KVM: ioapic: fix assignment of ioapic->rtc_status.pending_eoi (CVE-2014-0155)
authorPaolo Bonzini <pbonzini@redhat.com>
Fri, 28 Mar 2014 19:41:50 +0000 (20:41 +0100)
committerPaolo Bonzini <pbonzini@redhat.com>
Fri, 4 Apr 2014 15:17:14 +0000 (17:17 +0200)
QE reported that they got the BUG_ON in ioapic_service to trigger.
I cannot reproduce it, but there are two reasons why this could happen.

The less likely but also easiest one, is when kvm_irq_delivery_to_apic
does not deliver to any APIC and returns -1.

Because irqe.shorthand == 0, the kvm_for_each_vcpu loop in that
function is never reached.  However, you can target the similar loop in
kvm_irq_delivery_to_apic_fast; just program a zero logical destination
address into the IOAPIC, or an out-of-range physical destination address.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
virt/kvm/ioapic.c

index d4b601547f1f13c8f336b2352b46d087bb94e7d6..d98d107efb05c60e298afa9966a6b25b10c08bac 100644 (file)
@@ -356,7 +356,7 @@ static int ioapic_service(struct kvm_ioapic *ioapic, int irq, bool line_status)
                BUG_ON(ioapic->rtc_status.pending_eoi != 0);
                ret = kvm_irq_delivery_to_apic(ioapic->kvm, NULL, &irqe,
                                ioapic->rtc_status.dest_map);
-               ioapic->rtc_status.pending_eoi = ret;
+               ioapic->rtc_status.pending_eoi = (ret < 0 ? 0 : ret);
        } else
                ret = kvm_irq_delivery_to_apic(ioapic->kvm, NULL, &irqe, NULL);