From: Eric Northup <digitaleric@xxxxxxxxxx> 3.4.111-rc1 review patch. If anyone has any objections, please let me know. ------------------ 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@xxxxxxxxxx> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> [lizf: Backported to 3.4: - adjust filename - adjust context - add definition of AC_VECTOR] Signed-off-by: Zefan Li <lizefan@xxxxxxxxxx> --- arch/x86/include/asm/kvm_host.h | 1 + arch/x86/kvm/svm.c | 8 ++++++++ arch/x86/kvm/trace.h | 1 + arch/x86/kvm/vmx.c | 5 ++++- 4 files changed, 14 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index d60facb..493b026 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -87,6 +87,7 @@ #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 86c74c0..56dd88a 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -1081,6 +1081,7 @@ 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); @@ -1776,6 +1777,12 @@ 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); @@ -3291,6 +3298,7 @@ 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 911d264..d26a7e2 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 4ad0d71..defd510 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -1169,7 +1169,7 @@ 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)) @@ -4260,6 +4260,9 @@ 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 & -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html