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    Subject[PATCH 4.19 17/91] net: x25: Increase refcnt of "struct x25_neigh" in x25_rx_call_request
    Date
    From: Xie He <xie.he.0141@gmail.com>

    [ Upstream commit 4ee18c179e5e815fa5575e0d2db0c05795a804ee ]

    The x25_disconnect function in x25_subr.c would decrease the refcount of
    "x25->neighbour" (struct x25_neigh) and reset this pointer to NULL.

    However, the x25_rx_call_request function in af_x25.c, which is called
    when we receive a connection request, does not increase the refcount when
    it assigns the pointer.

    Fix this issue by increasing the refcount of "struct x25_neigh" in
    x25_rx_call_request.

    This patch fixes frequent kernel crashes when using AF_X25 sockets.

    Fixes: 4becb7ee5b3d ("net/x25: Fix x25_neigh refcnt leak when x25 disconnect")
    Cc: Martin Schiller <ms@dev.tdt.de>
    Signed-off-by: Xie He <xie.he.0141@gmail.com>
    Link: https://lore.kernel.org/r/20201112103506.5875-1-xie.he.0141@gmail.com
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/x25/af_x25.c | 1 +
    1 file changed, 1 insertion(+)

    --- a/net/x25/af_x25.c
    +++ b/net/x25/af_x25.c
    @@ -1049,6 +1049,7 @@ int x25_rx_call_request(struct sk_buff *
    makex25->lci = lci;
    makex25->dest_addr = dest_addr;
    makex25->source_addr = source_addr;
    + x25_neigh_hold(nb);
    makex25->neighbour = nb;
    makex25->facilities = facilities;
    makex25->dte_facilities= dte_facilities;

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