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authorAndy Honig <ahonig@google.com>2013-11-19 14:12:18 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-12-20 07:45:07 -0800
commit9913f77411d04f56f600d900a6533c9518e6ee68 (patch)
tree714df4800481e327ce24fef0efd87dc8259bb4a6 /arch/x86
parentf4d838225e0cbdc8099c2eb8d55dd9406def1f33 (diff)
downloadlinaro-lsk-9913f77411d04f56f600d900a6533c9518e6ee68.tar.gz
KVM: x86: Fix potential divide by 0 in lapic (CVE-2013-6367)
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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch/x86')
-rw-r--r--arch/x86/kvm/lapic.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 0eee2c8b64d..b78a624edae 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -855,7 +855,8 @@ 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);