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KVM: x86: Improve thread safety in pit

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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.

Cc: stable@vger.kernel.org
Signed-off-by: Andrew Honig <ahonig@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Andy Honig 2014-08-27 14:42:54 -07:00 committed by Paolo Bonzini
parent 8b3c3104c3
commit 2febc83913
1 changed files with 2 additions and 0 deletions
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2
arch/x86/kvm/i8254.c
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@ -262,8 +262,10 @@ void __kvm_migrate_pit_timer(struct kvm_vcpu *vcpu)
return; return;
timer = &pit->pit_state.timer; timer = &pit->pit_state.timer;
mutex_lock(&pit->pit_state.lock);
if (hrtimer_cancel(timer)) if (hrtimer_cancel(timer))
hrtimer_start_expires(timer, HRTIMER_MODE_ABS); hrtimer_start_expires(timer, HRTIMER_MODE_ABS);
mutex_unlock(&pit->pit_state.lock);
} }
static void destroy_pit_timer(struct kvm_pit *pit) static void destroy_pit_timer(struct kvm_pit *pit)