diff --git a/fs/mount.h b/fs/mount.h
index f39bc9da4d73..6250de544760 100644
--- a/fs/mount.h
+++ b/fs/mount.h
@@ -146,3 +146,8 @@ static inline bool is_local_mountpoint(struct dentry *dentry)
 
 	return __is_local_mountpoint(dentry);
 }
+
+static inline bool is_anon_ns(struct mnt_namespace *ns)
+{
+	return ns->seq == 0;
+}
diff --git a/fs/namespace.c b/fs/namespace.c
index 9ed2f2930dfd..f0b8a8ca08df 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2873,7 +2873,8 @@ static void dec_mnt_namespaces(struct ucounts *ucounts)
 
 static void free_mnt_ns(struct mnt_namespace *ns)
 {
-	ns_free_inum(&ns->ns);
+	if (!is_anon_ns(ns))
+		ns_free_inum(&ns->ns);
 	dec_mnt_namespaces(ns->ucounts);
 	put_user_ns(ns->user_ns);
 	kfree(ns);
@@ -2888,7 +2889,7 @@ static void free_mnt_ns(struct mnt_namespace *ns)
  */
 static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1);
 
-static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns)
+static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns, bool anon)
 {
 	struct mnt_namespace *new_ns;
 	struct ucounts *ucounts;
@@ -2898,28 +2899,27 @@ static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns)
 	if (!ucounts)
 		return ERR_PTR(-ENOSPC);
 
-	new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
+	new_ns = kzalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
 	if (!new_ns) {
 		dec_mnt_namespaces(ucounts);
 		return ERR_PTR(-ENOMEM);
 	}
-	ret = ns_alloc_inum(&new_ns->ns);
-	if (ret) {
-		kfree(new_ns);
-		dec_mnt_namespaces(ucounts);
-		return ERR_PTR(ret);
+	if (!anon) {
+		ret = ns_alloc_inum(&new_ns->ns);
+		if (ret) {
+			kfree(new_ns);
+			dec_mnt_namespaces(ucounts);
+			return ERR_PTR(ret);
+		}
 	}
 	new_ns->ns.ops = &mntns_operations;
-	new_ns->seq = atomic64_add_return(1, &mnt_ns_seq);
+	if (!anon)
+		new_ns->seq = atomic64_add_return(1, &mnt_ns_seq);
 	atomic_set(&new_ns->count, 1);
-	new_ns->root = NULL;
 	INIT_LIST_HEAD(&new_ns->list);
 	init_waitqueue_head(&new_ns->poll);
-	new_ns->event = 0;
 	new_ns->user_ns = get_user_ns(user_ns);
 	new_ns->ucounts = ucounts;
-	new_ns->mounts = 0;
-	new_ns->pending_mounts = 0;
 	return new_ns;
 }
 
@@ -2943,7 +2943,7 @@ struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
 
 	old = ns->root;
 
-	new_ns = alloc_mnt_ns(user_ns);
+	new_ns = alloc_mnt_ns(user_ns, false);
 	if (IS_ERR(new_ns))
 		return new_ns;
 
@@ -3003,37 +3003,25 @@ struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
 	return new_ns;
 }
 
-/**
- * create_mnt_ns - creates a private namespace and adds a root filesystem
- * @mnt: pointer to the new root filesystem mountpoint
- */
-static struct mnt_namespace *create_mnt_ns(struct vfsmount *m)
-{
-	struct mnt_namespace *new_ns = alloc_mnt_ns(&init_user_ns);
-	if (!IS_ERR(new_ns)) {
-		struct mount *mnt = real_mount(m);
-		mnt->mnt_ns = new_ns;
-		new_ns->root = mnt;
-		new_ns->mounts++;
-		list_add(&mnt->mnt_list, &new_ns->list);
-	} else {
-		mntput(m);
-	}
-	return new_ns;
-}
-
-struct dentry *mount_subtree(struct vfsmount *mnt, const char *name)
+struct dentry *mount_subtree(struct vfsmount *m, const char *name)
 {
+	struct mount *mnt = real_mount(m);
 	struct mnt_namespace *ns;
 	struct super_block *s;
 	struct path path;
 	int err;
 
-	ns = create_mnt_ns(mnt);
-	if (IS_ERR(ns))
+	ns = alloc_mnt_ns(&init_user_ns, true);
+	if (IS_ERR(ns)) {
+		mntput(m);
 		return ERR_CAST(ns);
+	}
+	mnt->mnt_ns = ns;
+	ns->root = mnt;
+	ns->mounts++;
+	list_add(&mnt->mnt_list, &ns->list);
 
-	err = vfs_path_lookup(mnt->mnt_root, mnt,
+	err = vfs_path_lookup(m->mnt_root, m,
 			name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path);
 
 	put_mnt_ns(ns);
@@ -3243,6 +3231,7 @@ SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
 static void __init init_mount_tree(void)
 {
 	struct vfsmount *mnt;
+	struct mount *m;
 	struct mnt_namespace *ns;
 	struct path root;
 	struct file_system_type *type;
@@ -3255,10 +3244,14 @@ static void __init init_mount_tree(void)
 	if (IS_ERR(mnt))
 		panic("Can't create rootfs");
 
-	ns = create_mnt_ns(mnt);
+	ns = alloc_mnt_ns(&init_user_ns, false);
 	if (IS_ERR(ns))
 		panic("Can't allocate initial namespace");
-
+	m = real_mount(mnt);
+	m->mnt_ns = ns;
+	ns->root = m;
+	ns->mounts = 1;
+	list_add(&m->mnt_list, &ns->list);
 	init_task.nsproxy->mnt_ns = ns;
 	get_mnt_ns(ns);
 
@@ -3499,6 +3492,9 @@ static int mntns_install(struct nsproxy *nsproxy, struct ns_common *ns)
 	    !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
 		return -EPERM;
 
+	if (is_anon_ns(mnt_ns))
+		return -EINVAL;
+
 	if (fs->users != 1)
 		return -EINVAL;