can: j1939: j1939_sk_init(): set SOCK_RCU_FREE to call sk_destruct() after RCU is...

Set SOCK_RCU_FREE to let RCU to call sk_destruct() on completion.
Without this patch, we will run in to j1939_can_recv() after priv was
freed by j1939_sk_release()->j1939_sk_sock_destruct()

Fixes: 25fe97cb7620 ("can: j1939: move j1939_priv_put() into sk_destruct callback")
Link: https://lore.kernel.org/r/20210617130623.12705-1-o.rempel@pengutronix.de
Cc: linux-stable <stable@vger.kernel.org>
Reported-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Reported-by: syzbot+bdf710cfc41c186fdff3@syzkaller.appspotmail.com
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

diff --git a/net/can/j1939/main.c b/net/can/j1939/main.c
index da3a7a7..08c8606 100644 (file)
--- a/net/can/j1939/main.c
+++ b/net/can/j1939/main.c
@@ -193,6 +193,10 @@ static void j1939_can_rx_unregister(struct j1939_priv *priv)
        can_rx_unregister(dev_net(ndev), ndev, J1939_CAN_ID, J1939_CAN_MASK,
                          j1939_can_recv, priv);
 
+       /* The last reference of priv is dropped by the RCU deferred
+        * j1939_sk_sock_destruct() of the last socket, so we can
+        * safely drop this reference here.
+        */
        j1939_priv_put(priv);
 }
 

diff --git a/net/can/j1939/socket.c b/net/can/j1939/socket.c
index 56aa661..fce8bc8 100644 (file)
--- a/net/can/j1939/socket.c
+++ b/net/can/j1939/socket.c
@@ -398,6 +398,9 @@ static int j1939_sk_init(struct sock *sk)
        atomic_set(&jsk->skb_pending, 0);
        spin_lock_init(&jsk->sk_session_queue_lock);
        INIT_LIST_HEAD(&jsk->sk_session_queue);
+
+       /* j1939_sk_sock_destruct() depends on SOCK_RCU_FREE flag */
+       sock_set_flag(sk, SOCK_RCU_FREE);
        sk->sk_destruct = j1939_sk_sock_destruct;
        sk->sk_protocol = CAN_J1939;