diff options
Diffstat (limited to 'kernel/nstree.c')
| -rw-r--r-- | kernel/nstree.c | 813 |
1 files changed, 813 insertions, 0 deletions
diff --git a/kernel/nstree.c b/kernel/nstree.c new file mode 100644 index 000000000000..f36c59e6951d --- /dev/null +++ b/kernel/nstree.c @@ -0,0 +1,813 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* Copyright (c) 2025 Christian Brauner <brauner@kernel.org> */ + +#include <linux/nstree.h> +#include <linux/proc_ns.h> +#include <linux/rculist.h> +#include <linux/vfsdebug.h> +#include <linux/syscalls.h> +#include <linux/user_namespace.h> + +static __cacheline_aligned_in_smp DEFINE_SEQLOCK(ns_tree_lock); + +DEFINE_LOCK_GUARD_0(ns_tree_writer, + write_seqlock(&ns_tree_lock), + write_sequnlock(&ns_tree_lock)) + +DEFINE_LOCK_GUARD_0(ns_tree_locked_reader, + read_seqlock_excl(&ns_tree_lock), + read_sequnlock_excl(&ns_tree_lock)) + +static struct ns_tree_root ns_unified_root = { /* protected by ns_tree_lock */ + .ns_rb = RB_ROOT, + .ns_list_head = LIST_HEAD_INIT(ns_unified_root.ns_list_head), +}; + +struct ns_tree_root mnt_ns_tree = { + .ns_rb = RB_ROOT, + .ns_list_head = LIST_HEAD_INIT(mnt_ns_tree.ns_list_head), +}; + +struct ns_tree_root net_ns_tree = { + .ns_rb = RB_ROOT, + .ns_list_head = LIST_HEAD_INIT(net_ns_tree.ns_list_head), +}; +EXPORT_SYMBOL_GPL(net_ns_tree); + +struct ns_tree_root uts_ns_tree = { + .ns_rb = RB_ROOT, + .ns_list_head = LIST_HEAD_INIT(uts_ns_tree.ns_list_head), +}; + +struct ns_tree_root user_ns_tree = { + .ns_rb = RB_ROOT, + .ns_list_head = LIST_HEAD_INIT(user_ns_tree.ns_list_head), +}; + +struct ns_tree_root ipc_ns_tree = { + .ns_rb = RB_ROOT, + .ns_list_head = LIST_HEAD_INIT(ipc_ns_tree.ns_list_head), +}; + +struct ns_tree_root pid_ns_tree = { + .ns_rb = RB_ROOT, + .ns_list_head = LIST_HEAD_INIT(pid_ns_tree.ns_list_head), +}; + +struct ns_tree_root cgroup_ns_tree = { + .ns_rb = RB_ROOT, + .ns_list_head = LIST_HEAD_INIT(cgroup_ns_tree.ns_list_head), +}; + +struct ns_tree_root time_ns_tree = { + .ns_rb = RB_ROOT, + .ns_list_head = LIST_HEAD_INIT(time_ns_tree.ns_list_head), +}; + +/** + * ns_tree_node_init - Initialize a namespace tree node + * @node: The node to initialize + * + * Initializes both the rbtree node and list entry. + */ +void ns_tree_node_init(struct ns_tree_node *node) +{ + RB_CLEAR_NODE(&node->ns_node); + INIT_LIST_HEAD(&node->ns_list_entry); +} + +/** + * ns_tree_root_init - Initialize a namespace tree root + * @root: The root to initialize + * + * Initializes both the rbtree root and list head. + */ +void ns_tree_root_init(struct ns_tree_root *root) +{ + root->ns_rb = RB_ROOT; + INIT_LIST_HEAD(&root->ns_list_head); +} + +/** + * ns_tree_node_empty - Check if a namespace tree node is empty + * @node: The node to check + * + * Returns true if the node is not in any tree. + */ +bool ns_tree_node_empty(const struct ns_tree_node *node) +{ + return RB_EMPTY_NODE(&node->ns_node); +} + +/** + * ns_tree_node_add - Add a node to a namespace tree + * @node: The node to add + * @root: The tree root to add to + * @cmp: Comparison function for rbtree insertion + * + * Adds the node to both the rbtree and the list, maintaining sorted order. + * The list is maintained in the same order as the rbtree to enable efficient + * iteration. + * + * Returns: NULL if insertion succeeded, existing node if duplicate found + */ +struct rb_node *ns_tree_node_add(struct ns_tree_node *node, + struct ns_tree_root *root, + int (*cmp)(struct rb_node *, const struct rb_node *)) +{ + struct rb_node *ret, *prev; + + /* Add to rbtree */ + ret = rb_find_add_rcu(&node->ns_node, &root->ns_rb, cmp); + + /* Add to list in sorted order */ + prev = rb_prev(&node->ns_node); + if (!prev) { + /* No previous node, add at head */ + list_add_rcu(&node->ns_list_entry, &root->ns_list_head); + } else { + /* Add after previous node */ + struct ns_tree_node *prev_node; + prev_node = rb_entry(prev, struct ns_tree_node, ns_node); + list_add_rcu(&node->ns_list_entry, &prev_node->ns_list_entry); + } + + return ret; +} + +/** + * ns_tree_node_del - Remove a node from a namespace tree + * @node: The node to remove + * @root: The tree root to remove from + * + * Removes the node from both the rbtree and the list atomically. + */ +void ns_tree_node_del(struct ns_tree_node *node, struct ns_tree_root *root) +{ + rb_erase(&node->ns_node, &root->ns_rb); + RB_CLEAR_NODE(&node->ns_node); + list_bidir_del_rcu(&node->ns_list_entry); +} + +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.ns_node); +} + +static inline struct ns_common *node_to_ns_unified(const struct rb_node *node) +{ + if (!node) + return NULL; + return rb_entry(node, struct ns_common, ns_unified_node.ns_node); +} + +static inline struct ns_common *node_to_ns_owner(const struct rb_node *node) +{ + if (!node) + return NULL; + return rb_entry(node, struct ns_common, ns_owner_node.ns_node); +} + +static int ns_id_cmp(u64 id_a, u64 id_b) +{ + if (id_a < id_b) + return -1; + if (id_a > id_b) + return 1; + return 0; +} + +static int ns_cmp(struct rb_node *a, const struct rb_node *b) +{ + return ns_id_cmp(node_to_ns(a)->ns_id, node_to_ns(b)->ns_id); +} + +static int ns_cmp_unified(struct rb_node *a, const struct rb_node *b) +{ + return ns_id_cmp(node_to_ns_unified(a)->ns_id, node_to_ns_unified(b)->ns_id); +} + +static int ns_cmp_owner(struct rb_node *a, const struct rb_node *b) +{ + return ns_id_cmp(node_to_ns_owner(a)->ns_id, node_to_ns_owner(b)->ns_id); +} + +void __ns_tree_add_raw(struct ns_common *ns, struct ns_tree_root *ns_tree) +{ + struct rb_node *node; + const struct proc_ns_operations *ops = ns->ops; + + VFS_WARN_ON_ONCE(!ns->ns_id); + + guard(ns_tree_writer)(); + + /* Add to per-type tree and list */ + node = ns_tree_node_add(&ns->ns_tree_node, ns_tree, ns_cmp); + + /* Add to unified tree and list */ + ns_tree_node_add(&ns->ns_unified_node, &ns_unified_root, ns_cmp_unified); + + /* Add to owner's tree if applicable */ + if (ops) { + struct user_namespace *user_ns; + + VFS_WARN_ON_ONCE(!ops->owner); + user_ns = ops->owner(ns); + if (user_ns) { + struct ns_common *owner = &user_ns->ns; + VFS_WARN_ON_ONCE(owner->ns_type != CLONE_NEWUSER); + + /* Insert into owner's tree and list */ + ns_tree_node_add(&ns->ns_owner_node, &owner->ns_owner_root, ns_cmp_owner); + } else { + /* Only the initial user namespace doesn't have an owner. */ + VFS_WARN_ON_ONCE(ns != to_ns_common(&init_user_ns)); + } + } + + VFS_WARN_ON_ONCE(node); +} + +void __ns_tree_remove(struct ns_common *ns, struct ns_tree_root *ns_tree) +{ + const struct proc_ns_operations *ops = ns->ops; + struct user_namespace *user_ns; + + VFS_WARN_ON_ONCE(ns_tree_node_empty(&ns->ns_tree_node)); + VFS_WARN_ON_ONCE(list_empty(&ns->ns_tree_node.ns_list_entry)); + + write_seqlock(&ns_tree_lock); + + /* Remove from per-type tree and list */ + ns_tree_node_del(&ns->ns_tree_node, ns_tree); + + /* Remove from unified tree and list */ + ns_tree_node_del(&ns->ns_unified_node, &ns_unified_root); + + /* Remove from owner's tree if applicable */ + if (ops) { + user_ns = ops->owner(ns); + if (user_ns) { + struct ns_common *owner = &user_ns->ns; + ns_tree_node_del(&ns->ns_owner_node, &owner->ns_owner_root); + } + } + + write_sequnlock(&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 int ns_find_unified(const void *key, const struct rb_node *node) +{ + const u64 ns_id = *(u64 *)key; + const struct ns_common *ns = node_to_ns_unified(node); + + if (ns_id < ns->ns_id) + return -1; + if (ns_id > ns->ns_id) + return 1; + return 0; +} + +static struct ns_tree_root *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; +} + +static struct ns_common *__ns_unified_tree_lookup_rcu(u64 ns_id) +{ + struct rb_node *node; + unsigned int seq; + + do { + seq = read_seqbegin(&ns_tree_lock); + node = rb_find_rcu(&ns_id, &ns_unified_root.ns_rb, ns_find_unified); + if (node) + break; + } while (read_seqretry(&ns_tree_lock, seq)); + + return node_to_ns_unified(node); +} + +static struct ns_common *__ns_tree_lookup_rcu(u64 ns_id, int ns_type) +{ + struct ns_tree_root *ns_tree; + struct rb_node *node; + unsigned int seq; + + ns_tree = ns_tree_from_type(ns_type); + if (!ns_tree) + return NULL; + + do { + seq = read_seqbegin(&ns_tree_lock); + node = rb_find_rcu(&ns_id, &ns_tree->ns_rb, ns_find); + if (node) + break; + } while (read_seqretry(&ns_tree_lock, seq)); + + return node_to_ns(node); +} + +struct ns_common *ns_tree_lookup_rcu(u64 ns_id, int ns_type) +{ + RCU_LOCKDEP_WARN(!rcu_read_lock_held(), "suspicious ns_tree_lookup_rcu() usage"); + + if (ns_type) + return __ns_tree_lookup_rcu(ns_id, ns_type); + + return __ns_unified_tree_lookup_rcu(ns_id); +} + +/** + * __ns_tree_adjoined_rcu - find the next/previous namespace in the same + * tree + * @ns: namespace to start from + * @ns_tree: namespace tree to search in + * @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_root *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_tree_node.ns_list_entry)); + else + list = rcu_dereference(list_next_rcu(&ns->ns_tree_node.ns_list_entry)); + if (list_is_head(list, &ns_tree->ns_list_head)) + return ERR_PTR(-ENOENT); + + return list_entry_rcu(list, struct ns_common, ns_tree_node.ns_list_entry); +} + +/** + * __ns_tree_gen_id - generate a new namespace id + * @ns: namespace to generate id for + * @id: if non-zero, this is the initial namespace and this is a fixed id + * + * 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, u64 id) +{ + static atomic64_t namespace_cookie = ATOMIC64_INIT(NS_LAST_INIT_ID + 1); + + if (id) + ns->ns_id = id; + else + ns->ns_id = atomic64_inc_return(&namespace_cookie); + return ns->ns_id; +} + +struct klistns { + u64 __user *uns_ids; + u32 nr_ns_ids; + u64 last_ns_id; + u64 user_ns_id; + u32 ns_type; + struct user_namespace *user_ns; + bool userns_capable; + struct ns_common *first_ns; +}; + +static void __free_klistns_free(const struct klistns *kls) +{ + if (kls->user_ns_id != LISTNS_CURRENT_USER) + put_user_ns(kls->user_ns); + if (kls->first_ns && kls->first_ns->ops) + kls->first_ns->ops->put(kls->first_ns); +} + +#define NS_ALL (PID_NS | USER_NS | MNT_NS | UTS_NS | IPC_NS | NET_NS | CGROUP_NS | TIME_NS) + +static int copy_ns_id_req(const struct ns_id_req __user *req, + struct ns_id_req *kreq) +{ + int ret; + size_t usize; + + BUILD_BUG_ON(sizeof(struct ns_id_req) != NS_ID_REQ_SIZE_VER0); + + ret = get_user(usize, &req->size); + if (ret) + return -EFAULT; + if (unlikely(usize > PAGE_SIZE)) + return -E2BIG; + if (unlikely(usize < NS_ID_REQ_SIZE_VER0)) + return -EINVAL; + memset(kreq, 0, sizeof(*kreq)); + ret = copy_struct_from_user(kreq, sizeof(*kreq), req, usize); + if (ret) + return ret; + if (kreq->spare != 0) + return -EINVAL; + if (kreq->ns_type & ~NS_ALL) + return -EOPNOTSUPP; + return 0; +} + +static inline int prepare_klistns(struct klistns *kls, struct ns_id_req *kreq, + u64 __user *ns_ids, size_t nr_ns_ids) +{ + kls->last_ns_id = kreq->ns_id; + kls->user_ns_id = kreq->user_ns_id; + kls->nr_ns_ids = nr_ns_ids; + kls->ns_type = kreq->ns_type; + kls->uns_ids = ns_ids; + return 0; +} + +/* + * Lookup a namespace owned by owner with id >= ns_id. + * Returns the namespace with the smallest id that is >= ns_id. + */ +static struct ns_common *lookup_ns_owner_at(u64 ns_id, struct ns_common *owner) +{ + struct ns_common *ret = NULL; + struct rb_node *node; + + VFS_WARN_ON_ONCE(owner->ns_type != CLONE_NEWUSER); + + guard(ns_tree_locked_reader)(); + + node = owner->ns_owner_root.ns_rb.rb_node; + while (node) { + struct ns_common *ns; + + ns = node_to_ns_owner(node); + if (ns_id <= ns->ns_id) { + ret = ns; + if (ns_id == ns->ns_id) + break; + node = node->rb_left; + } else { + node = node->rb_right; + } + } + + if (ret) + ret = ns_get_unless_inactive(ret); + return ret; +} + +static struct ns_common *lookup_ns_id(u64 mnt_ns_id, int ns_type) +{ + struct ns_common *ns; + + guard(rcu)(); + ns = ns_tree_lookup_rcu(mnt_ns_id, ns_type); + if (!ns) + return NULL; + + if (!ns_get_unless_inactive(ns)) + return NULL; + + return ns; +} + +static inline bool __must_check ns_requested(const struct klistns *kls, + const struct ns_common *ns) +{ + return !kls->ns_type || (kls->ns_type & ns->ns_type); +} + +static inline bool __must_check may_list_ns(const struct klistns *kls, + struct ns_common *ns) +{ + if (kls->user_ns) { + if (kls->userns_capable) + return true; + } else { + struct ns_common *owner; + struct user_namespace *user_ns; + + owner = ns_owner(ns); + if (owner) + user_ns = to_user_ns(owner); + else + user_ns = &init_user_ns; + if (ns_capable_noaudit(user_ns, CAP_SYS_ADMIN)) + return true; + } + + if (is_current_namespace(ns)) + return true; + + if (ns->ns_type != CLONE_NEWUSER) + return false; + + if (ns_capable_noaudit(to_user_ns(ns), CAP_SYS_ADMIN)) + return true; + + return false; +} + +static inline void ns_put(struct ns_common *ns) +{ + if (ns && ns->ops) + ns->ops->put(ns); +} + +DEFINE_FREE(ns_put, struct ns_common *, if (!IS_ERR_OR_NULL(_T)) ns_put(_T)) + +static inline struct ns_common *__must_check legitimize_ns(const struct klistns *kls, + struct ns_common *candidate) +{ + struct ns_common *ns __free(ns_put) = NULL; + + if (!ns_requested(kls, candidate)) + return NULL; + + ns = ns_get_unless_inactive(candidate); + if (!ns) + return NULL; + + if (!may_list_ns(kls, ns)) + return NULL; + + return no_free_ptr(ns); +} + +static ssize_t do_listns_userns(struct klistns *kls) +{ + u64 __user *ns_ids = kls->uns_ids; + size_t nr_ns_ids = kls->nr_ns_ids; + struct ns_common *ns = NULL, *first_ns = NULL, *prev = NULL; + const struct list_head *head; + ssize_t ret; + + VFS_WARN_ON_ONCE(!kls->user_ns_id); + + if (kls->user_ns_id == LISTNS_CURRENT_USER) + ns = to_ns_common(current_user_ns()); + else if (kls->user_ns_id) + ns = lookup_ns_id(kls->user_ns_id, CLONE_NEWUSER); + if (!ns) + return -EINVAL; + kls->user_ns = to_user_ns(ns); + + /* + * Use the rbtree to find the first namespace we care about and + * then use it's list entry to iterate from there. + */ + if (kls->last_ns_id) { + kls->first_ns = lookup_ns_owner_at(kls->last_ns_id + 1, ns); + if (!kls->first_ns) + return -ENOENT; + first_ns = kls->first_ns; + } + + ret = 0; + head = &to_ns_common(kls->user_ns)->ns_owner_root.ns_list_head; + kls->userns_capable = ns_capable_noaudit(kls->user_ns, CAP_SYS_ADMIN); + + rcu_read_lock(); + + if (!first_ns) + first_ns = list_entry_rcu(head->next, typeof(*first_ns), ns_owner_node.ns_list_entry); + + ns = first_ns; + list_for_each_entry_from_rcu(ns, head, ns_owner_node.ns_list_entry) { + struct ns_common *valid; + + if (!nr_ns_ids) + break; + + valid = legitimize_ns(kls, ns); + if (!valid) + continue; + + rcu_read_unlock(); + + ns_put(prev); + prev = valid; + + if (put_user(valid->ns_id, ns_ids + ret)) { + ns_put(prev); + return -EFAULT; + } + + nr_ns_ids--; + ret++; + + rcu_read_lock(); + } + + rcu_read_unlock(); + ns_put(prev); + return ret; +} + +/* + * Lookup a namespace with id >= ns_id in either the unified tree or a type-specific tree. + * Returns the namespace with the smallest id that is >= ns_id. + */ +static struct ns_common *lookup_ns_id_at(u64 ns_id, int ns_type) +{ + struct ns_common *ret = NULL; + struct ns_tree_root *ns_tree = NULL; + struct rb_node *node; + + if (ns_type) { + ns_tree = ns_tree_from_type(ns_type); + if (!ns_tree) + return NULL; + } + + guard(ns_tree_locked_reader)(); + + if (ns_tree) + node = ns_tree->ns_rb.rb_node; + else + node = ns_unified_root.ns_rb.rb_node; + + while (node) { + struct ns_common *ns; + + if (ns_type) + ns = node_to_ns(node); + else + ns = node_to_ns_unified(node); + + if (ns_id <= ns->ns_id) { + if (ns_type) + ret = node_to_ns(node); + else + ret = node_to_ns_unified(node); + if (ns_id == ns->ns_id) + break; + node = node->rb_left; + } else { + node = node->rb_right; + } + } + + if (ret) + ret = ns_get_unless_inactive(ret); + return ret; +} + +static inline struct ns_common *first_ns_common(const struct list_head *head, + struct ns_tree_root *ns_tree) +{ + if (ns_tree) + return list_entry_rcu(head->next, struct ns_common, ns_tree_node.ns_list_entry); + return list_entry_rcu(head->next, struct ns_common, ns_unified_node.ns_list_entry); +} + +static inline struct ns_common *next_ns_common(struct ns_common *ns, + struct ns_tree_root *ns_tree) +{ + if (ns_tree) + return list_entry_rcu(ns->ns_tree_node.ns_list_entry.next, struct ns_common, ns_tree_node.ns_list_entry); + return list_entry_rcu(ns->ns_unified_node.ns_list_entry.next, struct ns_common, ns_unified_node.ns_list_entry); +} + +static inline bool ns_common_is_head(struct ns_common *ns, + const struct list_head *head, + struct ns_tree_root *ns_tree) +{ + if (ns_tree) + return &ns->ns_tree_node.ns_list_entry == head; + return &ns->ns_unified_node.ns_list_entry == head; +} + +static ssize_t do_listns(struct klistns *kls) +{ + u64 __user *ns_ids = kls->uns_ids; + size_t nr_ns_ids = kls->nr_ns_ids; + struct ns_common *ns, *first_ns = NULL, *prev = NULL; + struct ns_tree_root *ns_tree = NULL; + const struct list_head *head; + u32 ns_type; + ssize_t ret; + + if (hweight32(kls->ns_type) == 1) + ns_type = kls->ns_type; + else + ns_type = 0; + + if (ns_type) { + ns_tree = ns_tree_from_type(ns_type); + if (!ns_tree) + return -EINVAL; + } + + if (kls->last_ns_id) { + kls->first_ns = lookup_ns_id_at(kls->last_ns_id + 1, ns_type); + if (!kls->first_ns) + return -ENOENT; + first_ns = kls->first_ns; + } + + ret = 0; + if (ns_tree) + head = &ns_tree->ns_list_head; + else + head = &ns_unified_root.ns_list_head; + + rcu_read_lock(); + + if (!first_ns) + first_ns = first_ns_common(head, ns_tree); + + for (ns = first_ns; !ns_common_is_head(ns, head, ns_tree) && nr_ns_ids; + ns = next_ns_common(ns, ns_tree)) { + struct ns_common *valid; + + valid = legitimize_ns(kls, ns); + if (!valid) + continue; + + rcu_read_unlock(); + + ns_put(prev); + prev = valid; + + if (put_user(valid->ns_id, ns_ids + ret)) { + ns_put(prev); + return -EFAULT; + } + + nr_ns_ids--; + ret++; + + rcu_read_lock(); + } + + rcu_read_unlock(); + ns_put(prev); + return ret; +} + +SYSCALL_DEFINE4(listns, const struct ns_id_req __user *, req, + u64 __user *, ns_ids, size_t, nr_ns_ids, unsigned int, flags) +{ + struct klistns klns __free(klistns_free) = {}; + const size_t maxcount = 1000000; + struct ns_id_req kreq; + ssize_t ret; + + if (flags) + return -EINVAL; + + if (unlikely(nr_ns_ids > maxcount)) + return -EOVERFLOW; + + if (!access_ok(ns_ids, nr_ns_ids * sizeof(*ns_ids))) + return -EFAULT; + + ret = copy_ns_id_req(req, &kreq); + if (ret) + return ret; + + ret = prepare_klistns(&klns, &kreq, ns_ids, nr_ns_ids); + if (ret) + return ret; + + if (kreq.user_ns_id) + return do_listns_userns(&klns); + + return do_listns(&klns); +} |