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/namei.h>
  28 #include <linux/netlink.h>
  29 #include <linux/sched.h>
  30 #include <linux/inotify.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 IN_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;  /* associated rules */
  54 };
  55
  56 struct audit_parent {
  57         struct list_head        ilist;  /* entry in inotify registration list */
  58         struct list_head        watches; /* associated watches */
  59         struct inotify_watch    wdata;  /* inotify watch data */
  60         unsigned                flags;  /* status flags */
  61 };
  62
  63 /* Inotify handle. */
  64 struct inotify_handle *audit_ih;
  65
  66 /*
  67  * audit_parent status flags:
  68  *
  69  * AUDIT_PARENT_INVALID - set anytime rules/watches are auto-removed due to
  70  * a filesystem event to ensure we're adding audit watches to a valid parent.
  71  * Technically not needed for IN_DELETE_SELF or IN_UNMOUNT events, as we cannot
  72  * receive them while we have nameidata, but must be used for IN_MOVE_SELF which
  73  * we can receive while holding nameidata.
  74  */
  75 #define AUDIT_PARENT_INVALID    0x001
  76
  77 /* Inotify events we care about. */
  78 #define AUDIT_IN_WATCH IN_MOVE|IN_CREATE|IN_DELETE|IN_DELETE_SELF|IN_MOVE_SELF
  79
  80 static void audit_free_parent(struct inotify_watch *i_watch)
  81 {
  82         struct audit_parent *parent;
  83
  84         parent = container_of(i_watch, struct audit_parent, wdata);
  85         WARN_ON(!list_empty(&parent->watches));
  86         kfree(parent);
  87 }
  88
  89 void audit_get_watch(struct audit_watch *watch)
  90 {
  91         atomic_inc(&watch->count);
  92 }
  93
  94 void audit_put_watch(struct audit_watch *watch)
  95 {
  96         if (atomic_dec_and_test(&watch->count)) {
  97                 WARN_ON(watch->parent);
  98                 WARN_ON(!list_empty(&watch->rules));
  99                 kfree(watch->path);
 100                 kfree(watch);
 101         }
 102 }
 103
 104 void audit_remove_watch(struct audit_watch *watch)
 105 {
 106         list_del(&watch->wlist);
 107         put_inotify_watch(&watch->parent->wdata);
 108         watch->parent = NULL;
 109         audit_put_watch(watch); /* match initial get */
 110 }
 111
 112 char *audit_watch_path(struct audit_watch *watch)
 113 {
 114         return watch->path;
 115 }
 116
 117 struct list_head *audit_watch_rules(struct audit_watch *watch)
 118 {
 119         return &watch->rules;
 120 }
 121
 122 unsigned long audit_watch_inode(struct audit_watch *watch)
 123 {
 124         return watch->ino;
 125 }
 126
 127 dev_t audit_watch_dev(struct audit_watch *watch)
 128 {
 129         return watch->dev;
 130 }
 131
 132 /* Initialize a parent watch entry. */
 133 static struct audit_parent *audit_init_parent(struct nameidata *ndp)
 134 {
 135         struct audit_parent *parent;
 136         s32 wd;
 137
 138         parent = kzalloc(sizeof(*parent), GFP_KERNEL);
 139         if (unlikely(!parent))
 140                 return ERR_PTR(-ENOMEM);
 141
 142         INIT_LIST_HEAD(&parent->watches);
 143         parent->flags = 0;
 144
 145         inotify_init_watch(&parent->wdata);
 146         /* grab a ref so inotify watch hangs around until we take audit_filter_mutex */
 147         get_inotify_watch(&parent->wdata);
 148         wd = inotify_add_watch(audit_ih, &parent->wdata,
 149                                ndp->path.dentry->d_inode, AUDIT_IN_WATCH);
 150         if (wd < 0) {
 151                 audit_free_parent(&parent->wdata);
 152                 return ERR_PTR(wd);
 153         }
 154
 155         return parent;
 156 }
 157
 158 /* Initialize a watch entry. */
 159 static struct audit_watch *audit_init_watch(char *path)
 160 {
 161         struct audit_watch *watch;
 162
 163         watch = kzalloc(sizeof(*watch), GFP_KERNEL);
 164         if (unlikely(!watch))
 165                 return ERR_PTR(-ENOMEM);
 166
 167         INIT_LIST_HEAD(&watch->rules);
 168         atomic_set(&watch->count, 1);
 169         watch->path = path;
 170         watch->dev = (dev_t)-1;
 171         watch->ino = (unsigned long)-1;
 172
 173         return watch;
 174 }
 175
 176 /* Translate a watch string to kernel respresentation. */
 177 int audit_to_watch(struct audit_krule *krule, char *path, int len, u32 op)
 178 {
 179         struct audit_watch *watch;
 180
 181         if (!audit_ih)
 182                 return -EOPNOTSUPP;
 183
 184         if (path[0] != '/' || path[len-1] == '/' ||
 185             krule->listnr != AUDIT_FILTER_EXIT ||
 186             op != Audit_equal ||
 187             krule->inode_f || krule->watch || krule->tree)
 188                 return -EINVAL;
 189
 190         watch = audit_init_watch(path);
 191         if (IS_ERR(watch))
 192                 return PTR_ERR(watch);
 193
 194         audit_get_watch(watch);
 195         krule->watch = watch;
 196
 197         return 0;
 198 }
 199
 200 /* Duplicate the given audit watch.  The new watch's rules list is initialized
 201  * to an empty list and wlist is undefined. */
 202 static struct audit_watch *audit_dupe_watch(struct audit_watch *old)
 203 {
 204         char *path;
 205         struct audit_watch *new;
 206
 207         path = kstrdup(old->path, GFP_KERNEL);
 208         if (unlikely(!path))
 209                 return ERR_PTR(-ENOMEM);
 210
 211         new = audit_init_watch(path);
 212         if (IS_ERR(new)) {
 213                 kfree(path);
 214                 goto out;
 215         }
 216
 217         new->dev = old->dev;
 218         new->ino = old->ino;
 219         get_inotify_watch(&old->parent->wdata);
 220         new->parent = old->parent;
 221
 222 out:
 223         return new;
 224 }
 225
 226 static void audit_watch_log_rule_change(struct audit_krule *r, struct audit_watch *w, char *op)
 227 {
 228         if (audit_enabled) {
 229                 struct audit_buffer *ab;
 230                 ab = audit_log_start(NULL, GFP_NOFS, AUDIT_CONFIG_CHANGE);
 231                 audit_log_format(ab, "auid=%u ses=%u op=",
 232                                  audit_get_loginuid(current),
 233                                  audit_get_sessionid(current));
 234                 audit_log_string(ab, op);
 235                 audit_log_format(ab, " path=");
 236                 audit_log_untrustedstring(ab, w->path);
 237                 audit_log_key(ab, r->filterkey);
 238                 audit_log_format(ab, " list=%d res=1", r->listnr);
 239                 audit_log_end(ab);
 240         }
 241 }
 242
 243 /* Update inode info in audit rules based on filesystem event. */
 244 static void audit_update_watch(struct audit_parent *parent,
 245                                const char *dname, dev_t dev,
 246                                unsigned long ino, unsigned invalidating)
 247 {
 248         struct audit_watch *owatch, *nwatch, *nextw;
 249         struct audit_krule *r, *nextr;
 250         struct audit_entry *oentry, *nentry;
 251
 252         mutex_lock(&audit_filter_mutex);
 253         list_for_each_entry_safe(owatch, nextw, &parent->watches, wlist) {
 254                 if (audit_compare_dname_path(dname, owatch->path, NULL))
 255                         continue;
 256
 257                 /* If the update involves invalidating rules, do the inode-based
 258                  * filtering now, so we don't omit records. */
 259                 if (invalidating && current->audit_context)
 260                         audit_filter_inodes(current, current->audit_context);
 261
 262                 nwatch = audit_dupe_watch(owatch);
 263                 if (IS_ERR(nwatch)) {
 264                         mutex_unlock(&audit_filter_mutex);
 265                         audit_panic("error updating watch, skipping");
 266                         return;
 267                 }
 268                 nwatch->dev = dev;
 269                 nwatch->ino = ino;
 270
 271                 list_for_each_entry_safe(r, nextr, &owatch->rules, rlist) {
 272
 273                         oentry = container_of(r, struct audit_entry, rule);
 274                         list_del(&oentry->rule.rlist);
 275                         list_del_rcu(&oentry->list);
 276
 277                         nentry = audit_dupe_rule(&oentry->rule, nwatch);
 278                         if (IS_ERR(nentry)) {
 279                                 list_del(&oentry->rule.list);
 280                                 audit_panic("error updating watch, removing");
 281                         } else {
 282                                 int h = audit_hash_ino((u32)ino);
 283                                 list_add(&nentry->rule.rlist, &nwatch->rules);
 284                                 list_add_rcu(&nentry->list, &audit_inode_hash[h]);
 285                                 list_replace(&oentry->rule.list,
 286                                              &nentry->rule.list);
 287                         }
 288
 289                         audit_watch_log_rule_change(r, owatch, "updated rules");
 290
 291                         call_rcu(&oentry->rcu, audit_free_rule_rcu);
 292                 }
 293
 294                 audit_remove_watch(owatch);
 295                 goto add_watch_to_parent; /* event applies to a single watch */
 296         }
 297         mutex_unlock(&audit_filter_mutex);
 298         return;
 299
 300 add_watch_to_parent:
 301         list_add(&nwatch->wlist, &parent->watches);
 302         mutex_unlock(&audit_filter_mutex);
 303         return;
 304 }
 305
 306 /* Remove all watches & rules associated with a parent that is going away. */
 307 static void audit_remove_parent_watches(struct audit_parent *parent)
 308 {
 309         struct audit_watch *w, *nextw;
 310         struct audit_krule *r, *nextr;
 311         struct audit_entry *e;
 312
 313         mutex_lock(&audit_filter_mutex);
 314         parent->flags |= AUDIT_PARENT_INVALID;
 315         list_for_each_entry_safe(w, nextw, &parent->watches, wlist) {
 316                 list_for_each_entry_safe(r, nextr, &w->rules, rlist) {
 317                         e = container_of(r, struct audit_entry, rule);
 318                         audit_watch_log_rule_change(r, w, "remove rule");
 319                         list_del(&r->rlist);
 320                         list_del(&r->list);
 321                         list_del_rcu(&e->list);
 322                         call_rcu(&e->rcu, audit_free_rule_rcu);
 323                 }
 324                 audit_remove_watch(w);
 325         }
 326         mutex_unlock(&audit_filter_mutex);
 327 }
 328
 329 /* Unregister inotify watches for parents on in_list.
 330  * Generates an IN_IGNORED event. */
 331 void audit_inotify_unregister(struct list_head *in_list)
 332 {
 333         struct audit_parent *p, *n;
 334
 335         list_for_each_entry_safe(p, n, in_list, ilist) {
 336                 list_del(&p->ilist);
 337                 inotify_rm_watch(audit_ih, &p->wdata);
 338                 /* the unpin matching the pin in audit_do_del_rule() */
 339                 unpin_inotify_watch(&p->wdata);
 340         }
 341 }
 342
 343 /* Get path information necessary for adding watches. */
 344 static int audit_get_nd(char *path, struct nameidata **ndp, struct nameidata **ndw)
 345 {
 346         struct nameidata *ndparent, *ndwatch;
 347         int err;
 348
 349         ndparent = kmalloc(sizeof(*ndparent), GFP_KERNEL);
 350         if (unlikely(!ndparent))
 351                 return -ENOMEM;
 352
 353         ndwatch = kmalloc(sizeof(*ndwatch), GFP_KERNEL);
 354         if (unlikely(!ndwatch)) {
 355                 kfree(ndparent);
 356                 return -ENOMEM;
 357         }
 358
 359         err = path_lookup(path, LOOKUP_PARENT, ndparent);
 360         if (err) {
 361                 kfree(ndparent);
 362                 kfree(ndwatch);
 363                 return err;
 364         }
 365
 366         err = path_lookup(path, 0, ndwatch);
 367         if (err) {
 368                 kfree(ndwatch);
 369                 ndwatch = NULL;
 370         }
 371
 372         *ndp = ndparent;
 373         *ndw = ndwatch;
 374
 375         return 0;
 376 }
 377
 378 /* Release resources used for watch path information. */
 379 static void audit_put_nd(struct nameidata *ndp, struct nameidata *ndw)
 380 {
 381         if (ndp) {
 382                 path_put(&ndp->path);
 383                 kfree(ndp);
 384         }
 385         if (ndw) {
 386                 path_put(&ndw->path);
 387                 kfree(ndw);
 388         }
 389 }
 390
 391 /* Associate the given rule with an existing parent inotify_watch.
 392  * Caller must hold audit_filter_mutex. */
 393 static void audit_add_to_parent(struct audit_krule *krule,
 394                                 struct audit_parent *parent)
 395 {
 396         struct audit_watch *w, *watch = krule->watch;
 397         int watch_found = 0;
 398
 399         list_for_each_entry(w, &parent->watches, wlist) {
 400                 if (strcmp(watch->path, w->path))
 401                         continue;
 402
 403                 watch_found = 1;
 404
 405                 /* put krule's and initial refs to temporary watch */
 406                 audit_put_watch(watch);
 407                 audit_put_watch(watch);
 408
 409                 audit_get_watch(w);
 410                 krule->watch = watch = w;
 411                 break;
 412         }
 413
 414         if (!watch_found) {
 415                 get_inotify_watch(&parent->wdata);
 416                 watch->parent = parent;
 417
 418                 list_add(&watch->wlist, &parent->watches);
 419         }
 420         list_add(&krule->rlist, &watch->rules);
 421 }
 422
 423 /* Find a matching watch entry, or add this one.
 424  * Caller must hold audit_filter_mutex. */
 425 int audit_add_watch(struct audit_krule *krule)
 426 {
 427         struct audit_watch *watch = krule->watch;
 428         struct inotify_watch *i_watch;
 429         struct audit_parent *parent;
 430         struct nameidata *ndp = NULL, *ndw = NULL;
 431         int ret = 0;
 432
 433         mutex_unlock(&audit_filter_mutex);
 434
 435         /* Avoid calling path_lookup under audit_filter_mutex. */
 436         ret = audit_get_nd(watch->path, &ndp, &ndw);
 437         if (ret) {
 438                 /* caller expects mutex locked */
 439                 mutex_lock(&audit_filter_mutex);
 440                 goto error;
 441         }
 442
 443         /* update watch filter fields */
 444         if (ndw) {
 445                 watch->dev = ndw->path.dentry->d_inode->i_sb->s_dev;
 446                 watch->ino = ndw->path.dentry->d_inode->i_ino;
 447         }
 448
 449         /* The audit_filter_mutex must not be held during inotify calls because
 450          * we hold it during inotify event callback processing.  If an existing
 451          * inotify watch is found, inotify_find_watch() grabs a reference before
 452          * returning.
 453          */
 454         if (inotify_find_watch(audit_ih, ndp->path.dentry->d_inode,
 455                                &i_watch) < 0) {
 456                 parent = audit_init_parent(ndp);
 457                 if (IS_ERR(parent)) {
 458                         /* caller expects mutex locked */
 459                         mutex_lock(&audit_filter_mutex);
 460                         ret = PTR_ERR(parent);
 461                         goto error;
 462                 }
 463         } else
 464                 parent = container_of(i_watch, struct audit_parent, wdata);
 465
 466         mutex_lock(&audit_filter_mutex);
 467
 468         /* parent was moved before we took audit_filter_mutex */
 469         if (parent->flags & AUDIT_PARENT_INVALID)
 470                 ret = -ENOENT;
 471         else
 472                 audit_add_to_parent(krule, parent);
 473
 474         /* match get in audit_init_parent or inotify_find_watch */
 475         put_inotify_watch(&parent->wdata);
 476
 477 error:
 478         audit_put_nd(ndp, ndw);         /* NULL args OK */
 479         return ret;
 480
 481 }
 482
 483 void audit_remove_watch_rule(struct audit_krule *krule, struct list_head *list)
 484 {
 485         struct audit_watch *watch = krule->watch;
 486         struct audit_parent *parent = watch->parent;
 487
 488         list_del(&krule->rlist);
 489
 490         if (list_empty(&watch->rules)) {
 491                 audit_remove_watch(watch);
 492
 493                 if (list_empty(&parent->watches)) {
 494                         /* Put parent on the inotify un-registration
 495                          * list.  Grab a reference before releasing
 496                          * audit_filter_mutex, to be released in
 497                          * audit_inotify_unregister().
 498                          * If filesystem is going away, just leave
 499                          * the sucker alone, eviction will take
 500                          * care of it. */
 501                         if (pin_inotify_watch(&parent->wdata))
 502                                 list_add(&parent->ilist, list);
 503                 }
 504         }
 505 }
 506
 507 /* Update watch data in audit rules based on inotify events. */
 508 static void audit_handle_ievent(struct inotify_watch *i_watch, u32 wd, u32 mask,
 509                          u32 cookie, const char *dname, struct inode *inode)
 510 {
 511         struct audit_parent *parent;
 512
 513         parent = container_of(i_watch, struct audit_parent, wdata);
 514
 515         if (mask & (IN_CREATE|IN_MOVED_TO) && inode)
 516                 audit_update_watch(parent, dname, inode->i_sb->s_dev,
 517                                    inode->i_ino, 0);
 518         else if (mask & (IN_DELETE|IN_MOVED_FROM))
 519                 audit_update_watch(parent, dname, (dev_t)-1, (unsigned long)-1, 1);
 520         /* inotify automatically removes the watch and sends IN_IGNORED */
 521         else if (mask & (IN_DELETE_SELF|IN_UNMOUNT))
 522                 audit_remove_parent_watches(parent);
 523         /* inotify does not remove the watch, so remove it manually */
 524         else if(mask & IN_MOVE_SELF) {
 525                 audit_remove_parent_watches(parent);
 526                 inotify_remove_watch_locked(audit_ih, i_watch);
 527         } else if (mask & IN_IGNORED)
 528                 put_inotify_watch(i_watch);
 529 }
 530
 531 static const struct inotify_operations audit_inotify_ops = {
 532         .handle_event   = audit_handle_ievent,
 533         .destroy_watch  = audit_free_parent,
 534 };
 535
 536 static int __init audit_watch_init(void)
 537 {
 538         audit_ih = inotify_init(&audit_inotify_ops);
 539         if (IS_ERR(audit_ih))
 540                 audit_panic("cannot initialize inotify handle");
 541         return 0;
 542 }
 543 subsys_initcall(audit_watch_init);