CVE-2015-7813

Xen 4.4.x, 4.5.x, and 4.6.x does not limit the number of printk console
messages when reporting unimplemented hypercalls, which allows local guests
to cause a denial of service via a sequence of (1) HYPERVISOR_physdev_op
hypercalls, which are not properly handled in the do_physdev_op function in
arch/arm/physdev.c, or (2) HYPERVISOR_hvm_op hypercalls, which are not
properly handled in the do_hvm_op function in arch/arm/hvm.c.