|Denial of service
A security issue was found in the Linux kernel before version 5.11.11, as used by Xen. The fix for CVE-2021-26930, a.k.a. 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.
Workaround ========== Avoiding the use of persistent grants will avoid the vulnerability. This can be achieved by passing the "feature_persistent=0" module option to the xen-blkback driver.