[PATCH] audit: watching subtrees

New kind of audit rule predicates: "object is visible in given subtree".
The part that can be sanely implemented, that is.  Limitations:
	* if you have hardlink from outside of tree, you'd better watch
it too (or just watch the object itself, obviously)
	* if you mount something under a watched tree, tell audit
that new chunk should be added to watched subtrees
	* if you umount something in a watched tree and it's still mounted
elsewhere, you will get matches on events happening there.  New command
tells audit to recalculate the trees, trimming such sources of false
positives.

Note that it's _not_ about path - if something mounted in several places
(multiple mount, bindings, different namespaces, etc.), the match does
_not_ depend on which one we are using for access.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 903 insertions, 0 deletions

diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
new file mode 100644
index 00000000000..f4fcf58f20f
--- /dev/null
+++ b/kernel/audit_tree.c
@@ -0,0 +1,903 @@
+#include "audit.h"
+#include <linux/inotify.h>
+#include <linux/namei.h>
+#include <linux/mount.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 inotify_watch watch;
+        struct list_head trees;         /* with root here */
+        int dead;
+        int count;
+        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 inotify_watch.
+ *
+ * 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 inotify_handle *rtree_ih;
+
+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 void __put_tree(struct rcu_head *rcu)
+{
+        struct audit_tree *tree = container_of(rcu, struct audit_tree, head);
+        kfree(tree);
+}
+
+static inline void put_tree(struct audit_tree *tree)
+{
+        if (atomic_dec_and_test(&tree->count))
+                call_rcu(&tree->head, __put_tree);
+}
+
+/* to avoid bringing the entire thing in audit.h */
+const char *audit_tree_path(struct audit_tree *tree)
+{
+        return tree->pathname;
+}
+
+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;
+        for (i = 0; i < count; i++) {
+                INIT_LIST_HEAD(&chunk->owners[i].list);
+                chunk->owners[i].index = i;
+        }
+        inotify_init_watch(&chunk->watch);
+        return chunk;
+}
+
+static void __free_chunk(struct rcu_head *rcu)
+{
+        struct audit_chunk *chunk = container_of(rcu, struct audit_chunk, head);
+        int i;
+
+        for (i = 0; i < chunk->count; i++) {
+                if (chunk->owners[i].owner)
+                        put_tree(chunk->owners[i].owner);
+        }
+        kfree(chunk);
+}
+
+static inline void free_chunk(struct audit_chunk *chunk)
+{
+        call_rcu(&chunk->head, __free_chunk);
+}
+
+void audit_put_chunk(struct audit_chunk *chunk)
+{
+        put_inotify_watch(&chunk->watch);
+}
+
+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 is held by caller */
+static void insert_hash(struct audit_chunk *chunk)
+{
+        struct list_head *list = chunk_hash(chunk->watch.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 list_head *pos;
+
+        list_for_each_rcu(pos, list) {
+                struct audit_chunk *p = container_of(pos, struct audit_chunk, hash);
+                if (p->watch.inode == inode) {
+                        get_inotify_watch(&p->watch);
+                        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 void untag_chunk(struct audit_chunk *chunk, struct node *p)
+{
+        struct audit_chunk *new;
+        struct audit_tree *owner;
+        int size = chunk->count - 1;
+        int i, j;
+
+        mutex_lock(&chunk->watch.inode->inotify_mutex);
+        if (chunk->dead) {
+                mutex_unlock(&chunk->watch.inode->inotify_mutex);
+                return;
+        }
+
+        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);
+                inotify_evict_watch(&chunk->watch);
+                mutex_unlock(&chunk->watch.inode->inotify_mutex);
+                put_inotify_watch(&chunk->watch);
+                return;
+        }
+
+        new = alloc_chunk(size);
+        if (!new)
+                goto Fallback;
+        if (inotify_clone_watch(&chunk->watch, &new->watch) < 0) {
+                free_chunk(new);
+                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; i < 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[i].list, &new->owners[j].list);
+        }
+
+        list_replace_rcu(&chunk->hash, &new->hash);
+        list_for_each_entry(owner, &new->trees, same_root)
+                owner->root = new;
+        spin_unlock(&hash_lock);
+        inotify_evict_watch(&chunk->watch);
+        mutex_unlock(&chunk->watch.inode->inotify_mutex);
+        put_inotify_watch(&chunk->watch);
+        return;
+
+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);
+        mutex_unlock(&chunk->watch.inode->inotify_mutex);
+}
+
+static int create_chunk(struct inode *inode, struct audit_tree *tree)
+{
+        struct audit_chunk *chunk = alloc_chunk(1);
+        if (!chunk)
+                return -ENOMEM;
+
+        if (inotify_add_watch(rtree_ih, &chunk->watch, inode, IN_IGNORED | IN_DELETE_SELF) < 0) {
+                free_chunk(chunk);
+                return -ENOSPC;
+        }
+
+        mutex_lock(&inode->inotify_mutex);
+        spin_lock(&hash_lock);
+        if (tree->goner) {
+                spin_unlock(&hash_lock);
+                chunk->dead = 1;
+                inotify_evict_watch(&chunk->watch);
+                mutex_unlock(&inode->inotify_mutex);
+                put_inotify_watch(&chunk->watch);
+                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);
+        mutex_unlock(&inode->inotify_mutex);
+        return 0;
+}
+
+/* the first tagged inode becomes root of tree */
+static int tag_chunk(struct inode *inode, struct audit_tree *tree)
+{
+        struct inotify_watch *watch;
+        struct audit_tree *owner;
+        struct audit_chunk *chunk, *old;
+        struct node *p;
+        int n;
+
+        if (inotify_find_watch(rtree_ih, inode, &watch) < 0)
+                return create_chunk(inode, tree);
+
+        old = container_of(watch, struct audit_chunk, watch);
+
+        /* 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);
+                        put_inotify_watch(watch);
+                        return 0;
+                }
+        }
+        spin_unlock(&hash_lock);
+
+        chunk = alloc_chunk(old->count + 1);
+        if (!chunk)
+                return -ENOMEM;
+
+        mutex_lock(&inode->inotify_mutex);
+        if (inotify_clone_watch(&old->watch, &chunk->watch) < 0) {
+                mutex_unlock(&inode->inotify_mutex);
+                free_chunk(chunk);
+                return -ENOSPC;
+        }
+        spin_lock(&hash_lock);
+        if (tree->goner) {
+                spin_unlock(&hash_lock);
+                chunk->dead = 1;
+                inotify_evict_watch(&chunk->watch);
+                mutex_unlock(&inode->inotify_mutex);
+                put_inotify_watch(&chunk->watch);
+                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);
+        inotify_evict_watch(&old->watch);
+        mutex_unlock(&inode->inotify_mutex);
+        put_inotify_watch(&old->watch);
+        return 0;
+}
+
+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 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=remove rule dir=");
+                        audit_log_untrustedstring(ab, rule->tree->pathname);
+                        if (rule->filterkey) {
+                                audit_log_format(ab, " key=");
+                                audit_log_untrustedstring(ab, rule->filterkey);
+                        } else
+                                audit_log_format(ab, " key=(null)");
+                        audit_log_format(ab, " list=%d res=1", rule->listnr);
+                        audit_log_end(ab);
+                        rule->tree = NULL;
+                        list_del_rcu(&entry->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;
+                struct audit_chunk *chunk;
+
+                p = list_entry(victim->chunks.next, struct node, list);
+                chunk = find_chunk(p);
+                get_inotify_watch(&chunk->watch);
+                spin_unlock(&hash_lock);
+
+                untag_chunk(chunk, p);
+
+                put_inotify_watch(&chunk->watch);
+                spin_lock(&hash_lock);
+        }
+        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;
+                struct audit_chunk *chunk;
+
+                node = list_entry(tree->chunks.next, struct node, list);
+
+                /* have we run out of marked? */
+                if (!(node->index & (1U<<31)))
+                        break;
+
+                chunk = find_chunk(node);
+                get_inotify_watch(&chunk->watch);
+                spin_unlock(&hash_lock);
+
+                untag_chunk(chunk, node);
+
+                put_inotify_watch(&chunk->watch);
+                spin_lock(&hash_lock);
+        }
+        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);
+        }
+}
+
+/* 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;
+}
+
+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 nameidata nd;
+                struct vfsmount *root_mnt;
+                struct node *node;
+                struct list_head list;
+                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 = path_lookup(tree->pathname, 0, &nd);
+                if (err)
+                        goto skip_it;
+
+                root_mnt = collect_mounts(nd.mnt, nd.dentry);
+                path_release(&nd);
+                if (!root_mnt)
+                        goto skip_it;
+
+                list_add_tail(&list, &root_mnt->mnt_list);
+                spin_lock(&hash_lock);
+                list_for_each_entry(node, &tree->chunks, list) {
+                        struct audit_chunk *chunk = find_chunk(node);
+                        struct inode *inode = chunk->watch.inode;
+                        struct vfsmount *mnt;
+                        node->index |= 1U<<31;
+                        list_for_each_entry(mnt, &list, mnt_list) {
+                                if (mnt->mnt_root->d_inode == inode) {
+                                        node->index &= ~(1U<<31);
+                                        break;
+                                }
+                        }
+                }
+                spin_unlock(&hash_lock);
+                trim_marked(tree);
+                put_tree(tree);
+                list_del_init(&list);
+                drop_collected_mounts(root_mnt);
+skip_it:
+                mutex_lock(&audit_filter_mutex);
+        }
+        list_del(&cursor);
+        mutex_unlock(&audit_filter_mutex);
+}
+
+static int is_under(struct vfsmount *mnt, struct dentry *dentry,
+                    struct nameidata *nd)
+{
+        if (mnt != nd->mnt) {
+                for (;;) {
+                        if (mnt->mnt_parent == mnt)
+                                return 0;
+                        if (mnt->mnt_parent == nd->mnt)
+                                        break;
+                        mnt = mnt->mnt_parent;
+                }
+                dentry = mnt->mnt_mountpoint;
+        }
+        return is_subdir(dentry, nd->dentry);
+}
+
+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);
+}
+
+/* called with audit_filter_mutex */
+int audit_add_tree_rule(struct audit_krule *rule)
+{
+        struct audit_tree *seed = rule->tree, *tree;
+        struct nameidata nd;
+        struct vfsmount *mnt, *p;
+        struct list_head list;
+        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 = path_lookup(tree->pathname, 0, &nd);
+        if (err)
+                goto Err;
+        mnt = collect_mounts(nd.mnt, nd.dentry);
+        path_release(&nd);
+        if (!mnt) {
+                err = -ENOMEM;
+                goto Err;
+        }
+        list_add_tail(&list, &mnt->mnt_list);
+
+        get_tree(tree);
+        list_for_each_entry(p, &list, mnt_list) {
+                err = tag_chunk(p->mnt_root->d_inode, tree);
+                if (err)
+                        break;
+        }
+
+        list_del(&list);
+        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 nameidata nd;
+        struct vfsmount *tagged;
+        struct list_head list;
+        struct vfsmount *mnt;
+        struct dentry *dentry;
+        int err;
+
+        err = path_lookup(new, 0, &nd);
+        if (err)
+                return err;
+        tagged = collect_mounts(nd.mnt, nd.dentry);
+        path_release(&nd);
+        if (!tagged)
+                return -ENOMEM;
+
+        err = path_lookup(old, 0, &nd);
+        if (err) {
+                drop_collected_mounts(tagged);
+                return err;
+        }
+        mnt = mntget(nd.mnt);
+        dentry = dget(nd.dentry);
+        path_release(&nd);
+
+        if (dentry == tagged->mnt_root && dentry == mnt->mnt_root)
+                follow_up(&mnt, &dentry);
+
+        list_add_tail(&list, &tagged->mnt_list);
+
+        mutex_lock(&audit_filter_mutex);
+        list_add(&barrier, &tree_list);
+        list_add(&cursor, &barrier);
+
+        while (cursor.next != &tree_list) {
+                struct audit_tree *tree;
+                struct vfsmount *p;
+
+                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 = path_lookup(tree->pathname, 0, &nd);
+                if (err) {
+                        put_tree(tree);
+                        mutex_lock(&audit_filter_mutex);
+                        continue;
+                }
+
+                spin_lock(&vfsmount_lock);
+                if (!is_under(mnt, dentry, &nd)) {
+                        spin_unlock(&vfsmount_lock);
+                        path_release(&nd);
+                        put_tree(tree);
+                        mutex_lock(&audit_filter_mutex);
+                        continue;
+                }
+                spin_unlock(&vfsmount_lock);
+                path_release(&nd);
+
+                list_for_each_entry(p, &list, mnt_list) {
+                        failed = tag_chunk(p->mnt_root->d_inode, tree);
+                        if (failed)
+                                break;
+                }
+
+                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);
+        list_del(&list);
+        mutex_unlock(&audit_filter_mutex);
+        dput(dentry);
+        mntput(mnt);
+        drop_collected_mounts(tagged);
+        return failed;
+}
+
+/*
+ * That gets run when evict_chunk() ends up needing to kill audit_tree.
+ * Runs from a separate thread, with audit_cmd_mutex held.
+ */
+void audit_prune_trees(void)
+{
+        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);
+}
+
+/*
+ *  Here comes the stuff asynchronous to auditctl operations
+ */
+
+/* inode->inotify_mutex is locked */
+static void evict_chunk(struct audit_chunk *chunk)
+{
+        struct audit_tree *owner;
+        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);
+                kill_rules(owner);
+                list_move(&owner->list, &prune_list);
+                audit_schedule_prune();
+                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);
+        mutex_unlock(&audit_filter_mutex);
+}
+
+static void handle_event(struct inotify_watch *watch, u32 wd, u32 mask,
+                         u32 cookie, const char *dname, struct inode *inode)
+{
+        struct audit_chunk *chunk = container_of(watch, struct audit_chunk, watch);
+
+        if (mask & IN_IGNORED) {
+                evict_chunk(chunk);
+                put_inotify_watch(watch);
+        }
+}
+
+static void destroy_watch(struct inotify_watch *watch)
+{
+        struct audit_chunk *chunk = container_of(watch, struct audit_chunk, watch);
+        free_chunk(chunk);
+}
+
+static const struct inotify_operations rtree_inotify_ops = {
+        .handle_event   = handle_event,
+        .destroy_watch  = destroy_watch,
+};
+
+static int __init audit_tree_init(void)
+{
+        int i;
+
+        rtree_ih = inotify_init(&rtree_inotify_ops);
+        if (IS_ERR(rtree_ih))
+                audit_panic("cannot initialize inotify handle for rectree watches");
+
+        for (i = 0; i < HASH_SIZE; i++)
+                INIT_LIST_HEAD(&chunk_hash_heads[i]);
+
+        return 0;
+}
+__initcall(audit_tree_init);