netns: Add a limit on the number of net namespaces

Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index 0933c74..fc4f757 100644
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -60,6 +60,7 @@
 	struct list_head	exit_list;	/* Use only net_mutex */
 
 	struct user_namespace   *user_ns;	/* Owning user namespace */
+	struct ucounts		*ucounts;
 	spinlock_t		nsid_lock;
 	struct idr		netns_ids;