This is a note to let you know that I've just added the patch titled
KVM: x86: Fix potential divide by 0 in lapic (CVE-2013-6367)
to the 3.12-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kvm-x86-fix-potential-divide-by-0-in-lapic-cve-2013-6367.patch
and it can be found in the queue-3.12 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From b963a22e6d1a266a67e9eecc88134713fd54775c Mon Sep 17 00:00:00 2001
From: Andy Honig <ahonig@xxxxxxxxxx>
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@xxxxxxxxxx>
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@xxxxxxxxxx>
Signed-off-by: Andrew Honig <ahonig@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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
@@ -841,7 +841,8 @@ static u32 apic_get_tmcct(struct kvm_lap
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);
Patches currently in stable-queue which might be from ahonig@xxxxxxxxxx are
queue-3.12/kvm-x86-convert-vapic-synchronization-to-_cached-functions-cve-2013-6368.patch
queue-3.12/kvm-improve-create-vcpu-parameter-cve-2013-4587.patch
queue-3.12/kvm-x86-fix-potential-divide-by-0-in-lapic-cve-2013-6367.patch
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