libspice: Relying on guest provided data structures to indicate memory allocation

libspice, as used in QEMU-KVM in the Hypervisor aka rhev-hypervisor in Red Hat Enterprise Virtualization RHEV 2.2 and qspice 0.3.0, does not properly restrict the addresses upon which memory-management actions are performed, which allows guest OS users to cause a denial of service guest OS crash ...