The grant-table feature in Xen through 4.8.x mishandles a GNTMAP_device_map and GNTMAP_host_map mapping, when followed by only a GNTMAP_host_map unmapping, which allows guest OS users to cause a denial of service (count mismanagement and memory corruption) or obtain privileged host OS access, aka XSA-224 bug 1.
Gentoo Linux Security Advisory 201710-17 - Multiple vulnerabilities have been found in Xen, the worst of which may allow local attackers to escalate privileges. Versions less than 4.7.3 are affected.