netdev - [PATCH net 15/15] can: j1939: j1939_session

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Message-ID: <20241202090040.1110280-16-mkl@pengutronix.de>
Date: Mon,  2 Dec 2024 09:55:49 +0100
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,
	Dmitry Antipov <dmantipov@...dex.ru>,
	syzbot+d4e8dc385d9258220c31@...kaller.appspotmail.com,
	Oleksij Rempel <o.rempel@...gutronix.de>,
	Marc Kleine-Budde <mkl@...gutronix.de>
Subject: [PATCH net 15/15] can: j1939: j1939_session_new(): fix skb reference counting

From: Dmitry Antipov <dmantipov@...dex.ru>

Since j1939_session_skb_queue() does an extra skb_get() for each new
skb, do the same for the initial one in j1939_session_new() to avoid
refcount underflow.

Reported-by: syzbot+d4e8dc385d9258220c31@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=d4e8dc385d9258220c31
Fixes: 9d71dd0c7009 ("can: add support of SAE J1939 protocol")
Signed-off-by: Dmitry Antipov <dmantipov@...dex.ru>
Tested-by: Oleksij Rempel <o.rempel@...gutronix.de>
Acked-by: Oleksij Rempel <o.rempel@...gutronix.de>
Link: https://patch.msgid.link/20241105094823.2403806-1-dmantipov@yandex.ru
[mkl: clean up commit message]
Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
---
 net/can/j1939/transport.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/can/j1939/transport.c b/net/can/j1939/transport.c
index 319f47df3330..95f7a7e65a73 100644
--- a/net/can/j1939/transport.c
+++ b/net/can/j1939/transport.c
@@ -1505,7 +1505,7 @@ static struct j1939_session *j1939_session_new(struct j1939_priv *priv,
 	session->state = J1939_SESSION_NEW;
 
 	skb_queue_head_init(&session->skb_queue);
-	skb_queue_tail(&session->skb_queue, skb);
+	skb_queue_tail(&session->skb_queue, skb_get(skb));
 
 	skcb = j1939_skb_to_cb(skb);
 	memcpy(&session->skcb, skcb, sizeof(session->skcb));
-- 
2.45.2