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/file.h>
  23 #include <linux/kernel.h>
  24 #include <linux/audit.h>
  25 #include <linux/kthread.h>
  26 #include <linux/mutex.h>
  27 #include <linux/fs.h>
  28 #include <linux/fsnotify_backend.h>
  29 #include <linux/namei.h>
  30 #include <linux/netlink.h>
  31 #include <linux/refcount.h>
  32 #include <linux/sched.h>
  33 #include <linux/slab.h>
  34 #include <linux/security.h>
  35 #include "audit.h"
  36
  37 /*
  38  * Reference counting:
  39  *
  40  * audit_parent: lifetime is from audit_init_parent() to receipt of an FS_IGNORED
  41  *      event.  Each audit_watch holds a reference to its associated parent.
  42  *
  43  * audit_watch: if added to lists, lifetime is from audit_init_watch() to
  44  *      audit_remove_watch().  Additionally, an audit_watch may exist
  45  *      temporarily to assist in searching existing filter data.  Each
  46  *      audit_krule holds a reference to its associated watch.
  47  */
  48
  49 struct audit_watch {
  50         refcount_t              count;  /* reference count */
  51         dev_t                   dev;    /* associated superblock device */
  52         char                    *path;  /* insertion path */
  53         unsigned long           ino;    /* associated inode number */
  54         struct audit_parent     *parent; /* associated parent */
  55         struct list_head        wlist;  /* entry in parent->watches list */
  56         struct list_head        rules;  /* anchor for krule->rlist */
  57 };
  58
  59 struct audit_parent {
  60         struct list_head        watches; /* anchor for audit_watch->wlist */
  61         struct fsnotify_mark mark; /* fsnotify mark on the inode */
  62 };
  63
  64 /* fsnotify handle. */
  65 static struct fsnotify_group *audit_watch_group;
  66
  67 /* fsnotify events we care about. */
  68 #define AUDIT_FS_WATCH (FS_MOVE | FS_CREATE | FS_DELETE | FS_DELETE_SELF |\
  69                         FS_MOVE_SELF | FS_EVENT_ON_CHILD | FS_UNMOUNT)
  70
  71 static void audit_free_parent(struct audit_parent *parent)
  72 {
  73         WARN_ON(!list_empty(&parent->watches));
  74         kfree(parent);
  75 }
  76
  77 static void audit_watch_free_mark(struct fsnotify_mark *entry)
  78 {
  79         struct audit_parent *parent;
  80
  81         parent = container_of(entry, struct audit_parent, mark);
  82         audit_free_parent(parent);
  83 }
  84
  85 static void audit_get_parent(struct audit_parent *parent)
  86 {
  87         if (likely(parent))
  88                 fsnotify_get_mark(&parent->mark);
  89 }
  90
  91 static void audit_put_parent(struct audit_parent *parent)
  92 {
  93         if (likely(parent))
  94                 fsnotify_put_mark(&parent->mark);
  95 }
  96
  97 /*
  98  * Find and return the audit_parent on the given inode.  If found a reference
  99  * is taken on this parent.
 100  */
 101 static inline struct audit_parent *audit_find_parent(struct inode *inode)
 102 {
 103         struct audit_parent *parent = NULL;
 104         struct fsnotify_mark *entry;
 105
 106         entry = fsnotify_find_mark(&inode->i_fsnotify_marks, audit_watch_group);
 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         refcount_inc(&watch->count);
 116 }
 117
 118 void audit_put_watch(struct audit_watch *watch)
 119 {
 120         if (refcount_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 static 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 != AUDIT_INO_UNSET) &&
 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 path *path)
 150 {
 151         struct inode *inode = d_backing_inode(path->dentry);
 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_group);
 162         parent->mark.mask = AUDIT_FS_WATCH;
 163         ret = fsnotify_add_inode_mark(&parent->mark, 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         refcount_set(&watch->count, 1);
 183         watch->path = path;
 184         watch->dev = AUDIT_DEV_UNSET;
 185         watch->ino = AUDIT_INO_UNSET;
 186
 187         return watch;
 188 }
 189
 190 /* Translate a watch string to kernel representation. */
 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         krule->watch = watch;
 209
 210         return 0;
 211 }
 212
 213 /* Duplicate the given audit watch.  The new watch's rules list is initialized
 214  * to an empty list and wlist is undefined. */
 215 static struct audit_watch *audit_dupe_watch(struct audit_watch *old)
 216 {
 217         char *path;
 218         struct audit_watch *new;
 219
 220         path = kstrdup(old->path, GFP_KERNEL);
 221         if (unlikely(!path))
 222                 return ERR_PTR(-ENOMEM);
 223
 224         new = audit_init_watch(path);
 225         if (IS_ERR(new)) {
 226                 kfree(path);
 227                 goto out;
 228         }
 229
 230         new->dev = old->dev;
 231         new->ino = old->ino;
 232         audit_get_parent(old->parent);
 233         new->parent = old->parent;
 234
 235 out:
 236         return new;
 237 }
 238
 239 static void audit_watch_log_rule_change(struct audit_krule *r, struct audit_watch *w, char *op)
 240 {
 241         struct audit_buffer *ab;
 242
 243         if (!audit_enabled)
 244                 return;
 245         ab = audit_log_start(audit_context(), GFP_NOFS, AUDIT_CONFIG_CHANGE);
 246         if (!ab)
 247                 return;
 248         audit_log_session_info(ab);
 249         audit_log_format(ab, "op=%s path=", op);
 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 /* Update inode info in audit rules based on filesystem event. */
 257 static void audit_update_watch(struct audit_parent *parent,
 258                                const char *dname, dev_t dev,
 259                                unsigned long ino, unsigned invalidating)
 260 {
 261         struct audit_watch *owatch, *nwatch, *nextw;
 262         struct audit_krule *r, *nextr;
 263         struct audit_entry *oentry, *nentry;
 264
 265         mutex_lock(&audit_filter_mutex);
 266         /* Run all of the watches on this parent looking for the one that
 267          * matches the given dname */
 268         list_for_each_entry_safe(owatch, nextw, &parent->watches, wlist) {
 269                 if (audit_compare_dname_path(dname, owatch->path,
 270                                              AUDIT_NAME_FULL))
 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, 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                         if (oentry->rule.exe)
 316                                 audit_remove_mark(oentry->rule.exe);
 317
 318                         audit_watch_log_rule_change(r, owatch, "updated_rules");
 319
 320                         call_rcu(&oentry->rcu, audit_free_rule_rcu);
 321                 }
 322
 323                 audit_remove_watch(owatch);
 324                 goto add_watch_to_parent; /* event applies to a single watch */
 325         }
 326         mutex_unlock(&audit_filter_mutex);
 327         return;
 328
 329 add_watch_to_parent:
 330         list_add(&nwatch->wlist, &parent->watches);
 331         mutex_unlock(&audit_filter_mutex);
 332         return;
 333 }
 334
 335 /* Remove all watches & rules associated with a parent that is going away. */
 336 static void audit_remove_parent_watches(struct audit_parent *parent)
 337 {
 338         struct audit_watch *w, *nextw;
 339         struct audit_krule *r, *nextr;
 340         struct audit_entry *e;
 341
 342         mutex_lock(&audit_filter_mutex);
 343         list_for_each_entry_safe(w, nextw, &parent->watches, wlist) {
 344                 list_for_each_entry_safe(r, nextr, &w->rules, rlist) {
 345                         e = container_of(r, struct audit_entry, rule);
 346                         audit_watch_log_rule_change(r, w, "remove_rule");
 347                         if (e->rule.exe)
 348                                 audit_remove_mark(e->rule.exe);
 349                         list_del(&r->rlist);
 350                         list_del(&r->list);
 351                         list_del_rcu(&e->list);
 352                         call_rcu(&e->rcu, audit_free_rule_rcu);
 353                 }
 354                 audit_remove_watch(w);
 355         }
 356         mutex_unlock(&audit_filter_mutex);
 357
 358         fsnotify_destroy_mark(&parent->mark, audit_watch_group);
 359 }
 360
 361 /* Get path information necessary for adding watches. */
 362 static int audit_get_nd(struct audit_watch *watch, struct path *parent)
 363 {
 364         struct dentry *d = kern_path_locked(watch->path, parent);
 365         if (IS_ERR(d))
 366                 return PTR_ERR(d);
 367         inode_unlock(d_backing_inode(parent->dentry));
 368         if (d_is_positive(d)) {
 369                 /* update watch filter fields */
 370                 watch->dev = d->d_sb->s_dev;
 371                 watch->ino = d_backing_inode(d)->i_ino;
 372         }
 373         dput(d);
 374         return 0;
 375 }
 376
 377 /* Associate the given rule with an existing parent.
 378  * Caller must hold audit_filter_mutex. */
 379 static void audit_add_to_parent(struct audit_krule *krule,
 380                                 struct audit_parent *parent)
 381 {
 382         struct audit_watch *w, *watch = krule->watch;
 383         int watch_found = 0;
 384
 385         BUG_ON(!mutex_is_locked(&audit_filter_mutex));
 386
 387         list_for_each_entry(w, &parent->watches, wlist) {
 388                 if (strcmp(watch->path, w->path))
 389                         continue;
 390
 391                 watch_found = 1;
 392
 393                 /* put krule's ref to temporary watch */
 394                 audit_put_watch(watch);
 395
 396                 audit_get_watch(w);
 397                 krule->watch = watch = w;
 398
 399                 audit_put_parent(parent);
 400                 break;
 401         }
 402
 403         if (!watch_found) {
 404                 watch->parent = parent;
 405
 406                 audit_get_watch(watch);
 407                 list_add(&watch->wlist, &parent->watches);
 408         }
 409         list_add(&krule->rlist, &watch->rules);
 410 }
 411
 412 /* Find a matching watch entry, or add this one.
 413  * Caller must hold audit_filter_mutex. */
 414 int audit_add_watch(struct audit_krule *krule, struct list_head **list)
 415 {
 416         struct audit_watch *watch = krule->watch;
 417         struct audit_parent *parent;
 418         struct path parent_path;
 419         int h, ret = 0;
 420
 421         /*
 422          * When we will be calling audit_add_to_parent, krule->watch might have
 423          * been updated and watch might have been freed.
 424          * So we need to keep a reference of watch.
 425          */
 426         audit_get_watch(watch);
 427
 428         mutex_unlock(&audit_filter_mutex);
 429
 430         /* Avoid calling path_lookup under audit_filter_mutex. */
 431         ret = audit_get_nd(watch, &parent_path);
 432
 433         /* caller expects mutex locked */
 434         mutex_lock(&audit_filter_mutex);
 435
 436         if (ret) {
 437                 audit_put_watch(watch);
 438                 return ret;
 439         }
 440
 441         /* either find an old parent or attach a new one */
 442         parent = audit_find_parent(d_backing_inode(parent_path.dentry));
 443         if (!parent) {
 444                 parent = audit_init_parent(&parent_path);
 445                 if (IS_ERR(parent)) {
 446                         ret = PTR_ERR(parent);
 447                         goto error;
 448                 }
 449         }
 450
 451         audit_add_to_parent(krule, parent);
 452
 453         h = audit_hash_ino((u32)watch->ino);
 454         *list = &audit_inode_hash[h];
 455 error:
 456         path_put(&parent_path);
 457         audit_put_watch(watch);
 458         return ret;
 459 }
 460
 461 void audit_remove_watch_rule(struct audit_krule *krule)
 462 {
 463         struct audit_watch *watch = krule->watch;
 464         struct audit_parent *parent = watch->parent;
 465
 466         list_del(&krule->rlist);
 467
 468         if (list_empty(&watch->rules)) {
 469                 /*
 470                  * audit_remove_watch() drops our reference to 'parent' which
 471                  * can get freed. Grab our own reference to be safe.
 472                  */
 473                 audit_get_parent(parent);
 474                 audit_remove_watch(watch);
 475                 if (list_empty(&parent->watches))
 476                         fsnotify_destroy_mark(&parent->mark, audit_watch_group);
 477                 audit_put_parent(parent);
 478         }
 479 }
 480
 481 /* Update watch data in audit rules based on fsnotify events. */
 482 static int audit_watch_handle_event(struct fsnotify_group *group,
 483                                     struct inode *to_tell,
 484                                     u32 mask, const void *data, int data_type,
 485                                     const unsigned char *dname, u32 cookie,
 486                                     struct fsnotify_iter_info *iter_info)
 487 {
 488         struct fsnotify_mark *inode_mark = fsnotify_iter_inode_mark(iter_info);
 489         const struct inode *inode;
 490         struct audit_parent *parent;
 491
 492         parent = container_of(inode_mark, struct audit_parent, mark);
 493
 494         BUG_ON(group != audit_watch_group);
 495
 496         switch (data_type) {
 497         case (FSNOTIFY_EVENT_PATH):
 498                 inode = d_backing_inode(((const struct path *)data)->dentry);
 499                 break;
 500         case (FSNOTIFY_EVENT_INODE):
 501                 inode = (const struct inode *)data;
 502                 break;
 503         default:
 504                 BUG();
 505                 inode = NULL;
 506                 break;
 507         }
 508
 509         if (mask & (FS_CREATE|FS_MOVED_TO) && inode)
 510                 audit_update_watch(parent, dname, inode->i_sb->s_dev, inode->i_ino, 0);
 511         else if (mask & (FS_DELETE|FS_MOVED_FROM))
 512                 audit_update_watch(parent, dname, AUDIT_DEV_UNSET, AUDIT_INO_UNSET, 1);
 513         else if (mask & (FS_DELETE_SELF|FS_UNMOUNT|FS_MOVE_SELF))
 514                 audit_remove_parent_watches(parent);
 515
 516         return 0;
 517 }
 518
 519 static const struct fsnotify_ops audit_watch_fsnotify_ops = {
 520         .handle_event =         audit_watch_handle_event,
 521         .free_mark =            audit_watch_free_mark,
 522 };
 523
 524 static int __init audit_watch_init(void)
 525 {
 526         audit_watch_group = fsnotify_alloc_group(&audit_watch_fsnotify_ops);
 527         if (IS_ERR(audit_watch_group)) {
 528                 audit_watch_group = NULL;
 529                 audit_panic("cannot create audit fsnotify group");
 530         }
 531         return 0;
 532 }
 533 device_initcall(audit_watch_init);
 534
 535 int audit_dupe_exe(struct audit_krule *new, struct audit_krule *old)
 536 {
 537         struct audit_fsnotify_mark *audit_mark;
 538         char *pathname;
 539
 540         pathname = kstrdup(audit_mark_path(old->exe), GFP_KERNEL);
 541         if (!pathname)
 542                 return -ENOMEM;
 543
 544         audit_mark = audit_alloc_mark(new, pathname, strlen(pathname));
 545         if (IS_ERR(audit_mark)) {
 546                 kfree(pathname);
 547                 return PTR_ERR(audit_mark);
 548         }
 549         new->exe = audit_mark;
 550
 551         return 0;
 552 }
 553
 554 int audit_exe_compare(struct task_struct *tsk, struct audit_fsnotify_mark *mark)
 555 {
 556         struct file *exe_file;
 557         unsigned long ino;
 558         dev_t dev;
 559
 560         exe_file = get_task_exe_file(tsk);
 561         if (!exe_file)
 562                 return 0;
 563         ino = file_inode(exe_file)->i_ino;
 564         dev = file_inode(exe_file)->i_sb->s_dev;
 565         fput(exe_file);
 566         return audit_mark_compare(mark, ino, dev);
 567 }