[linux] 01/02: [x86] KVM: Intercept #AC to avoid guest->host denial-of-service (CVE-2015-5307)

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benh pushed a commit to branch sid
in repository linux.

commit ef1fd62260fd74bd9749f2249d19bb79807ee197
Author: Ben Hutchings <ben at decadent.org.uk>
Date:   Sun Nov 8 15:13:48 2015 +0000

    [x86] KVM: Intercept #AC to avoid guest->host denial-of-service (CVE-2015-5307)
---
 debian/changelog                                   |  2 ++
 ...-intercept-ac-to-avoid-guest-host-exploit.patch | 38 ++++++++++++++++++++++
 ...x-avoid-guest-host-dos-by-intercepting-ac.patch | 34 +++++++++++++++++++
 debian/patches/series                              |  2 ++
 4 files changed, 76 insertions(+)

diff --git a/debian/changelog b/debian/changelog
index 22996d8..090d5a3 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -4,6 +4,8 @@ linux (4.2.5-2) UNRELEASED; urgency=medium
   * RDS: fix race condition when sending a message on unbound socket
     (CVE-2015-7990)
   * media/vivid-osd: fix info leak in ioctl (CVE-2015-7884)
+  * [x86] KVM: Intercept #AC to avoid guest->host denial-of-service
+    (CVE-2015-5307)
 
  -- Ben Hutchings <ben at decadent.org.uk>  Sun, 08 Nov 2015 14:47:40 +0000
 
diff --git a/debian/patches/bugfix/x86/kvm-x86-svm-intercept-ac-to-avoid-guest-host-exploit.patch b/debian/patches/bugfix/x86/kvm-x86-svm-intercept-ac-to-avoid-guest-host-exploit.patch
new file mode 100644
index 0000000..b8ffd07
--- /dev/null
+++ b/debian/patches/bugfix/x86/kvm-x86-svm-intercept-ac-to-avoid-guest-host-exploit.patch
@@ -0,0 +1,38 @@
+Subject: KVM x86 SVM: intercept #AC to avoid guest->host exploit
+
+---
+M arch/x86/kvm/svm.c
+1 file changed, 8 insertions(+), 0 deletions(-)
+
+
+--- a/arch/x86/kvm/svm.c
++++ b/arch/x86/kvm/svm.c
+@@ -1106,6 +1106,7 @@ static void init_vmcb(struct vcpu_svm *s
+ 	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);
+@@ -1795,6 +1796,12 @@ static int ud_interception(struct vcpu_s
+ 	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);
+@@ -3369,6 +3376,7 @@ static int (*const svm_exit_handlers[])(
+ 	[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/debian/patches/bugfix/x86/kvm-x86-vmx-avoid-guest-host-dos-by-intercepting-ac.patch b/debian/patches/bugfix/x86/kvm-x86-vmx-avoid-guest-host-dos-by-intercepting-ac.patch
new file mode 100644
index 0000000..79ed624
--- /dev/null
+++ b/debian/patches/bugfix/x86/kvm-x86-vmx-avoid-guest-host-dos-by-intercepting-ac.patch
@@ -0,0 +1,34 @@
+From: Eric Northup <digitaleric at google.com>
+Date: Thu Sep 10 11:36:28 2015 -0700
+Subject: KVM x86 vmx: avoid guest->host DOS by intercepting #AC
+
+A pathological (or malicious) guest can hang a host core by
+mis-configuring its GDT/IDT and enabling alignment checks.
+
+[bwh: Forward-ported to 4.2: AC_VECTOR is already defined so don't add it]
+
+--- a/arch/x86/kvm/vmx.c
++++ b/arch/x86/kvm/vmx.c
+@@ -1567,7 +1567,7 @@ static void update_exception_bitmap(stru
+ 	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))
+@@ -5146,6 +5146,13 @@ static int handle_exception(struct kvm_v
+ 		kvm_run->debug.arch.pc = vmcs_readl(GUEST_CS_BASE) + rip;
+ 		kvm_run->debug.arch.exception = ex_no;
+ 		break;
++	case AC_VECTOR:
++		/*
++		 * We have already enabled interrupts and pre-emption, so
++		 * it's OK to loop here if that is what will happen.
++		 */
++		kvm_queue_exception_e(vcpu, AC_VECTOR, error_code);
++		return 1;
+ 	default:
+ 		kvm_run->exit_reason = KVM_EXIT_EXCEPTION;
+ 		kvm_run->ex.exception = ex_no;
diff --git a/debian/patches/series b/debian/patches/series
index 45d3d1c..e22ac4a 100644
--- a/debian/patches/series
+++ b/debian/patches/series
@@ -107,3 +107,5 @@ debian/signal-fix-abi-change-in-4.2.4.patch
 bugfix/all/usbvision-fix-overflow-of-interfaces-array.patch
 bugfix/all/rds-fix-race-condition-when-sending-a-message-on-unbound-socket.patch
 bugfix/all/media-media-vivid-osd-fix-info-leak-in-ioctl.patch
+bugfix/x86/kvm-x86-vmx-avoid-guest-host-dos-by-intercepting-ac.patch
+bugfix/x86/kvm-x86-svm-intercept-ac-to-avoid-guest-host-exploit.patch

-- 
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