CVE-2025-40343: nvmet-fc: avoid scheduling association deletion twice

In the Linux kernel, the following vulnerability has been resolved:

nvmet-fc: avoid scheduling association deletion twice

When forcefully shutting down a port via the configfs interface, nvmetportsubsysdroplink() first calls nvmetportdelctrls() and then nvmetdisableport(). Both functions will eventually schedule all remaining associations for deletion.

The current implementation checks whether an association is about to be removed, but only after the work item has already been scheduled. As a result, it is possible for the first scheduled work item to free all resources, and then for the same work item to be scheduled again for deletion.

Because the association list is an RCU list, it is not possible to take a lock and remove the list entry directly, so it cannot be looked up again. Instead, a flag (terminating) must be used to determine whether the association is already in the process of being deleted.