kernel/audit_tree.c

   1 #include "audit.h"
   2 #include <linux/fsnotify_backend.h>
   3 #include <linux/namei.h>
   4 #include <linux/mount.h>
   5 #include <linux/kthread.h>
   6 #include <linux/slab.h>
   7
   8 struct audit_tree;
   9 struct audit_chunk;
  10
  11 struct audit_tree {
  12         atomic_t count;
  13         int goner;
  14         struct audit_chunk *root;
  15         struct list_head chunks;
  16         struct list_head rules;
  17         struct list_head list;
  18         struct list_head same_root;
  19         struct rcu_head head;
  20         char pathname[];
  21 };
  22
  23 struct audit_chunk {
  24         struct list_head hash;
  25         struct fsnotify_mark mark;
  26         struct list_head trees;         /* with root here */
  27         int dead;
  28         int count;
  29         atomic_long_t refs;
  30         struct rcu_head head;
  31         struct node {
  32                 struct list_head list;
  33                 struct audit_tree *owner;
  34                 unsigned index;         /* index; upper bit indicates 'will prune' */
  35         } owners[];
  36 };
  37
  38 static LIST_HEAD(tree_list);
  39 static LIST_HEAD(prune_list);
  40
  41 /*
  42  * One struct chunk is attached to each inode of interest.
  43  * We replace struct chunk on tagging/untagging.
  44  * Rules have pointer to struct audit_tree.
  45  * Rules have struct list_head rlist forming a list of rules over
  46  * the same tree.
  47  * References to struct chunk are collected at audit_inode{,_child}()
  48  * time and used in AUDIT_TREE rule matching.
  49  * These references are dropped at the same time we are calling
  50  * audit_free_names(), etc.
  51  *
  52  * Cyclic lists galore:
  53  * tree.chunks anchors chunk.owners[].list                      hash_lock
  54  * tree.rules anchors rule.rlist                                audit_filter_mutex
  55  * chunk.trees anchors tree.same_root                           hash_lock
  56  * chunk.hash is a hash with middle bits of watch.inode as
  57  * a hash function.                                             RCU, hash_lock
  58  *
  59  * tree is refcounted; one reference for "some rules on rules_list refer to
  60  * it", one for each chunk with pointer to it.
  61  *
  62  * chunk is refcounted by embedded fsnotify_mark + .refs (non-zero refcount
  63  * of watch contributes 1 to .refs).
  64  *
  65  * node.index allows to get from node.list to containing chunk.
  66  * MSB of that sucker is stolen to mark taggings that we might have to
  67  * revert - several operations have very unpleasant cleanup logics and
  68  * that makes a difference.  Some.
  69  */
  70
  71 static struct fsnotify_group *audit_tree_group;
  72
  73 static struct audit_tree *alloc_tree(const char *s)
  74 {
  75         struct audit_tree *tree;
  76
  77         tree = kmalloc(sizeof(struct audit_tree) + strlen(s) + 1, GFP_KERNEL);
  78         if (tree) {
  79                 atomic_set(&tree->count, 1);
  80                 tree->goner = 0;
  81                 INIT_LIST_HEAD(&tree->chunks);
  82                 INIT_LIST_HEAD(&tree->rules);
  83                 INIT_LIST_HEAD(&tree->list);
  84                 INIT_LIST_HEAD(&tree->same_root);
  85                 tree->root = NULL;
  86                 strcpy(tree->pathname, s);
  87         }
  88         return tree;
  89 }
  90
  91 static inline void get_tree(struct audit_tree *tree)
  92 {
  93         atomic_inc(&tree->count);
  94 }
  95
  96 static void __put_tree(struct rcu_head *rcu)
  97 {
  98         struct audit_tree *tree = container_of(rcu, struct audit_tree, head);
  99         kfree(tree);
 100 }
 101
 102 static inline void put_tree(struct audit_tree *tree)
 103 {
 104         if (atomic_dec_and_test(&tree->count))
 105                 call_rcu(&tree->head, __put_tree);
 106 }
 107
 108 /* to avoid bringing the entire thing in audit.h */
 109 const char *audit_tree_path(struct audit_tree *tree)
 110 {
 111         return tree->pathname;
 112 }
 113
 114 static void free_chunk(struct audit_chunk *chunk)
 115 {
 116         int i;
 117
 118         for (i = 0; i < chunk->count; i++) {
 119                 if (chunk->owners[i].owner)
 120                         put_tree(chunk->owners[i].owner);
 121         }
 122         kfree(chunk);
 123 }
 124
 125 void audit_put_chunk(struct audit_chunk *chunk)
 126 {
 127         if (atomic_long_dec_and_test(&chunk->refs))
 128                 free_chunk(chunk);
 129 }
 130
 131 static void __put_chunk(struct rcu_head *rcu)
 132 {
 133         struct audit_chunk *chunk = container_of(rcu, struct audit_chunk, head);
 134         audit_put_chunk(chunk);
 135 }
 136
 137 static void audit_tree_destroy_watch(struct fsnotify_mark *entry)
 138 {
 139         struct audit_chunk *chunk = container_of(entry, struct audit_chunk, mark);
 140         call_rcu(&chunk->head, __put_chunk);
 141 }
 142
 143 static struct audit_chunk *alloc_chunk(int count)
 144 {
 145         struct audit_chunk *chunk;
 146         size_t size;
 147         int i;
 148
 149         size = offsetof(struct audit_chunk, owners) + count * sizeof(struct node);
 150         chunk = kzalloc(size, GFP_KERNEL);
 151         if (!chunk)
 152                 return NULL;
 153
 154         INIT_LIST_HEAD(&chunk->hash);
 155         INIT_LIST_HEAD(&chunk->trees);
 156         chunk->count = count;
 157         atomic_long_set(&chunk->refs, 1);
 158         for (i = 0; i < count; i++) {
 159                 INIT_LIST_HEAD(&chunk->owners[i].list);
 160                 chunk->owners[i].index = i;
 161         }
 162         fsnotify_init_mark(&chunk->mark, audit_tree_destroy_watch);
 163         return chunk;
 164 }
 165
 166 enum {HASH_SIZE = 128};
 167 static struct list_head chunk_hash_heads[HASH_SIZE];
 168 static __cacheline_aligned_in_smp DEFINE_SPINLOCK(hash_lock);
 169
 170 static inline struct list_head *chunk_hash(const struct inode *inode)
 171 {
 172         unsigned long n = (unsigned long)inode / L1_CACHE_BYTES;
 173         return chunk_hash_heads + n % HASH_SIZE;
 174 }
 175
 176 /* hash_lock & entry->lock is held by caller */
 177 static void insert_hash(struct audit_chunk *chunk)
 178 {
 179         struct fsnotify_mark *entry = &chunk->mark;
 180         struct list_head *list;
 181
 182         if (!entry->i.inode)
 183                 return;
 184         list = chunk_hash(entry->i.inode);
 185         list_add_rcu(&chunk->hash, list);
 186 }
 187
 188 /* called under rcu_read_lock */
 189 struct audit_chunk *audit_tree_lookup(const struct inode *inode)
 190 {
 191         struct list_head *list = chunk_hash(inode);
 192         struct audit_chunk *p;
 193
 194         list_for_each_entry_rcu(p, list, hash) {
 195                 /* mark.inode may have gone NULL, but who cares? */
 196                 if (p->mark.i.inode == inode) {
 197                         atomic_long_inc(&p->refs);
 198                         return p;
 199                 }
 200         }
 201         return NULL;
 202 }
 203
 204 int audit_tree_match(struct audit_chunk *chunk, struct audit_tree *tree)
 205 {
 206         int n;
 207         for (n = 0; n < chunk->count; n++)
 208                 if (chunk->owners[n].owner == tree)
 209                         return 1;
 210         return 0;
 211 }
 212
 213 /* tagging and untagging inodes with trees */
 214
 215 static struct audit_chunk *find_chunk(struct node *p)
 216 {
 217         int index = p->index & ~(1U<<31);
 218         p -= index;
 219         return container_of(p, struct audit_chunk, owners[0]);
 220 }
 221
 222 static void untag_chunk(struct node *p)
 223 {
 224         struct audit_chunk *chunk = find_chunk(p);
 225         struct fsnotify_mark *entry = &chunk->mark;
 226         struct audit_chunk *new;
 227         struct audit_tree *owner;
 228         int size = chunk->count - 1;
 229         int i, j;
 230
 231         fsnotify_get_mark(entry);
 232
 233         spin_unlock(&hash_lock);
 234
 235         spin_lock(&entry->lock);
 236         if (chunk->dead || !entry->i.inode) {
 237                 spin_unlock(&entry->lock);
 238                 goto out;
 239         }
 240
 241         owner = p->owner;
 242
 243         if (!size) {
 244                 chunk->dead = 1;
 245                 spin_lock(&hash_lock);
 246                 list_del_init(&chunk->trees);
 247                 if (owner->root == chunk)
 248                         owner->root = NULL;
 249                 list_del_init(&p->list);
 250                 list_del_rcu(&chunk->hash);
 251                 spin_unlock(&hash_lock);
 252                 spin_unlock(&entry->lock);
 253                 fsnotify_destroy_mark(entry);
 254                 fsnotify_put_mark(entry);
 255                 goto out;
 256         }
 257
 258         new = alloc_chunk(size);
 259         if (!new)
 260                 goto Fallback;
 261         fsnotify_duplicate_mark(&new->mark, entry);
 262         if (fsnotify_add_mark(&new->mark, new->mark.group, new->mark.i.inode, NULL, 1)) {
 263                 free_chunk(new);
 264                 goto Fallback;
 265         }
 266
 267         chunk->dead = 1;
 268         spin_lock(&hash_lock);
 269         list_replace_init(&chunk->trees, &new->trees);
 270         if (owner->root == chunk) {
 271                 list_del_init(&owner->same_root);
 272                 owner->root = NULL;
 273         }
 274
 275         for (i = j = 0; j <= size; i++, j++) {
 276                 struct audit_tree *s;
 277                 if (&chunk->owners[j] == p) {
 278                         list_del_init(&p->list);
 279                         i--;
 280                         continue;
 281                 }
 282                 s = chunk->owners[j].owner;
 283                 new->owners[i].owner = s;
 284                 new->owners[i].index = chunk->owners[j].index - j + i;
 285                 if (!s) /* result of earlier fallback */
 286                         continue;
 287                 get_tree(s);
 288                 list_replace_init(&chunk->owners[j].list, &new->owners[i].list);
 289         }
 290
 291         list_replace_rcu(&chunk->hash, &new->hash);
 292         list_for_each_entry(owner, &new->trees, same_root)
 293                 owner->root = new;
 294         spin_unlock(&hash_lock);
 295         spin_unlock(&entry->lock);
 296         fsnotify_destroy_mark(entry);
 297         fsnotify_put_mark(entry);
 298         goto out;
 299
 300 Fallback:
 301         // do the best we can
 302         spin_lock(&hash_lock);
 303         if (owner->root == chunk) {
 304                 list_del_init(&owner->same_root);
 305                 owner->root = NULL;
 306         }
 307         list_del_init(&p->list);
 308         p->owner = NULL;
 309         put_tree(owner);
 310         spin_unlock(&hash_lock);
 311         spin_unlock(&entry->lock);
 312 out:
 313         fsnotify_put_mark(entry);
 314         spin_lock(&hash_lock);
 315 }
 316
 317 static int create_chunk(struct inode *inode, struct audit_tree *tree)
 318 {
 319         struct fsnotify_mark *entry;
 320         struct audit_chunk *chunk = alloc_chunk(1);
 321         if (!chunk)
 322                 return -ENOMEM;
 323
 324         entry = &chunk->mark;
 325         if (fsnotify_add_mark(entry, audit_tree_group, inode, NULL, 0)) {
 326                 free_chunk(chunk);
 327                 return -ENOSPC;
 328         }
 329
 330         spin_lock(&entry->lock);
 331         spin_lock(&hash_lock);
 332         if (tree->goner) {
 333                 spin_unlock(&hash_lock);
 334                 chunk->dead = 1;
 335                 spin_unlock(&entry->lock);
 336                 fsnotify_destroy_mark(entry);
 337                 fsnotify_put_mark(entry);
 338                 return 0;
 339         }
 340         chunk->owners[0].index = (1U << 31);
 341         chunk->owners[0].owner = tree;
 342         get_tree(tree);
 343         list_add(&chunk->owners[0].list, &tree->chunks);
 344         if (!tree->root) {
 345                 tree->root = chunk;
 346                 list_add(&tree->same_root, &chunk->trees);
 347         }
 348         insert_hash(chunk);
 349         spin_unlock(&hash_lock);
 350         spin_unlock(&entry->lock);
 351         return 0;
 352 }
 353
 354 /* the first tagged inode becomes root of tree */
 355 static int tag_chunk(struct inode *inode, struct audit_tree *tree)
 356 {
 357         struct fsnotify_mark *old_entry, *chunk_entry;
 358         struct audit_tree *owner;
 359         struct audit_chunk *chunk, *old;
 360         struct node *p;
 361         int n;
 362
 363         old_entry = fsnotify_find_inode_mark(audit_tree_group, inode);
 364         if (!old_entry)
 365                 return create_chunk(inode, tree);
 366
 367         old = container_of(old_entry, struct audit_chunk, mark);
 368
 369         /* are we already there? */
 370         spin_lock(&hash_lock);
 371         for (n = 0; n < old->count; n++) {
 372                 if (old->owners[n].owner == tree) {
 373                         spin_unlock(&hash_lock);
 374                         fsnotify_put_mark(old_entry);
 375                         return 0;
 376                 }
 377         }
 378         spin_unlock(&hash_lock);
 379
 380         chunk = alloc_chunk(old->count + 1);
 381         if (!chunk) {
 382                 fsnotify_put_mark(old_entry);
 383                 return -ENOMEM;
 384         }
 385
 386         chunk_entry = &chunk->mark;
 387
 388         spin_lock(&old_entry->lock);
 389         if (!old_entry->i.inode) {
 390                 /* old_entry is being shot, lets just lie */
 391                 spin_unlock(&old_entry->lock);
 392                 fsnotify_put_mark(old_entry);
 393                 free_chunk(chunk);
 394                 return -ENOENT;
 395         }
 396
 397         fsnotify_duplicate_mark(chunk_entry, old_entry);
 398         if (fsnotify_add_mark(chunk_entry, chunk_entry->group, chunk_entry->i.inode, NULL, 1)) {
 399                 spin_unlock(&old_entry->lock);
 400                 free_chunk(chunk);
 401                 fsnotify_put_mark(old_entry);
 402                 return -ENOSPC;
 403         }
 404
 405         /* even though we hold old_entry->lock, this is safe since chunk_entry->lock could NEVER have been grabbed before */
 406         spin_lock(&chunk_entry->lock);
 407         spin_lock(&hash_lock);
 408
 409         /* we now hold old_entry->lock, chunk_entry->lock, and hash_lock */
 410         if (tree->goner) {
 411                 spin_unlock(&hash_lock);
 412                 chunk->dead = 1;
 413                 spin_unlock(&chunk_entry->lock);
 414                 spin_unlock(&old_entry->lock);
 415
 416                 fsnotify_destroy_mark(chunk_entry);
 417
 418                 fsnotify_put_mark(chunk_entry);
 419                 fsnotify_put_mark(old_entry);
 420                 return 0;
 421         }
 422         list_replace_init(&old->trees, &chunk->trees);
 423         for (n = 0, p = chunk->owners; n < old->count; n++, p++) {
 424                 struct audit_tree *s = old->owners[n].owner;
 425                 p->owner = s;
 426                 p->index = old->owners[n].index;
 427                 if (!s) /* result of fallback in untag */
 428                         continue;
 429                 get_tree(s);
 430                 list_replace_init(&old->owners[n].list, &p->list);
 431         }
 432         p->index = (chunk->count - 1) | (1U<<31);
 433         p->owner = tree;
 434         get_tree(tree);
 435         list_add(&p->list, &tree->chunks);
 436         list_replace_rcu(&old->hash, &chunk->hash);
 437         list_for_each_entry(owner, &chunk->trees, same_root)
 438                 owner->root = chunk;
 439         old->dead = 1;
 440         if (!tree->root) {
 441                 tree->root = chunk;
 442                 list_add(&tree->same_root, &chunk->trees);
 443         }
 444         spin_unlock(&hash_lock);
 445         spin_unlock(&chunk_entry->lock);
 446         spin_unlock(&old_entry->lock);
 447         fsnotify_destroy_mark(old_entry);
 448         fsnotify_put_mark(old_entry); /* pair to fsnotify_find mark_entry */
 449         fsnotify_put_mark(old_entry); /* and kill it */
 450         return 0;
 451 }
 452
 453 static void kill_rules(struct audit_tree *tree)
 454 {
 455         struct audit_krule *rule, *next;
 456         struct audit_entry *entry;
 457         struct audit_buffer *ab;
 458
 459         list_for_each_entry_safe(rule, next, &tree->rules, rlist) {
 460                 entry = container_of(rule, struct audit_entry, rule);
 461
 462                 list_del_init(&rule->rlist);
 463                 if (rule->tree) {
 464                         /* not a half-baked one */
 465                         ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE);
 466                         audit_log_format(ab, "op=");
 467                         audit_log_string(ab, "remove rule");
 468                         audit_log_format(ab, " dir=");
 469                         audit_log_untrustedstring(ab, rule->tree->pathname);
 470                         audit_log_key(ab, rule->filterkey);
 471                         audit_log_format(ab, " list=%d res=1", rule->listnr);
 472                         audit_log_end(ab);
 473                         rule->tree = NULL;
 474                         list_del_rcu(&entry->list);
 475                         list_del(&entry->rule.list);
 476                         call_rcu(&entry->rcu, audit_free_rule_rcu);
 477                 }
 478         }
 479 }
 480
 481 /*
 482  * finish killing struct audit_tree
 483  */
 484 static void prune_one(struct audit_tree *victim)
 485 {
 486         spin_lock(&hash_lock);
 487         while (!list_empty(&victim->chunks)) {
 488                 struct node *p;
 489
 490                 p = list_entry(victim->chunks.next, struct node, list);
 491
 492                 untag_chunk(p);
 493         }
 494         spin_unlock(&hash_lock);
 495         put_tree(victim);
 496 }
 497
 498 /* trim the uncommitted chunks from tree */
 499
 500 static void trim_marked(struct audit_tree *tree)
 501 {
 502         struct list_head *p, *q;
 503         spin_lock(&hash_lock);
 504         if (tree->goner) {
 505                 spin_unlock(&hash_lock);
 506                 return;
 507         }
 508         /* reorder */
 509         for (p = tree->chunks.next; p != &tree->chunks; p = q) {
 510                 struct node *node = list_entry(p, struct node, list);
 511                 q = p->next;
 512                 if (node->index & (1U<<31)) {
 513                         list_del_init(p);
 514                         list_add(p, &tree->chunks);
 515                 }
 516         }
 517
 518         while (!list_empty(&tree->chunks)) {
 519                 struct node *node;
 520
 521                 node = list_entry(tree->chunks.next, struct node, list);
 522
 523                 /* have we run out of marked? */
 524                 if (!(node->index & (1U<<31)))
 525                         break;
 526
 527                 untag_chunk(node);
 528         }
 529         if (!tree->root && !tree->goner) {
 530                 tree->goner = 1;
 531                 spin_unlock(&hash_lock);
 532                 mutex_lock(&audit_filter_mutex);
 533                 kill_rules(tree);
 534                 list_del_init(&tree->list);
 535                 mutex_unlock(&audit_filter_mutex);
 536                 prune_one(tree);
 537         } else {
 538                 spin_unlock(&hash_lock);
 539         }
 540 }
 541
 542 static void audit_schedule_prune(void);
 543
 544 /* called with audit_filter_mutex */
 545 int audit_remove_tree_rule(struct audit_krule *rule)
 546 {
 547         struct audit_tree *tree;
 548         tree = rule->tree;
 549         if (tree) {
 550                 spin_lock(&hash_lock);
 551                 list_del_init(&rule->rlist);
 552                 if (list_empty(&tree->rules) && !tree->goner) {
 553                         tree->root = NULL;
 554                         list_del_init(&tree->same_root);
 555                         tree->goner = 1;
 556                         list_move(&tree->list, &prune_list);
 557                         rule->tree = NULL;
 558                         spin_unlock(&hash_lock);
 559                         audit_schedule_prune();
 560                         return 1;
 561                 }
 562                 rule->tree = NULL;
 563                 spin_unlock(&hash_lock);
 564                 return 1;
 565         }
 566         return 0;
 567 }
 568
 569 static int compare_root(struct vfsmount *mnt, void *arg)
 570 {
 571         return mnt->mnt_root->d_inode == arg;
 572 }
 573
 574 void audit_trim_trees(void)
 575 {
 576         struct list_head cursor;
 577
 578         mutex_lock(&audit_filter_mutex);
 579         list_add(&cursor, &tree_list);
 580         while (cursor.next != &tree_list) {
 581                 struct audit_tree *tree;
 582                 struct path path;
 583                 struct vfsmount *root_mnt;
 584                 struct node *node;
 585                 int err;
 586
 587                 tree = container_of(cursor.next, struct audit_tree, list);
 588                 get_tree(tree);
 589                 list_del(&cursor);
 590                 list_add(&cursor, &tree->list);
 591                 mutex_unlock(&audit_filter_mutex);
 592
 593                 err = kern_path(tree->pathname, 0, &path);
 594                 if (err)
 595                         goto skip_it;
 596
 597                 root_mnt = collect_mounts(&path);
 598                 path_put(&path);
 599                 if (!root_mnt)
 600                         goto skip_it;
 601
 602                 spin_lock(&hash_lock);
 603                 list_for_each_entry(node, &tree->chunks, list) {
 604                         struct audit_chunk *chunk = find_chunk(node);
 605                         /* this could be NULL if the watch is dieing else where... */
 606                         struct inode *inode = chunk->mark.i.inode;
 607                         node->index |= 1U<<31;
 608                         if (iterate_mounts(compare_root, inode, root_mnt))
 609                                 node->index &= ~(1U<<31);
 610                 }
 611                 spin_unlock(&hash_lock);
 612                 trim_marked(tree);
 613                 put_tree(tree);
 614                 drop_collected_mounts(root_mnt);
 615 skip_it:
 616                 mutex_lock(&audit_filter_mutex);
 617         }
 618         list_del(&cursor);
 619         mutex_unlock(&audit_filter_mutex);
 620 }
 621
 622 int audit_make_tree(struct audit_krule *rule, char *pathname, u32 op)
 623 {
 624
 625         if (pathname[0] != '/' ||
 626             rule->listnr != AUDIT_FILTER_EXIT ||
 627             op != Audit_equal ||
 628             rule->inode_f || rule->watch || rule->tree)
 629                 return -EINVAL;
 630         rule->tree = alloc_tree(pathname);
 631         if (!rule->tree)
 632                 return -ENOMEM;
 633         return 0;
 634 }
 635
 636 void audit_put_tree(struct audit_tree *tree)
 637 {
 638         put_tree(tree);
 639 }
 640
 641 static int tag_mount(struct vfsmount *mnt, void *arg)
 642 {
 643         return tag_chunk(mnt->mnt_root->d_inode, arg);
 644 }
 645
 646 /* called with audit_filter_mutex */
 647 int audit_add_tree_rule(struct audit_krule *rule)
 648 {
 649         struct audit_tree *seed = rule->tree, *tree;
 650         struct path path;
 651         struct vfsmount *mnt;
 652         int err;
 653
 654         list_for_each_entry(tree, &tree_list, list) {
 655                 if (!strcmp(seed->pathname, tree->pathname)) {
 656                         put_tree(seed);
 657                         rule->tree = tree;
 658                         list_add(&rule->rlist, &tree->rules);
 659                         return 0;
 660                 }
 661         }
 662         tree = seed;
 663         list_add(&tree->list, &tree_list);
 664         list_add(&rule->rlist, &tree->rules);
 665         /* do not set rule->tree yet */
 666         mutex_unlock(&audit_filter_mutex);
 667
 668         err = kern_path(tree->pathname, 0, &path);
 669         if (err)
 670                 goto Err;
 671         mnt = collect_mounts(&path);
 672         path_put(&path);
 673         if (!mnt) {
 674                 err = -ENOMEM;
 675                 goto Err;
 676         }
 677
 678         get_tree(tree);
 679         err = iterate_mounts(tag_mount, tree, mnt);
 680         drop_collected_mounts(mnt);
 681
 682         if (!err) {
 683                 struct node *node;
 684                 spin_lock(&hash_lock);
 685                 list_for_each_entry(node, &tree->chunks, list)
 686                         node->index &= ~(1U<<31);
 687                 spin_unlock(&hash_lock);
 688         } else {
 689                 trim_marked(tree);
 690                 goto Err;
 691         }
 692
 693         mutex_lock(&audit_filter_mutex);
 694         if (list_empty(&rule->rlist)) {
 695                 put_tree(tree);
 696                 return -ENOENT;
 697         }
 698         rule->tree = tree;
 699         put_tree(tree);
 700
 701         return 0;
 702 Err:
 703         mutex_lock(&audit_filter_mutex);
 704         list_del_init(&tree->list);
 705         list_del_init(&tree->rules);
 706         put_tree(tree);
 707         return err;
 708 }
 709
 710 int audit_tag_tree(char *old, char *new)
 711 {
 712         struct list_head cursor, barrier;
 713         int failed = 0;
 714         struct path path1, path2;
 715         struct vfsmount *tagged;
 716         int err;
 717
 718         err = kern_path(new, 0, &path2);
 719         if (err)
 720                 return err;
 721         tagged = collect_mounts(&path2);
 722         path_put(&path2);
 723         if (!tagged)
 724                 return -ENOMEM;
 725
 726         err = kern_path(old, 0, &path1);
 727         if (err) {
 728                 drop_collected_mounts(tagged);
 729                 return err;
 730         }
 731
 732         mutex_lock(&audit_filter_mutex);
 733         list_add(&barrier, &tree_list);
 734         list_add(&cursor, &barrier);
 735
 736         while (cursor.next != &tree_list) {
 737                 struct audit_tree *tree;
 738                 int good_one = 0;
 739
 740                 tree = container_of(cursor.next, struct audit_tree, list);
 741                 get_tree(tree);
 742                 list_del(&cursor);
 743                 list_add(&cursor, &tree->list);
 744                 mutex_unlock(&audit_filter_mutex);
 745
 746                 err = kern_path(tree->pathname, 0, &path2);
 747                 if (!err) {
 748                         good_one = path_is_under(&path1, &path2);
 749                         path_put(&path2);
 750                 }
 751
 752                 if (!good_one) {
 753                         put_tree(tree);
 754                         mutex_lock(&audit_filter_mutex);
 755                         continue;
 756                 }
 757
 758                 failed = iterate_mounts(tag_mount, tree, tagged);
 759                 if (failed) {
 760                         put_tree(tree);
 761                         mutex_lock(&audit_filter_mutex);
 762                         break;
 763                 }
 764
 765                 mutex_lock(&audit_filter_mutex);
 766                 spin_lock(&hash_lock);
 767                 if (!tree->goner) {
 768                         list_del(&tree->list);
 769                         list_add(&tree->list, &tree_list);
 770                 }
 771                 spin_unlock(&hash_lock);
 772                 put_tree(tree);
 773         }
 774
 775         while (barrier.prev != &tree_list) {
 776                 struct audit_tree *tree;
 777
 778                 tree = container_of(barrier.prev, struct audit_tree, list);
 779                 get_tree(tree);
 780                 list_del(&tree->list);
 781                 list_add(&tree->list, &barrier);
 782                 mutex_unlock(&audit_filter_mutex);
 783
 784                 if (!failed) {
 785                         struct node *node;
 786                         spin_lock(&hash_lock);
 787                         list_for_each_entry(node, &tree->chunks, list)
 788                                 node->index &= ~(1U<<31);
 789                         spin_unlock(&hash_lock);
 790                 } else {
 791                         trim_marked(tree);
 792                 }
 793
 794                 put_tree(tree);
 795                 mutex_lock(&audit_filter_mutex);
 796         }
 797         list_del(&barrier);
 798         list_del(&cursor);
 799         mutex_unlock(&audit_filter_mutex);
 800         path_put(&path1);
 801         drop_collected_mounts(tagged);
 802         return failed;
 803 }
 804
 805 /*
 806  * That gets run when evict_chunk() ends up needing to kill audit_tree.
 807  * Runs from a separate thread.
 808  */
 809 static int prune_tree_thread(void *unused)
 810 {
 811         mutex_lock(&audit_cmd_mutex);
 812         mutex_lock(&audit_filter_mutex);
 813
 814         while (!list_empty(&prune_list)) {
 815                 struct audit_tree *victim;
 816
 817                 victim = list_entry(prune_list.next, struct audit_tree, list);
 818                 list_del_init(&victim->list);
 819
 820                 mutex_unlock(&audit_filter_mutex);
 821
 822                 prune_one(victim);
 823
 824                 mutex_lock(&audit_filter_mutex);
 825         }
 826
 827         mutex_unlock(&audit_filter_mutex);
 828         mutex_unlock(&audit_cmd_mutex);
 829         return 0;
 830 }
 831
 832 static void audit_schedule_prune(void)
 833 {
 834         kthread_run(prune_tree_thread, NULL, "audit_prune_tree");
 835 }
 836
 837 /*
 838  * ... and that one is done if evict_chunk() decides to delay until the end
 839  * of syscall.  Runs synchronously.
 840  */
 841 void audit_kill_trees(struct list_head *list)
 842 {
 843         mutex_lock(&audit_cmd_mutex);
 844         mutex_lock(&audit_filter_mutex);
 845
 846         while (!list_empty(list)) {
 847                 struct audit_tree *victim;
 848
 849                 victim = list_entry(list->next, struct audit_tree, list);
 850                 kill_rules(victim);
 851                 list_del_init(&victim->list);
 852
 853                 mutex_unlock(&audit_filter_mutex);
 854
 855                 prune_one(victim);
 856
 857                 mutex_lock(&audit_filter_mutex);
 858         }
 859
 860         mutex_unlock(&audit_filter_mutex);
 861         mutex_unlock(&audit_cmd_mutex);
 862 }
 863
 864 /*
 865  *  Here comes the stuff asynchronous to auditctl operations
 866  */
 867
 868 static void evict_chunk(struct audit_chunk *chunk)
 869 {
 870         struct audit_tree *owner;
 871         struct list_head *postponed = audit_killed_trees();
 872         int need_prune = 0;
 873         int n;
 874
 875         if (chunk->dead)
 876                 return;
 877
 878         chunk->dead = 1;
 879         mutex_lock(&audit_filter_mutex);
 880         spin_lock(&hash_lock);
 881         while (!list_empty(&chunk->trees)) {
 882                 owner = list_entry(chunk->trees.next,
 883                                    struct audit_tree, same_root);
 884                 owner->goner = 1;
 885                 owner->root = NULL;
 886                 list_del_init(&owner->same_root);
 887                 spin_unlock(&hash_lock);
 888                 if (!postponed) {
 889                         kill_rules(owner);
 890                         list_move(&owner->list, &prune_list);
 891                         need_prune = 1;
 892                 } else {
 893                         list_move(&owner->list, postponed);
 894                 }
 895                 spin_lock(&hash_lock);
 896         }
 897         list_del_rcu(&chunk->hash);
 898         for (n = 0; n < chunk->count; n++)
 899                 list_del_init(&chunk->owners[n].list);
 900         spin_unlock(&hash_lock);
 901         if (need_prune)
 902                 audit_schedule_prune();
 903         mutex_unlock(&audit_filter_mutex);
 904 }
 905
 906 static int audit_tree_handle_event(struct fsnotify_group *group,
 907                                    struct fsnotify_mark *inode_mark,
 908                                    struct fsnotify_mark *vfsmonut_mark,
 909                                    struct fsnotify_event *event)
 910 {
 911         BUG();
 912         return -EOPNOTSUPP;
 913 }
 914
 915 static void audit_tree_freeing_mark(struct fsnotify_mark *entry, struct fsnotify_group *group)
 916 {
 917         struct audit_chunk *chunk = container_of(entry, struct audit_chunk, mark);
 918
 919         evict_chunk(chunk);
 920         fsnotify_put_mark(entry);
 921 }
 922
 923 static bool audit_tree_send_event(struct fsnotify_group *group, struct inode *inode,
 924                                   struct fsnotify_mark *inode_mark,
 925                                   struct fsnotify_mark *vfsmount_mark,
 926                                   __u32 mask, void *data, int data_type)
 927 {
 928         return false;
 929 }
 930
 931 static const struct fsnotify_ops audit_tree_ops = {
 932         .handle_event = audit_tree_handle_event,
 933         .should_send_event = audit_tree_send_event,
 934         .free_group_priv = NULL,
 935         .free_event_priv = NULL,
 936         .freeing_mark = audit_tree_freeing_mark,
 937 };
 938
 939 static int __init audit_tree_init(void)
 940 {
 941         int i;
 942
 943         audit_tree_group = fsnotify_alloc_group(&audit_tree_ops);
 944         if (IS_ERR(audit_tree_group))
 945                 audit_panic("cannot initialize fsnotify group for rectree watches");
 946
 947         for (i = 0; i < HASH_SIZE; i++)
 948                 INIT_LIST_HEAD(&chunk_hash_heads[i]);
 949
 950         return 0;
 951 }
 952 __initcall(audit_tree_init);