can: j1939: add missing calls in NETDEV_UNREGISTER notification handler

jira KERNEL-311
cve CVE-2025-39925
Rebuild_History Non-Buildable kernel-5.14.0-611.13.1.el9_7
commit-author Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
commit 93a27b5

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 <penguin-kernel@I-love.SAKURA.ne.jp>
	Tested-by: Oleksij Rempel <o.rempel@pengutronix.de>
	Acked-by: Oleksij Rempel <o.rempel@pengutronix.de>
Link: https://patch.msgid.link/3ad3c7f8-5a74-4b07-a193-cb0725823558@I-love.SAKURA.ne.jp
	Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
(cherry picked from commit 93a27b5)
	Signed-off-by: Jonathan Maple <jmaple@ciq.com>

Author: PlaidCat

net/can/j1939/main.c

@@ -382,6 +382,8 @@ 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;
 	}