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