can: j1939: add missing calls in NETDEV_UNREGISTER notification handler

Currently NETDEV_UNREGISTER event handler is not calling
j1939_cancel_active_session() and j1939_sk_queue_drop_all().
This will result in these calls being skipped when j1939_sk_release() is
called. And I guess that the reason syzbot is still reporting

  unregister_netdevice: waiting for vcan0 to become free. Usage count = 2

is caused by lack of these calls.

Calling j1939_cancel_active_session(priv, sk) from j1939_sk_release() can
be covered by calling j1939_cancel_active_session(priv, NULL) from
j1939_netdev_notify().

Calling j1939_sk_queue_drop_all() from j1939_sk_release() can be covered
by calling j1939_sk_netdev_event_netdown() from j1939_netdev_notify().

Therefore, we can reuse j1939_cancel_active_session(priv, NULL) and
j1939_sk_netdev_event_netdown(priv) for NETDEV_UNREGISTER event handler.

Fixes: 7fcbe5b ("can: j1939: implement NETDEV_UNREGISTER notification handler")
Signed-off-by: Tetsuo Handa <[email protected]>
Tested-by: Oleksij Rempel <[email protected]>
Acked-by: Oleksij Rempel <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Marc Kleine-Budde <[email protected]>

Author: Tetsuo Handa

net/can/j1939/main.c

@@ -378,6 +378,8 @@ static int j1939_netdev_notify(struct notifier_block *nb,
 		j1939_ecu_unmap_all(priv);
 		break;
 	case NETDEV_UNREGISTER:
+		j1939_cancel_active_session(priv, NULL);
+		j1939_sk_netdev_event_netdown(priv);
 		j1939_sk_netdev_event_unregister(priv);
 		break;
 	}