From: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxx
Cc: linux-stable <stable@xxxxxxxxxxxxxxx>
Reported-by: Thadeu Lima de Souza Cascardo <cascardo@xxxxxxxxxxxxx>
Reported-by: syzbot+bdf710cfc41c186fdff3@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>
Signed-off-by: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>
---
net/can/j1939/main.c | 4 ++++
net/can/j1939/socket.c | 3 +++
2 files changed, 7 insertions(+)
diff --git a/net/can/j1939/main.c b/net/can/j1939/main.c
index da3a7a7bcff2..08c8606cfd9c 100644
--- 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 56aa66147d5a..fce8bc8afeb7 100644
--- 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;
--
2.30.2
