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KVM: ioapic: fix assignment of ioapic->rtc_status.pending_eoi (CVE-2014-0155)

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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>
This commit is contained in:
Paolo Bonzini 2014-03-28 20:41:50 +01:00
parent 7cbb39d4d4
commit 5678de3f15
1 changed files with 1 additions and 1 deletions
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2
virt/kvm/ioapic.c
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@ -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); BUG_ON(ioapic->rtc_status.pending_eoi != 0);
ret = kvm_irq_delivery_to_apic(ioapic->kvm, NULL, &irqe, ret = kvm_irq_delivery_to_apic(ioapic->kvm, NULL, &irqe,
ioapic->rtc_status.dest_map); ioapic->rtc_status.dest_map);
ioapic->rtc_status.pending_eoi = ret; ioapic->rtc_status.pending_eoi = (ret < 0 ? 0 : ret);
} else } else
ret = kvm_irq_delivery_to_apic(ioapic->kvm, NULL, &irqe, NULL); ret = kvm_irq_delivery_to_apic(ioapic->kvm, NULL, &irqe, NULL);