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