The ioapic_deliver function in virt/kvm/ioapic.c in the Linux kernel through 3.14.1 does not properly validate the kvm_irq_delivery_to_apic return value, which allows guest OS users to cause a denial of service (host OS crash) via a crafted entry in the redirection table of an I/O APIC.  NOTE: the affected code was moved to the ioapic_service function before the vulnerability was announced.