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CVE-2015-5307 kvm: DoS infinite loop in microcode AC exception (rhbz 1277172 1279688)

This commit is contained in:
Josh Boyer 2015-11-10 07:41:35 -05:00
parent fcfcde1280
commit d39f93a369
2 changed files with 96 additions and 0 deletions
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92
KVM-x86-work-around-infinite-loop-in-microcode-when-.patch Normal file
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@ -0,0 +1,92 @@
From adceca1789584fe567828afb7246bd35a8549e94 Mon Sep 17 00:00:00 2001
From: Eric Northup <digitaleric@google.com>
Date: Tue, 10 Nov 2015 13:22:52 +0100
Subject: [PATCH 1/2] KVM: x86: work around infinite loop in microcode when #AC
is delivered
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>
---
arch/x86/include/uapi/asm/svm.h | 1 +
arch/x86/kvm/svm.c | 8 ++++++++
arch/x86/kvm/vmx.c | 5 ++++-
3 files changed, 13 insertions(+), 1 deletion(-)
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 f2c8e4917688..7203b3cc71b5 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1110,6 +1110,7 @@ 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);
@@ -1798,6 +1799,12 @@ 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);
@@ -3362,6 +3369,7 @@ 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 5eb56ed77c1f..106aa940d3c0 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -1631,7 +1631,7 @@ 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))
@@ -5266,6 +5266,9 @@ 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 &
--
2.4.3

4
kernel.spec
View File

@ -599,6 +599,9 @@ Patch524: RDS-fix-race-condition-when-sending-a-message-on-unb.patch
Patch512: isdn_ppp-Add-checks-for-allocation-failure-in-isdn_p.patch
Patch513: ppp-slip-Validate-VJ-compression-slot-parameters-com.patch
#CVE-2015-5307 rhbz 1277172 1279688
Patch550: KVM-x86-work-around-infinite-loop-in-microcode-when-.patch
# END OF PATCH DEFINITIONS
%endif
@ -2045,6 +2048,7 @@ fi
%changelog
* Wed Nov 11 2015 Josh Boyer <jwboyer@fedoraproject.org>
- Linux v4.3
- CVE-2015-5307 kvm: DoS infinite loop in microcode AC exception (rhbz 1277172 1279688)
- Disable Exynos IOMMU as it crashes
- Enable some IIO sensors (temp/humidity) on ARMv7
- Move iscsi_tcp and related modules to kernel-core (rhbz 1249424)