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 static 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         entry = fsnotify_find_inode_mark(audit_watch_group, inode);
 105         if (entry)
 106                 parent = container_of(entry, struct audit_parent, mark);
 107
 108         return parent;
 109 }
 110
 111 void audit_get_watch(struct audit_watch *watch)
 112 {
 113         atomic_inc(&watch->count);
 114 }
 115
 116 void audit_put_watch(struct audit_watch *watch)
 117 {
 118         if (atomic_dec_and_test(&watch->count)) {
 119                 WARN_ON(watch->parent);
 120                 WARN_ON(!list_empty(&watch->rules));
 121                 kfree(watch->path);
 122                 kfree(watch);
 123         }
 124 }
 125
 126 static void audit_remove_watch(struct audit_watch *watch)
 127 {
 128         list_del(&watch->wlist);
 129         audit_put_parent(watch->parent);
 130         watch->parent = NULL;
 131         audit_put_watch(watch); /* match initial get */
 132 }
 133
 134 char *audit_watch_path(struct audit_watch *watch)
 135 {
 136         return watch->path;
 137 }
 138
 139 int audit_watch_compare(struct audit_watch *watch, unsigned long ino, dev_t dev)
 140 {
 141         return (watch->ino != (unsigned long)-1) &&
 142                 (watch->ino == ino) &&
 143                 (watch->dev == dev);
 144 }
 145
 146 /* Initialize a parent watch entry. */
 147 static struct audit_parent *audit_init_parent(struct path *path)
 148 {
 149         struct inode *inode = path->dentry->d_inode;
 150         struct audit_parent *parent;
 151         int ret;
 152
 153         parent = kzalloc(sizeof(*parent), GFP_KERNEL);
 154         if (unlikely(!parent))
 155                 return ERR_PTR(-ENOMEM);
 156
 157         INIT_LIST_HEAD(&parent->watches);
 158
 159         fsnotify_init_mark(&parent->mark, audit_watch_free_mark);
 160         parent->mark.mask = AUDIT_FS_WATCH;
 161         ret = fsnotify_add_mark(&parent->mark, audit_watch_group, inode, NULL, 0);
 162         if (ret < 0) {
 163                 audit_free_parent(parent);
 164                 return ERR_PTR(ret);
 165         }
 166
 167         return parent;
 168 }
 169
 170 /* Initialize a watch entry. */
 171 static struct audit_watch *audit_init_watch(char *path)
 172 {
 173         struct audit_watch *watch;
 174
 175         watch = kzalloc(sizeof(*watch), GFP_KERNEL);
 176         if (unlikely(!watch))
 177                 return ERR_PTR(-ENOMEM);
 178
 179         INIT_LIST_HEAD(&watch->rules);
 180         atomic_set(&watch->count, 1);
 181         watch->path = path;
 182         watch->dev = (dev_t)-1;
 183         watch->ino = (unsigned long)-1;
 184
 185         return watch;
 186 }
 187
 188 /* Translate a watch string to kernel respresentation. */
 189 int audit_to_watch(struct audit_krule *krule, char *path, int len, u32 op)
 190 {
 191         struct audit_watch *watch;
 192
 193         if (!audit_watch_group)
 194                 return -EOPNOTSUPP;
 195
 196         if (path[0] != '/' || path[len-1] == '/' ||
 197             krule->listnr != AUDIT_FILTER_EXIT ||
 198             op != Audit_equal ||
 199             krule->inode_f || krule->watch || krule->tree)
 200                 return -EINVAL;
 201
 202         watch = audit_init_watch(path);
 203         if (IS_ERR(watch))
 204                 return PTR_ERR(watch);
 205
 206         audit_get_watch(watch);
 207         krule->watch = watch;
 208
 209         return 0;
 210 }
 211
 212 /* Duplicate the given audit watch.  The new watch's rules list is initialized
 213  * to an empty list and wlist is undefined. */
 214 static struct audit_watch *audit_dupe_watch(struct audit_watch *old)
 215 {
 216         char *path;
 217         struct audit_watch *new;
 218
 219         path = kstrdup(old->path, GFP_KERNEL);
 220         if (unlikely(!path))
 221                 return ERR_PTR(-ENOMEM);
 222
 223         new = audit_init_watch(path);
 224         if (IS_ERR(new)) {
 225                 kfree(path);
 226                 goto out;
 227         }
 228
 229         new->dev = old->dev;
 230         new->ino = old->ino;
 231         audit_get_parent(old->parent);
 232         new->parent = old->parent;
 233
 234 out:
 235         return new;
 236 }
 237
 238 static void audit_watch_log_rule_change(struct audit_krule *r, struct audit_watch *w, char *op)
 239 {
 240         if (audit_enabled) {
 241                 struct audit_buffer *ab;
 242                 ab = audit_log_start(NULL, GFP_NOFS, AUDIT_CONFIG_CHANGE);
 243                 if (unlikely(!ab))
 244                         return;
 245                 audit_log_format(ab, "auid=%u ses=%u op=",
 246                                  from_kuid(&init_user_ns, 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,
 271                                              AUDIT_NAME_FULL))
 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(&parent->mark, audit_watch_group);
 356 }
 357
 358 /* Get path information necessary for adding watches. */
 359 static int audit_get_nd(struct audit_watch *watch, struct path *parent)
 360 {
 361         struct dentry *d = kern_path_locked(watch->path, parent);
 362         if (IS_ERR(d))
 363                 return PTR_ERR(d);
 364         mutex_unlock(&parent->dentry->d_inode->i_mutex);
 365         if (d->d_inode) {
 366                 /* update watch filter fields */
 367                 watch->dev = d->d_inode->i_sb->s_dev;
 368                 watch->ino = d->d_inode->i_ino;
 369         }
 370         dput(d);
 371         return 0;
 372 }
 373
 374 /* Associate the given rule with an existing parent.
 375  * Caller must hold audit_filter_mutex. */
 376 static void audit_add_to_parent(struct audit_krule *krule,
 377                                 struct audit_parent *parent)
 378 {
 379         struct audit_watch *w, *watch = krule->watch;
 380         int watch_found = 0;
 381
 382         BUG_ON(!mutex_is_locked(&audit_filter_mutex));
 383
 384         list_for_each_entry(w, &parent->watches, wlist) {
 385                 if (strcmp(watch->path, w->path))
 386                         continue;
 387
 388                 watch_found = 1;
 389
 390                 /* put krule's and initial refs to temporary watch */
 391                 audit_put_watch(watch);
 392                 audit_put_watch(watch);
 393
 394                 audit_get_watch(w);
 395                 krule->watch = watch = w;
 396                 break;
 397         }
 398
 399         if (!watch_found) {
 400                 audit_get_parent(parent);
 401                 watch->parent = parent;
 402
 403                 list_add(&watch->wlist, &parent->watches);
 404         }
 405         list_add(&krule->rlist, &watch->rules);
 406 }
 407
 408 /* Find a matching watch entry, or add this one.
 409  * Caller must hold audit_filter_mutex. */
 410 int audit_add_watch(struct audit_krule *krule, struct list_head **list)
 411 {
 412         struct audit_watch *watch = krule->watch;
 413         struct audit_parent *parent;
 414         struct path parent_path;
 415         int h, ret = 0;
 416
 417         mutex_unlock(&audit_filter_mutex);
 418
 419         /* Avoid calling path_lookup under audit_filter_mutex. */
 420         ret = audit_get_nd(watch, &parent_path);
 421
 422         /* caller expects mutex locked */
 423         mutex_lock(&audit_filter_mutex);
 424
 425         if (ret)
 426                 return ret;
 427
 428         /* either find an old parent or attach a new one */
 429         parent = audit_find_parent(parent_path.dentry->d_inode);
 430         if (!parent) {
 431                 parent = audit_init_parent(&parent_path);
 432                 if (IS_ERR(parent)) {
 433                         ret = PTR_ERR(parent);
 434                         goto error;
 435                 }
 436         }
 437
 438         audit_add_to_parent(krule, parent);
 439
 440         /* match get in audit_find_parent or audit_init_parent */
 441         audit_put_parent(parent);
 442
 443         h = audit_hash_ino((u32)watch->ino);
 444         *list = &audit_inode_hash[h];
 445 error:
 446         path_put(&parent_path);
 447         return ret;
 448 }
 449
 450 void audit_remove_watch_rule(struct audit_krule *krule)
 451 {
 452         struct audit_watch *watch = krule->watch;
 453         struct audit_parent *parent = watch->parent;
 454
 455         list_del(&krule->rlist);
 456
 457         if (list_empty(&watch->rules)) {
 458                 /*
 459                  * audit_remove_watch() drops our reference to 'parent' which
 460                  * can get freed. Grab our own reference to be safe.
 461                  */
 462                 audit_get_parent(parent);
 463                 audit_remove_watch(watch);
 464                 if (list_empty(&parent->watches))
 465                         fsnotify_destroy_mark(&parent->mark, audit_watch_group);
 466                 audit_put_parent(parent);
 467         }
 468 }
 469
 470 /* Update watch data in audit rules based on fsnotify events. */
 471 static int audit_watch_handle_event(struct fsnotify_group *group,
 472                                     struct inode *to_tell,
 473                                     struct fsnotify_mark *inode_mark,
 474                                     struct fsnotify_mark *vfsmount_mark,
 475                                     u32 mask, void *data, int data_type,
 476                                     const unsigned char *dname, u32 cookie)
 477 {
 478         struct inode *inode;
 479         struct audit_parent *parent;
 480
 481         parent = container_of(inode_mark, struct audit_parent, mark);
 482
 483         BUG_ON(group != audit_watch_group);
 484
 485         switch (data_type) {
 486         case (FSNOTIFY_EVENT_PATH):
 487                 inode = ((struct path *)data)->dentry->d_inode;
 488                 break;
 489         case (FSNOTIFY_EVENT_INODE):
 490                 inode = (struct inode *)data;
 491                 break;
 492         default:
 493                 BUG();
 494                 inode = NULL;
 495                 break;
 496         };
 497
 498         if (mask & (FS_CREATE|FS_MOVED_TO) && inode)
 499                 audit_update_watch(parent, dname, inode->i_sb->s_dev, inode->i_ino, 0);
 500         else if (mask & (FS_DELETE|FS_MOVED_FROM))
 501                 audit_update_watch(parent, dname, (dev_t)-1, (unsigned long)-1, 1);
 502         else if (mask & (FS_DELETE_SELF|FS_UNMOUNT|FS_MOVE_SELF))
 503                 audit_remove_parent_watches(parent);
 504
 505         return 0;
 506 }
 507
 508 static const struct fsnotify_ops audit_watch_fsnotify_ops = {
 509         .handle_event =         audit_watch_handle_event,
 510 };
 511
 512 static int __init audit_watch_init(void)
 513 {
 514         audit_watch_group = fsnotify_alloc_group(&audit_watch_fsnotify_ops);
 515         if (IS_ERR(audit_watch_group)) {
 516                 audit_watch_group = NULL;
 517                 audit_panic("cannot create audit fsnotify group");
 518         }
 519         return 0;
 520 }
 521 device_initcall(audit_watch_init);