1 files changed, 1061 insertions, 188 deletions

diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index f97652036754..a6e6a964a287 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-only
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
 #include <linux/workqueue.h>
@@ -15,6 +16,15 @@
 #include <linux/file.h>
 #include <linux/export.h>
 #include <linux/user_namespace.h>
+#include <linux/net_namespace.h>
+#include <linux/sched/task.h>
+#include <linux/uidgid.h>
+#include <linux/proc_fs.h>
+#include <linux/nstree.h>
+
+#include <net/aligned_data.h>
+#include <net/sock.h>
+#include <net/netlink.h>
 #include <net/net_namespace.h>
 #include <net/netns/generic.h>
 
@@ -24,47 +34,67 @@
 
 static LIST_HEAD(pernet_list);
 static struct list_head *first_device = &pernet_list;
-static DEFINE_MUTEX(net_mutex);
 
 LIST_HEAD(net_namespace_list);
 EXPORT_SYMBOL_GPL(net_namespace_list);
 
-struct net init_net = {
-	.dev_base_head = LIST_HEAD_INIT(init_net.dev_base_head),
-};
+/* Protects net_namespace_list. Nests iside rtnl_lock() */
+DECLARE_RWSEM(net_rwsem);
+EXPORT_SYMBOL_GPL(net_rwsem);
+
+#ifdef CONFIG_KEYS
+static struct key_tag init_net_key_domain = { .usage = REFCOUNT_INIT(1) };
+#endif
+
+struct net init_net;
 EXPORT_SYMBOL(init_net);
 
+static bool init_net_initialized;
+/*
+ * pernet_ops_rwsem: protects: pernet_list, net_generic_ids,
+ * init_net_initialized and first_device pointer.
+ * This is internal net namespace object. Please, don't use it
+ * outside.
+ */
+DECLARE_RWSEM(pernet_ops_rwsem);
+
+#define MIN_PERNET_OPS_ID	\
+	((sizeof(struct net_generic) + sizeof(void *) - 1) / sizeof(void *))
+
 #define INITIAL_NET_GEN_PTRS	13 /* +1 for len +2 for rcu_head */
 
 static unsigned int max_gen_ptrs = INITIAL_NET_GEN_PTRS;
 
 static struct net_generic *net_alloc_generic(void)
 {
+	unsigned int gen_ptrs = READ_ONCE(max_gen_ptrs);
+	unsigned int generic_size;
 	struct net_generic *ng;
-	size_t generic_size = offsetof(struct net_generic, ptr[max_gen_ptrs]);
+
+	generic_size = offsetof(struct net_generic, ptr[gen_ptrs]);
 
 	ng = kzalloc(generic_size, GFP_KERNEL);
 	if (ng)
-		ng->len = max_gen_ptrs;
+		ng->s.len = gen_ptrs;
 
 	return ng;
 }
 
-static int net_assign_generic(struct net *net, int id, void *data)
+static int net_assign_generic(struct net *net, unsigned int id, void *data)
 {
 	struct net_generic *ng, *old_ng;
 
-	BUG_ON(!mutex_is_locked(&net_mutex));
-	BUG_ON(id == 0);
+	BUG_ON(id < MIN_PERNET_OPS_ID);
 
 	old_ng = rcu_dereference_protected(net->gen,
-					   lockdep_is_held(&net_mutex));
-	ng = old_ng;
-	if (old_ng->len >= id)
-		goto assign;
+					   lockdep_is_held(&pernet_ops_rwsem));
+	if (old_ng->s.len > id) {
+		old_ng->ptr[id] = data;
+		return 0;
+	}
 
 	ng = net_alloc_generic();
-	if (ng == NULL)
+	if (!ng)
 		return -ENOMEM;
 
 	/*
@@ -78,21 +108,22 @@ static int net_assign_generic(struct net *net, int id, void *data)
 	 * the old copy for kfree after a grace period.
 	 */
 
-	memcpy(&ng->ptr, &old_ng->ptr, old_ng->len * sizeof(void*));
+	memcpy(&ng->ptr[MIN_PERNET_OPS_ID], &old_ng->ptr[MIN_PERNET_OPS_ID],
+	       (old_ng->s.len - MIN_PERNET_OPS_ID) * sizeof(void *));
+	ng->ptr[id] = data;
 
 	rcu_assign_pointer(net->gen, ng);
-	kfree_rcu(old_ng, rcu);
-assign:
-	ng->ptr[id - 1] = data;
+	kfree_rcu(old_ng, s.rcu);
 	return 0;
 }
 
 static int ops_init(const struct pernet_operations *ops, struct net *net)
 {
+	struct net_generic *ng;
 	int err = -ENOMEM;
 	void *data = NULL;
 
-	if (ops->id && ops->size) {
+	if (ops->id) {
 		data = kzalloc(ops->size, GFP_KERNEL);
 		if (!data)
 			goto out;
@@ -107,6 +138,12 @@ static int ops_init(const struct pernet_operations *ops, struct net *net)
 	if (!err)
 		return 0;
 
+	if (ops->id) {
+		ng = rcu_dereference_protected(net->gen,
+					       lockdep_is_held(&pernet_ops_rwsem));
+		ng->ptr[*ops->id] = NULL;
+	}
+
 cleanup:
 	kfree(data);
 
@@ -114,22 +151,56 @@ out:
 	return err;
 }
 
-static void ops_free(const struct pernet_operations *ops, struct net *net)
+static void ops_pre_exit_list(const struct pernet_operations *ops,
+			      struct list_head *net_exit_list)
 {
-	if (ops->id && ops->size) {
-		int id = *ops->id;
-		kfree(net_generic(net, id));
+	struct net *net;
+
+	if (ops->pre_exit) {
+		list_for_each_entry(net, net_exit_list, exit_list)
+			ops->pre_exit(net);
 	}
 }
 
+static void ops_exit_rtnl_list(const struct list_head *ops_list,
+			       const struct pernet_operations *ops,
+			       struct list_head *net_exit_list)
+{
+	const struct pernet_operations *saved_ops = ops;
+	LIST_HEAD(dev_kill_list);
+	struct net *net;
+
+	rtnl_lock();
+
+	list_for_each_entry(net, net_exit_list, exit_list) {
+		__rtnl_net_lock(net);
+
+		ops = saved_ops;
+		list_for_each_entry_continue_reverse(ops, ops_list, list) {
+			if (ops->exit_rtnl)
+				ops->exit_rtnl(net, &dev_kill_list);
+		}
+
+		__rtnl_net_unlock(net);
+	}
+
+	unregister_netdevice_many(&dev_kill_list);
+
+	rtnl_unlock();
+}
+
 static void ops_exit_list(const struct pernet_operations *ops,
 			  struct list_head *net_exit_list)
 {
-	struct net *net;
 	if (ops->exit) {
-		list_for_each_entry(net, net_exit_list, exit_list)
+		struct net *net;
+
+		list_for_each_entry(net, net_exit_list, exit_list) {
 			ops->exit(net);
+			cond_resched();
+		}
 	}
+
 	if (ops->exit_batch)
 		ops->exit_batch(net_exit_list);
 }
@@ -138,36 +209,248 @@ static void ops_free_list(const struct pernet_operations *ops,
 			  struct list_head *net_exit_list)
 {
 	struct net *net;
-	if (ops->size && ops->id) {
+
+	if (ops->id) {
 		list_for_each_entry(net, net_exit_list, exit_list)
-			ops_free(ops, net);
+			kfree(net_generic(net, *ops->id));
 	}
 }
 
-/*
- * setup_net runs the initializers for the network namespace object.
+static void ops_undo_list(const struct list_head *ops_list,
+			  const struct pernet_operations *ops,
+			  struct list_head *net_exit_list,
+			  bool expedite_rcu)
+{
+	const struct pernet_operations *saved_ops;
+	bool hold_rtnl = false;
+
+	if (!ops)
+		ops = list_entry(ops_list, typeof(*ops), list);
+
+	saved_ops = ops;
+
+	list_for_each_entry_continue_reverse(ops, ops_list, list) {
+		hold_rtnl |= !!ops->exit_rtnl;
+		ops_pre_exit_list(ops, net_exit_list);
+	}
+
+	/* Another CPU might be rcu-iterating the list, wait for it.
+	 * This needs to be before calling the exit() notifiers, so the
+	 * rcu_barrier() after ops_undo_list() isn't sufficient alone.
+	 * Also the pre_exit() and exit() methods need this barrier.
+	 */
+	if (expedite_rcu)
+		synchronize_rcu_expedited();
+	else
+		synchronize_rcu();
+
+	if (hold_rtnl)
+		ops_exit_rtnl_list(ops_list, saved_ops, net_exit_list);
+
+	ops = saved_ops;
+	list_for_each_entry_continue_reverse(ops, ops_list, list)
+		ops_exit_list(ops, net_exit_list);
+
+	ops = saved_ops;
+	list_for_each_entry_continue_reverse(ops, ops_list, list)
+		ops_free_list(ops, net_exit_list);
+}
+
+static void ops_undo_single(struct pernet_operations *ops,
+			    struct list_head *net_exit_list)
+{
+	LIST_HEAD(ops_list);
+
+	list_add(&ops->list, &ops_list);
+	ops_undo_list(&ops_list, NULL, net_exit_list, false);
+	list_del(&ops->list);
+}
+
+/* should be called with nsid_lock held */
+static int alloc_netid(struct net *net, struct net *peer, int reqid)
+{
+	int min = 0, max = 0;
+
+	if (reqid >= 0) {
+		min = reqid;
+		max = reqid + 1;
+	}
+
+	return idr_alloc(&net->netns_ids, peer, min, max, GFP_ATOMIC);
+}
+
+/* This function is used by idr_for_each(). If net is equal to peer, the
+ * function returns the id so that idr_for_each() stops. Because we cannot
+ * returns the id 0 (idr_for_each() will not stop), we return the magic value
+ * NET_ID_ZERO (-1) for it.
  */
-static __net_init int setup_net(struct net *net, struct user_namespace *user_ns)
+#define NET_ID_ZERO -1
+static int net_eq_idr(int id, void *net, void *peer)
 {
-	/* Must be called with net_mutex held */
-	const struct pernet_operations *ops, *saved_ops;
-	int error = 0;
-	LIST_HEAD(net_exit_list);
+	if (net_eq(net, peer))
+		return id ? : NET_ID_ZERO;
+	return 0;
+}
+
+/* Must be called from RCU-critical section or with nsid_lock held */
+static int __peernet2id(const struct net *net, struct net *peer)
+{
+	int id = idr_for_each(&net->netns_ids, net_eq_idr, peer);
+
+	/* Magic value for id 0. */
+	if (id == NET_ID_ZERO)
+		return 0;
+	if (id > 0)
+		return id;
+
+	return NETNSA_NSID_NOT_ASSIGNED;
+}
+
+static void rtnl_net_notifyid(struct net *net, int cmd, int id, u32 portid,
+			      struct nlmsghdr *nlh, gfp_t gfp);
+/* This function returns the id of a peer netns. If no id is assigned, one will
+ * be allocated and returned.
+ */
+int peernet2id_alloc(struct net *net, struct net *peer, gfp_t gfp)
+{
+	int id;
+
+	if (!check_net(net))
+		return NETNSA_NSID_NOT_ASSIGNED;
+
+	spin_lock(&net->nsid_lock);
+	id = __peernet2id(net, peer);
+	if (id >= 0) {
+		spin_unlock(&net->nsid_lock);
+		return id;
+	}
+
+	/* When peer is obtained from RCU lists, we may race with
+	 * its cleanup. Check whether it's alive, and this guarantees
+	 * we never hash a peer back to net->netns_ids, after it has
+	 * just been idr_remove()'d from there in cleanup_net().
+	 */
+	if (!maybe_get_net(peer)) {
+		spin_unlock(&net->nsid_lock);
+		return NETNSA_NSID_NOT_ASSIGNED;
+	}
+
+	id = alloc_netid(net, peer, -1);
+	spin_unlock(&net->nsid_lock);
 
-	atomic_set(&net->count, 1);
-	atomic_set(&net->passive, 1);
+	put_net(peer);
+	if (id < 0)
+		return NETNSA_NSID_NOT_ASSIGNED;
+
+	rtnl_net_notifyid(net, RTM_NEWNSID, id, 0, NULL, gfp);
+
+	return id;
+}
+EXPORT_SYMBOL_GPL(peernet2id_alloc);
+
+/* This function returns, if assigned, the id of a peer netns. */
+int peernet2id(const struct net *net, struct net *peer)
+{
+	int id;
+
+	rcu_read_lock();
+	id = __peernet2id(net, peer);
+	rcu_read_unlock();
+
+	return id;
+}
+EXPORT_SYMBOL(peernet2id);
+
+/* This function returns true is the peer netns has an id assigned into the
+ * current netns.
+ */
+bool peernet_has_id(const struct net *net, struct net *peer)
+{
+	return peernet2id(net, peer) >= 0;
+}
+
+struct net *get_net_ns_by_id(const struct net *net, int id)
+{
+	struct net *peer;
+
+	if (id < 0)
+		return NULL;
+
+	rcu_read_lock();
+	peer = idr_find(&net->netns_ids, id);
+	if (peer)
+		peer = maybe_get_net(peer);
+	rcu_read_unlock();
+
+	return peer;
+}
+EXPORT_SYMBOL_GPL(get_net_ns_by_id);
+
+static __net_init void preinit_net_sysctl(struct net *net)
+{
+	net->core.sysctl_somaxconn = SOMAXCONN;
+	/* Limits per socket sk_omem_alloc usage.
+	 * TCP zerocopy regular usage needs 128 KB.
+	 */
+	net->core.sysctl_optmem_max = 128 * 1024;
+	net->core.sysctl_txrehash = SOCK_TXREHASH_ENABLED;
+	net->core.sysctl_tstamp_allow_data = 1;
+	net->core.sysctl_txq_reselection = msecs_to_jiffies(1000);
+}
+
+/* init code that must occur even if setup_net() is not called. */
+static __net_init int preinit_net(struct net *net, struct user_namespace *user_ns)
+{
+	int ret;
+
+	ret = ns_common_init(net);
+	if (ret)
+		return ret;
+
+	refcount_set(&net->passive, 1);
+	ref_tracker_dir_init(&net->refcnt_tracker, 128, "net_refcnt");
+	ref_tracker_dir_init(&net->notrefcnt_tracker, 128, "net_notrefcnt");
+
+	get_random_bytes(&net->hash_mix, sizeof(u32));
 	net->dev_base_seq = 1;
 	net->user_ns = user_ns;
 
-#ifdef NETNS_REFCNT_DEBUG
-	atomic_set(&net->use_count, 0);
+	idr_init(&net->netns_ids);
+	spin_lock_init(&net->nsid_lock);
+	mutex_init(&net->ipv4.ra_mutex);
+
+#ifdef CONFIG_DEBUG_NET_SMALL_RTNL
+	mutex_init(&net->rtnl_mutex);
+	lock_set_cmp_fn(&net->rtnl_mutex, rtnl_net_lock_cmp_fn, NULL);
 #endif
 
+	INIT_LIST_HEAD(&net->ptype_all);
+	INIT_LIST_HEAD(&net->ptype_specific);
+	preinit_net_sysctl(net);
+	return 0;
+}
+
+/*
+ * setup_net runs the initializers for the network namespace object.
+ */
+static __net_init int setup_net(struct net *net)
+{
+	/* Must be called with pernet_ops_rwsem held */
+	const struct pernet_operations *ops;
+	LIST_HEAD(net_exit_list);
+	int error = 0;
+
+	net->net_cookie = ns_tree_gen_id(net);
+
 	list_for_each_entry(ops, &pernet_list, list) {
 		error = ops_init(ops, net);
 		if (error < 0)
 			goto out_undo;
 	}
+	down_write(&net_rwsem);
+	list_add_tail_rcu(&net->list, &net_namespace_list);
+	up_write(&net_rwsem);
+	ns_tree_add_raw(net);
 out:
 	return error;
 
@@ -176,21 +459,23 @@ out_undo:
 	 * for the pernet modules whose init functions did not fail.
 	 */
 	list_add(&net->exit_list, &net_exit_list);
-	saved_ops = ops;
-	list_for_each_entry_continue_reverse(ops, &pernet_list, list)
-		ops_exit_list(ops, &net_exit_list);
-
-	ops = saved_ops;
-	list_for_each_entry_continue_reverse(ops, &pernet_list, list)
-		ops_free_list(ops, &net_exit_list);
-
+	ops_undo_list(&pernet_list, ops, &net_exit_list, false);
 	rcu_barrier();
 	goto out;
 }
 
-
 #ifdef CONFIG_NET_NS
-static struct kmem_cache *net_cachep;
+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);
+}
+
+static struct kmem_cache *net_cachep __ro_after_init;
 static struct workqueue_struct *netns_wq;
 
 static struct net *net_alloc(void)
@@ -206,160 +491,293 @@ static struct net *net_alloc(void)
 	if (!net)
 		goto out_free;
 
+#ifdef CONFIG_KEYS
+	net->key_domain = kzalloc(sizeof(struct key_tag), GFP_KERNEL);
+	if (!net->key_domain)
+		goto out_free_2;
+	refcount_set(&net->key_domain->usage, 1);
+#endif
+
 	rcu_assign_pointer(net->gen, ng);
 out:
 	return net;
 
+#ifdef CONFIG_KEYS
+out_free_2:
+	kmem_cache_free(net_cachep, net);
+	net = NULL;
+#endif
 out_free:
 	kfree(ng);
 	goto out;
 }
 
-static void net_free(struct net *net)
+static LLIST_HEAD(defer_free_list);
+
+static void net_complete_free(void)
 {
-#ifdef NETNS_REFCNT_DEBUG
-	if (unlikely(atomic_read(&net->use_count) != 0)) {
-		pr_emerg("network namespace not free! Usage: %d\n",
-			 atomic_read(&net->use_count));
-		return;
+	struct llist_node *kill_list;
+	struct net *net, *next;
+
+	/* Get the list of namespaces to free from last round. */
+	kill_list = llist_del_all(&defer_free_list);
+
+	llist_for_each_entry_safe(net, next, kill_list, defer_free_list)
+		kmem_cache_free(net_cachep, net);
+
+}
+
+void net_passive_dec(struct net *net)
+{
+	if (refcount_dec_and_test(&net->passive)) {
+		kfree(rcu_access_pointer(net->gen));
+
+		/* There should not be any trackers left there. */
+		ref_tracker_dir_exit(&net->notrefcnt_tracker);
+
+		/* Wait for an extra rcu_barrier() before final free. */
+		llist_add(&net->defer_free_list, &defer_free_list);
 	}
-#endif
-	kfree(net->gen);
-	kmem_cache_free(net_cachep, net);
 }
 
 void net_drop_ns(void *p)
 {
-	struct net *ns = p;
-	if (ns && atomic_dec_and_test(&ns->passive))
-		net_free(ns);
+	struct net *net = (struct net *)p;
+
+	if (net)
+		net_passive_dec(net);
 }
 
-struct net *copy_net_ns(unsigned long flags,
+struct net *copy_net_ns(u64 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(-ENOSPC);
+
 	net = net_alloc();
-	if (!net)
-		return ERR_PTR(-ENOMEM);
+	if (!net) {
+		rv = -ENOMEM;
+		goto dec_ucounts;
+	}
 
+	rv = preinit_net(net, user_ns);
+	if (rv < 0)
+		goto dec_ucounts;
+	net->ucounts = ucounts;
 	get_user_ns(user_ns);
 
-	mutex_lock(&net_mutex);
-	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);
+	rv = down_read_killable(&pernet_ops_rwsem);
+	if (rv < 0)
+		goto put_userns;
+
+	rv = setup_net(net);
+
+	up_read(&pernet_ops_rwsem);
+
 	if (rv < 0) {
+put_userns:
+		ns_common_free(net);
+#ifdef CONFIG_KEYS
+		key_remove_domain(net->key_domain);
+#endif
 		put_user_ns(user_ns);
-		net_drop_ns(net);
+		net_passive_dec(net);
+dec_ucounts:
+		dec_net_namespaces(ucounts);
 		return ERR_PTR(rv);
 	}
 	return net;
 }
 
-static DEFINE_SPINLOCK(cleanup_list_lock);
-static LIST_HEAD(cleanup_list);  /* Must hold cleanup_list_lock to touch */
+/**
+ * net_ns_get_ownership - get sysfs ownership data for @net
+ * @net: network namespace in question (can be NULL)
+ * @uid: kernel user ID for sysfs objects
+ * @gid: kernel group ID for sysfs objects
+ *
+ * Returns the uid/gid pair of root in the user namespace associated with the
+ * given network namespace.
+ */
+void net_ns_get_ownership(const struct net *net, kuid_t *uid, kgid_t *gid)
+{
+	if (net) {
+		kuid_t ns_root_uid = make_kuid(net->user_ns, 0);
+		kgid_t ns_root_gid = make_kgid(net->user_ns, 0);
+
+		if (uid_valid(ns_root_uid))
+			*uid = ns_root_uid;
+
+		if (gid_valid(ns_root_gid))
+			*gid = ns_root_gid;
+	} else {
+		*uid = GLOBAL_ROOT_UID;
+		*gid = GLOBAL_ROOT_GID;
+	}
+}
+EXPORT_SYMBOL_GPL(net_ns_get_ownership);
+
+static void unhash_nsid(struct net *net, struct net *last)
+{
+	struct net *tmp;
+	/* This function is only called from cleanup_net() work,
+	 * and this work is the only process, that may delete
+	 * a net from net_namespace_list. So, when the below
+	 * is executing, the list may only grow. Thus, we do not
+	 * use for_each_net_rcu() or net_rwsem.
+	 */
+	for_each_net(tmp) {
+		int id;
+
+		spin_lock(&tmp->nsid_lock);
+		id = __peernet2id(tmp, net);
+		if (id >= 0)
+			idr_remove(&tmp->netns_ids, id);
+		spin_unlock(&tmp->nsid_lock);
+		if (id >= 0)
+			rtnl_net_notifyid(tmp, RTM_DELNSID, id, 0, NULL,
+					  GFP_KERNEL);
+		if (tmp == last)
+			break;
+	}
+	spin_lock(&net->nsid_lock);
+	idr_destroy(&net->netns_ids);
+	spin_unlock(&net->nsid_lock);
+}
+
+static LLIST_HEAD(cleanup_list);
+
+struct task_struct *cleanup_net_task;
 
 static void cleanup_net(struct work_struct *work)
 {
-	const struct pernet_operations *ops;
-	struct net *net, *tmp;
-	LIST_HEAD(net_kill_list);
+	struct llist_node *net_kill_list;
+	struct net *net, *tmp, *last;
 	LIST_HEAD(net_exit_list);
 
+	WRITE_ONCE(cleanup_net_task, current);
+
 	/* Atomically snapshot the list of namespaces to cleanup */
-	spin_lock_irq(&cleanup_list_lock);
-	list_replace_init(&cleanup_list, &net_kill_list);
-	spin_unlock_irq(&cleanup_list_lock);
+	net_kill_list = llist_del_all(&cleanup_list);
 
-	mutex_lock(&net_mutex);
+	down_read(&pernet_ops_rwsem);
 
 	/* Don't let anyone else find us. */
-	rtnl_lock();
-	list_for_each_entry(net, &net_kill_list, cleanup_list) {
+	down_write(&net_rwsem);
+	llist_for_each_entry(net, net_kill_list, cleanup_list) {
+		ns_tree_remove(net);
 		list_del_rcu(&net->list);
-		list_add_tail(&net->exit_list, &net_exit_list);
 	}
-	rtnl_unlock();
-
-	/*
-	 * Another CPU might be rcu-iterating the list, wait for it.
-	 * This needs to be before calling the exit() notifiers, so
-	 * the rcu_barrier() below isn't sufficient alone.
+	/* Cache last net. After we unlock rtnl, no one new net
+	 * added to net_namespace_list can assign nsid pointer
+	 * to a net from net_kill_list (see peernet2id_alloc()).
+	 * So, we skip them in unhash_nsid().
+	 *
+	 * Note, that unhash_nsid() does not delete nsid links
+	 * between net_kill_list's nets, as they've already
+	 * deleted from net_namespace_list. But, this would be
+	 * useless anyway, as netns_ids are destroyed there.
 	 */
-	synchronize_rcu();
+	last = list_last_entry(&net_namespace_list, struct net, list);
+	up_write(&net_rwsem);
 
-	/* Run all of the network namespace exit methods */
-	list_for_each_entry_reverse(ops, &pernet_list, list)
-		ops_exit_list(ops, &net_exit_list);
+	llist_for_each_entry(net, net_kill_list, cleanup_list) {
+		unhash_nsid(net, last);
+		list_add_tail(&net->exit_list, &net_exit_list);
+	}
 
-	/* Free the net generic variables */
-	list_for_each_entry_reverse(ops, &pernet_list, list)
-		ops_free_list(ops, &net_exit_list);
+	ops_undo_list(&pernet_list, NULL, &net_exit_list, true);
 
-	mutex_unlock(&net_mutex);
+	up_read(&pernet_ops_rwsem);
 
 	/* Ensure there are no outstanding rcu callbacks using this
 	 * network namespace.
 	 */
 	rcu_barrier();
 
+	net_complete_free();
+
 	/* 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);
+		ns_common_free(net);
+		dec_net_namespaces(net->ucounts);
+#ifdef CONFIG_KEYS
+		key_remove_domain(net->key_domain);
+#endif
 		put_user_ns(net->user_ns);
-		net_drop_ns(net);
+		net_passive_dec(net);
 	}
+	WRITE_ONCE(cleanup_net_task, NULL);
 }
+
+/**
+ * net_ns_barrier - wait until concurrent net_cleanup_work is done
+ *
+ * cleanup_net runs from work queue and will first remove namespaces
+ * from the global list, then run net exit functions.
+ *
+ * Call this in module exit path to make sure that all netns
+ * ->exit ops have been invoked before the function is removed.
+ */
+void net_ns_barrier(void)
+{
+	down_write(&pernet_ops_rwsem);
+	up_write(&pernet_ops_rwsem);
+}
+EXPORT_SYMBOL(net_ns_barrier);
+
 static DECLARE_WORK(net_cleanup_work, cleanup_net);
 
 void __put_net(struct net *net)
 {
+	ref_tracker_dir_exit(&net->refcnt_tracker);
 	/* Cleanup the network namespace in process context */
-	unsigned long flags;
-
-	spin_lock_irqsave(&cleanup_list_lock, flags);
-	list_add(&net->cleanup_list, &cleanup_list);
-	spin_unlock_irqrestore(&cleanup_list_lock, flags);
-
-	queue_work(netns_wq, &net_cleanup_work);
+	if (llist_add(&net->cleanup_list, &cleanup_list))
+		queue_work(netns_wq, &net_cleanup_work);
 }
 EXPORT_SYMBOL_GPL(__put_net);
 
-struct net *get_net_ns_by_fd(int fd)
+/**
+ * get_net_ns - increment the refcount of the network namespace
+ * @ns: common namespace (net)
+ *
+ * Returns the net's common namespace or ERR_PTR() if ref is zero.
+ */
+struct ns_common *get_net_ns(struct ns_common *ns)
 {
-	struct proc_ns *ei;
-	struct file *file;
 	struct net *net;
 
-	file = proc_ns_fget(fd);
-	if (IS_ERR(file))
-		return ERR_CAST(file);
-
-	ei = get_proc_ns(file_inode(file));
-	if (ei->ns_ops == &netns_operations)
-		net = get_net(ei->ns);
-	else
-		net = ERR_PTR(-EINVAL);
-
-	fput(file);
-	return net;
+	net = maybe_get_net(container_of(ns, struct net, ns));
+	if (net)
+		return &net->ns;
+	return ERR_PTR(-EINVAL);
 }
+EXPORT_SYMBOL_GPL(get_net_ns);
 
-#else
 struct net *get_net_ns_by_fd(int fd)
 {
+	CLASS(fd, f)(fd);
+
+	if (fd_empty(f))
+		return ERR_PTR(-EBADF);
+
+	if (proc_ns_file(fd_file(f))) {
+		struct ns_common *ns = get_proc_ns(file_inode(fd_file(f)));
+		if (ns->ops == &netns_operations)
+			return get_net(container_of(ns, struct net, ns));
+	}
+
 	return ERR_PTR(-EINVAL);
 }
+EXPORT_SYMBOL_GPL(get_net_ns_by_fd);
 #endif
 
 struct net *get_net_ns_by_pid(pid_t pid)
@@ -373,38 +791,474 @@ struct net *get_net_ns_by_pid(pid_t pid)
 	tsk = find_task_by_vpid(pid);
 	if (tsk) {
 		struct nsproxy *nsproxy;
-		nsproxy = task_nsproxy(tsk);
+		task_lock(tsk);
+		nsproxy = tsk->nsproxy;
 		if (nsproxy)
 			net = get_net(nsproxy->net_ns);
+		task_unlock(tsk);
 	}
 	rcu_read_unlock();
 	return net;
 }
 EXPORT_SYMBOL_GPL(get_net_ns_by_pid);
 
-static __net_init int net_ns_net_init(struct net *net)
+#ifdef CONFIG_NET_NS_REFCNT_TRACKER
+static void net_ns_net_debugfs(struct net *net)
+{
+	ref_tracker_dir_symlink(&net->refcnt_tracker, "netns-%llx-%u-refcnt",
+				net->net_cookie, net->ns.inum);
+	ref_tracker_dir_symlink(&net->notrefcnt_tracker, "netns-%llx-%u-notrefcnt",
+				net->net_cookie, net->ns.inum);
+}
+
+static int __init init_net_debugfs(void)
+{
+	ref_tracker_dir_debugfs(&init_net.refcnt_tracker);
+	ref_tracker_dir_debugfs(&init_net.notrefcnt_tracker);
+	net_ns_net_debugfs(&init_net);
+	return 0;
+}
+late_initcall(init_net_debugfs);
+#else
+static void net_ns_net_debugfs(struct net *net)
 {
-	return proc_alloc_inum(&net->proc_inum);
 }
+#endif
 
-static __net_exit void net_ns_net_exit(struct net *net)
+static __net_init int net_ns_net_init(struct net *net)
 {
-	proc_free_inum(net->proc_inum);
+	net_ns_net_debugfs(net);
+	return 0;
 }
 
 static struct pernet_operations __net_initdata net_ns_ops = {
 	.init = net_ns_net_init,
-	.exit = net_ns_net_exit,
 };
 
-static int __init net_ns_init(void)
+static const struct nla_policy rtnl_net_policy[NETNSA_MAX + 1] = {
+	[NETNSA_NONE]		= { .type = NLA_UNSPEC },
+	[NETNSA_NSID]		= { .type = NLA_S32 },
+	[NETNSA_PID]		= { .type = NLA_U32 },
+	[NETNSA_FD]		= { .type = NLA_U32 },
+	[NETNSA_TARGET_NSID]	= { .type = NLA_S32 },
+};
+
+static int rtnl_net_newid(struct sk_buff *skb, struct nlmsghdr *nlh,
+			  struct netlink_ext_ack *extack)
+{
+	struct net *net = sock_net(skb->sk);
+	struct nlattr *tb[NETNSA_MAX + 1];
+	struct nlattr *nla;
+	struct net *peer;
+	int nsid, err;
+
+	err = nlmsg_parse_deprecated(nlh, sizeof(struct rtgenmsg), tb,
+				     NETNSA_MAX, rtnl_net_policy, extack);
+	if (err < 0)
+		return err;
+	if (!tb[NETNSA_NSID]) {
+		NL_SET_ERR_MSG(extack, "nsid is missing");
+		return -EINVAL;
+	}
+	nsid = nla_get_s32(tb[NETNSA_NSID]);
+
+	if (tb[NETNSA_PID]) {
+		peer = get_net_ns_by_pid(nla_get_u32(tb[NETNSA_PID]));
+		nla = tb[NETNSA_PID];
+	} else if (tb[NETNSA_FD]) {
+		peer = get_net_ns_by_fd(nla_get_u32(tb[NETNSA_FD]));
+		nla = tb[NETNSA_FD];
+	} else {
+		NL_SET_ERR_MSG(extack, "Peer netns reference is missing");
+		return -EINVAL;
+	}
+	if (IS_ERR(peer)) {
+		NL_SET_BAD_ATTR(extack, nla);
+		NL_SET_ERR_MSG(extack, "Peer netns reference is invalid");
+		return PTR_ERR(peer);
+	}
+
+	spin_lock(&net->nsid_lock);
+	if (__peernet2id(net, peer) >= 0) {
+		spin_unlock(&net->nsid_lock);
+		err = -EEXIST;
+		NL_SET_BAD_ATTR(extack, nla);
+		NL_SET_ERR_MSG(extack,
+			       "Peer netns already has a nsid assigned");
+		goto out;
+	}
+
+	err = alloc_netid(net, peer, nsid);
+	spin_unlock(&net->nsid_lock);
+	if (err >= 0) {
+		rtnl_net_notifyid(net, RTM_NEWNSID, err, NETLINK_CB(skb).portid,
+				  nlh, GFP_KERNEL);
+		err = 0;
+	} else if (err == -ENOSPC && nsid >= 0) {
+		err = -EEXIST;
+		NL_SET_BAD_ATTR(extack, tb[NETNSA_NSID]);
+		NL_SET_ERR_MSG(extack, "The specified nsid is already used");
+	}
+out:
+	put_net(peer);
+	return err;
+}
+
+static int rtnl_net_get_size(void)
+{
+	return NLMSG_ALIGN(sizeof(struct rtgenmsg))
+	       + nla_total_size(sizeof(s32)) /* NETNSA_NSID */
+	       + nla_total_size(sizeof(s32)) /* NETNSA_CURRENT_NSID */
+	       ;
+}
+
+struct net_fill_args {
+	u32 portid;
+	u32 seq;
+	int flags;
+	int cmd;
+	int nsid;
+	bool add_ref;
+	int ref_nsid;
+};
+
+static int rtnl_net_fill(struct sk_buff *skb, struct net_fill_args *args)
+{
+	struct nlmsghdr *nlh;
+	struct rtgenmsg *rth;
+
+	nlh = nlmsg_put(skb, args->portid, args->seq, args->cmd, sizeof(*rth),
+			args->flags);
+	if (!nlh)
+		return -EMSGSIZE;
+
+	rth = nlmsg_data(nlh);
+	rth->rtgen_family = AF_UNSPEC;
+
+	if (nla_put_s32(skb, NETNSA_NSID, args->nsid))
+		goto nla_put_failure;
+
+	if (args->add_ref &&
+	    nla_put_s32(skb, NETNSA_CURRENT_NSID, args->ref_nsid))
+		goto nla_put_failure;
+
+	nlmsg_end(skb, nlh);
+	return 0;
+
+nla_put_failure:
+	nlmsg_cancel(skb, nlh);
+	return -EMSGSIZE;
+}
+
+static int rtnl_net_valid_getid_req(struct sk_buff *skb,
+				    const struct nlmsghdr *nlh,
+				    struct nlattr **tb,
+				    struct netlink_ext_ack *extack)
+{
+	int i, err;
+
+	if (!netlink_strict_get_check(skb))
+		return nlmsg_parse_deprecated(nlh, sizeof(struct rtgenmsg),
+					      tb, NETNSA_MAX, rtnl_net_policy,
+					      extack);
+
+	err = nlmsg_parse_deprecated_strict(nlh, sizeof(struct rtgenmsg), tb,
+					    NETNSA_MAX, rtnl_net_policy,
+					    extack);
+	if (err)
+		return err;
+
+	for (i = 0; i <= NETNSA_MAX; i++) {
+		if (!tb[i])
+			continue;
+
+		switch (i) {
+		case NETNSA_PID:
+		case NETNSA_FD:
+		case NETNSA_NSID:
+		case NETNSA_TARGET_NSID:
+			break;
+		default:
+			NL_SET_ERR_MSG(extack, "Unsupported attribute in peer netns getid request");
+			return -EINVAL;
+		}
+	}
+
+	return 0;
+}
+
+static int rtnl_net_getid(struct sk_buff *skb, struct nlmsghdr *nlh,
+			  struct netlink_ext_ack *extack)
+{
+	struct net *net = sock_net(skb->sk);
+	struct nlattr *tb[NETNSA_MAX + 1];
+	struct net_fill_args fillargs = {
+		.portid = NETLINK_CB(skb).portid,
+		.seq = nlh->nlmsg_seq,
+		.cmd = RTM_NEWNSID,
+	};
+	struct net *peer, *target = net;
+	struct nlattr *nla;
+	struct sk_buff *msg;
+	int err;
+
+	err = rtnl_net_valid_getid_req(skb, nlh, tb, extack);
+	if (err < 0)
+		return err;
+	if (tb[NETNSA_PID]) {
+		peer = get_net_ns_by_pid(nla_get_u32(tb[NETNSA_PID]));
+		nla = tb[NETNSA_PID];
+	} else if (tb[NETNSA_FD]) {
+		peer = get_net_ns_by_fd(nla_get_u32(tb[NETNSA_FD]));
+		nla = tb[NETNSA_FD];
+	} else if (tb[NETNSA_NSID]) {
+		peer = get_net_ns_by_id(net, nla_get_s32(tb[NETNSA_NSID]));
+		if (!peer)
+			peer = ERR_PTR(-ENOENT);
+		nla = tb[NETNSA_NSID];
+	} else {
+		NL_SET_ERR_MSG(extack, "Peer netns reference is missing");
+		return -EINVAL;
+	}
+
+	if (IS_ERR(peer)) {
+		NL_SET_BAD_ATTR(extack, nla);
+		NL_SET_ERR_MSG(extack, "Peer netns reference is invalid");
+		return PTR_ERR(peer);
+	}
+
+	if (tb[NETNSA_TARGET_NSID]) {
+		int id = nla_get_s32(tb[NETNSA_TARGET_NSID]);
+
+		target = rtnl_get_net_ns_capable(NETLINK_CB(skb).sk, id);
+		if (IS_ERR(target)) {
+			NL_SET_BAD_ATTR(extack, tb[NETNSA_TARGET_NSID]);
+			NL_SET_ERR_MSG(extack,
+				       "Target netns reference is invalid");
+			err = PTR_ERR(target);
+			goto out;
+		}
+		fillargs.add_ref = true;
+		fillargs.ref_nsid = peernet2id(net, peer);
+	}
+
+	msg = nlmsg_new(rtnl_net_get_size(), GFP_KERNEL);
+	if (!msg) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	fillargs.nsid = peernet2id(target, peer);
+	err = rtnl_net_fill(msg, &fillargs);
+	if (err < 0)
+		goto err_out;
+
+	err = rtnl_unicast(msg, net, NETLINK_CB(skb).portid);
+	goto out;
+
+err_out:
+	nlmsg_free(msg);
+out:
+	if (fillargs.add_ref)
+		put_net(target);
+	put_net(peer);
+	return err;
+}
+
+struct rtnl_net_dump_cb {
+	struct net *tgt_net;
+	struct net *ref_net;
+	struct sk_buff *skb;
+	struct net_fill_args fillargs;
+	int idx;
+	int s_idx;
+};
+
+/* Runs in RCU-critical section. */
+static int rtnl_net_dumpid_one(int id, void *peer, void *data)
+{
+	struct rtnl_net_dump_cb *net_cb = (struct rtnl_net_dump_cb *)data;
+	int ret;
+
+	if (net_cb->idx < net_cb->s_idx)
+		goto cont;
+
+	net_cb->fillargs.nsid = id;
+	if (net_cb->fillargs.add_ref)
+		net_cb->fillargs.ref_nsid = __peernet2id(net_cb->ref_net, peer);
+	ret = rtnl_net_fill(net_cb->skb, &net_cb->fillargs);
+	if (ret < 0)
+		return ret;
+
+cont:
+	net_cb->idx++;
+	return 0;
+}
+
+static int rtnl_valid_dump_net_req(const struct nlmsghdr *nlh, struct sock *sk,
+				   struct rtnl_net_dump_cb *net_cb,
+				   struct netlink_callback *cb)
+{
+	struct netlink_ext_ack *extack = cb->extack;
+	struct nlattr *tb[NETNSA_MAX + 1];
+	int err, i;
+
+	err = nlmsg_parse_deprecated_strict(nlh, sizeof(struct rtgenmsg), tb,
+					    NETNSA_MAX, rtnl_net_policy,
+					    extack);
+	if (err < 0)
+		return err;
+
+	for (i = 0; i <= NETNSA_MAX; i++) {
+		if (!tb[i])
+			continue;
+
+		if (i == NETNSA_TARGET_NSID) {
+			struct net *net;
+
+			net = rtnl_get_net_ns_capable(sk, nla_get_s32(tb[i]));
+			if (IS_ERR(net)) {
+				NL_SET_BAD_ATTR(extack, tb[i]);
+				NL_SET_ERR_MSG(extack,
+					       "Invalid target network namespace id");
+				return PTR_ERR(net);
+			}
+			net_cb->fillargs.add_ref = true;
+			net_cb->ref_net = net_cb->tgt_net;
+			net_cb->tgt_net = net;
+		} else {
+			NL_SET_BAD_ATTR(extack, tb[i]);
+			NL_SET_ERR_MSG(extack,
+				       "Unsupported attribute in dump request");
+			return -EINVAL;
+		}
+	}
+
+	return 0;
+}
+
+static int rtnl_net_dumpid(struct sk_buff *skb, struct netlink_callback *cb)
+{
+	struct rtnl_net_dump_cb net_cb = {
+		.tgt_net = sock_net(skb->sk),
+		.skb = skb,
+		.fillargs = {
+			.portid = NETLINK_CB(cb->skb).portid,
+			.seq = cb->nlh->nlmsg_seq,
+			.flags = NLM_F_MULTI,
+			.cmd = RTM_NEWNSID,
+		},
+		.idx = 0,
+		.s_idx = cb->args[0],
+	};
+	int err = 0;
+
+	if (cb->strict_check) {
+		err = rtnl_valid_dump_net_req(cb->nlh, skb->sk, &net_cb, cb);
+		if (err < 0)
+			goto end;
+	}
+
+	rcu_read_lock();
+	idr_for_each(&net_cb.tgt_net->netns_ids, rtnl_net_dumpid_one, &net_cb);
+	rcu_read_unlock();
+
+	cb->args[0] = net_cb.idx;
+end:
+	if (net_cb.fillargs.add_ref)
+		put_net(net_cb.tgt_net);
+	return err;
+}
+
+static void rtnl_net_notifyid(struct net *net, int cmd, int id, u32 portid,
+			      struct nlmsghdr *nlh, gfp_t gfp)
+{
+	struct net_fill_args fillargs = {
+		.portid = portid,
+		.seq = nlh ? nlh->nlmsg_seq : 0,
+		.cmd = cmd,
+		.nsid = id,
+	};
+	struct sk_buff *msg;
+	int err = -ENOMEM;
+
+	msg = nlmsg_new(rtnl_net_get_size(), gfp);
+	if (!msg)
+		goto out;
+
+	err = rtnl_net_fill(msg, &fillargs);
+	if (err < 0)
+		goto err_out;
+
+	rtnl_notify(msg, net, portid, RTNLGRP_NSID, nlh, gfp);
+	return;
+
+err_out:
+	nlmsg_free(msg);
+out:
+	rtnl_set_sk_err(net, RTNLGRP_NSID, err);
+}
+
+#ifdef CONFIG_NET_NS
+static void __init netns_ipv4_struct_check(void)
+{
+	/* TX readonly hotpath cache lines */
+	CACHELINE_ASSERT_GROUP_MEMBER(struct netns_ipv4, netns_ipv4_read_tx,
+				      sysctl_tcp_early_retrans);
+	CACHELINE_ASSERT_GROUP_MEMBER(struct netns_ipv4, netns_ipv4_read_tx,
+				      sysctl_tcp_tso_win_divisor);
+	CACHELINE_ASSERT_GROUP_MEMBER(struct netns_ipv4, netns_ipv4_read_tx,
+				      sysctl_tcp_tso_rtt_log);
+	CACHELINE_ASSERT_GROUP_MEMBER(struct netns_ipv4, netns_ipv4_read_tx,
+				      sysctl_tcp_autocorking);
+	CACHELINE_ASSERT_GROUP_MEMBER(struct netns_ipv4, netns_ipv4_read_tx,
+				      sysctl_tcp_min_snd_mss);
+	CACHELINE_ASSERT_GROUP_MEMBER(struct netns_ipv4, netns_ipv4_read_tx,
+				      sysctl_tcp_notsent_lowat);
+	CACHELINE_ASSERT_GROUP_MEMBER(struct netns_ipv4, netns_ipv4_read_tx,
+				      sysctl_tcp_limit_output_bytes);
+	CACHELINE_ASSERT_GROUP_MEMBER(struct netns_ipv4, netns_ipv4_read_tx,
+				      sysctl_tcp_min_rtt_wlen);
+	CACHELINE_ASSERT_GROUP_MEMBER(struct netns_ipv4, netns_ipv4_read_tx,
+				      sysctl_tcp_wmem);
+	CACHELINE_ASSERT_GROUP_MEMBER(struct netns_ipv4, netns_ipv4_read_tx,
+				      sysctl_ip_fwd_use_pmtu);
+
+	/* RX readonly hotpath cache line */
+	CACHELINE_ASSERT_GROUP_MEMBER(struct netns_ipv4, netns_ipv4_read_rx,
+				      sysctl_tcp_moderate_rcvbuf);
+	CACHELINE_ASSERT_GROUP_MEMBER(struct netns_ipv4, netns_ipv4_read_rx,
+				      sysctl_tcp_rcvbuf_low_rtt);
+	CACHELINE_ASSERT_GROUP_MEMBER(struct netns_ipv4, netns_ipv4_read_rx,
+				      sysctl_ip_early_demux);
+	CACHELINE_ASSERT_GROUP_MEMBER(struct netns_ipv4, netns_ipv4_read_rx,
+				      sysctl_tcp_early_demux);
+	CACHELINE_ASSERT_GROUP_MEMBER(struct netns_ipv4, netns_ipv4_read_rx,
+				      sysctl_tcp_l3mdev_accept);
+	CACHELINE_ASSERT_GROUP_MEMBER(struct netns_ipv4, netns_ipv4_read_rx,
+				      sysctl_tcp_reordering);
+	CACHELINE_ASSERT_GROUP_MEMBER(struct netns_ipv4, netns_ipv4_read_rx,
+				      sysctl_tcp_rmem);
+}
+#endif
+
+static const struct rtnl_msg_handler net_ns_rtnl_msg_handlers[] __initconst = {
+	{.msgtype = RTM_NEWNSID, .doit = rtnl_net_newid,
+	 .flags = RTNL_FLAG_DOIT_UNLOCKED},
+	{.msgtype = RTM_GETNSID, .doit = rtnl_net_getid,
+	 .dumpit = rtnl_net_dumpid,
+	 .flags = RTNL_FLAG_DOIT_UNLOCKED | RTNL_FLAG_DUMP_UNLOCKED},
+};
+
+void __init net_ns_init(void)
 {
 	struct net_generic *ng;
 
 #ifdef CONFIG_NET_NS
+	netns_ipv4_struct_check();
 	net_cachep = kmem_cache_create("net_namespace", sizeof(struct net),
 					SMP_CACHE_BYTES,
-					SLAB_PANIC, NULL);
+					SLAB_PANIC|SLAB_ACCOUNT, NULL);
 
 	/* Create workqueue for cleanup */
 	netns_wq = create_singlethread_workqueue("netns");
@@ -418,33 +1272,42 @@ static int __init net_ns_init(void)
 
 	rcu_assign_pointer(init_net.gen, ng);
 
-	mutex_lock(&net_mutex);
-	if (setup_net(&init_net, &init_user_ns))
-		panic("Could not setup the initial network namespace");
+#ifdef CONFIG_KEYS
+	init_net.key_domain = &init_net_key_domain;
+#endif
+	/*
+	 * This currently cannot fail as the initial network namespace
+	 * has a static inode number.
+	 */
+	if (preinit_net(&init_net, &init_user_ns))
+		panic("Could not preinitialize the initial network namespace");
 
-	rtnl_lock();
-	list_add_tail_rcu(&init_net.list, &net_namespace_list);
-	rtnl_unlock();
+	down_write(&pernet_ops_rwsem);
+	if (setup_net(&init_net))
+		panic("Could not setup the initial network namespace");
 
-	mutex_unlock(&net_mutex);
+	init_net_initialized = true;
+	up_write(&pernet_ops_rwsem);
 
-	register_pernet_subsys(&net_ns_ops);
+	if (register_pernet_subsys(&net_ns_ops))
+		panic("Could not register network namespace subsystems");
 
-	return 0;
+	rtnl_register_many(net_ns_rtnl_msg_handlers);
 }
 
-pure_initcall(net_ns_init);
-
 #ifdef CONFIG_NET_NS
 static int __register_pernet_operations(struct list_head *list,
 					struct pernet_operations *ops)
 {
+	LIST_HEAD(net_exit_list);
 	struct net *net;
 	int error;
-	LIST_HEAD(net_exit_list);
 
 	list_add_tail(&ops->list, list);
-	if (ops->init || (ops->id && ops->size)) {
+	if (ops->init || ops->id) {
+		/* We held write locked pernet_ops_rwsem, and parallel
+		 * setup_net() and cleanup_net() are not possible.
+		 */
 		for_each_net(net) {
 			error = ops_init(ops, net);
 			if (error)
@@ -457,21 +1320,21 @@ static int __register_pernet_operations(struct list_head *list,
 out_undo:
 	/* If I have an error cleanup all namespaces I initialized */
 	list_del(&ops->list);
-	ops_exit_list(ops, &net_exit_list);
-	ops_free_list(ops, &net_exit_list);
+	ops_undo_single(ops, &net_exit_list);
 	return error;
 }
 
 static void __unregister_pernet_operations(struct pernet_operations *ops)
 {
-	struct net *net;
 	LIST_HEAD(net_exit_list);
+	struct net *net;
 
-	list_del(&ops->list);
+	/* See comment in __register_pernet_operations() */
 	for_each_net(net)
 		list_add_tail(&net->exit_list, &net_exit_list);
-	ops_exit_list(ops, &net_exit_list);
-	ops_free_list(ops, &net_exit_list);
+
+	list_del(&ops->list);
+	ops_undo_single(ops, &net_exit_list);
 }
 
 #else
@@ -479,15 +1342,24 @@ static void __unregister_pernet_operations(struct pernet_operations *ops)
 static int __register_pernet_operations(struct list_head *list,
 					struct pernet_operations *ops)
 {
+	if (!init_net_initialized) {
+		list_add_tail(&ops->list, list);
+		return 0;
+	}
+
 	return ops_init(ops, &init_net);
 }
 
 static void __unregister_pernet_operations(struct pernet_operations *ops)
 {
-	LIST_HEAD(net_exit_list);
-	list_add(&init_net.exit_list, &net_exit_list);
-	ops_exit_list(ops, &net_exit_list);
-	ops_free_list(ops, &net_exit_list);
+	if (!init_net_initialized) {
+		list_del(&ops->list);
+	} else {
+		LIST_HEAD(net_exit_list);
+
+		list_add(&init_net.exit_list, &net_exit_list);
+		ops_undo_single(ops, &net_exit_list);
+	}
 }
 
 #endif /* CONFIG_NET_NS */
@@ -499,23 +1371,26 @@ static int register_pernet_operations(struct list_head *list,
 {
 	int error;
 
+	if (WARN_ON(!!ops->id ^ !!ops->size))
+		return -EINVAL;
+
 	if (ops->id) {
-again:
-		error = ida_get_new_above(&net_generic_ids, 1, ops->id);
-		if (error < 0) {
-			if (error == -EAGAIN) {
-				ida_pre_get(&net_generic_ids, GFP_KERNEL);
-				goto again;
-			}
+		error = ida_alloc_min(&net_generic_ids, MIN_PERNET_OPS_ID,
+				GFP_KERNEL);
+		if (error < 0)
 			return error;
-		}
-		max_gen_ptrs = max_t(unsigned int, max_gen_ptrs, *ops->id);
+		*ops->id = error;
+		/* This does not require READ_ONCE as writers already hold
+		 * pernet_ops_rwsem. But WRITE_ONCE is needed to protect
+		 * net_alloc_generic.
+		 */
+		WRITE_ONCE(max_gen_ptrs, max(max_gen_ptrs, *ops->id + 1));
 	}
 	error = __register_pernet_operations(list, ops);
 	if (error) {
 		rcu_barrier();
 		if (ops->id)
-			ida_remove(&net_generic_ids, *ops->id);
+			ida_free(&net_generic_ids, *ops->id);
 	}
 
 	return error;
@@ -523,11 +1398,10 @@ again:
 
 static void unregister_pernet_operations(struct pernet_operations *ops)
 {
-	
 	__unregister_pernet_operations(ops);
 	rcu_barrier();
 	if (ops->id)
-		ida_remove(&net_generic_ids, *ops->id);
+		ida_free(&net_generic_ids, *ops->id);
 }
 
 /**
@@ -552,9 +1426,9 @@ static void unregister_pernet_operations(struct pernet_operations *ops)
 int register_pernet_subsys(struct pernet_operations *ops)
 {
 	int error;
-	mutex_lock(&net_mutex);
+	down_write(&pernet_ops_rwsem);
 	error =  register_pernet_operations(first_device, ops);
-	mutex_unlock(&net_mutex);
+	up_write(&pernet_ops_rwsem);
 	return error;
 }
 EXPORT_SYMBOL_GPL(register_pernet_subsys);
@@ -570,9 +1444,9 @@ EXPORT_SYMBOL_GPL(register_pernet_subsys);
  */
 void unregister_pernet_subsys(struct pernet_operations *ops)
 {
-	mutex_lock(&net_mutex);
+	down_write(&pernet_ops_rwsem);
 	unregister_pernet_operations(ops);
-	mutex_unlock(&net_mutex);
+	up_write(&pernet_ops_rwsem);
 }
 EXPORT_SYMBOL_GPL(unregister_pernet_subsys);
 
@@ -598,11 +1472,11 @@ EXPORT_SYMBOL_GPL(unregister_pernet_subsys);
 int register_pernet_device(struct pernet_operations *ops)
 {
 	int error;
-	mutex_lock(&net_mutex);
+	down_write(&pernet_ops_rwsem);
 	error = register_pernet_operations(&pernet_list, ops);
 	if (!error && (first_device == &pernet_list))
 		first_device = &ops->list;
-	mutex_unlock(&net_mutex);
+	up_write(&pernet_ops_rwsem);
 	return error;
 }
 EXPORT_SYMBOL_GPL(register_pernet_device);
@@ -618,40 +1492,41 @@ EXPORT_SYMBOL_GPL(register_pernet_device);
  */
 void unregister_pernet_device(struct pernet_operations *ops)
 {
-	mutex_lock(&net_mutex);
+	down_write(&pernet_ops_rwsem);
 	if (&ops->list == first_device)
 		first_device = first_device->next;
 	unregister_pernet_operations(ops);
-	mutex_unlock(&net_mutex);
+	up_write(&pernet_ops_rwsem);
 }
 EXPORT_SYMBOL_GPL(unregister_pernet_device);
 
 #ifdef CONFIG_NET_NS
-static void *netns_get(struct task_struct *task)
+static struct ns_common *netns_get(struct task_struct *task)
 {
 	struct net *net = NULL;
 	struct nsproxy *nsproxy;
 
-	rcu_read_lock();
-	nsproxy = task_nsproxy(task);
+	task_lock(task);
+	nsproxy = task->nsproxy;
 	if (nsproxy)
 		net = get_net(nsproxy->net_ns);
-	rcu_read_unlock();
+	task_unlock(task);
 
-	return net;
+	return net ? &net->ns : NULL;
 }
 
-static void netns_put(void *ns)
+static void netns_put(struct ns_common *ns)
 {
-	put_net(ns);
+	put_net(to_net_ns(ns));
 }
 
-static int netns_install(struct nsproxy *nsproxy, void *ns)
+static int netns_install(struct nsset *nsset, struct ns_common *ns)
 {
-	struct net *net = ns;
+	struct nsproxy *nsproxy = nsset->nsproxy;
+	struct net *net = to_net_ns(ns);
 
 	if (!ns_capable(net->user_ns, CAP_SYS_ADMIN) ||
-	    !nsown_capable(CAP_SYS_ADMIN))
+	    !ns_capable(nsset->cred->user_ns, CAP_SYS_ADMIN))
 		return -EPERM;
 
 	put_net(nsproxy->net_ns);
@@ -659,18 +1534,16 @@ static int netns_install(struct nsproxy *nsproxy, void *ns)
 	return 0;
 }
 
-static unsigned int netns_inum(void *ns)
+static struct user_namespace *netns_owner(struct ns_common *ns)
 {
-	struct net *net = ns;
-	return net->proc_inum;
+	return to_net_ns(ns)->user_ns;
 }
 
 const struct proc_ns_operations netns_operations = {
 	.name		= "net",
-	.type		= CLONE_NEWNET,
 	.get		= netns_get,
 	.put		= netns_put,
 	.install	= netns_install,
-	.inum		= netns_inum,
+	.owner		= netns_owner,
 };
 #endif