can: j1939: j1939_session_destroy(): fix memory leak of skbs

stable inclusion
from stable-v5.10.138
commit a220ff343396bae8d3b6abee72ab51f1f34b3027
category: bugfix
bugzilla: 187869, https://gitee.com/src-openeuler/kernel/issues/I5X3MU
CVE: CVE-2022-3633

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a220ff343396bae8d3b6abee72ab51f1f34b3027

--------------------------------

commit 8c21c54a upstream.

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: 9d71dd0c ("can: add support of SAE J1939 protocol")
Suggested-by: NOleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: NFedor Pchelkin <pchelkin@ispras.ru>
Signed-off-by: NAlexey Khoroshilov <khoroshilov@ispras.ru>
Acked-by: NOleksij Rempel <o.rempel@pengutronix.de>
Link: https://lore.kernel.org/all/20220805150216.66313-1-pchelkin@ispras.ruSigned-off-by: NMarc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NDong Chenchen <dongchenchen2@huawei.com>
Reviewed-by: NYue Haibing <yuehaibing@huawei.com>
Reviewed-by: NXiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

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->err)
 		j1939_sk_errqueue(session, J1939_ERRQUEUE_ABORT);
 	else
@@ -270,7 +272,11 @@ 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);