can: j1939: transport: j1939_session_skb_drop_old(): spin_unlock_irqrestore() before kfree_skb()

It is not allowed to call kfree_skb() from hardware interrupt context
or with interrupts being disabled. The skb is unlinked from the queue,
so it can be freed after spin_unlock_irqrestore().

Fixes: 9d71dd0c ("can: add support of SAE J1939 protocol")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Acked-by: Oleksij Rempel <o.rempel@pengutronix.de>
Link: https://lore.kernel.org/all/20221027091237.2290111-1-yangyingliang@huawei.com
Cc: stable@vger.kernel.org
[mkl: adjust subject]
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

net/can/j1939/transport.c

@@ -342,10 +342,12 @@ static void j1939_session_skb_drop_old(struct j1939_session *session)
 		__skb_unlink(do_skb, &session->skb_queue);
 		/* drop ref taken in j1939_session_skb_queue() */
 		skb_unref(do_skb);
+		spin_unlock_irqrestore(&session->skb_queue.lock, flags);
 
 		kfree_skb(do_skb);
+	} else {
+		spin_unlock_irqrestore(&session->skb_queue.lock, flags);
 	}
-	spin_unlock_irqrestore(&session->skb_queue.lock, flags);
 }
 
 void j1939_session_skb_queue(struct j1939_session *session,