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    Subject[PATCH 4.19 059/131] net: netrom: Fix potential nr_neigh refcnt leak in nr_add_node
    Date
    From: Xiyu Yang <xiyuyang19@fudan.edu.cn>

    [ Upstream commit d03f228470a8c0a22b774d1f8d47071e0de4f6dd ]

    nr_add_node() invokes nr_neigh_get_dev(), which returns a local
    reference of the nr_neigh object to "nr_neigh" with increased refcnt.

    When nr_add_node() returns, "nr_neigh" becomes invalid, so the refcount
    should be decreased to keep refcount balanced.

    The issue happens in one normal path of nr_add_node(), which forgets to
    decrease the refcnt increased by nr_neigh_get_dev() and causes a refcnt
    leak. It should decrease the refcnt before the function returns like
    other normal paths do.

    Fix this issue by calling nr_neigh_put() before the nr_add_node()
    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/netrom/nr_route.c | 1 +
    1 file changed, 1 insertion(+)

    --- a/net/netrom/nr_route.c
    +++ b/net/netrom/nr_route.c
    @@ -211,6 +211,7 @@ static int __must_check nr_add_node(ax25
    /* refcount initialized at 1 */
    spin_unlock_bh(&nr_node_list_lock);

    + nr_neigh_put(nr_neigh);
    return 0;
    }
    nr_node_lock(nr_node);

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