#include "audit.h" #include <linux/fsnotify_backend.h> #include <linux/namei.h> #include <linux/mount.h> #include <linux/kthread.h> #include <linux/slab.h> struct audit_tree; struct audit_chunk; struct audit_tree { atomic_t count; int goner; struct audit_chunk *root; struct list_head chunks; struct list_head rules; struct list_head list; struct list_head same_root; struct rcu_head head; char pathname[]; }; struct audit_chunk { struct list_head hash; struct fsnotify_mark mark; struct list_head trees; /* with root here */ int dead; int count; atomic_long_t refs; struct rcu_head head; struct node { struct list_head list; struct audit_tree *owner; unsigned index; /* index; upper bit indicates 'will prune' */ } owners[]; }; static LIST_HEAD(tree_list); static LIST_HEAD(prune_list); /* * One struct chunk is attached to each inode of interest. * We replace struct chunk on tagging/untagging. * Rules have pointer to struct audit_tree. * Rules have struct list_head rlist forming a list of rules over * the same tree. * References to struct chunk are collected at audit_inode{,_child}() * time and used in AUDIT_TREE rule matching. * These references are dropped at the same time we are calling * audit_free_names(), etc. * * Cyclic lists galore: * tree.chunks anchors chunk.owners[].list hash_lock * tree.rules anchors rule.rlist audit_filter_mutex * chunk.trees anchors tree.same_root hash_lock * chunk.hash is a hash with middle bits of watch.inode as * a hash function. RCU, hash_lock * * tree is refcounted; one reference for "some rules on rules_list refer to * it", one for each chunk with pointer to it. * * chunk is refcounted by embedded fsnotify_mark + .refs (non-zero refcount * of watch contributes 1 to .refs). * * node.index allows to get from node.list to containing chunk. * MSB of that sucker is stolen to mark taggings that we might have to * revert - several operations have very unpleasant cleanup logics and * that makes a difference. Some. */ static struct fsnotify_group *audit_tree_group; static struct audit_tree *alloc_tree(const char *s) { struct audit_tree *tree; tree = kmalloc(sizeof(struct audit_tree) + strlen(s) + 1, GFP_KERNEL); if (tree) { atomic_set(&tree->count, 1); tree->goner = 0; INIT_LIST_HEAD(&tree->chunks); INIT_LIST_HEAD(&tree->rules); INIT_LIST_HEAD(&tree->list); INIT_LIST_HEAD(&tree->same_root); tree->root = NULL; strcpy(tree->pathname, s); } return tree; } static inline void get_tree(struct audit_tree *tree) { atomic_inc(&tree->count); } static inline void put_tree(struct audit_tree *tree) { if (atomic_dec_and_test(&tree->count)) kfree_rcu(tree, head); } /* to avoid bringing the entire thing in audit.h */ const char *audit_tree_path(struct audit_tree *tree) { return tree->pathname; } static void free_chunk(struct audit_chunk *chunk) { int i; for (i = 0; i < chunk->count; i++) { if (chunk->owners[i].owner) put_tree(chunk->owners[i].owner); } kfree(chunk); } void audit_put_chunk(struct audit_chunk *chunk) { if (atomic_long_dec_and_test(&chunk->refs)) free_chunk(chunk); } static void __put_chunk(struct rcu_head *rcu) { struct audit_chunk *chunk = container_of(rcu, struct audit_chunk, head); audit_put_chunk(chunk); } static void audit_tree_destroy_watch(struct fsnotify_mark *entry) { struct audit_chunk *chunk = container_of(entry, struct audit_chunk, mark); call_rcu(&chunk->head, __put_chunk); } static struct audit_chunk *alloc_chunk(int count) { struct audit_chunk *chunk; size_t size; int i; size = offsetof(struct audit_chunk, owners) + count * sizeof(struct node); chunk = kzalloc(size, GFP_KERNEL); if (!chunk) return NULL; INIT_LIST_HEAD(&chunk->hash); INIT_LIST_HEAD(&chunk->trees); chunk->count = count; atomic_long_set(&chunk->refs, 1); for (i = 0; i < count; i++) { INIT_LIST_HEAD(&chunk->owners[i].list); chunk->owners[i].index = i; } fsnotify_init_mark(&chunk->mark, audit_tree_destroy_watch); return chunk; } enum {HASH_SIZE = 128}; static struct list_head chunk_hash_heads[HASH_SIZE]; static __cacheline_aligned_in_smp DEFINE_SPINLOCK(hash_lock); static inline struct list_head *chunk_hash(const struct inode *inode) { unsigned long n = (unsigned long)inode / L1_CACHE_BYTES; return chunk_hash_heads + n % HASH_SIZE; } /* hash_lock & entry->lock is held by caller */ static void insert_hash(struct audit_chunk *chunk) { struct fsnotify_mark *entry = &chunk->mark; struct list_head *list; if (!entry->i.inode) return; list = chunk_hash(entry->i.inode); list_add_rcu(&chunk->hash, list); } /* called under rcu_read_lock */ struct audit_chunk *audit_tree_lookup(const struct inode *inode) { struct list_head *list = chunk_hash(inode); struct audit_chunk *p; list_for_each_entry_rcu(p, list, hash) { /* mark.inode may have gone NULL, but who cares? */ if (p->mark.i.inode == inode) { atomic_long_inc(&p->refs); return p; } } return NULL; } int audit_tree_match(struct audit_chunk *chunk, struct audit_tree *tree) { int n; for (n = 0; n < chunk->count; n++) if (chunk->owners[n].owner == tree) return 1; return 0; } /* tagging and untagging inodes with trees */ static struct audit_chunk *find_chunk(struct node *p) { int index = p->index & ~(1U<<31); p -= index; return container_of(p, struct audit_chunk, owners[0]); } static void untag_chunk(struct node *p) { struct audit_chunk *chunk = find_chunk(p); struct fsnotify_mark *entry = &chunk->mark; struct audit_chunk *new = NULL; struct audit_tree *owner; int size = chunk->count - 1; int i, j; fsnotify_get_mark(entry); spin_unlock(&hash_lock); if (size) new = alloc_chunk(size); spin_lock(&entry->lock); if (chunk->dead || !entry->i.inode) { spin_unlock(&entry->lock); if (new) free_chunk(new); goto out; } owner = p->owner; if (!size) { chunk->dead = 1; spin_lock(&hash_lock); list_del_init(&chunk->trees); if (owner->root == chunk) owner->root = NULL; list_del_init(&p->list); list_del_rcu(&chunk->hash); spin_unlock(&hash_lock); spin_unlock(&entry->lock); fsnotify_destroy_mark(entry); goto out; } if (!new) goto Fallback; fsnotify_duplicate_mark(&new->mark, entry); if (fsnotify_add_mark(&new->mark, new->mark.group, new->mark.i.inode, NULL, 1)) { fsnotify_put_mark(&new->mark); goto Fallback; } chunk->dead = 1; spin_lock(&hash_lock); list_replace_init(&chunk->trees, &new->trees); if (owner->root == chunk) { list_del_init(&owner->same_root); owner->root = NULL; } for (i = j = 0; j <= size; i++, j++) { struct audit_tree *s; if (&chunk->owners[j] == p) { list_del_init(&p->list); i--; continue; } s = chunk->owners[j].owner; new->owners[i].owner = s; new->owners[i].index = chunk->owners[j].index - j + i; if (!s) /* result of earlier fallback */ continue; get_tree(s); list_replace_init(&chunk->owners[j].list, &new->owners[i].list); } list_replace_rcu(&chunk->hash, &new->hash); list_for_each_entry(owner, &new->trees, same_root) owner->root = new; spin_unlock(&hash_lock); spin_unlock(&entry->lock); fsnotify_destroy_mark(entry); fsnotify_put_mark(&new->mark); /* drop initial reference */ goto out; Fallback: // do the best we can spin_lock(&hash_lock); if (owner->root == chunk) { list_del_init(&owner->same_root); owner->root = NULL; } list_del_init(&p->list); p->owner = NULL; put_tree(owner); spin_unlock(&hash_lock); spin_unlock(&entry->lock); out: fsnotify_put_mark(entry); spin_lock(&hash_lock); } static int create_chunk(struct inode *inode, struct audit_tree *tree) { struct fsnotify_mark *entry; struct audit_chunk *chunk = alloc_chunk(1); if (!chunk) return -ENOMEM; entry = &chunk->mark; if (fsnotify_add_mark(entry, audit_tree_group, inode, NULL, 0)) { fsnotify_put_mark(entry); return -ENOSPC; } spin_lock(&entry->lock); spin_lock(&hash_lock); if (tree->goner) { spin_unlock(&hash_lock); chunk->dead = 1; spin_unlock(&entry->lock); fsnotify_destroy_mark(entry); fsnotify_put_mark(entry); return 0; } chunk->owners[0].index = (1U << 31); chunk->owners[0].owner = tree; get_tree(tree); list_add(&chunk->owners[0].list, &tree->chunks); if (!tree->root) { tree->root = chunk; list_add(&tree->same_root, &chunk->trees); } insert_hash(chunk); spin_unlock(&hash_lock); spin_unlock(&entry->lock); fsnotify_put_mark(entry); /* drop initial reference */ return 0; } /* the first tagged inode becomes root of tree */ static int tag_chunk(struct inode *inode, struct audit_tree *tree) { struct fsnotify_mark *old_entry, *chunk_entry; struct audit_tree *owner; struct audit_chunk *chunk, *old; struct node *p; int n; old_entry = fsnotify_find_inode_mark(audit_tree_group, inode); if (!old_entry) return create_chunk(inode, tree); old = container_of(old_entry, struct audit_chunk, mark); /* are we already there? */ spin_lock(&hash_lock); for (n = 0; n < old->count; n++) { if (old->owners[n].owner == tree) { spin_unlock(&hash_lock); fsnotify_put_mark(old_entry); return 0; } } spin_unlock(&hash_lock); chunk = alloc_chunk(old->count + 1); if (!chunk) { fsnotify_put_mark(old_entry); return -ENOMEM; } chunk_entry = &chunk->mark; spin_lock(&old_entry->lock); if (!old_entry->i.inode) { /* old_entry is being shot, lets just lie */ spin_unlock(&old_entry->lock); fsnotify_put_mark(old_entry); free_chunk(chunk); return -ENOENT; } fsnotify_duplicate_mark(chunk_entry, old_entry); if (fsnotify_add_mark(chunk_entry, chunk_entry->group, chunk_entry->i.inode, NULL, 1)) { spin_unlock(&old_entry->lock); fsnotify_put_mark(chunk_entry); fsnotify_put_mark(old_entry); return -ENOSPC; } /* even though we hold old_entry->lock, this is safe since chunk_entry->lock could NEVER have been grabbed before */ spin_lock(&chunk_entry->lock); spin_lock(&hash_lock); /* we now hold old_entry->lock, chunk_entry->lock, and hash_lock */ if (tree->goner) { spin_unlock(&hash_lock); chunk->dead = 1; spin_unlock(&chunk_entry->lock); spin_unlock(&old_entry->lock); fsnotify_destroy_mark(chunk_entry); fsnotify_put_mark(chunk_entry); fsnotify_put_mark(old_entry); return 0; } list_replace_init(&old->trees, &chunk->trees); for (n = 0, p = chunk->owners; n < old->count; n++, p++) { struct audit_tree *s = old->owners[n].owner; p->owner = s; p->index = old->owners[n].index; if (!s) /* result of fallback in untag */ continue; get_tree(s); list_replace_init(&old->owners[n].list, &p->list); } p->index = (chunk->count - 1) | (1U<<31); p->owner = tree; get_tree(tree); list_add(&p->list, &tree->chunks); list_replace_rcu(&old->hash, &chunk->hash); list_for_each_entry(owner, &chunk->trees, same_root) owner->root = chunk; old->dead = 1; if (!tree->root) { tree->root = chunk; list_add(&tree->same_root, &chunk->trees); } spin_unlock(&hash_lock); spin_unlock(&chunk_entry->lock); spin_unlock(&old_entry->lock); fsnotify_destroy_mark(old_entry); fsnotify_put_mark(chunk_entry); /* drop initial reference */ fsnotify_put_mark(old_entry); /* pair to fsnotify_find mark_entry */ return 0; } static void kill_rules(struct audit_tree *tree) { struct audit_krule *rule, *next; struct audit_entry *entry; struct audit_buffer *ab; list_for_each_entry_safe(rule, next, &tree->rules, rlist) { entry = container_of(rule, struct audit_entry, rule); list_del_init(&rule->rlist); if (rule->tree) { /* not a half-baked one */ ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE); audit_log_format(ab, "op="); audit_log_string(ab, "remove rule"); audit_log_format(ab, " dir="); audit_log_untrustedstring(ab, rule->tree->pathname); audit_log_key(ab, rule->filterkey); audit_log_format(ab, " list=%d res=1", rule->listnr); audit_log_end(ab); rule->tree = NULL; list_del_rcu(&entry->list); list_del(&entry->rule.list); call_rcu(&entry->rcu, audit_free_rule_rcu); } } } /* * finish killing struct audit_tree */ static void prune_one(struct audit_tree *victim) { spin_lock(&hash_lock); while (!list_empty(&victim->chunks)) { struct node *p; p = list_entry(victim->chunks.next, struct node, list); untag_chunk(p); } spin_unlock(&hash_lock); put_tree(victim); } /* trim the uncommitted chunks from tree */ static void trim_marked(struct audit_tree *tree) { struct list_head *p, *q; spin_lock(&hash_lock); if (tree->goner) { spin_unlock(&hash_lock); return; } /* reorder */ for (p = tree->chunks.next; p != &tree->chunks; p = q) { struct node *node = list_entry(p, struct node, list); q = p->next; if (node->index & (1U<<31)) { list_del_init(p); list_add(p, &tree->chunks); } } while (!list_empty(&tree->chunks)) { struct node *node; node = list_entry(tree->chunks.next, struct node, list); /* have we run out of marked? */ if (!(node->index & (1U<<31))) break; untag_chunk(node); } if (!tree->root && !tree->goner) { tree->goner = 1; spin_unlock(&hash_lock); mutex_lock(&audit_filter_mutex); kill_rules(tree); list_del_init(&tree->list); mutex_unlock(&audit_filter_mutex); prune_one(tree); } else { spin_unlock(&hash_lock); } } static void audit_schedule_prune(void); /* called with audit_filter_mutex */ int audit_remove_tree_rule(struct audit_krule *rule) { struct audit_tree *tree; tree = rule->tree; if (tree) { spin_lock(&hash_lock); list_del_init(&rule->rlist); if (list_empty(&tree->rules) && !tree->goner) { tree->root = NULL; list_del_init(&tree->same_root); tree->goner = 1; list_move(&tree->list, &prune_list); rule->tree = NULL; spin_unlock(&hash_lock); audit_schedule_prune(); return 1; } rule->tree = NULL; spin_unlock(&hash_lock); return 1; } return 0; } static int compare_root(struct vfsmount *mnt, void *arg) { return mnt->mnt_root->d_inode == arg; } void audit_trim_trees(void) { struct list_head cursor; mutex_lock(&audit_filter_mutex); list_add(&cursor, &tree_list); while (cursor.next != &tree_list) { struct audit_tree *tree; struct path path; struct vfsmount *root_mnt; struct node *node; int err; tree = container_of(cursor.next, struct audit_tree, list); get_tree(tree); list_del(&cursor); list_add(&cursor, &tree->list); mutex_unlock(&audit_filter_mutex); err = kern_path(tree->pathname, 0, &path); if (err) goto skip_it; root_mnt = collect_mounts(&path); path_put(&path); if (IS_ERR(root_mnt)) goto skip_it; spin_lock(&hash_lock); list_for_each_entry(node, &tree->chunks, list) { struct audit_chunk *chunk = find_chunk(node); /* this could be NULL if the watch is dying else where... */ struct inode *inode = chunk->mark.i.inode; node->index |= 1U<<31; if (iterate_mounts(compare_root, inode, root_mnt)) node->index &= ~(1U<<31); } spin_unlock(&hash_lock); trim_marked(tree); put_tree(tree); drop_collected_mounts(root_mnt); skip_it: mutex_lock(&audit_filter_mutex); } list_del(&cursor); mutex_unlock(&audit_filter_mutex); } int audit_make_tree(struct audit_krule *rule, char *pathname, u32 op) { if (pathname[0] != '/' || rule->listnr != AUDIT_FILTER_EXIT || op != Audit_equal || rule->inode_f || rule->watch || rule->tree) return -EINVAL; rule->tree = alloc_tree(pathname); if (!rule->tree) return -ENOMEM; return 0; } void audit_put_tree(struct audit_tree *tree) { put_tree(tree); } static int tag_mount(struct vfsmount *mnt, void *arg) { return tag_chunk(mnt->mnt_root->d_inode, arg); } /* called with audit_filter_mutex */ int audit_add_tree_rule(struct audit_krule *rule) { struct audit_tree *seed = rule->tree, *tree; struct path path; struct vfsmount *mnt; int err; list_for_each_entry(tree, &tree_list, list) { if (!strcmp(seed->pathname, tree->pathname)) { put_tree(seed); rule->tree = tree; list_add(&rule->rlist, &tree->rules); return 0; } } tree = seed; list_add(&tree->list, &tree_list); list_add(&rule->rlist, &tree->rules); /* do not set rule->tree yet */ mutex_unlock(&audit_filter_mutex); err = kern_path(tree->pathname, 0, &path); if (err) goto Err; mnt = collect_mounts(&path); path_put(&path); if (IS_ERR(mnt)) { err = PTR_ERR(mnt); goto Err; } get_tree(tree); err = iterate_mounts(tag_mount, tree, mnt); drop_collected_mounts(mnt); if (!err) { struct node *node; spin_lock(&hash_lock); list_for_each_entry(node, &tree->chunks, list) node->index &= ~(1U<<31); spin_unlock(&hash_lock); } else { trim_marked(tree); goto Err; } mutex_lock(&audit_filter_mutex); if (list_empty(&rule->rlist)) { put_tree(tree); return -ENOENT; } rule->tree = tree; put_tree(tree); return 0; Err: mutex_lock(&audit_filter_mutex); list_del_init(&tree->list); list_del_init(&tree->rules); put_tree(tree); return err; } int audit_tag_tree(char *old, char *new) { struct list_head cursor, barrier; int failed = 0; struct path path1, path2; struct vfsmount *tagged; int err; err = kern_path(new, 0, &path2); if (err) return err; tagged = collect_mounts(&path2); path_put(&path2); if (IS_ERR(tagged)) return PTR_ERR(tagged); err = kern_path(old, 0, &path1); if (err) { drop_collected_mounts(tagged); return err; } mutex_lock(&audit_filter_mutex); list_add(&barrier, &tree_list); list_add(&cursor, &barrier); while (cursor.next != &tree_list) { struct audit_tree *tree; int good_one = 0; tree = container_of(cursor.next, struct audit_tree, list); get_tree(tree); list_del(&cursor); list_add(&cursor, &tree->list); mutex_unlock(&audit_filter_mutex); err = kern_path(tree->pathname, 0, &path2); if (!err) { good_one = path_is_under(&path1, &path2); path_put(&path2); } if (!good_one) { put_tree(tree); mutex_lock(&audit_filter_mutex); continue; } failed = iterate_mounts(tag_mount, tree, tagged); if (failed) { put_tree(tree); mutex_lock(&audit_filter_mutex); break; } mutex_lock(&audit_filter_mutex); spin_lock(&hash_lock); if (!tree->goner) { list_del(&tree->list); list_add(&tree->list, &tree_list); } spin_unlock(&hash_lock); put_tree(tree); } while (barrier.prev != &tree_list) { struct audit_tree *tree; tree = container_of(barrier.prev, struct audit_tree, list); get_tree(tree); list_del(&tree->list); list_add(&tree->list, &barrier); mutex_unlock(&audit_filter_mutex); if (!failed) { struct node *node; spin_lock(&hash_lock); list_for_each_entry(node, &tree->chunks, list) node->index &= ~(1U<<31); spin_unlock(&hash_lock); } else { trim_marked(tree); } put_tree(tree); mutex_lock(&audit_filter_mutex); } list_del(&barrier); list_del(&cursor); mutex_unlock(&audit_filter_mutex); path_put(&path1); drop_collected_mounts(tagged); return failed; } /* * That gets run when evict_chunk() ends up needing to kill audit_tree. * Runs from a separate thread. */ static int prune_tree_thread(void *unused) { mutex_lock(&audit_cmd_mutex); mutex_lock(&audit_filter_mutex); while (!list_empty(&prune_list)) { struct audit_tree *victim; victim = list_entry(prune_list.next, struct audit_tree, list); list_del_init(&victim->list); mutex_unlock(&audit_filter_mutex); prune_one(victim); mutex_lock(&audit_filter_mutex); } mutex_unlock(&audit_filter_mutex); mutex_unlock(&audit_cmd_mutex); return 0; } static void audit_schedule_prune(void) { kthread_run(prune_tree_thread, NULL, "audit_prune_tree"); } /* * ... and that one is done if evict_chunk() decides to delay until the end * of syscall. Runs synchronously. */ void audit_kill_trees(struct list_head *list) { mutex_lock(&audit_cmd_mutex); mutex_lock(&audit_filter_mutex); while (!list_empty(list)) { struct audit_tree *victim; victim = list_entry(list->next, struct audit_tree, list); kill_rules(victim); list_del_init(&victim->list); mutex_unlock(&audit_filter_mutex); prune_one(victim); mutex_lock(&audit_filter_mutex); } mutex_unlock(&audit_filter_mutex); mutex_unlock(&audit_cmd_mutex); } /* * Here comes the stuff asynchronous to auditctl operations */ static void evict_chunk(struct audit_chunk *chunk) { struct audit_tree *owner; struct list_head *postponed = audit_killed_trees(); int need_prune = 0; int n; if (chunk->dead) return; chunk->dead = 1; mutex_lock(&audit_filter_mutex); spin_lock(&hash_lock); while (!list_empty(&chunk->trees)) { owner = list_entry(chunk->trees.next, struct audit_tree, same_root); owner->goner = 1; owner->root = NULL; list_del_init(&owner->same_root); spin_unlock(&hash_lock); if (!postponed) { kill_rules(owner); list_move(&owner->list, &prune_list); need_prune = 1; } else { list_move(&owner->list, postponed); } spin_lock(&hash_lock); } list_del_rcu(&chunk->hash); for (n = 0; n < chunk->count; n++) list_del_init(&chunk->owners[n].list); spin_unlock(&hash_lock); if (need_prune) audit_schedule_prune(); mutex_unlock(&audit_filter_mutex); } static int audit_tree_handle_event(struct fsnotify_group *group, struct fsnotify_mark *inode_mark, struct fsnotify_mark *vfsmonut_mark, struct fsnotify_event *event) { BUG(); return -EOPNOTSUPP; } static void audit_tree_freeing_mark(struct fsnotify_mark *entry, struct fsnotify_group *group) { struct audit_chunk *chunk = container_of(entry, struct audit_chunk, mark); evict_chunk(chunk); /* * We are guaranteed to have at least one reference to the mark from * either the inode or the caller of fsnotify_destroy_mark(). */ BUG_ON(atomic_read(&entry->refcnt) < 1); } static bool audit_tree_send_event(struct fsnotify_group *group, struct inode *inode, struct fsnotify_mark *inode_mark, struct fsnotify_mark *vfsmount_mark, __u32 mask, void *data, int data_type) { return false; } static const struct fsnotify_ops audit_tree_ops = { .handle_event = audit_tree_handle_event, .should_send_event = audit_tree_send_event, .free_group_priv = NULL, .free_event_priv = NULL, .freeing_mark = audit_tree_freeing_mark, }; static int __init audit_tree_init(void) { int i; audit_tree_group = fsnotify_alloc_group(&audit_tree_ops); if (IS_ERR(audit_tree_group)) audit_panic("cannot initialize fsnotify group for rectree watches"); for (i = 0; i < HASH_SIZE; i++) INIT_LIST_HEAD(&chunk_hash_heads[i]); return 0; } __initcall(audit_tree_init);