FreeBSD : xen-kernel -- vulnerability in the iret hypercall handler (8c31b288-27ec-11e5-a4a5-002590263bf5)

The Xen Project reports : A buggy loop in Xen's compatiret function iterates the wrong way around a 32-bit index. Any 32-bit PV guest kernel can trigger this vulnerability by attempting a hypercalliret with EFLAGS.VM set. Given the use of get/putuser, and that the virtual addresses in question ar...