[AX25]: UID fixes

 o Brown paperbag bug - ax25_findbyuid() was always returning a NULL pointer
   as the result.  Breaks ROSE completly and AX.25 if UID policy set to deny.

 o While the list structure of AX.25's UID to callsign mapping table was
   properly protected by a spinlock, it's elements were not refcounted
   resulting in a race between removal and usage of an element.

Signed-off-by: Ralf Baechle DL5RB <ralf@linux-mips.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ax25/ax25_route.c b/net/ax25/ax25_route.c
index 44b99b1f..c288526 100644
--- a/net/ax25/ax25_route.c
+++ b/net/ax25/ax25_route.c
@@ -422,8 +422,8 @@
  */
 int ax25_rt_autobind(ax25_cb *ax25, ax25_address *addr)
 {
+	ax25_uid_assoc *user;
 	ax25_route *ax25_rt;
-	ax25_address *call;
 	int err;
 
 	if ((ax25_rt = ax25_get_route(addr, NULL)) == NULL)
@@ -434,16 +434,18 @@
 		goto put;
 	}
 
-	if ((call = ax25_findbyuid(current->euid)) == NULL) {
+	user = ax25_findbyuid(current->euid);
+	if (user) {
+		ax25->source_addr = user->call;
+		ax25_uid_put(user);
+	} else {
 		if (ax25_uid_policy && !capable(CAP_NET_BIND_SERVICE)) {
 			err = -EPERM;
 			goto put;
 		}
-		call = (ax25_address *)ax25->ax25_dev->dev->dev_addr;
+		ax25->source_addr = *(ax25_address *)ax25->ax25_dev->dev->dev_addr;
 	}
 
-	ax25->source_addr = *call;
-
 	if (ax25_rt->digipeat != NULL) {
 		if ((ax25->digipeat = kmalloc(sizeof(ax25_digi), GFP_ATOMIC)) == NULL) {
 			err = -ENOMEM;