netdev - [PATCH net 10/10] can: j1939: add missing calls in NETDEV

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Message-ID: <20251014122140.990472-11-mkl@pengutronix.de>
Date: Tue, 14 Oct 2025 14:17:57 +0200
From: Marc Kleine-Budde <mkl@...gutronix.de>
To: netdev@...r.kernel.org
Cc: davem@...emloft.net,
	kuba@...nel.org,
	linux-can@...r.kernel.org,
	kernel@...gutronix.de,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	Oleksij Rempel <o.rempel@...gutronix.de>,
	Marc Kleine-Budde <mkl@...gutronix.de>
Subject: [PATCH net 10/10] can: j1939: add missing calls in NETDEV_UNREGISTER notification handler

From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>

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: 7fcbe5b2c6a4 ("can: j1939: implement NETDEV_UNREGISTER notification handler")
Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Tested-by: Oleksij Rempel <o.rempel@...gutronix.de>
Acked-by: Oleksij Rempel <o.rempel@...gutronix.de>
Link: https://patch.msgid.link/3ad3c7f8-5a74-4b07-a193-cb0725823558@I-love.SAKURA.ne.jp
Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
---
 net/can/j1939/main.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/can/j1939/main.c b/net/can/j1939/main.c
index 3706a872ecaf..a93af55df5fd 100644
--- a/net/can/j1939/main.c
+++ b/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;
 	}
-- 
2.51.0