--- /dev/null
+From 245d4b4480c20ffb50f0eddadcc6516b9017d863 Mon Sep 17 00:00:00 2001
+From: Andy Honig <ahonig@google.com>
+Date: Tue, 19 Nov 2013 14:12:18 -0800
+Subject: KVM: x86: Fix potential divide by 0 in lapic (CVE-2013-6367)
+
+From: Andy Honig <ahonig@google.com>
+
+commit b963a22e6d1a266a67e9eecc88134713fd54775c upstream.
+
+Under guest controllable circumstances apic_get_tmcct will execute a
+divide by zero and cause a crash. If the guest cpuid support
+tsc deadline timers and performs the following sequence of requests
+the host will crash.
+- Set the mode to periodic
+- Set the TMICT to 0
+- Set the mode bits to 11 (neither periodic, nor one shot, nor tsc deadline)
+- Set the TMICT to non-zero.
+Then the lapic_timer.period will be 0, but the TMICT will not be. If the
+guest then reads from the TMCCT then the host will perform a divide by 0.
+
+This patch ensures that if the lapic_timer.period is 0, then the division
+does not occur.
+
+Reported-by: Andrew Honig <ahonig@google.com>
+Signed-off-by: Andrew Honig <ahonig@google.com>
+Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
+[bwh: Backported to 3.2: s/kvm_apic_get_reg/apic_get_reg/]
+Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
+Cc: Vinson Lee <vlee@twopensource.com>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+
+---
+ arch/x86/kvm/lapic.c | 3 ++-
+ 1 file changed, 2 insertions(+), 1 deletion(-)
+
+--- a/arch/x86/kvm/lapic.c
++++ b/arch/x86/kvm/lapic.c
+@@ -538,7 +538,8 @@ static u32 apic_get_tmcct(struct kvm_lap
+ ASSERT(apic != NULL);
+
+ /* if initial count is 0, current count should also be 0 */
+- if (apic_get_reg(apic, APIC_TMICT) == 0)
++ if (apic_get_reg(apic, APIC_TMICT) == 0 ||
++ apic->lapic_timer.period == 0)
+ return 0;
+
+ remaining = hrtimer_get_remaining(&apic->lapic_timer.timer);