The fix for XSA-365 includes initialization of pointers such that
subsequent cleanup code wouldn't use uninitialized or stale values. This
initialization went too far and may under certain conditions also overwrite
pointers which are in need of cleaning up. The lack of cleanup would result
in leaking persistent grants. The leak in turn would prevent fully cleaning
up after a respective guest has died, leaving around zombie domains. All
Linux versions having the fix for XSA-365 applied are vulnerable. XSA-365
was classified to affect versions back to at least 3.11.

It was discovered that the Xen paravirtualization backend in the Linux
kernel did not properly deallocate memory in some situations. A local
attacker could use this to cause a denial of service (memory exhaustion).