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    Subject[PATCH 4.9 024/212] net/x25: Fix x25_neigh refcnt leak when x25 disconnect
    Date
    From: Xiyu Yang <xiyuyang19@fudan.edu.cn>

    commit 4becb7ee5b3d2829ed7b9261a245a77d5b7de902 upstream.

    x25_connect() invokes x25_get_neigh(), which returns a reference of the
    specified x25_neigh object to "x25->neighbour" with increased refcnt.

    When x25 connect success and returns, the reference still be hold by
    "x25->neighbour", so the refcount should be decreased in
    x25_disconnect() to keep refcount balanced.

    The reference counting issue happens in x25_disconnect(), which forgets
    to decrease the refcnt increased by x25_get_neigh() in x25_connect(),
    causing a refcnt leak.

    Fix this issue by calling x25_neigh_put() before x25_disconnect()
    returns.

    Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
    Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    net/x25/x25_subr.c | 4 ++++
    1 file changed, 4 insertions(+)

    --- a/net/x25/x25_subr.c
    +++ b/net/x25/x25_subr.c
    @@ -368,6 +368,10 @@ void x25_disconnect(struct sock *sk, int
    sk->sk_state_change(sk);
    sock_set_flag(sk, SOCK_DEAD);
    }
    + read_lock_bh(&x25_list_lock);
    + x25_neigh_put(x25->neighbour);
    + x25->neighbour = NULL;
    + read_unlock_bh(&x25_list_lock);
    }

    /*

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