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| author | Eric Northup <digitaleric@google.com> | 2015-11-03 18:03:53 +0100 |
|---|---|---|
| committer | Sasha Levin <sasha.levin@oracle.com> | 2015-12-14 12:17:32 -0500 |
| commit | 79e62de2efb2f586726e46342c792360a9644319 (patch) | |
| tree | 9704642dc5d7c1cc956df554835d575c8b728456 | |
| parent | a62b833dd4af3c58b839317367b0586a5ca12669 (diff) | |
| download | lwn-79e62de2efb2f586726e46342c792360a9644319.tar.gz lwn-79e62de2efb2f586726e46342c792360a9644319.zip | |
KVM: x86: work around infinite loop in microcode when #AC is delivered
[ Upstream commit 54a20552e1eae07aa240fa370a0293e006b5faed ]
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>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
| -rw-r--r-- | arch/x86/include/uapi/asm/svm.h | 1 | ||||
| -rw-r--r-- | arch/x86/kvm/svm.c | 8 | ||||
| -rw-r--r-- | arch/x86/kvm/vmx.c | 5 |
3 files changed, 13 insertions, 1 deletions
diff --git a/arch/x86/include/uapi/asm/svm.h b/arch/x86/include/uapi/asm/svm.h index b5d7640abc5d..8a4add8e4639 100644 --- a/arch/x86/include/uapi/asm/svm.h +++ b/arch/x86/include/uapi/asm/svm.h @@ -100,6 +100,7 @@ { 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/svm.c b/arch/x86/kvm/svm.c index f98baebfa9a7..9dc0aa0dae96 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -1103,6 +1103,7 @@ 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); @@ -1789,6 +1790,12 @@ 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); @@ -3350,6 +3357,7 @@ static int (*const 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/vmx.c b/arch/x86/kvm/vmx.c index 0d7f1dcfcdac..84de207a8848 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -1493,7 +1493,7 @@ 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)) @@ -4933,6 +4933,9 @@ static int handle_exception(struct kvm_vcpu *vcpu) return handle_rmode_exception(vcpu, ex_no, error_code); 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 & |