Commit 5678de3f authored Mar 28, 2014 by Paolo Bonzini

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

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>

parent 7cbb39d4

virt/kvm/ioapic.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -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);

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