netdev - [PATCH v1] can: j1939: j1939_sk_init(): set SOCK_RCU_FREE to call sk

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Date:   Thu, 17 Jun 2021 15:06:23 +0200
From:   Oleksij Rempel <o.rempel@...gutronix.de>
To:     mkl@...gutronix.de, "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Oliver Hartkopp <socketcan@...tkopp.net>,
        Robin van der Gracht <robin@...tonic.nl>
Cc:     Oleksij Rempel <o.rempel@...gutronix.de>,
        Thadeu Lima de Souza Cascardo <cascardo@...onical.com>,
        syzbot+bdf710cfc41c186fdff3@...kaller.appspotmail.com,
        kernel@...gutronix.de, linux-can@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v1] can: j1939: j1939_sk_init(): set SOCK_RCU_FREE to call sk_destruct() after RCU is done

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()

Reported-by: Thadeu Lima de Souza Cascardo <cascardo@...onical.com>
Reported-by: syzbot+bdf710cfc41c186fdff3@...kaller.appspotmail.com
Fixes: 25fe97cb7620 ("can: j1939: move j1939_priv_put() into sk_destruct callback")
Signed-off-by: Oleksij Rempel <o.rempel@...gutronix.de>
---
 net/can/j1939/socket.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/can/j1939/socket.c b/net/can/j1939/socket.c
index 56aa66147d5a..c7c1b4d4c0fb 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);
+
+	sock_set_flag(sk, SOCK_RCU_FREE);
+	/* j1939_sk_sock_destruct() depends on SOCK_RCU_FREE flag */
 	sk->sk_destruct = j1939_sk_sock_destruct;
 	sk->sk_protocol = CAN_J1939;
 
-- 
2.29.2