| From | Luis Henriques <> | Subject | [PATCH 3.16.y-ckt 050/170] KVM: x86: Improve thread safety in pit | Date | Tue, 11 Nov 2014 11:06:49 +0000 |
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3.16.7-ckt1 -stable review patch. If anyone has any objections, please let me know.
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From: Andy Honig <ahonig@google.com>
commit 2febc839133280d5a5e8e1179c94ea674489dae2 upstream.
There's a race condition in the PIT emulation code in KVM. In __kvm_migrate_pit_timer the pit_timer object is accessed without synchronization. If the race condition occurs at the wrong time this can crash the host kernel.
This fixes CVE-2014-3611.
Signed-off-by: Andrew Honig <ahonig@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Luis Henriques <luis.henriques@canonical.com> --- arch/x86/kvm/i8254.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c index 518d86471b76..298781d4cfb4 100644 --- a/arch/x86/kvm/i8254.c +++ b/arch/x86/kvm/i8254.c @@ -262,8 +262,10 @@ void __kvm_migrate_pit_timer(struct kvm_vcpu *vcpu) return; timer = &pit->pit_state.timer; + mutex_lock(&pit->pit_state.lock); if (hrtimer_cancel(timer)) hrtimer_start_expires(timer, HRTIMER_MODE_ABS); + mutex_unlock(&pit->pit_state.lock); } static void destroy_pit_timer(struct kvm_pit *pit) -- 2.1.0
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