netdev - [PATCH net 4/4] can: j1939: transport: j1939_session_skb_drop_old(): spin_unlock_irqrestore() before kfree

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Message-Id: <20221027114356.1939821-5-mkl@pengutronix.de>
Date:   Thu, 27 Oct 2022 13:43:56 +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, Yang Yingliang <yangyingliang@...wei.com>,
        Oleksij Rempel <o.rempel@...gutronix.de>,
        stable@...r.kernel.org, Marc Kleine-Budde <mkl@...gutronix.de>
Subject: [PATCH net 4/4] can: j1939: transport: j1939_session_skb_drop_old(): spin_unlock_irqrestore() before kfree_skb()

From: Yang Yingliang <yangyingliang@...wei.com>

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: 9d71dd0c7009 ("can: add support of SAE J1939 protocol")
Signed-off-by: Yang Yingliang <yangyingliang@...wei.com>
Acked-by: Oleksij Rempel <o.rempel@...gutronix.de>
Link: https://lore.kernel.org/all/20221027091237.2290111-1-yangyingliang@huawei.com
Cc: stable@...r.kernel.org
[mkl: adjust subject]
Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
---
 net/can/j1939/transport.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/can/j1939/transport.c b/net/can/j1939/transport.c
index d7d86c944d76..55f29c9f9e08 100644
--- a/net/can/j1939/transport.c
+++ b/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,
-- 
2.35.1