CVE-2022-49295 nbd: call genl_unregister_family() first in nbd_cleanup()

In the Linux kernel, the following vulnerability has been resolved: nbd: call genlunregisterfamily first in nbdcleanup Otherwise there may be race between module removal and the handling of netlink command, which can lead to the oops as shown below: BUG: kernel NULL pointer dereference, address:...