kernel/audit_tree.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include "audit.h"
   3 #include <linux/fsnotify_backend.h>
   4 #include <linux/namei.h>
   5 #include <linux/mount.h>
   6 #include <linux/kthread.h>
   7 #include <linux/refcount.h>
   8 #include <linux/slab.h>
   9
  10 struct audit_tree;
  11 struct audit_chunk;
  12
  13 struct audit_tree {
  14         refcount_t count;
  15         int goner;
  16         struct audit_chunk *root;
  17         struct list_head chunks;
  18         struct list_head rules;
  19         struct list_head list;
  20         struct list_head same_root;
  21         struct rcu_head head;
  22         char pathname[];
  23 };
  24
  25 struct audit_chunk {
  26         struct list_head hash;
  27         unsigned long key;
  28         struct fsnotify_mark *mark;
  29         struct list_head trees;         /* with root here */
  30         int count;
  31         atomic_long_t refs;
  32         struct rcu_head head;
  33         struct node {
  34                 struct list_head list;
  35                 struct audit_tree *owner;
  36                 unsigned index;         /* index; upper bit indicates 'will prune' */
  37         } owners[];
  38 };
  39
  40 struct audit_tree_mark {
  41         struct fsnotify_mark mark;
  42         struct audit_chunk *chunk;
  43 };
  44
  45 static LIST_HEAD(tree_list);
  46 static LIST_HEAD(prune_list);
  47 static struct task_struct *prune_thread;
  48
  49 /*
  50  * One struct chunk is attached to each inode of interest through
  51  * audit_tree_mark (fsnotify mark). We replace struct chunk on tagging /
  52  * untagging, the mark is stable as long as there is chunk attached. The
  53  * association between mark and chunk is protected by hash_lock and
  54  * audit_tree_group->mark_mutex. Thus as long as we hold
  55  * audit_tree_group->mark_mutex and check that the mark is alive by
  56  * FSNOTIFY_MARK_FLAG_ATTACHED flag check, we are sure the mark points to
  57  * the current chunk.
  58  *
  59  * Rules have pointer to struct audit_tree.
  60  * Rules have struct list_head rlist forming a list of rules over
  61  * the same tree.
  62  * References to struct chunk are collected at audit_inode{,_child}()
  63  * time and used in AUDIT_TREE rule matching.
  64  * These references are dropped at the same time we are calling
  65  * audit_free_names(), etc.
  66  *
  67  * Cyclic lists galore:
  68  * tree.chunks anchors chunk.owners[].list                      hash_lock
  69  * tree.rules anchors rule.rlist                                audit_filter_mutex
  70  * chunk.trees anchors tree.same_root                           hash_lock
  71  * chunk.hash is a hash with middle bits of watch.inode as
  72  * a hash function.                                             RCU, hash_lock
  73  *
  74  * tree is refcounted; one reference for "some rules on rules_list refer to
  75  * it", one for each chunk with pointer to it.
  76  *
  77  * chunk is refcounted by embedded .refs. Mark associated with the chunk holds
  78  * one chunk reference. This reference is dropped either when a mark is going
  79  * to be freed (corresponding inode goes away) or when chunk attached to the
  80  * mark gets replaced. This reference must be dropped using
  81  * audit_mark_put_chunk() to make sure the reference is dropped only after RCU
  82  * grace period as it protects RCU readers of the hash table.
  83  *
  84  * node.index allows to get from node.list to containing chunk.
  85  * MSB of that sucker is stolen to mark taggings that we might have to
  86  * revert - several operations have very unpleasant cleanup logics and
  87  * that makes a difference.  Some.
  88  */
  89
  90 static struct fsnotify_group *audit_tree_group;
  91 static struct kmem_cache *audit_tree_mark_cachep __read_mostly;
  92
  93 static struct audit_tree *alloc_tree(const char *s)
  94 {
  95         struct audit_tree *tree;
  96
  97         tree = kmalloc(sizeof(struct audit_tree) + strlen(s) + 1, GFP_KERNEL);
  98         if (tree) {
  99                 refcount_set(&tree->count, 1);
 100                 tree->goner = 0;
 101                 INIT_LIST_HEAD(&tree->chunks);
 102                 INIT_LIST_HEAD(&tree->rules);
 103                 INIT_LIST_HEAD(&tree->list);
 104                 INIT_LIST_HEAD(&tree->same_root);
 105                 tree->root = NULL;
 106                 strcpy(tree->pathname, s);
 107         }
 108         return tree;
 109 }
 110
 111 static inline void get_tree(struct audit_tree *tree)
 112 {
 113         refcount_inc(&tree->count);
 114 }
 115
 116 static inline void put_tree(struct audit_tree *tree)
 117 {
 118         if (refcount_dec_and_test(&tree->count))
 119                 kfree_rcu(tree, head);
 120 }
 121
 122 /* to avoid bringing the entire thing in audit.h */
 123 const char *audit_tree_path(struct audit_tree *tree)
 124 {
 125         return tree->pathname;
 126 }
 127
 128 static void free_chunk(struct audit_chunk *chunk)
 129 {
 130         int i;
 131
 132         for (i = 0; i < chunk->count; i++) {
 133                 if (chunk->owners[i].owner)
 134                         put_tree(chunk->owners[i].owner);
 135         }
 136         kfree(chunk);
 137 }
 138
 139 void audit_put_chunk(struct audit_chunk *chunk)
 140 {
 141         if (atomic_long_dec_and_test(&chunk->refs))
 142                 free_chunk(chunk);
 143 }
 144
 145 static void __put_chunk(struct rcu_head *rcu)
 146 {
 147         struct audit_chunk *chunk = container_of(rcu, struct audit_chunk, head);
 148         audit_put_chunk(chunk);
 149 }
 150
 151 /*
 152  * Drop reference to the chunk that was held by the mark. This is the reference
 153  * that gets dropped after we've removed the chunk from the hash table and we
 154  * use it to make sure chunk cannot be freed before RCU grace period expires.
 155  */
 156 static void audit_mark_put_chunk(struct audit_chunk *chunk)
 157 {
 158         call_rcu(&chunk->head, __put_chunk);
 159 }
 160
 161 static inline struct audit_tree_mark *audit_mark(struct fsnotify_mark *mark)
 162 {
 163         return container_of(mark, struct audit_tree_mark, mark);
 164 }
 165
 166 static struct audit_chunk *mark_chunk(struct fsnotify_mark *mark)
 167 {
 168         return audit_mark(mark)->chunk;
 169 }
 170
 171 static void audit_tree_destroy_watch(struct fsnotify_mark *mark)
 172 {
 173         kmem_cache_free(audit_tree_mark_cachep, audit_mark(mark));
 174 }
 175
 176 static struct fsnotify_mark *alloc_mark(void)
 177 {
 178         struct audit_tree_mark *amark;
 179
 180         amark = kmem_cache_zalloc(audit_tree_mark_cachep, GFP_KERNEL);
 181         if (!amark)
 182                 return NULL;
 183         fsnotify_init_mark(&amark->mark, audit_tree_group);
 184         amark->mark.mask = FS_IN_IGNORED;
 185         return &amark->mark;
 186 }
 187
 188 static struct audit_chunk *alloc_chunk(int count)
 189 {
 190         struct audit_chunk *chunk;
 191         size_t size;
 192         int i;
 193
 194         size = offsetof(struct audit_chunk, owners) + count * sizeof(struct node);
 195         chunk = kzalloc(size, GFP_KERNEL);
 196         if (!chunk)
 197                 return NULL;
 198
 199         INIT_LIST_HEAD(&chunk->hash);
 200         INIT_LIST_HEAD(&chunk->trees);
 201         chunk->count = count;
 202         atomic_long_set(&chunk->refs, 1);
 203         for (i = 0; i < count; i++) {
 204                 INIT_LIST_HEAD(&chunk->owners[i].list);
 205                 chunk->owners[i].index = i;
 206         }
 207         return chunk;
 208 }
 209
 210 enum {HASH_SIZE = 128};
 211 static struct list_head chunk_hash_heads[HASH_SIZE];
 212 static __cacheline_aligned_in_smp DEFINE_SPINLOCK(hash_lock);
 213
 214 /* Function to return search key in our hash from inode. */
 215 static unsigned long inode_to_key(const struct inode *inode)
 216 {
 217         /* Use address pointed to by connector->obj as the key */
 218         return (unsigned long)&inode->i_fsnotify_marks;
 219 }
 220
 221 static inline struct list_head *chunk_hash(unsigned long key)
 222 {
 223         unsigned long n = key / L1_CACHE_BYTES;
 224         return chunk_hash_heads + n % HASH_SIZE;
 225 }
 226
 227 /* hash_lock & mark->group->mark_mutex is held by caller */
 228 static void insert_hash(struct audit_chunk *chunk)
 229 {
 230         struct list_head *list;
 231
 232         /*
 233          * Make sure chunk is fully initialized before making it visible in the
 234          * hash. Pairs with a data dependency barrier in READ_ONCE() in
 235          * audit_tree_lookup().
 236          */
 237         smp_wmb();
 238         WARN_ON_ONCE(!chunk->key);
 239         list = chunk_hash(chunk->key);
 240         list_add_rcu(&chunk->hash, list);
 241 }
 242
 243 /* called under rcu_read_lock */
 244 struct audit_chunk *audit_tree_lookup(const struct inode *inode)
 245 {
 246         unsigned long key = inode_to_key(inode);
 247         struct list_head *list = chunk_hash(key);
 248         struct audit_chunk *p;
 249
 250         list_for_each_entry_rcu(p, list, hash) {
 251                 /*
 252                  * We use a data dependency barrier in READ_ONCE() to make sure
 253                  * the chunk we see is fully initialized.
 254                  */
 255                 if (READ_ONCE(p->key) == key) {
 256                         atomic_long_inc(&p->refs);
 257                         return p;
 258                 }
 259         }
 260         return NULL;
 261 }
 262
 263 bool audit_tree_match(struct audit_chunk *chunk, struct audit_tree *tree)
 264 {
 265         int n;
 266         for (n = 0; n < chunk->count; n++)
 267                 if (chunk->owners[n].owner == tree)
 268                         return true;
 269         return false;
 270 }
 271
 272 /* tagging and untagging inodes with trees */
 273
 274 static struct audit_chunk *find_chunk(struct node *p)
 275 {
 276         int index = p->index & ~(1U<<31);
 277         p -= index;
 278         return container_of(p, struct audit_chunk, owners[0]);
 279 }
 280
 281 static void replace_mark_chunk(struct fsnotify_mark *mark,
 282                                struct audit_chunk *chunk)
 283 {
 284         struct audit_chunk *old;
 285
 286         assert_spin_locked(&hash_lock);
 287         old = mark_chunk(mark);
 288         audit_mark(mark)->chunk = chunk;
 289         if (chunk)
 290                 chunk->mark = mark;
 291         if (old)
 292                 old->mark = NULL;
 293 }
 294
 295 static void replace_chunk(struct audit_chunk *new, struct audit_chunk *old)
 296 {
 297         struct audit_tree *owner;
 298         int i, j;
 299
 300         new->key = old->key;
 301         list_splice_init(&old->trees, &new->trees);
 302         list_for_each_entry(owner, &new->trees, same_root)
 303                 owner->root = new;
 304         for (i = j = 0; j < old->count; i++, j++) {
 305                 if (!old->owners[j].owner) {
 306                         i--;
 307                         continue;
 308                 }
 309                 owner = old->owners[j].owner;
 310                 new->owners[i].owner = owner;
 311                 new->owners[i].index = old->owners[j].index - j + i;
 312                 if (!owner) /* result of earlier fallback */
 313                         continue;
 314                 get_tree(owner);
 315                 list_replace_init(&old->owners[j].list, &new->owners[i].list);
 316         }
 317         replace_mark_chunk(old->mark, new);
 318         /*
 319          * Make sure chunk is fully initialized before making it visible in the
 320          * hash. Pairs with a data dependency barrier in READ_ONCE() in
 321          * audit_tree_lookup().
 322          */
 323         smp_wmb();
 324         list_replace_rcu(&old->hash, &new->hash);
 325 }
 326
 327 static void remove_chunk_node(struct audit_chunk *chunk, struct node *p)
 328 {
 329         struct audit_tree *owner = p->owner;
 330
 331         if (owner->root == chunk) {
 332                 list_del_init(&owner->same_root);
 333                 owner->root = NULL;
 334         }
 335         list_del_init(&p->list);
 336         p->owner = NULL;
 337         put_tree(owner);
 338 }
 339
 340 static int chunk_count_trees(struct audit_chunk *chunk)
 341 {
 342         int i;
 343         int ret = 0;
 344
 345         for (i = 0; i < chunk->count; i++)
 346                 if (chunk->owners[i].owner)
 347                         ret++;
 348         return ret;
 349 }
 350
 351 static void untag_chunk(struct audit_chunk *chunk, struct fsnotify_mark *mark)
 352 {
 353         struct audit_chunk *new;
 354         int size;
 355
 356         mutex_lock(&audit_tree_group->mark_mutex);
 357         /*
 358          * mark_mutex stabilizes chunk attached to the mark so we can check
 359          * whether it didn't change while we've dropped hash_lock.
 360          */
 361         if (!(mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED) ||
 362             mark_chunk(mark) != chunk)
 363                 goto out_mutex;
 364
 365         size = chunk_count_trees(chunk);
 366         if (!size) {
 367                 spin_lock(&hash_lock);
 368                 list_del_init(&chunk->trees);
 369                 list_del_rcu(&chunk->hash);
 370                 replace_mark_chunk(mark, NULL);
 371                 spin_unlock(&hash_lock);
 372                 fsnotify_detach_mark(mark);
 373                 mutex_unlock(&audit_tree_group->mark_mutex);
 374                 audit_mark_put_chunk(chunk);
 375                 fsnotify_free_mark(mark);
 376                 return;
 377         }
 378
 379         new = alloc_chunk(size);
 380         if (!new)
 381                 goto out_mutex;
 382
 383         spin_lock(&hash_lock);
 384         /*
 385          * This has to go last when updating chunk as once replace_chunk() is
 386          * called, new RCU readers can see the new chunk.
 387          */
 388         replace_chunk(new, chunk);
 389         spin_unlock(&hash_lock);
 390         mutex_unlock(&audit_tree_group->mark_mutex);
 391         audit_mark_put_chunk(chunk);
 392         return;
 393
 394 out_mutex:
 395         mutex_unlock(&audit_tree_group->mark_mutex);
 396 }
 397
 398 /* Call with group->mark_mutex held, releases it */
 399 static int create_chunk(struct inode *inode, struct audit_tree *tree)
 400 {
 401         struct fsnotify_mark *mark;
 402         struct audit_chunk *chunk = alloc_chunk(1);
 403
 404         if (!chunk) {
 405                 mutex_unlock(&audit_tree_group->mark_mutex);
 406                 return -ENOMEM;
 407         }
 408
 409         mark = alloc_mark();
 410         if (!mark) {
 411                 mutex_unlock(&audit_tree_group->mark_mutex);
 412                 kfree(chunk);
 413                 return -ENOMEM;
 414         }
 415
 416         if (fsnotify_add_inode_mark_locked(mark, inode, 0)) {
 417                 mutex_unlock(&audit_tree_group->mark_mutex);
 418                 fsnotify_put_mark(mark);
 419                 kfree(chunk);
 420                 return -ENOSPC;
 421         }
 422
 423         spin_lock(&hash_lock);
 424         if (tree->goner) {
 425                 spin_unlock(&hash_lock);
 426                 fsnotify_detach_mark(mark);
 427                 mutex_unlock(&audit_tree_group->mark_mutex);
 428                 fsnotify_free_mark(mark);
 429                 fsnotify_put_mark(mark);
 430                 kfree(chunk);
 431                 return 0;
 432         }
 433         replace_mark_chunk(mark, chunk);
 434         chunk->owners[0].index = (1U << 31);
 435         chunk->owners[0].owner = tree;
 436         get_tree(tree);
 437         list_add(&chunk->owners[0].list, &tree->chunks);
 438         if (!tree->root) {
 439                 tree->root = chunk;
 440                 list_add(&tree->same_root, &chunk->trees);
 441         }
 442         chunk->key = inode_to_key(inode);
 443         /*
 444          * Inserting into the hash table has to go last as once we do that RCU
 445          * readers can see the chunk.
 446          */
 447         insert_hash(chunk);
 448         spin_unlock(&hash_lock);
 449         mutex_unlock(&audit_tree_group->mark_mutex);
 450         /*
 451          * Drop our initial reference. When mark we point to is getting freed,
 452          * we get notification through ->freeing_mark callback and cleanup
 453          * chunk pointing to this mark.
 454          */
 455         fsnotify_put_mark(mark);
 456         return 0;
 457 }
 458
 459 /* the first tagged inode becomes root of tree */
 460 static int tag_chunk(struct inode *inode, struct audit_tree *tree)
 461 {
 462         struct fsnotify_mark *mark;
 463         struct audit_chunk *chunk, *old;
 464         struct node *p;
 465         int n;
 466
 467         mutex_lock(&audit_tree_group->mark_mutex);
 468         mark = fsnotify_find_mark(&inode->i_fsnotify_marks, audit_tree_group);
 469         if (!mark)
 470                 return create_chunk(inode, tree);
 471
 472         /*
 473          * Found mark is guaranteed to be attached and mark_mutex protects mark
 474          * from getting detached and thus it makes sure there is chunk attached
 475          * to the mark.
 476          */
 477         /* are we already there? */
 478         spin_lock(&hash_lock);
 479         old = mark_chunk(mark);
 480         for (n = 0; n < old->count; n++) {
 481                 if (old->owners[n].owner == tree) {
 482                         spin_unlock(&hash_lock);
 483                         mutex_unlock(&audit_tree_group->mark_mutex);
 484                         fsnotify_put_mark(mark);
 485                         return 0;
 486                 }
 487         }
 488         spin_unlock(&hash_lock);
 489
 490         chunk = alloc_chunk(old->count + 1);
 491         if (!chunk) {
 492                 mutex_unlock(&audit_tree_group->mark_mutex);
 493                 fsnotify_put_mark(mark);
 494                 return -ENOMEM;
 495         }
 496
 497         spin_lock(&hash_lock);
 498         if (tree->goner) {
 499                 spin_unlock(&hash_lock);
 500                 mutex_unlock(&audit_tree_group->mark_mutex);
 501                 fsnotify_put_mark(mark);
 502                 kfree(chunk);
 503                 return 0;
 504         }
 505         p = &chunk->owners[chunk->count - 1];
 506         p->index = (chunk->count - 1) | (1U<<31);
 507         p->owner = tree;
 508         get_tree(tree);
 509         list_add(&p->list, &tree->chunks);
 510         if (!tree->root) {
 511                 tree->root = chunk;
 512                 list_add(&tree->same_root, &chunk->trees);
 513         }
 514         /*
 515          * This has to go last when updating chunk as once replace_chunk() is
 516          * called, new RCU readers can see the new chunk.
 517          */
 518         replace_chunk(chunk, old);
 519         spin_unlock(&hash_lock);
 520         mutex_unlock(&audit_tree_group->mark_mutex);
 521         fsnotify_put_mark(mark); /* pair to fsnotify_find_mark */
 522         audit_mark_put_chunk(old);
 523
 524         return 0;
 525 }
 526
 527 static void audit_tree_log_remove_rule(struct audit_krule *rule)
 528 {
 529         struct audit_buffer *ab;
 530
 531         if (!audit_enabled)
 532                 return;
 533         ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE);
 534         if (unlikely(!ab))
 535                 return;
 536         audit_log_format(ab, "op=remove_rule dir=");
 537         audit_log_untrustedstring(ab, rule->tree->pathname);
 538         audit_log_key(ab, rule->filterkey);
 539         audit_log_format(ab, " list=%d res=1", rule->listnr);
 540         audit_log_end(ab);
 541 }
 542
 543 static void kill_rules(struct audit_tree *tree)
 544 {
 545         struct audit_krule *rule, *next;
 546         struct audit_entry *entry;
 547
 548         list_for_each_entry_safe(rule, next, &tree->rules, rlist) {
 549                 entry = container_of(rule, struct audit_entry, rule);
 550
 551                 list_del_init(&rule->rlist);
 552                 if (rule->tree) {
 553                         /* not a half-baked one */
 554                         audit_tree_log_remove_rule(rule);
 555                         if (entry->rule.exe)
 556                                 audit_remove_mark(entry->rule.exe);
 557                         rule->tree = NULL;
 558                         list_del_rcu(&entry->list);
 559                         list_del(&entry->rule.list);
 560                         call_rcu(&entry->rcu, audit_free_rule_rcu);
 561                 }
 562         }
 563 }
 564
 565 /*
 566  * Remove tree from chunks. If 'tagged' is set, remove tree only from tagged
 567  * chunks. The function expects tagged chunks are all at the beginning of the
 568  * chunks list.
 569  */
 570 static void prune_tree_chunks(struct audit_tree *victim, bool tagged)
 571 {
 572         spin_lock(&hash_lock);
 573         while (!list_empty(&victim->chunks)) {
 574                 struct node *p;
 575                 struct audit_chunk *chunk;
 576                 struct fsnotify_mark *mark;
 577
 578                 p = list_first_entry(&victim->chunks, struct node, list);
 579                 /* have we run out of marked? */
 580                 if (tagged && !(p->index & (1U<<31)))
 581                         break;
 582                 chunk = find_chunk(p);
 583                 mark = chunk->mark;
 584                 remove_chunk_node(chunk, p);
 585                 /* Racing with audit_tree_freeing_mark()? */
 586                 if (!mark)
 587                         continue;
 588                 fsnotify_get_mark(mark);
 589                 spin_unlock(&hash_lock);
 590
 591                 untag_chunk(chunk, mark);
 592                 fsnotify_put_mark(mark);
 593
 594                 spin_lock(&hash_lock);
 595         }
 596         spin_unlock(&hash_lock);
 597         put_tree(victim);
 598 }
 599
 600 /*
 601  * finish killing struct audit_tree
 602  */
 603 static void prune_one(struct audit_tree *victim)
 604 {
 605         prune_tree_chunks(victim, false);
 606 }
 607
 608 /* trim the uncommitted chunks from tree */
 609
 610 static void trim_marked(struct audit_tree *tree)
 611 {
 612         struct list_head *p, *q;
 613         spin_lock(&hash_lock);
 614         if (tree->goner) {
 615                 spin_unlock(&hash_lock);
 616                 return;
 617         }
 618         /* reorder */
 619         for (p = tree->chunks.next; p != &tree->chunks; p = q) {
 620                 struct node *node = list_entry(p, struct node, list);
 621                 q = p->next;
 622                 if (node->index & (1U<<31)) {
 623                         list_del_init(p);
 624                         list_add(p, &tree->chunks);
 625                 }
 626         }
 627         spin_unlock(&hash_lock);
 628
 629         prune_tree_chunks(tree, true);
 630
 631         spin_lock(&hash_lock);
 632         if (!tree->root && !tree->goner) {
 633                 tree->goner = 1;
 634                 spin_unlock(&hash_lock);
 635                 mutex_lock(&audit_filter_mutex);
 636                 kill_rules(tree);
 637                 list_del_init(&tree->list);
 638                 mutex_unlock(&audit_filter_mutex);
 639                 prune_one(tree);
 640         } else {
 641                 spin_unlock(&hash_lock);
 642         }
 643 }
 644
 645 static void audit_schedule_prune(void);
 646
 647 /* called with audit_filter_mutex */
 648 int audit_remove_tree_rule(struct audit_krule *rule)
 649 {
 650         struct audit_tree *tree;
 651         tree = rule->tree;
 652         if (tree) {
 653                 spin_lock(&hash_lock);
 654                 list_del_init(&rule->rlist);
 655                 if (list_empty(&tree->rules) && !tree->goner) {
 656                         tree->root = NULL;
 657                         list_del_init(&tree->same_root);
 658                         tree->goner = 1;
 659                         list_move(&tree->list, &prune_list);
 660                         rule->tree = NULL;
 661                         spin_unlock(&hash_lock);
 662                         audit_schedule_prune();
 663                         return 1;
 664                 }
 665                 rule->tree = NULL;
 666                 spin_unlock(&hash_lock);
 667                 return 1;
 668         }
 669         return 0;
 670 }
 671
 672 static int compare_root(struct vfsmount *mnt, void *arg)
 673 {
 674         return inode_to_key(d_backing_inode(mnt->mnt_root)) ==
 675                (unsigned long)arg;
 676 }
 677
 678 void audit_trim_trees(void)
 679 {
 680         struct list_head cursor;
 681
 682         mutex_lock(&audit_filter_mutex);
 683         list_add(&cursor, &tree_list);
 684         while (cursor.next != &tree_list) {
 685                 struct audit_tree *tree;
 686                 struct path path;
 687                 struct vfsmount *root_mnt;
 688                 struct node *node;
 689                 int err;
 690
 691                 tree = container_of(cursor.next, struct audit_tree, list);
 692                 get_tree(tree);
 693                 list_del(&cursor);
 694                 list_add(&cursor, &tree->list);
 695                 mutex_unlock(&audit_filter_mutex);
 696
 697                 err = kern_path(tree->pathname, 0, &path);
 698                 if (err)
 699                         goto skip_it;
 700
 701                 root_mnt = collect_mounts(&path);
 702                 path_put(&path);
 703                 if (IS_ERR(root_mnt))
 704                         goto skip_it;
 705
 706                 spin_lock(&hash_lock);
 707                 list_for_each_entry(node, &tree->chunks, list) {
 708                         struct audit_chunk *chunk = find_chunk(node);
 709                         /* this could be NULL if the watch is dying else where... */
 710                         node->index |= 1U<<31;
 711                         if (iterate_mounts(compare_root,
 712                                            (void *)(chunk->key),
 713                                            root_mnt))
 714                                 node->index &= ~(1U<<31);
 715                 }
 716                 spin_unlock(&hash_lock);
 717                 trim_marked(tree);
 718                 drop_collected_mounts(root_mnt);
 719 skip_it:
 720                 put_tree(tree);
 721                 mutex_lock(&audit_filter_mutex);
 722         }
 723         list_del(&cursor);
 724         mutex_unlock(&audit_filter_mutex);
 725 }
 726
 727 int audit_make_tree(struct audit_krule *rule, char *pathname, u32 op)
 728 {
 729
 730         if (pathname[0] != '/' ||
 731             rule->listnr != AUDIT_FILTER_EXIT ||
 732             op != Audit_equal ||
 733             rule->inode_f || rule->watch || rule->tree)
 734                 return -EINVAL;
 735         rule->tree = alloc_tree(pathname);
 736         if (!rule->tree)
 737                 return -ENOMEM;
 738         return 0;
 739 }
 740
 741 void audit_put_tree(struct audit_tree *tree)
 742 {
 743         put_tree(tree);
 744 }
 745
 746 static int tag_mount(struct vfsmount *mnt, void *arg)
 747 {
 748         return tag_chunk(d_backing_inode(mnt->mnt_root), arg);
 749 }
 750
 751 /*
 752  * That gets run when evict_chunk() ends up needing to kill audit_tree.
 753  * Runs from a separate thread.
 754  */
 755 static int prune_tree_thread(void *unused)
 756 {
 757         for (;;) {
 758                 if (list_empty(&prune_list)) {
 759                         set_current_state(TASK_INTERRUPTIBLE);
 760                         schedule();
 761                 }
 762
 763                 audit_ctl_lock();
 764                 mutex_lock(&audit_filter_mutex);
 765
 766                 while (!list_empty(&prune_list)) {
 767                         struct audit_tree *victim;
 768
 769                         victim = list_entry(prune_list.next,
 770                                         struct audit_tree, list);
 771                         list_del_init(&victim->list);
 772
 773                         mutex_unlock(&audit_filter_mutex);
 774
 775                         prune_one(victim);
 776
 777                         mutex_lock(&audit_filter_mutex);
 778                 }
 779
 780                 mutex_unlock(&audit_filter_mutex);
 781                 audit_ctl_unlock();
 782         }
 783         return 0;
 784 }
 785
 786 static int audit_launch_prune(void)
 787 {
 788         if (prune_thread)
 789                 return 0;
 790         prune_thread = kthread_run(prune_tree_thread, NULL,
 791                                 "audit_prune_tree");
 792         if (IS_ERR(prune_thread)) {
 793                 pr_err("cannot start thread audit_prune_tree");
 794                 prune_thread = NULL;
 795                 return -ENOMEM;
 796         }
 797         return 0;
 798 }
 799
 800 /* called with audit_filter_mutex */
 801 int audit_add_tree_rule(struct audit_krule *rule)
 802 {
 803         struct audit_tree *seed = rule->tree, *tree;
 804         struct path path;
 805         struct vfsmount *mnt;
 806         int err;
 807
 808         rule->tree = NULL;
 809         list_for_each_entry(tree, &tree_list, list) {
 810                 if (!strcmp(seed->pathname, tree->pathname)) {
 811                         put_tree(seed);
 812                         rule->tree = tree;
 813                         list_add(&rule->rlist, &tree->rules);
 814                         return 0;
 815                 }
 816         }
 817         tree = seed;
 818         list_add(&tree->list, &tree_list);
 819         list_add(&rule->rlist, &tree->rules);
 820         /* do not set rule->tree yet */
 821         mutex_unlock(&audit_filter_mutex);
 822
 823         if (unlikely(!prune_thread)) {
 824                 err = audit_launch_prune();
 825                 if (err)
 826                         goto Err;
 827         }
 828
 829         err = kern_path(tree->pathname, 0, &path);
 830         if (err)
 831                 goto Err;
 832         mnt = collect_mounts(&path);
 833         path_put(&path);
 834         if (IS_ERR(mnt)) {
 835                 err = PTR_ERR(mnt);
 836                 goto Err;
 837         }
 838
 839         get_tree(tree);
 840         err = iterate_mounts(tag_mount, tree, mnt);
 841         drop_collected_mounts(mnt);
 842
 843         if (!err) {
 844                 struct node *node;
 845                 spin_lock(&hash_lock);
 846                 list_for_each_entry(node, &tree->chunks, list)
 847                         node->index &= ~(1U<<31);
 848                 spin_unlock(&hash_lock);
 849         } else {
 850                 trim_marked(tree);
 851                 goto Err;
 852         }
 853
 854         mutex_lock(&audit_filter_mutex);
 855         if (list_empty(&rule->rlist)) {
 856                 put_tree(tree);
 857                 return -ENOENT;
 858         }
 859         rule->tree = tree;
 860         put_tree(tree);
 861
 862         return 0;
 863 Err:
 864         mutex_lock(&audit_filter_mutex);
 865         list_del_init(&tree->list);
 866         list_del_init(&tree->rules);
 867         put_tree(tree);
 868         return err;
 869 }
 870
 871 int audit_tag_tree(char *old, char *new)
 872 {
 873         struct list_head cursor, barrier;
 874         int failed = 0;
 875         struct path path1, path2;
 876         struct vfsmount *tagged;
 877         int err;
 878
 879         err = kern_path(new, 0, &path2);
 880         if (err)
 881                 return err;
 882         tagged = collect_mounts(&path2);
 883         path_put(&path2);
 884         if (IS_ERR(tagged))
 885                 return PTR_ERR(tagged);
 886
 887         err = kern_path(old, 0, &path1);
 888         if (err) {
 889                 drop_collected_mounts(tagged);
 890                 return err;
 891         }
 892
 893         mutex_lock(&audit_filter_mutex);
 894         list_add(&barrier, &tree_list);
 895         list_add(&cursor, &barrier);
 896
 897         while (cursor.next != &tree_list) {
 898                 struct audit_tree *tree;
 899                 int good_one = 0;
 900
 901                 tree = container_of(cursor.next, struct audit_tree, list);
 902                 get_tree(tree);
 903                 list_del(&cursor);
 904                 list_add(&cursor, &tree->list);
 905                 mutex_unlock(&audit_filter_mutex);
 906
 907                 err = kern_path(tree->pathname, 0, &path2);
 908                 if (!err) {
 909                         good_one = path_is_under(&path1, &path2);
 910                         path_put(&path2);
 911                 }
 912
 913                 if (!good_one) {
 914                         put_tree(tree);
 915                         mutex_lock(&audit_filter_mutex);
 916                         continue;
 917                 }
 918
 919                 failed = iterate_mounts(tag_mount, tree, tagged);
 920                 if (failed) {
 921                         put_tree(tree);
 922                         mutex_lock(&audit_filter_mutex);
 923                         break;
 924                 }
 925
 926                 mutex_lock(&audit_filter_mutex);
 927                 spin_lock(&hash_lock);
 928                 if (!tree->goner) {
 929                         list_del(&tree->list);
 930                         list_add(&tree->list, &tree_list);
 931                 }
 932                 spin_unlock(&hash_lock);
 933                 put_tree(tree);
 934         }
 935
 936         while (barrier.prev != &tree_list) {
 937                 struct audit_tree *tree;
 938
 939                 tree = container_of(barrier.prev, struct audit_tree, list);
 940                 get_tree(tree);
 941                 list_del(&tree->list);
 942                 list_add(&tree->list, &barrier);
 943                 mutex_unlock(&audit_filter_mutex);
 944
 945                 if (!failed) {
 946                         struct node *node;
 947                         spin_lock(&hash_lock);
 948                         list_for_each_entry(node, &tree->chunks, list)
 949                                 node->index &= ~(1U<<31);
 950                         spin_unlock(&hash_lock);
 951                 } else {
 952                         trim_marked(tree);
 953                 }
 954
 955                 put_tree(tree);
 956                 mutex_lock(&audit_filter_mutex);
 957         }
 958         list_del(&barrier);
 959         list_del(&cursor);
 960         mutex_unlock(&audit_filter_mutex);
 961         path_put(&path1);
 962         drop_collected_mounts(tagged);
 963         return failed;
 964 }
 965
 966
 967 static void audit_schedule_prune(void)
 968 {
 969         wake_up_process(prune_thread);
 970 }
 971
 972 /*
 973  * ... and that one is done if evict_chunk() decides to delay until the end
 974  * of syscall.  Runs synchronously.
 975  */
 976 void audit_kill_trees(struct list_head *list)
 977 {
 978         audit_ctl_lock();
 979         mutex_lock(&audit_filter_mutex);
 980
 981         while (!list_empty(list)) {
 982                 struct audit_tree *victim;
 983
 984                 victim = list_entry(list->next, struct audit_tree, list);
 985                 kill_rules(victim);
 986                 list_del_init(&victim->list);
 987
 988                 mutex_unlock(&audit_filter_mutex);
 989
 990                 prune_one(victim);
 991
 992                 mutex_lock(&audit_filter_mutex);
 993         }
 994
 995         mutex_unlock(&audit_filter_mutex);
 996         audit_ctl_unlock();
 997 }
 998
 999 /*
1000  *  Here comes the stuff asynchronous to auditctl operations
1001  */
1002
1003 static void evict_chunk(struct audit_chunk *chunk)
1004 {
1005         struct audit_tree *owner;
1006         struct list_head *postponed = audit_killed_trees();
1007         int need_prune = 0;
1008         int n;
1009
1010         mutex_lock(&audit_filter_mutex);
1011         spin_lock(&hash_lock);
1012         while (!list_empty(&chunk->trees)) {
1013                 owner = list_entry(chunk->trees.next,
1014                                    struct audit_tree, same_root);
1015                 owner->goner = 1;
1016                 owner->root = NULL;
1017                 list_del_init(&owner->same_root);
1018                 spin_unlock(&hash_lock);
1019                 if (!postponed) {
1020                         kill_rules(owner);
1021                         list_move(&owner->list, &prune_list);
1022                         need_prune = 1;
1023                 } else {
1024                         list_move(&owner->list, postponed);
1025                 }
1026                 spin_lock(&hash_lock);
1027         }
1028         list_del_rcu(&chunk->hash);
1029         for (n = 0; n < chunk->count; n++)
1030                 list_del_init(&chunk->owners[n].list);
1031         spin_unlock(&hash_lock);
1032         mutex_unlock(&audit_filter_mutex);
1033         if (need_prune)
1034                 audit_schedule_prune();
1035 }
1036
1037 static int audit_tree_handle_event(struct fsnotify_group *group,
1038                                    struct inode *to_tell,
1039                                    u32 mask, const void *data, int data_type,
1040                                    const unsigned char *file_name, u32 cookie,
1041                                    struct fsnotify_iter_info *iter_info)
1042 {
1043         return 0;
1044 }
1045
1046 static void audit_tree_freeing_mark(struct fsnotify_mark *mark,
1047                                     struct fsnotify_group *group)
1048 {
1049         struct audit_chunk *chunk;
1050
1051         mutex_lock(&mark->group->mark_mutex);
1052         spin_lock(&hash_lock);
1053         chunk = mark_chunk(mark);
1054         replace_mark_chunk(mark, NULL);
1055         spin_unlock(&hash_lock);
1056         mutex_unlock(&mark->group->mark_mutex);
1057         if (chunk) {
1058                 evict_chunk(chunk);
1059                 audit_mark_put_chunk(chunk);
1060         }
1061
1062         /*
1063          * We are guaranteed to have at least one reference to the mark from
1064          * either the inode or the caller of fsnotify_destroy_mark().
1065          */
1066         BUG_ON(refcount_read(&mark->refcnt) < 1);
1067 }
1068
1069 static const struct fsnotify_ops audit_tree_ops = {
1070         .handle_event = audit_tree_handle_event,
1071         .freeing_mark = audit_tree_freeing_mark,
1072         .free_mark = audit_tree_destroy_watch,
1073 };
1074
1075 static int __init audit_tree_init(void)
1076 {
1077         int i;
1078
1079         audit_tree_mark_cachep = KMEM_CACHE(audit_tree_mark, SLAB_PANIC);
1080
1081         audit_tree_group = fsnotify_alloc_group(&audit_tree_ops);
1082         if (IS_ERR(audit_tree_group))
1083                 audit_panic("cannot initialize fsnotify group for rectree watches");
1084
1085         for (i = 0; i < HASH_SIZE; i++)
1086                 INIT_LIST_HEAD(&chunk_hash_heads[i]);
1087
1088         return 0;
1089 }
1090 __initcall(audit_tree_init);