userns: make each net (net_ns) belong to a user_ns

The user namespace which creates a new network namespace owns that namespace and all resources created in it. This way we can target capability checks for privileged operations against network resources to the user_ns which created the network namespace in which the resource lives. Privilege to the user namespace which owns the network namespace, or any parent user namespace thereof, provides the same privilege to the network resource. This patch is reworked from a version originally by Serge E. Hallyn <[email protected]> Acked-by: Serge Hallyn <[email protected]> Signed-off-by: Eric W. Biederman <[email protected]>
klaby · Nov 19, 2012 · 038e733 · 038e733
1 parent d727abc
commit 038e733
Show file tree

Hide file tree

Showing 3 changed files with 20 additions and 7 deletions.
diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
@@ -23,6 +23,7 @@
 #endif
 #include <net/netns/xfrm.h>
 
+struct user_namespace;
 struct proc_dir_entry;
 struct net_device;
 struct sock;
@@ -53,6 +54,8 @@ struct net {
 	struct list_head	cleanup_list;	/* namespaces on death row */
 	struct list_head	exit_list;	/* Use only net_mutex */
 
+	struct user_namespace   *user_ns;	/* Owning user namespace */
+
 	struct proc_dir_entry 	*proc_net;
 	struct proc_dir_entry 	*proc_net_stat;
 
@@ -127,12 +130,14 @@ struct net {
 extern struct net init_net;
 
 #ifdef CONFIG_NET_NS
-extern struct net *copy_net_ns(unsigned long flags, struct net *net_ns);
+extern struct net *copy_net_ns(unsigned long flags,
+	struct user_namespace *user_ns, struct net *old_net);
 
 #else /* CONFIG_NET_NS */
 #include <linux/sched.h>
 #include <linux/nsproxy.h>
-static inline struct net *copy_net_ns(unsigned long flags, struct net *old_net)
+static inline struct net *copy_net_ns(unsigned long flags,
+	struct user_namespace *user_ns, struct net *old_net)
 {
 	if (flags & CLONE_NEWNET)
 		return ERR_PTR(-EINVAL);

diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
@@ -90,7 +90,7 @@ static struct nsproxy *create_new_namespaces(unsigned long flags,
 		goto out_pid;
 	}
 
-	new_nsp->net_ns = copy_net_ns(flags, tsk->nsproxy->net_ns);
+	new_nsp->net_ns = copy_net_ns(flags, task_cred_xxx(tsk, user_ns), tsk->nsproxy->net_ns);
 	if (IS_ERR(new_nsp->net_ns)) {
 		err = PTR_ERR(new_nsp->net_ns);
 		goto out_net;

diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
@@ -13,6 +13,7 @@
 #include <linux/proc_fs.h>
 #include <linux/file.h>
 #include <linux/export.h>
+#include <linux/user_namespace.h>
 #include <net/net_namespace.h>
 #include <net/netns/generic.h>
 
@@ -145,7 +146,7 @@ static void ops_free_list(const struct pernet_operations *ops,
 /*
  * setup_net runs the initializers for the network namespace object.
  */
-static __net_init int setup_net(struct net *net)
+static __net_init int setup_net(struct net *net, struct user_namespace *user_ns)
 {
 	/* Must be called with net_mutex held */
 	const struct pernet_operations *ops, *saved_ops;
@@ -155,6 +156,7 @@ static __net_init int setup_net(struct net *net)
 	atomic_set(&net->count, 1);
 	atomic_set(&net->passive, 1);
 	net->dev_base_seq = 1;
+	net->user_ns = user_ns;
 
 #ifdef NETNS_REFCNT_DEBUG
 	atomic_set(&net->use_count, 0);
@@ -232,7 +234,8 @@ void net_drop_ns(void *p)
 		net_free(ns);
 }
 
-struct net *copy_net_ns(unsigned long flags, struct net *old_net)
+struct net *copy_net_ns(unsigned long flags,
+			struct user_namespace *user_ns, struct net *old_net)
 {
 	struct net *net;
 	int rv;
@@ -243,15 +246,19 @@ struct net *copy_net_ns(unsigned long flags, struct net *old_net)
 	net = net_alloc();
 	if (!net)
 		return ERR_PTR(-ENOMEM);
+
+	get_user_ns(user_ns);
+
 	mutex_lock(&net_mutex);
-	rv = setup_net(net);
+	rv = setup_net(net, user_ns);
 	if (rv == 0) {
 		rtnl_lock();
 		list_add_tail_rcu(&net->list, &net_namespace_list);
 		rtnl_unlock();
 	}
 	mutex_unlock(&net_mutex);
 	if (rv < 0) {
+		put_user_ns(user_ns);
 		net_drop_ns(net);
 		return ERR_PTR(rv);
 	}
@@ -308,6 +315,7 @@ 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);
+		put_user_ns(net->user_ns);
 		net_drop_ns(net);
 	}
 }
@@ -395,7 +403,7 @@ static int __init net_ns_init(void)
 	rcu_assign_pointer(init_net.gen, ng);
 
 	mutex_lock(&net_mutex);
-	if (setup_net(&init_net))
+	if (setup_net(&init_net, &init_user_ns))
 		panic("Could not setup the initial network namespace");
 
 	rtnl_lock();