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

[Oleksij Rempel]

On Fri, Aug 05, 2022 at 06:02:16PM +0300, Fedor Pchelkin wrote:
> 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 at pengutronix.de>
> Signed-off-by: Fedor Pchelkin <pchelkin at ispras.ru>
> Signed-off-by: Alexey Khoroshilov <khoroshilov at ispras.ru>

Acked-by: Oleksij Rempel <o.rempel at pengutronix.de>

> ---
>  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
> 
> 
> 

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