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    Subject[PATCH 5.4 034/348] can: j1939: j1939_sk_init(): set SOCK_RCU_FREE to call sk_destruct() after RCU is done
    Date
    From: Oleksij Rempel <o.rempel@pengutronix.de>

    commit 22c696fed25c63c7f67508309820358b94a96b6d upstream.

    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>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    net/can/j1939/main.c | 4 ++++
    net/can/j1939/socket.c | 3 +++
    2 files changed, 7 insertions(+)

    --- a/net/can/j1939/main.c
    +++ b/net/can/j1939/main.c
    @@ -193,6 +193,10 @@ static void j1939_can_rx_unregister(stru
    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);
    }

    --- 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;


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