tipc: Fix skb_under_panic when configuring TIPC without privileges

This patch prevents a TIPC configuration command requiring network
administrator privileges from triggering an skbuff underrun if it
is issued by a process lacking those privileges.  The revised error
handling code avoids the use of a potentially uninitialized global
variable by transforming the unauthorized command into a new command,
then following the standard command processing path to generate the
required error message.

Signed-off-by: Allan Stephens <allan.stephens@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tipc/config.c

@@ -2,7 +2,7 @@
  * net/tipc/config.c: TIPC configuration management code
  *
  * Copyright (c) 2002-2006, Ericsson AB
- * Copyright (c) 2004-2006, Wind River Systems
+ * Copyright (c) 2004-2007, Wind River Systems
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -602,6 +602,10 @@ struct sk_buff *tipc_cfg_do_cmd(u32 orig_node, u16 cmd, const void *request_area
 	case TIPC_CMD_GET_NETID:
 		rep_tlv_buf = tipc_cfg_reply_unsigned(tipc_net_id);
 		break;
+	case TIPC_CMD_NOT_NET_ADMIN:
+		rep_tlv_buf =
+			tipc_cfg_reply_error_string(TIPC_CFG_NOT_NET_ADMIN);
+		break;
 	default:
 		rep_tlv_buf = tipc_cfg_reply_error_string(TIPC_CFG_NOT_SUPPORTED
 							  " (unknown command)");