE + PF_VECTOR, "PF excp" }, \ { SVM_EXIT_EXCP_BASE + NM_VECTOR, "NM excp" }, \ + { SVM_EXIT_EXCP_BASE + AC_VECTOR, "AC excp" }, \ { SVM_EXIT_EXCP_BASE + MC_VECTOR, "MC excp" }, \ { SVM_EXIT_INTR, "interrupt" }, \ { SVM_EXIT_NMI, "nmi" }, \ diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 421958f1b12e..fb8c23d2fdf6 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -1171,7 +1171,7 @@ static void update_exception_bitmap(struct kvm_vcpu *vcpu) u32 eb; eb = (1u << PF_VECTOR) | (1u << UD_VECTOR) | (1u << MC_VECTOR) | - (1u << NM_VECTOR) | (1u << DB_VECTOR); + (1u << NM_VECTOR) | (1u << DB_VECTOR) | (1u << AC_VECTOR); if ((vcpu->guest_debug & (KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_USE_SW_BP)) == (KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_USE_SW_BP)) @@ -4266,6 +4266,9 @@ static int handle_exception(struct kvm_vcpu *vcpu) ex_no = intr_info & INTR_INFO_VECTOR_MASK; switch (ex_no) { + case AC_VECTOR: + kvm_queue_exception_e(vcpu, AC_VECTOR, error_code); + return 1; case DB_VECTOR: dr6 = vmcs_readl(EXIT_QUALIFICATION); if (!(vcpu->guest_debug & |