kernel: can: j1939: implement NETDEV_UNREGISTER notification handler

A flaw was discovered in the J1939 protocol implementation in the Linux kernel. The NETDEVUNREGISTER notification handler was missing for undoing changes performed by j1939skbind. As a result, an extra reference remains on the j1939priv structure when unregistering a network device, preventing it...

CVE-2025-39925 can: j1939: implement NETDEV_UNREGISTER notification handler

In the Linux kernel, the following vulnerability has been resolved: can: j1939: implement NETDEVUNREGISTER notification handler syzbot is reporting unregisternetdevice: waiting for vcan0 to become free. Usage count = 2 problem, for j1939 protocol did not have NETDEVUNREGISTER notification handler...