ax25: Fix segfault after sock connection timeout

The ax.25 socket connection timed out & the sock struct has been
previously taken down ie. sock struct is now a NULL pointer. Checking
the sock_flag causes the segfault.  Check if the socket struct pointer
is NULL before checking sock_flag. This segfault is seen in
timed out netrom connections.

Please submit to -stable.

Signed-off-by: Basil Gunn <basil@pacabunga.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ax25/ax25_subr.c b/net/ax25/ax25_subr.c
index 4855d18a8511072b499043d1160ad1ff4b2f9f3e..038b109b2be70e8da91589a1bf3c82e73a3903ca 100644 (file)
--- a/net/ax25/ax25_subr.c
+++ b/net/ax25/ax25_subr.c
@@ -264,7 +264,7 @@ void ax25_disconnect(ax25_cb *ax25, int reason)
 {
        ax25_clear_queues(ax25);
 
-       if (!sock_flag(ax25->sk, SOCK_DESTROY))
+       if (!ax25->sk || !sock_flag(ax25->sk, SOCK_DESTROY))
                ax25_stop_heartbeat(ax25);
        ax25_stop_t1timer(ax25);
        ax25_stop_t2timer(ax25);