CVE-2026-43249 9p/xen: protect xen_9pfs_front_free against concurrent calls

In the Linux kernel, the following vulnerability has been resolved: 9p/xen: protect xen9pfsfrontfree against concurrent calls The xenwatch thread can race with other back-end change notifications and call xen9pfsfrontfree twice, hitting the observed general protection fault due to a double-free...