netdev - [PATCH] can: j1939: fix memory leak of skbs

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Date:   Fri,  5 Aug 2022 18:02:16 +0300
From:   Fedor Pchelkin <pchelkin@...ras.ru>
To:     Oleksij Rempel <o.rempel@...gutronix.de>,
        Robin van der Gracht <robin@...tonic.nl>
Cc:     Fedor Pchelkin <pchelkin@...ras.ru>, kernel@...gutronix.de,
        Oliver Hartkopp <socketcan@...tkopp.net>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, linux-can@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        ldv-project@...uxtesting.org,
        Alexey Khoroshilov <khoroshilov@...ras.ru>
Subject: [PATCH] can: j1939: fix memory leak of skbs

We need to drop skb references taken in j1939_session_skb_queue() when
destroying a session in j1939_session_destroy(). Otherwise those skbs
would be lost.

Link to Syzkaller info and repro: https://forge.ispras.ru/issues/11743.

Found by Linux Verification Center (linuxtesting.org) with Syzkaller.

Fixes: 9d71dd0c7009 ("can: add support of SAE J1939 protocol")
Suggested-by: Oleksij Rempel <o.rempel@...gutronix.de>
Signed-off-by: Fedor Pchelkin <pchelkin@...ras.ru>
Signed-off-by: Alexey Khoroshilov <khoroshilov@...ras.ru>
---
 net/can/j1939/transport.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/net/can/j1939/transport.c b/net/can/j1939/transport.c
index 307ee1174a6e..d7d86c944d76 100644
--- a/net/can/j1939/transport.c
+++ b/net/can/j1939/transport.c
@@ -260,6 +260,8 @@ static void __j1939_session_drop(struct j1939_session *session)
 
 static void j1939_session_destroy(struct j1939_session *session)
 {
+	struct sk_buff *skb;
+
 	if (session->transmission) {
 		if (session->err)
 			j1939_sk_errqueue(session, J1939_ERRQUEUE_TX_ABORT);
@@ -274,7 +276,11 @@ static void j1939_session_destroy(struct j1939_session *session)
 	WARN_ON_ONCE(!list_empty(&session->sk_session_queue_entry));
 	WARN_ON_ONCE(!list_empty(&session->active_session_list_entry));
 
-	skb_queue_purge(&session->skb_queue);
+	while ((skb = skb_dequeue(&session->skb_queue)) != NULL) {
+		/* drop ref taken in j1939_session_skb_queue() */
+		skb_unref(skb);
+		kfree_skb(skb);
+	}
 	__j1939_session_drop(session);
 	j1939_priv_put(session->priv);
 	kfree(session);
-- 
2.25.1