Citrix XenServer 6.5.0

The PV pagetable code in arch/x86/mm.c in Xen 4.7.x and earlier allows local 32-bit PV guest OS administrators to gain host OS privileges by leveraging fast-paths for updating pagetable entries.

Xen 4.5.x through 4.7.x do not implement Supervisor Mode Access Prevention (SMAP) whitelisting in 32-bit exception and event delivery, which allows local 32-bit PV guest OS kernels to cause a denial of service (hypervisor and VM crash) by triggering a safety check.