can: j1939: j1939_session_destroy(): 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.

V1: https://lore.kernel.org/all/20220708175949.539064-1-pchelkin@ispras.ru

Fixes: 9d71dd0c7009 ("can: add support of SAE J1939 protocol")
Suggested-by: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Acked-by: Oleksij Rempel <o.rempel@pengutronix.de>
Link: https://lore.kernel.org/all/20220805150216.66313-1-pchelkin@ispras.ru
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

diff --git a/net/can/j1939/transport.c b/net/can/j1939/transport.c
index 307ee11..d7d86c9 100644 (file)
--- 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);