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 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)
  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;
 103
 104         spin_lock(&inode->i_lock);
 105         entry = fsnotify_find_mark(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         fsnotify_recalc_group_mask(audit_watch_group);
 171
 172         return parent;
 173 }
 174
 175 /* Initialize a watch entry. */
 176 static struct audit_watch *audit_init_watch(char *path)
 177 {
 178         struct audit_watch *watch;
 179
 180         watch = kzalloc(sizeof(*watch), GFP_KERNEL);
 181         if (unlikely(!watch))
 182                 return ERR_PTR(-ENOMEM);
 183
 184         INIT_LIST_HEAD(&watch->rules);
 185         atomic_set(&watch->count, 1);
 186         watch->path = path;
 187         watch->dev = (dev_t)-1;
 188         watch->ino = (unsigned long)-1;
 189
 190         return watch;
 191 }
 192
 193 /* Translate a watch string to kernel respresentation. */
 194 int audit_to_watch(struct audit_krule *krule, char *path, int len, u32 op)
 195 {
 196         struct audit_watch *watch;
 197
 198         if (!audit_watch_group)
 199                 return -EOPNOTSUPP;
 200
 201         if (path[0] != '/' || path[len-1] == '/' ||
 202             krule->listnr != AUDIT_FILTER_EXIT ||
 203             op != Audit_equal ||
 204             krule->inode_f || krule->watch || krule->tree)
 205                 return -EINVAL;
 206
 207         watch = audit_init_watch(path);
 208         if (IS_ERR(watch))
 209                 return PTR_ERR(watch);
 210
 211         audit_get_watch(watch);
 212         krule->watch = watch;
 213
 214         return 0;
 215 }
 216
 217 /* Duplicate the given audit watch.  The new watch's rules list is initialized
 218  * to an empty list and wlist is undefined. */
 219 static struct audit_watch *audit_dupe_watch(struct audit_watch *old)
 220 {
 221         char *path;
 222         struct audit_watch *new;
 223
 224         path = kstrdup(old->path, GFP_KERNEL);
 225         if (unlikely(!path))
 226                 return ERR_PTR(-ENOMEM);
 227
 228         new = audit_init_watch(path);
 229         if (IS_ERR(new)) {
 230                 kfree(path);
 231                 goto out;
 232         }
 233
 234         new->dev = old->dev;
 235         new->ino = old->ino;
 236         audit_get_parent(old->parent);
 237         new->parent = old->parent;
 238
 239 out:
 240         return new;
 241 }
 242
 243 static void audit_watch_log_rule_change(struct audit_krule *r, struct audit_watch *w, char *op)
 244 {
 245         if (audit_enabled) {
 246                 struct audit_buffer *ab;
 247                 ab = audit_log_start(NULL, GFP_NOFS, AUDIT_CONFIG_CHANGE);
 248                 audit_log_format(ab, "auid=%u ses=%u op=",
 249                                  audit_get_loginuid(current),
 250                                  audit_get_sessionid(current));
 251                 audit_log_string(ab, op);
 252                 audit_log_format(ab, " path=");
 253                 audit_log_untrustedstring(ab, w->path);
 254                 audit_log_key(ab, r->filterkey);
 255                 audit_log_format(ab, " list=%d res=1", r->listnr);
 256                 audit_log_end(ab);
 257         }
 258 }
 259
 260 /* Update inode info in audit rules based on filesystem event. */
 261 static void audit_update_watch(struct audit_parent *parent,
 262                                const char *dname, dev_t dev,
 263                                unsigned long ino, unsigned invalidating)
 264 {
 265         struct audit_watch *owatch, *nwatch, *nextw;
 266         struct audit_krule *r, *nextr;
 267         struct audit_entry *oentry, *nentry;
 268
 269         mutex_lock(&audit_filter_mutex);
 270         /* Run all of the watches on this parent looking for the one that
 271          * matches the given dname */
 272         list_for_each_entry_safe(owatch, nextw, &parent->watches, wlist) {
 273                 if (audit_compare_dname_path(dname, owatch->path, NULL))
 274                         continue;
 275
 276                 /* If the update involves invalidating rules, do the inode-based
 277                  * filtering now, so we don't omit records. */
 278                 if (invalidating && !audit_dummy_context())
 279                         audit_filter_inodes(current, current->audit_context);
 280
 281                 /* updating ino will likely change which audit_hash_list we
 282                  * are on so we need a new watch for the new list */
 283                 nwatch = audit_dupe_watch(owatch);
 284                 if (IS_ERR(nwatch)) {
 285                         mutex_unlock(&audit_filter_mutex);
 286                         audit_panic("error updating watch, skipping");
 287                         return;
 288                 }
 289                 nwatch->dev = dev;
 290                 nwatch->ino = ino;
 291
 292                 list_for_each_entry_safe(r, nextr, &owatch->rules, rlist) {
 293
 294                         oentry = container_of(r, struct audit_entry, rule);
 295                         list_del(&oentry->rule.rlist);
 296                         list_del_rcu(&oentry->list);
 297
 298                         nentry = audit_dupe_rule(&oentry->rule);
 299                         if (IS_ERR(nentry)) {
 300                                 list_del(&oentry->rule.list);
 301                                 audit_panic("error updating watch, removing");
 302                         } else {
 303                                 int h = audit_hash_ino((u32)ino);
 304
 305                                 /*
 306                                  * nentry->rule.watch == oentry->rule.watch so
 307                                  * we must drop that reference and set it to our
 308                                  * new watch.
 309                                  */
 310                                 audit_put_watch(nentry->rule.watch);
 311                                 audit_get_watch(nwatch);
 312                                 nentry->rule.watch = nwatch;
 313                                 list_add(&nentry->rule.rlist, &nwatch->rules);
 314                                 list_add_rcu(&nentry->list, &audit_inode_hash[h]);
 315                                 list_replace(&oentry->rule.list,
 316                                              &nentry->rule.list);
 317                         }
 318
 319                         audit_watch_log_rule_change(r, owatch, "updated rules");
 320
 321                         call_rcu(&oentry->rcu, audit_free_rule_rcu);
 322                 }
 323
 324                 audit_remove_watch(owatch);
 325                 goto add_watch_to_parent; /* event applies to a single watch */
 326         }
 327         mutex_unlock(&audit_filter_mutex);
 328         return;
 329
 330 add_watch_to_parent:
 331         list_add(&nwatch->wlist, &parent->watches);
 332         mutex_unlock(&audit_filter_mutex);
 333         return;
 334 }
 335
 336 /* Remove all watches & rules associated with a parent that is going away. */
 337 static void audit_remove_parent_watches(struct audit_parent *parent)
 338 {
 339         struct audit_watch *w, *nextw;
 340         struct audit_krule *r, *nextr;
 341         struct audit_entry *e;
 342
 343         mutex_lock(&audit_filter_mutex);
 344         list_for_each_entry_safe(w, nextw, &parent->watches, wlist) {
 345                 list_for_each_entry_safe(r, nextr, &w->rules, rlist) {
 346                         e = container_of(r, struct audit_entry, rule);
 347                         audit_watch_log_rule_change(r, w, "remove rule");
 348                         list_del(&r->rlist);
 349                         list_del(&r->list);
 350                         list_del_rcu(&e->list);
 351                         call_rcu(&e->rcu, audit_free_rule_rcu);
 352                 }
 353                 audit_remove_watch(w);
 354         }
 355         mutex_unlock(&audit_filter_mutex);
 356
 357         fsnotify_destroy_mark(&parent->mark);
 358
 359         fsnotify_recalc_group_mask(audit_watch_group);
 360
 361 }
 362
 363 /* Get path information necessary for adding watches. */
 364 static int audit_get_nd(char *path, struct nameidata **ndp, struct nameidata **ndw)
 365 {
 366         struct nameidata *ndparent, *ndwatch;
 367         int err;
 368
 369         ndparent = kmalloc(sizeof(*ndparent), GFP_KERNEL);
 370         if (unlikely(!ndparent))
 371                 return -ENOMEM;
 372
 373         ndwatch = kmalloc(sizeof(*ndwatch), GFP_KERNEL);
 374         if (unlikely(!ndwatch)) {
 375                 kfree(ndparent);
 376                 return -ENOMEM;
 377         }
 378
 379         err = path_lookup(path, LOOKUP_PARENT, ndparent);
 380         if (err) {
 381                 kfree(ndparent);
 382                 kfree(ndwatch);
 383                 return err;
 384         }
 385
 386         err = path_lookup(path, 0, ndwatch);
 387         if (err) {
 388                 kfree(ndwatch);
 389                 ndwatch = NULL;
 390         }
 391
 392         *ndp = ndparent;
 393         *ndw = ndwatch;
 394
 395         return 0;
 396 }
 397
 398 /* Release resources used for watch path information. */
 399 static void audit_put_nd(struct nameidata *ndp, struct nameidata *ndw)
 400 {
 401         if (ndp) {
 402                 path_put(&ndp->path);
 403                 kfree(ndp);
 404         }
 405         if (ndw) {
 406                 path_put(&ndw->path);
 407                 kfree(ndw);
 408         }
 409 }
 410
 411 /* Associate the given rule with an existing parent.
 412  * Caller must hold audit_filter_mutex. */
 413 static void audit_add_to_parent(struct audit_krule *krule,
 414                                 struct audit_parent *parent)
 415 {
 416         struct audit_watch *w, *watch = krule->watch;
 417         int watch_found = 0;
 418
 419         BUG_ON(!mutex_is_locked(&audit_filter_mutex));
 420
 421         list_for_each_entry(w, &parent->watches, wlist) {
 422                 if (strcmp(watch->path, w->path))
 423                         continue;
 424
 425                 watch_found = 1;
 426
 427                 /* put krule's and initial refs to temporary watch */
 428                 audit_put_watch(watch);
 429                 audit_put_watch(watch);
 430
 431                 audit_get_watch(w);
 432                 krule->watch = watch = w;
 433                 break;
 434         }
 435
 436         if (!watch_found) {
 437                 audit_get_parent(parent);
 438                 watch->parent = parent;
 439
 440                 list_add(&watch->wlist, &parent->watches);
 441         }
 442         list_add(&krule->rlist, &watch->rules);
 443 }
 444
 445 /* Find a matching watch entry, or add this one.
 446  * Caller must hold audit_filter_mutex. */
 447 int audit_add_watch(struct audit_krule *krule, struct list_head **list)
 448 {
 449         struct audit_watch *watch = krule->watch;
 450         struct audit_parent *parent;
 451         struct nameidata *ndp = NULL, *ndw = NULL;
 452         int h, ret = 0;
 453
 454         mutex_unlock(&audit_filter_mutex);
 455
 456         /* Avoid calling path_lookup under audit_filter_mutex. */
 457         ret = audit_get_nd(watch->path, &ndp, &ndw);
 458         if (ret) {
 459                 /* caller expects mutex locked */
 460                 mutex_lock(&audit_filter_mutex);
 461                 goto error;
 462         }
 463
 464         mutex_lock(&audit_filter_mutex);
 465
 466         /* update watch filter fields */
 467         if (ndw) {
 468                 watch->dev = ndw->path.dentry->d_inode->i_sb->s_dev;
 469                 watch->ino = ndw->path.dentry->d_inode->i_ino;
 470         }
 471
 472         /* either find an old parent or attach a new one */
 473         parent = audit_find_parent(ndp->path.dentry->d_inode);
 474         if (!parent) {
 475                 parent = audit_init_parent(ndp);
 476                 if (IS_ERR(parent)) {
 477                         ret = PTR_ERR(parent);
 478                         goto error;
 479                 }
 480         }
 481
 482         audit_add_to_parent(krule, parent);
 483
 484         /* match get in audit_find_parent or audit_init_parent */
 485         audit_put_parent(parent);
 486
 487         h = audit_hash_ino((u32)watch->ino);
 488         *list = &audit_inode_hash[h];
 489 error:
 490         audit_put_nd(ndp, ndw);         /* NULL args OK */
 491         return ret;
 492
 493 }
 494
 495 void audit_remove_watch_rule(struct audit_krule *krule)
 496 {
 497         struct audit_watch *watch = krule->watch;
 498         struct audit_parent *parent = watch->parent;
 499
 500         list_del(&krule->rlist);
 501
 502         if (list_empty(&watch->rules)) {
 503                 audit_remove_watch(watch);
 504
 505                 if (list_empty(&parent->watches)) {
 506                         audit_get_parent(parent);
 507                         fsnotify_destroy_mark(&parent->mark);
 508                         audit_put_parent(parent);
 509                 }
 510         }
 511
 512         fsnotify_recalc_group_mask(audit_watch_group);
 513
 514 }
 515
 516 static bool audit_watch_should_send_event(struct fsnotify_group *group, struct inode *inode,
 517                                           struct vfsmount *mnt, __u32 mask, void *data,
 518                                           int data_type)
 519 {
 520         struct fsnotify_mark *entry;
 521         bool send;
 522
 523         spin_lock(&inode->i_lock);
 524         entry = fsnotify_find_mark(group, inode);
 525         spin_unlock(&inode->i_lock);
 526         if (!entry)
 527                 return false;
 528
 529         mask = (mask & ~FS_EVENT_ON_CHILD);
 530         send = (entry->mask & mask);
 531
 532         /* find took a reference */
 533         fsnotify_put_mark(entry);
 534
 535         return send;
 536 }
 537
 538 /* Update watch data in audit rules based on fsnotify events. */
 539 static int audit_watch_handle_event(struct fsnotify_group *group, struct fsnotify_event *event)
 540 {
 541         struct inode *inode;
 542         __u32 mask = event->mask;
 543         const char *dname = event->file_name;
 544         struct audit_parent *parent;
 545
 546         BUG_ON(group != audit_watch_group);
 547
 548         parent = audit_find_parent(event->to_tell);
 549         if (unlikely(!parent))
 550                 return 0;
 551
 552         switch (event->data_type) {
 553         case (FSNOTIFY_EVENT_PATH):
 554                 inode = event->path.dentry->d_inode;
 555                 break;
 556         case (FSNOTIFY_EVENT_INODE):
 557                 inode = event->inode;
 558                 break;
 559         default:
 560                 BUG();
 561                 inode = NULL;
 562                 break;
 563         };
 564
 565         if (mask & (FS_CREATE|FS_MOVED_TO) && inode)
 566                 audit_update_watch(parent, dname, inode->i_sb->s_dev, inode->i_ino, 0);
 567         else if (mask & (FS_DELETE|FS_MOVED_FROM))
 568                 audit_update_watch(parent, dname, (dev_t)-1, (unsigned long)-1, 1);
 569         else if (mask & (FS_DELETE_SELF|FS_UNMOUNT|FS_MOVE_SELF))
 570                 audit_remove_parent_watches(parent);
 571         /* moved put_inotify_watch to freeing mark */
 572
 573         /* matched the ref taken by audit_find_parent */
 574         audit_put_parent(parent);
 575
 576         return 0;
 577 }
 578
 579 static const struct fsnotify_ops audit_watch_fsnotify_ops = {
 580         .should_send_event =    audit_watch_should_send_event,
 581         .handle_event =         audit_watch_handle_event,
 582         .free_group_priv =      NULL,
 583         .freeing_mark =         NULL,
 584         .free_event_priv =      NULL,
 585 };
 586
 587 static int __init audit_watch_init(void)
 588 {
 589         audit_watch_group = fsnotify_alloc_group(&audit_watch_fsnotify_ops);
 590         if (IS_ERR(audit_watch_group)) {
 591                 audit_watch_group = NULL;
 592                 audit_panic("cannot create audit fsnotify group");
 593         }
 594         return 0;
 595 }
 596 device_initcall(audit_watch_init);