1 files changed, 247 insertions, 0 deletions
diff --git a/kernel/nstree.c b/kernel/nstree.c
new file mode 100644
index 000000000000..b24a320a11a6
--- /dev/null
+++ b/kernel/nstree.c
@@ -0,0 +1,247 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/nstree.h>
+#include <linux/proc_ns.h>
+#include <linux/vfsdebug.h>
+
+/**
+ * struct ns_tree - Namespace tree
+ * @ns_tree: Rbtree of namespaces of a particular type
+ * @ns_list: Sequentially walkable list of all namespaces of this type
+ * @ns_tree_lock: Seqlock to protect the tree and list
+ * @type: type of namespaces in this tree
+ */
+struct ns_tree {
+       struct rb_root ns_tree;
+       struct list_head ns_list;
+       seqlock_t ns_tree_lock;
+       int type;
+};
+
+struct ns_tree mnt_ns_tree = {
+	.ns_tree = RB_ROOT,
+	.ns_list = LIST_HEAD_INIT(mnt_ns_tree.ns_list),
+	.ns_tree_lock = __SEQLOCK_UNLOCKED(mnt_ns_tree.ns_tree_lock),
+	.type = CLONE_NEWNS,
+};
+
+struct ns_tree net_ns_tree = {
+	.ns_tree = RB_ROOT,
+	.ns_list = LIST_HEAD_INIT(net_ns_tree.ns_list),
+	.ns_tree_lock = __SEQLOCK_UNLOCKED(net_ns_tree.ns_tree_lock),
+	.type = CLONE_NEWNET,
+};
+EXPORT_SYMBOL_GPL(net_ns_tree);
+
+struct ns_tree uts_ns_tree = {
+	.ns_tree = RB_ROOT,
+	.ns_list = LIST_HEAD_INIT(uts_ns_tree.ns_list),
+	.ns_tree_lock = __SEQLOCK_UNLOCKED(uts_ns_tree.ns_tree_lock),
+	.type = CLONE_NEWUTS,
+};
+
+struct ns_tree user_ns_tree = {
+	.ns_tree = RB_ROOT,
+	.ns_list = LIST_HEAD_INIT(user_ns_tree.ns_list),
+	.ns_tree_lock = __SEQLOCK_UNLOCKED(user_ns_tree.ns_tree_lock),
+	.type = CLONE_NEWUSER,
+};
+
+struct ns_tree ipc_ns_tree = {
+	.ns_tree = RB_ROOT,
+	.ns_list = LIST_HEAD_INIT(ipc_ns_tree.ns_list),
+	.ns_tree_lock = __SEQLOCK_UNLOCKED(ipc_ns_tree.ns_tree_lock),
+	.type = CLONE_NEWIPC,
+};
+
+struct ns_tree pid_ns_tree = {
+	.ns_tree = RB_ROOT,
+	.ns_list = LIST_HEAD_INIT(pid_ns_tree.ns_list),
+	.ns_tree_lock = __SEQLOCK_UNLOCKED(pid_ns_tree.ns_tree_lock),
+	.type = CLONE_NEWPID,
+};
+
+struct ns_tree cgroup_ns_tree = {
+	.ns_tree = RB_ROOT,
+	.ns_list = LIST_HEAD_INIT(cgroup_ns_tree.ns_list),
+	.ns_tree_lock = __SEQLOCK_UNLOCKED(cgroup_ns_tree.ns_tree_lock),
+	.type = CLONE_NEWCGROUP,
+};
+
+struct ns_tree time_ns_tree = {
+	.ns_tree = RB_ROOT,
+	.ns_list = LIST_HEAD_INIT(time_ns_tree.ns_list),
+	.ns_tree_lock = __SEQLOCK_UNLOCKED(time_ns_tree.ns_tree_lock),
+	.type = CLONE_NEWTIME,
+};
+
+DEFINE_COOKIE(namespace_cookie);
+
+static inline struct ns_common *node_to_ns(const struct rb_node *node)
+{
+	if (!node)
+		return NULL;
+	return rb_entry(node, struct ns_common, ns_tree_node);
+}
+
+static inline int ns_cmp(struct rb_node *a, const struct rb_node *b)
+{
+	struct ns_common *ns_a = node_to_ns(a);
+	struct ns_common *ns_b = node_to_ns(b);
+	u64 ns_id_a = ns_a->ns_id;
+	u64 ns_id_b = ns_b->ns_id;
+
+	if (ns_id_a < ns_id_b)
+		return -1;
+	if (ns_id_a > ns_id_b)
+		return 1;
+	return 0;
+}
+
+void __ns_tree_add_raw(struct ns_common *ns, struct ns_tree *ns_tree)
+{
+	struct rb_node *node, *prev;
+
+	VFS_WARN_ON_ONCE(!ns->ns_id);
+
+	write_seqlock(&ns_tree->ns_tree_lock);
+
+	VFS_WARN_ON_ONCE(ns->ns_type != ns_tree->type);
+
+	node = rb_find_add_rcu(&ns->ns_tree_node, &ns_tree->ns_tree, ns_cmp);
+	/*
+	 * If there's no previous entry simply add it after the
+	 * head and if there is add it after the previous entry.
+	 */
+	prev = rb_prev(&ns->ns_tree_node);
+	if (!prev)
+		list_add_rcu(&ns->ns_list_node, &ns_tree->ns_list);
+	else
+		list_add_rcu(&ns->ns_list_node, &node_to_ns(prev)->ns_list_node);
+
+	write_sequnlock(&ns_tree->ns_tree_lock);
+
+	VFS_WARN_ON_ONCE(node);
+}
+
+void __ns_tree_remove(struct ns_common *ns, struct ns_tree *ns_tree)
+{
+	VFS_WARN_ON_ONCE(RB_EMPTY_NODE(&ns->ns_tree_node));
+	VFS_WARN_ON_ONCE(list_empty(&ns->ns_list_node));
+	VFS_WARN_ON_ONCE(ns->ns_type != ns_tree->type);
+
+	write_seqlock(&ns_tree->ns_tree_lock);
+	rb_erase(&ns->ns_tree_node, &ns_tree->ns_tree);
+	list_bidir_del_rcu(&ns->ns_list_node);
+	RB_CLEAR_NODE(&ns->ns_tree_node);
+	write_sequnlock(&ns_tree->ns_tree_lock);
+}
+EXPORT_SYMBOL_GPL(__ns_tree_remove);
+
+static int ns_find(const void *key, const struct rb_node *node)
+{
+	const u64 ns_id = *(u64 *)key;
+	const struct ns_common *ns = node_to_ns(node);
+
+	if (ns_id < ns->ns_id)
+		return -1;
+	if (ns_id > ns->ns_id)
+		return 1;
+	return 0;
+}
+
+
+static struct ns_tree *ns_tree_from_type(int ns_type)
+{
+	switch (ns_type) {
+	case CLONE_NEWCGROUP:
+		return &cgroup_ns_tree;
+	case CLONE_NEWIPC:
+		return &ipc_ns_tree;
+	case CLONE_NEWNS:
+		return &mnt_ns_tree;
+	case CLONE_NEWNET:
+		return &net_ns_tree;
+	case CLONE_NEWPID:
+		return &pid_ns_tree;
+	case CLONE_NEWUSER:
+		return &user_ns_tree;
+	case CLONE_NEWUTS:
+		return &uts_ns_tree;
+	case CLONE_NEWTIME:
+		return &time_ns_tree;
+	}
+
+	return NULL;
+}
+
+struct ns_common *ns_tree_lookup_rcu(u64 ns_id, int ns_type)
+{
+	struct ns_tree *ns_tree;
+	struct rb_node *node;
+	unsigned int seq;
+
+	RCU_LOCKDEP_WARN(!rcu_read_lock_held(), "suspicious ns_tree_lookup_rcu() usage");
+
+	ns_tree = ns_tree_from_type(ns_type);
+	if (!ns_tree)
+		return NULL;
+
+	do {
+		seq = read_seqbegin(&ns_tree->ns_tree_lock);
+		node = rb_find_rcu(&ns_id, &ns_tree->ns_tree, ns_find);
+		if (node)
+			break;
+	} while (read_seqretry(&ns_tree->ns_tree_lock, seq));
+
+	if (!node)
+		return NULL;
+
+	VFS_WARN_ON_ONCE(node_to_ns(node)->ns_type != ns_type);
+
+	return node_to_ns(node);
+}
+
+/**
+ * ns_tree_adjoined_rcu - find the next/previous namespace in the same
+ * tree
+ * @ns: namespace to start from
+ * @previous: if true find the previous namespace, otherwise the next
+ *
+ * Find the next or previous namespace in the same tree as @ns. If
+ * there is no next/previous namespace, -ENOENT is returned.
+ */
+struct ns_common *__ns_tree_adjoined_rcu(struct ns_common *ns,
+					 struct ns_tree *ns_tree, bool previous)
+{
+	struct list_head *list;
+
+	RCU_LOCKDEP_WARN(!rcu_read_lock_held(), "suspicious ns_tree_adjoined_rcu() usage");
+
+	if (previous)
+		list = rcu_dereference(list_bidir_prev_rcu(&ns->ns_list_node));
+	else
+		list = rcu_dereference(list_next_rcu(&ns->ns_list_node));
+	if (list_is_head(list, &ns_tree->ns_list))
+		return ERR_PTR(-ENOENT);
+
+	VFS_WARN_ON_ONCE(list_entry_rcu(list, struct ns_common, ns_list_node)->ns_type != ns_tree->type);
+
+	return list_entry_rcu(list, struct ns_common, ns_list_node);
+}
+
+/**
+ * ns_tree_gen_id - generate a new namespace id
+ * @ns: namespace to generate id for
+ *
+ * Generates a new namespace id and assigns it to the namespace. All
+ * namespaces types share the same id space and thus can be compared
+ * directly. IOW, when two ids of two namespace are equal, they are
+ * identical.
+ */
+u64 ns_tree_gen_id(struct ns_common *ns)
+{
+	guard(preempt)();
+	ns->ns_id = gen_cookie_next(&namespace_cookie);
+	return ns->ns_id;
+}