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>

1 files changed, 21 insertions, 1 deletions

diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index 2c2eb1b629b1..3e2812aeceb7 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -266,6 +266,16 @@ struct net *get_net_ns_by_id(struct net *net, int id)
 	return peer;
 }
 
+static struct ucounts *inc_net_namespaces(struct user_namespace *ns)
+{
+	return inc_ucount(ns, current_euid(), UCOUNT_NET_NAMESPACES);
+}
+
+static void dec_net_namespaces(struct ucounts *ucounts)
+{
+	dec_ucount(ucounts, UCOUNT_NET_NAMESPACES);
+}
+
 /*
  * setup_net runs the initializers for the network namespace object.
  */
@@ -351,19 +361,27 @@ void net_drop_ns(void *p)
 struct net *copy_net_ns(unsigned long flags,
 			struct user_namespace *user_ns, struct net *old_net)
 {
+	struct ucounts *ucounts;
 	struct net *net;
 	int rv;
 
 	if (!(flags & CLONE_NEWNET))
 		return get_net(old_net);
 
+	ucounts = inc_net_namespaces(user_ns);
+	if (!ucounts)
+		return ERR_PTR(-ENFILE);
+
 	net = net_alloc();
-	if (!net)
+	if (!net) {
+		dec_net_namespaces(ucounts);
 		return ERR_PTR(-ENOMEM);
+	}
 
 	get_user_ns(user_ns);
 
 	mutex_lock(&net_mutex);
+	net->ucounts = ucounts;
 	rv = setup_net(net, user_ns);
 	if (rv == 0) {
 		rtnl_lock();
@@ -372,6 +390,7 @@ struct net *copy_net_ns(unsigned long flags,
 	}
 	mutex_unlock(&net_mutex);
 	if (rv < 0) {
+		dec_net_namespaces(ucounts);
 		put_user_ns(user_ns);
 		net_drop_ns(net);
 		return ERR_PTR(rv);
@@ -444,6 +463,7 @@ static void cleanup_net(struct work_struct *work)
 	/* Finally it is safe to free my network namespace structure */
 	list_for_each_entry_safe(net, tmp, &net_exit_list, exit_list) {
 		list_del_init(&net->exit_list);
+		dec_net_namespaces(net->ucounts);
 		put_user_ns(net->user_ns);
 		net_drop_ns(net);
 	}