[NETLINK]: Do precise netlink message allocations where possible

Account for the netlink message header size directly in nlmsg_new()
instead of relying on the caller calculate it correctly.

Replaces error handling of message construction functions when
constructing notifications with bug traps since a failure implies
a bug in calculating the size of the skb.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Acked-by: Paul Moore <paul.moore@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/netlabel/netlabel_mgmt.c b/net/netlabel/netlabel_mgmt.c
index 53c9079a..c529622 100644
--- a/net/netlabel/netlabel_mgmt.c
+++ b/net/netlabel/netlabel_mgmt.c
@@ -356,7 +356,7 @@
 	void *data;
 	struct netlbl_dom_map *entry;
 
-	ans_skb = nlmsg_new(NLMSG_GOODSIZE, GFP_KERNEL);
+	ans_skb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
 	if (ans_skb == NULL)
 		return -ENOMEM;
 	data = netlbl_netlink_hdr_put(ans_skb,
@@ -492,7 +492,7 @@
 	struct sk_buff *ans_skb = NULL;
 	void *data;
 
-	ans_skb = nlmsg_new(NLMSG_GOODSIZE, GFP_KERNEL);
+	ans_skb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
 	if (ans_skb == NULL)
 		return -ENOMEM;
 	data = netlbl_netlink_hdr_put(ans_skb,