kernel/audit_watch.c

   1 /* audit_watch.c -- watching inodes
   2  *
   3  * Copyright 2003-2009 Red Hat, Inc.
   4  * Copyright 2005 Hewlett-Packard Development Company, L.P.
   5  * Copyright 2005 IBM Corporation
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  20  */
  21
  22 #include <linux/kernel.h>
  23 #include <linux/audit.h>
  24 #include <linux/kthread.h>
  25 #include <linux/mutex.h>
  26 #include <linux/fs.h>
  27 #include <linux/fsnotify_backend.h>
  28 #include <linux/namei.h>
  29 #include <linux/netlink.h>
  30 #include <linux/sched.h>
  31 #include <linux/security.h>
  32 #include "audit.h"
  33
  34 /*
  35  * Reference counting:
  36  *
  37  * audit_parent: lifetime is from audit_init_parent() to receipt of an FS_IGNORED
  38  *      event.  Each audit_watch holds a reference to its associated parent.
  39  *
  40  * audit_watch: if added to lists, lifetime is from audit_init_watch() to
  41  *      audit_remove_watch().  Additionally, an audit_watch may exist
  42  *      temporarily to assist in searching existing filter data.  Each
  43  *      audit_krule holds a reference to its associated watch.
  44  */
  45
  46 struct audit_watch {
  47         atomic_t                count;  /* reference count */
  48         dev_t                   dev;    /* associated superblock device */
  49         char                    *path;  /* insertion path */
  50         unsigned long           ino;    /* associated inode number */
  51         struct audit_parent     *parent; /* associated parent */
  52         struct list_head        wlist;  /* entry in parent->watches list */
  53         struct list_head        rules;  /* anchor for krule->rlist */
  54 };
  55
  56 struct audit_parent {
  57         struct list_head        watches; /* anchor for audit_watch->wlist */
  58         struct fsnotify_mark_entry mark; /* fsnotify mark on the inode */
  59 };
  60
  61 /* fsnotify handle. */
  62 struct fsnotify_group *audit_watch_group;
  63
  64 /* fsnotify events we care about. */
  65 #define AUDIT_FS_WATCH (FS_MOVE | FS_CREATE | FS_DELETE | FS_DELETE_SELF |\
  66                         FS_MOVE_SELF | FS_EVENT_ON_CHILD)
  67
  68 static void audit_free_parent(struct audit_parent *parent)
  69 {
  70         WARN_ON(!list_empty(&parent->watches));
  71         kfree(parent);
  72 }
  73
  74 static void audit_watch_free_mark(struct fsnotify_mark_entry *entry)
  75 {
  76         struct audit_parent *parent;
  77
  78         parent = container_of(entry, struct audit_parent, mark);
  79         audit_free_parent(parent);
  80 }
  81
  82 static void audit_get_parent(struct audit_parent *parent)
  83 {
  84         if (likely(parent))
  85                 fsnotify_get_mark(&parent->mark);
  86 }
  87
  88 static void audit_put_parent(struct audit_parent *parent)
  89 {
  90         if (likely(parent))
  91                 fsnotify_put_mark(&parent->mark);
  92 }
  93
  94 /*
  95  * Find and return the audit_parent on the given inode.  If found a reference
  96  * is taken on this parent.
  97  */
  98 static inline struct audit_parent *audit_find_parent(struct inode *inode)
  99 {
 100         struct audit_parent *parent = NULL;
 101         struct fsnotify_mark_entry *entry;
 102
 103         spin_lock(&inode->i_lock);
 104         entry = fsnotify_find_mark_entry(audit_watch_group, inode);
 105         spin_unlock(&inode->i_lock);
 106
 107         if (entry)
 108                 parent = container_of(entry, struct audit_parent, mark);
 109
 110         return parent;
 111 }
 112
 113 void audit_get_watch(struct audit_watch *watch)
 114 {
 115         atomic_inc(&watch->count);
 116 }
 117
 118 void audit_put_watch(struct audit_watch *watch)
 119 {
 120         if (atomic_dec_and_test(&watch->count)) {
 121                 WARN_ON(watch->parent);
 122                 WARN_ON(!list_empty(&watch->rules));
 123                 kfree(watch->path);
 124                 kfree(watch);
 125         }
 126 }
 127
 128 void audit_remove_watch(struct audit_watch *watch)
 129 {
 130         list_del(&watch->wlist);
 131         audit_put_parent(watch->parent);
 132         watch->parent = NULL;
 133         audit_put_watch(watch); /* match initial get */
 134 }
 135
 136 char *audit_watch_path(struct audit_watch *watch)
 137 {
 138         return watch->path;
 139 }
 140
 141 int audit_watch_compare(struct audit_watch *watch, unsigned long ino, dev_t dev)
 142 {
 143         return (watch->ino != (unsigned long)-1) &&
 144                 (watch->ino == ino) &&
 145                 (watch->dev == dev);
 146 }
 147
 148 /* Initialize a parent watch entry. */
 149 static struct audit_parent *audit_init_parent(struct nameidata *ndp)
 150 {
 151         struct inode *inode = ndp->path.dentry->d_inode;
 152         struct audit_parent *parent;
 153         int ret;
 154
 155         parent = kzalloc(sizeof(*parent), GFP_KERNEL);
 156         if (unlikely(!parent))
 157                 return ERR_PTR(-ENOMEM);
 158
 159         INIT_LIST_HEAD(&parent->watches);
 160
 161         fsnotify_init_mark(&parent->mark, audit_watch_free_mark);
 162         parent->mark.mask = AUDIT_FS_WATCH;
 163         ret = fsnotify_add_mark(&parent->mark, audit_watch_group, inode, 0);
 164         if (ret < 0) {
 165                 audit_free_parent(parent);
 166                 return ERR_PTR(ret);
 167         }
 168
 169         return parent;
 170 }
 171
 172 /* Initialize a watch entry. */
 173 static struct audit_watch *audit_init_watch(char *path)
 174 {
 175         struct audit_watch *watch;
 176
 177         watch = kzalloc(sizeof(*watch), GFP_KERNEL);
 178         if (unlikely(!watch))
 179                 return ERR_PTR(-ENOMEM);
 180
 181         INIT_LIST_HEAD(&watch->rules);
 182         atomic_set(&watch->count, 1);
 183         watch->path = path;
 184         watch->dev = (dev_t)-1;
 185         watch->ino = (unsigned long)-1;
 186
 187         return watch;
 188 }
 189
 190 /* Translate a watch string to kernel respresentation. */
 191 int audit_to_watch(struct audit_krule *krule, char *path, int len, u32 op)
 192 {
 193         struct audit_watch *watch;
 194
 195         if (!audit_watch_group)
 196                 return -EOPNOTSUPP;
 197
 198         if (path[0] != '/' || path[len-1] == '/' ||
 199             krule->listnr != AUDIT_FILTER_EXIT ||
 200             op != Audit_equal ||
 201             krule->inode_f || krule->watch || krule->tree)
 202                 return -EINVAL;
 203
 204         watch = audit_init_watch(path);
 205         if (IS_ERR(watch))
 206                 return PTR_ERR(watch);
 207
 208         audit_get_watch(watch);
 209         krule->watch = watch;
 210
 211         return 0;
 212 }
 213
 214 /* Duplicate the given audit watch.  The new watch's rules list is initialized
 215  * to an empty list and wlist is undefined. */
 216 static struct audit_watch *audit_dupe_watch(struct audit_watch *old)
 217 {
 218         char *path;
 219         struct audit_watch *new;
 220
 221         path = kstrdup(old->path, GFP_KERNEL);
 222         if (unlikely(!path))
 223                 return ERR_PTR(-ENOMEM);
 224
 225         new = audit_init_watch(path);
 226         if (IS_ERR(new)) {
 227                 kfree(path);
 228                 goto out;
 229         }
 230
 231         new->dev = old->dev;
 232         new->ino = old->ino;
 233         audit_get_parent(old->parent);
 234         new->parent = old->parent;
 235
 236 out:
 237         return new;
 238 }
 239
 240 static void audit_watch_log_rule_change(struct audit_krule *r, struct audit_watch *w, char *op)
 241 {
 242         if (audit_enabled) {
 243                 struct audit_buffer *ab;
 244                 ab = audit_log_start(NULL, GFP_NOFS, AUDIT_CONFIG_CHANGE);
 245                 audit_log_format(ab, "auid=%u ses=%u op=",
 246                                  audit_get_loginuid(current),
 247                                  audit_get_sessionid(current));
 248                 audit_log_string(ab, op);
 249                 audit_log_format(ab, " path=");
 250                 audit_log_untrustedstring(ab, w->path);
 251                 audit_log_key(ab, r->filterkey);
 252                 audit_log_format(ab, " list=%d res=1", r->listnr);
 253                 audit_log_end(ab);
 254         }
 255 }
 256
 257 /* Update inode info in audit rules based on filesystem event. */
 258 static void audit_update_watch(struct audit_parent *parent,
 259                                const char *dname, dev_t dev,
 260                                unsigned long ino, unsigned invalidating)
 261 {
 262         struct audit_watch *owatch, *nwatch, *nextw;
 263         struct audit_krule *r, *nextr;
 264         struct audit_entry *oentry, *nentry;
 265
 266         mutex_lock(&audit_filter_mutex);
 267         /* Run all of the watches on this parent looking for the one that
 268          * matches the given dname */
 269         list_for_each_entry_safe(owatch, nextw, &parent->watches, wlist) {
 270                 if (audit_compare_dname_path(dname, owatch->path, NULL))
 271                         continue;
 272
 273                 /* If the update involves invalidating rules, do the inode-based
 274                  * filtering now, so we don't omit records. */
 275                 if (invalidating && !audit_dummy_context())
 276                         audit_filter_inodes(current, current->audit_context);
 277
 278                 /* updating ino will likely change which audit_hash_list we
 279                  * are on so we need a new watch for the new list */
 280                 nwatch = audit_dupe_watch(owatch);
 281                 if (IS_ERR(nwatch)) {
 282                         mutex_unlock(&audit_filter_mutex);
 283                         audit_panic("error updating watch, skipping");
 284                         return;
 285                 }
 286                 nwatch->dev = dev;
 287                 nwatch->ino = ino;
 288
 289                 list_for_each_entry_safe(r, nextr, &owatch->rules, rlist) {
 290
 291                         oentry = container_of(r, struct audit_entry, rule);
 292                         list_del(&oentry->rule.rlist);
 293                         list_del_rcu(&oentry->list);
 294
 295                         nentry = audit_dupe_rule(&oentry->rule);
 296                         if (IS_ERR(nentry)) {
 297                                 list_del(&oentry->rule.list);
 298                                 audit_panic("error updating watch, removing");
 299                         } else {
 300                                 int h = audit_hash_ino((u32)ino);
 301
 302                                 /*
 303                                  * nentry->rule.watch == oentry->rule.watch so
 304                                  * we must drop that reference and set it to our
 305                                  * new watch.
 306                                  */
 307                                 audit_put_watch(nentry->rule.watch);
 308                                 audit_get_watch(nwatch);
 309                                 nentry->rule.watch = nwatch;
 310                                 list_add(&nentry->rule.rlist, &nwatch->rules);
 311                                 list_add_rcu(&nentry->list, &audit_inode_hash[h]);
 312                                 list_replace(&oentry->rule.list,
 313                                              &nentry->rule.list);
 314                         }
 315
 316                         audit_watch_log_rule_change(r, owatch, "updated rules");
 317
 318                         call_rcu(&oentry->rcu, audit_free_rule_rcu);
 319                 }
 320
 321                 audit_remove_watch(owatch);
 322                 goto add_watch_to_parent; /* event applies to a single watch */
 323         }
 324         mutex_unlock(&audit_filter_mutex);
 325         return;
 326
 327 add_watch_to_parent:
 328         list_add(&nwatch->wlist, &parent->watches);
 329         mutex_unlock(&audit_filter_mutex);
 330         return;
 331 }
 332
 333 /* Remove all watches & rules associated with a parent that is going away. */
 334 static void audit_remove_parent_watches(struct audit_parent *parent)
 335 {
 336         struct audit_watch *w, *nextw;
 337         struct audit_krule *r, *nextr;
 338         struct audit_entry *e;
 339
 340         mutex_lock(&audit_filter_mutex);
 341         list_for_each_entry_safe(w, nextw, &parent->watches, wlist) {
 342                 list_for_each_entry_safe(r, nextr, &w->rules, rlist) {
 343                         e = container_of(r, struct audit_entry, rule);
 344                         audit_watch_log_rule_change(r, w, "remove rule");
 345                         list_del(&r->rlist);
 346                         list_del(&r->list);
 347                         list_del_rcu(&e->list);
 348                         call_rcu(&e->rcu, audit_free_rule_rcu);
 349                 }
 350                 audit_remove_watch(w);
 351         }
 352         mutex_unlock(&audit_filter_mutex);
 353
 354         fsnotify_destroy_mark_by_entry(&parent->mark);
 355 }
 356
 357 /* Get path information necessary for adding watches. */
 358 static int audit_get_nd(char *path, struct nameidata **ndp, struct nameidata **ndw)
 359 {
 360         struct nameidata *ndparent, *ndwatch;
 361         int err;
 362
 363         ndparent = kmalloc(sizeof(*ndparent), GFP_KERNEL);
 364         if (unlikely(!ndparent))
 365                 return -ENOMEM;
 366
 367         ndwatch = kmalloc(sizeof(*ndwatch), GFP_KERNEL);
 368         if (unlikely(!ndwatch)) {
 369                 kfree(ndparent);
 370                 return -ENOMEM;
 371         }
 372
 373         err = path_lookup(path, LOOKUP_PARENT, ndparent);
 374         if (err) {
 375                 kfree(ndparent);
 376                 kfree(ndwatch);
 377                 return err;
 378         }
 379
 380         err = path_lookup(path, 0, ndwatch);
 381         if (err) {
 382                 kfree(ndwatch);
 383                 ndwatch = NULL;
 384         }
 385
 386         *ndp = ndparent;
 387         *ndw = ndwatch;
 388
 389         return 0;
 390 }
 391
 392 /* Release resources used for watch path information. */
 393 static void audit_put_nd(struct nameidata *ndp, struct nameidata *ndw)
 394 {
 395         if (ndp) {
 396                 path_put(&ndp->path);
 397                 kfree(ndp);
 398         }
 399         if (ndw) {
 400                 path_put(&ndw->path);
 401                 kfree(ndw);
 402         }
 403 }
 404
 405 /* Associate the given rule with an existing parent.
 406  * Caller must hold audit_filter_mutex. */
 407 static void audit_add_to_parent(struct audit_krule *krule,
 408                                 struct audit_parent *parent)
 409 {
 410         struct audit_watch *w, *watch = krule->watch;
 411         int watch_found = 0;
 412
 413         BUG_ON(!mutex_is_locked(&audit_filter_mutex));
 414
 415         list_for_each_entry(w, &parent->watches, wlist) {
 416                 if (strcmp(watch->path, w->path))
 417                         continue;
 418
 419                 watch_found = 1;
 420
 421                 /* put krule's and initial refs to temporary watch */
 422                 audit_put_watch(watch);
 423                 audit_put_watch(watch);
 424
 425                 audit_get_watch(w);
 426                 krule->watch = watch = w;
 427                 break;
 428         }
 429
 430         if (!watch_found) {
 431                 audit_get_parent(parent);
 432                 watch->parent = parent;
 433
 434                 list_add(&watch->wlist, &parent->watches);
 435         }
 436         list_add(&krule->rlist, &watch->rules);
 437 }
 438
 439 /* Find a matching watch entry, or add this one.
 440  * Caller must hold audit_filter_mutex. */
 441 int audit_add_watch(struct audit_krule *krule, struct list_head **list)
 442 {
 443         struct audit_watch *watch = krule->watch;
 444         struct audit_parent *parent;
 445         struct nameidata *ndp = NULL, *ndw = NULL;
 446         int h, ret = 0;
 447
 448         mutex_unlock(&audit_filter_mutex);
 449
 450         /* Avoid calling path_lookup under audit_filter_mutex. */
 451         ret = audit_get_nd(watch->path, &ndp, &ndw);
 452         if (ret) {
 453                 /* caller expects mutex locked */
 454                 mutex_lock(&audit_filter_mutex);
 455                 goto error;
 456         }
 457
 458         mutex_lock(&audit_filter_mutex);
 459
 460         /* update watch filter fields */
 461         if (ndw) {
 462                 watch->dev = ndw->path.dentry->d_inode->i_sb->s_dev;
 463                 watch->ino = ndw->path.dentry->d_inode->i_ino;
 464         }
 465
 466         /* either find an old parent or attach a new one */
 467         parent = audit_find_parent(ndp->path.dentry->d_inode);
 468         if (!parent) {
 469                 parent = audit_init_parent(ndp);
 470                 if (IS_ERR(parent)) {
 471                         ret = PTR_ERR(parent);
 472                         goto error;
 473                 }
 474         }
 475
 476         audit_add_to_parent(krule, parent);
 477
 478         /* match get in audit_find_parent or audit_init_parent */
 479         audit_put_parent(parent);
 480
 481         h = audit_hash_ino((u32)watch->ino);
 482         *list = &audit_inode_hash[h];
 483 error:
 484         audit_put_nd(ndp, ndw);         /* NULL args OK */
 485         return ret;
 486
 487 }
 488
 489 void audit_remove_watch_rule(struct audit_krule *krule)
 490 {
 491         struct audit_watch *watch = krule->watch;
 492         struct audit_parent *parent = watch->parent;
 493
 494         list_del(&krule->rlist);
 495
 496         if (list_empty(&watch->rules)) {
 497                 audit_remove_watch(watch);
 498
 499                 if (list_empty(&parent->watches)) {
 500                         audit_get_parent(parent);
 501                         fsnotify_destroy_mark_by_entry(&parent->mark);
 502                         audit_put_parent(parent);
 503                 }
 504         }
 505 }
 506
 507 static bool audit_watch_should_send_event(struct fsnotify_group *group, struct inode *inode,
 508                                           __u32 mask, void *data, int data_type)
 509 {
 510         struct fsnotify_mark_entry *entry;
 511         bool send;
 512
 513         spin_lock(&inode->i_lock);
 514         entry = fsnotify_find_mark_entry(group, inode);
 515         spin_unlock(&inode->i_lock);
 516         if (!entry)
 517                 return false;
 518
 519         mask = (mask & ~FS_EVENT_ON_CHILD);
 520         send = (entry->mask & mask);
 521
 522         /* find took a reference */
 523         fsnotify_put_mark(entry);
 524
 525         return send;
 526 }
 527
 528 /* Update watch data in audit rules based on fsnotify events. */
 529 static int audit_watch_handle_event(struct fsnotify_group *group, struct fsnotify_event *event)
 530 {
 531         struct inode *inode;
 532         __u32 mask = event->mask;
 533         const char *dname = event->file_name;
 534         struct audit_parent *parent;
 535
 536         BUG_ON(group != audit_watch_group);
 537
 538         parent = audit_find_parent(event->to_tell);
 539         if (unlikely(!parent))
 540                 return 0;
 541
 542         switch (event->data_type) {
 543         case (FSNOTIFY_EVENT_PATH):
 544                 inode = event->path.dentry->d_inode;
 545                 break;
 546         case (FSNOTIFY_EVENT_INODE):
 547                 inode = event->inode;
 548                 break;
 549         default:
 550                 BUG();
 551                 inode = NULL;
 552                 break;
 553         };
 554
 555         if (mask & (FS_CREATE|FS_MOVED_TO) && inode)
 556                 audit_update_watch(parent, dname, inode->i_sb->s_dev, inode->i_ino, 0);
 557         else if (mask & (FS_DELETE|FS_MOVED_FROM))
 558                 audit_update_watch(parent, dname, (dev_t)-1, (unsigned long)-1, 1);
 559         else if (mask & (FS_DELETE_SELF|FS_UNMOUNT|FS_MOVE_SELF))
 560                 audit_remove_parent_watches(parent);
 561         /* moved put_inotify_watch to freeing mark */
 562
 563         /* matched the ref taken by audit_find_parent */
 564         audit_put_parent(parent);
 565
 566         return 0;
 567 }
 568
 569 static const struct fsnotify_ops audit_watch_fsnotify_ops = {
 570         .should_send_event =    audit_watch_should_send_event,
 571         .handle_event =         audit_watch_handle_event,
 572         .free_group_priv =      NULL,
 573         .freeing_mark =         NULL,
 574         .free_event_priv =      NULL,
 575 };
 576
 577 static int __init audit_watch_init(void)
 578 {
 579         audit_watch_group = fsnotify_obtain_group(AUDIT_FS_WATCH,
 580                                                   &audit_watch_fsnotify_ops);
 581         if (IS_ERR(audit_watch_group)) {
 582                 audit_watch_group = NULL;
 583                 audit_panic("cannot create audit fsnotify group");
 584         }
 585         return 0;
 586 }
 587 device_initcall(audit_watch_init);