CVE-2013-6367 kvm: division by 0 in apic_get_tmcct (rhbz 1032207 1042081)

2 files changed, 111 insertions, 0 deletions

diff --git a/KVM-x86-Fix-potential-divide-by-0-in-lapic.patch b/KVM-x86-Fix-potential-divide-by-0-in-lapic.patch
new file mode 100644
index 000000000..8e144dff4
--- /dev/null
+++ b/KVM-x86-Fix-potential-divide-by-0-in-lapic.patch
@@ -0,0 +1,102 @@
+Bugzilla: 1042081
+Upstream-status: 3.13 and sent for stable                                                                                                                                                                                                                                                               
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+From:	Paolo Bonzini <pbonzini@redhat.com>
+To:	linux-kernel@vger.kernel.org
+Cc:	gleb@redhat.com, kvm@vger.kernel.org, pmatouse@redhat.com,
+	Andy Honig <ahonig@google.com>, stable@vger.kernel.org
+Subject: [PATCH] KVM: x86: Fix potential divide by 0 in lapic (CVE-2013-6367)
+Date:	Thu, 12 Dec 2013 21:36:52 +0100
+Message-Id: <1386880614-23300-2-git-send-email-pbonzini@redhat.com>
+X-Mailer: git-send-email 1.8.3.1
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+From: Andy Honig <ahonig@google.com>
+
+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>
+Cc: stable@vger.kernel.org
+Signed-off-by: Andrew Honig <ahonig@google.com>
+Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
+---
+ arch/x86/kvm/lapic.c | 3 ++-
+ 1 file changed, 2 insertions(+), 1 deletion(-)
+
+diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
+index 5439117d5c4c..89b52ec7d09c 100644
+--- a/arch/x86/kvm/lapic.c
++++ b/arch/x86/kvm/lapic.c
+@@ -841,7 +841,8 @@ static u32 apic_get_tmcct(struct kvm_lapic *apic)
+ 	ASSERT(apic != NULL);
+ 
+ 	/* if initial count is 0, current count should also be 0 */
+-	if (kvm_apic_get_reg(apic, APIC_TMICT) == 0)
++	if (kvm_apic_get_reg(apic, APIC_TMICT) == 0 ||
++		apic->lapic_timer.period == 0)
+ 		return 0;
+ 
+ 	remaining = hrtimer_get_remaining(&apic->lapic_timer.timer);
+-- 
+1.8.3.1
+
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diff --git a/kernel.spec b/kernel.spec
index e5bfecfef..609238567 100644
--- a/kernel.spec
+++ b/kernel.spec
@@ -714,6 +714,9 @@ Patch25170: 0001-drm-radeon-dpm-Fix-hwmon-crash.patch
 #rhbz 1030802
 Patch25171: elantech-Properly-differentiate-between-clickpads-an.patch
 
+#CVE-2013-6367 rhbz 1032207 1042081
+Patch25172: KVM-x86-Fix-potential-divide-by-0-in-lapic.patch
+
 # END OF PATCH DEFINITIONS
 
 %endif
@@ -1394,6 +1397,9 @@ ApplyPatch 0001-drm-radeon-dpm-Fix-hwmon-crash.patch
 #rhbz 1030802
 ApplyPatch elantech-Properly-differentiate-between-clickpads-an.patch
 
+#CVE-2013-6367 rhbz 1032207 1042081
+ApplyPatch KVM-x86-Fix-potential-divide-by-0-in-lapic.patch
+
 # END OF PATCH APPLICATIONS
 
 %endif
@@ -2206,6 +2212,9 @@ fi
 #                                    ||----w |
 #                                    ||     ||
 %changelog
+* Thu Dec 12 2013 Josh Boyer <jwboyer@fedoraproject.org>
+- CVE-2013-6367 kvm: division by 0 in apic_get_tmcct (rhbz 1032207 1042081)
+
 * Wed Dec 11 2013 Josh Boyer <jwboyer@fedoraproject.org> - 3.13.0-0.rc3.git2.1
 - Linux v3.13-rc3-174-g9538e10