KVM: Fix buffer overflow in kvm_set_irq()

CVE-2012-2137

BugLink: http://bugs.launchpad.net/bugs/1016298

kvm_set_irq() has an internal buffer of three irq routing entries, allowing
connecting a GSI to three IRQ chips or on MSI.  However setup_routing_entry()
does not properly enforce this, allowing three irqchip routes followed by
an MSI route to overflow the buffer.

Fix by ensuring that an MSI entry is added to an empty list.

Signed-off-by: Avi Kivity <[email protected]>
(cherry picked from commit f2ebd422f71cda9c791f76f85d2ca102ae34a1ed)

Signed-off-by: Tim Gardner <[email protected]>
Acked-by: Stefan Bader <[email protected]>

Author: avikivity

virt/kvm/irq_comm.c

@@ -300,6 +300,7 @@ static int setup_routing_entry(struct kvm_irq_routing_table *rt,
 	 */
 	hlist_for_each_entry(ei, n, &rt->map[ue->gsi], link)
 		if (ei->type == KVM_IRQ_ROUTING_MSI ||
+		    ue->type == KVM_IRQ_ROUTING_MSI ||
 		    ue->u.irqchip.irqchip == ei->irqchip.irqchip)
 			return r;