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        ilist;  /* tmp list used to free parents */
  59         struct list_head        watches; /* anchor for audit_watch->wlist */
  60         struct fsnotify_mark_entry mark; /* fsnotify mark on the inode */
  61 };
  62
  63 /* fsnotify handle. */
  64 struct fsnotify_group *audit_watch_group;
  65
  66 /* fsnotify events we care about. */
  67 #define AUDIT_FS_WATCH (FS_MOVE | FS_CREATE | FS_DELETE | FS_DELETE_SELF |\
  68                         FS_MOVE_SELF | FS_EVENT_ON_CHILD)
  69
  70 static void audit_free_parent(struct audit_parent *parent)
  71 {
  72         WARN_ON(!list_empty(&parent->watches));
  73         kfree(parent);
  74 }
  75
  76 static void audit_watch_free_mark(struct fsnotify_mark_entry *entry)
  77 {
  78         struct audit_parent *parent;
  79
  80         parent = container_of(entry, struct audit_parent, mark);
  81         audit_free_parent(parent);
  82 }
  83
  84 static void audit_get_parent(struct audit_parent *parent)
  85 {
  86         if (likely(parent))
  87                 fsnotify_get_mark(&parent->mark);
  88 }
  89
  90 static void audit_put_parent(struct audit_parent *parent)
  91 {
  92         if (likely(parent))
  93                 fsnotify_put_mark(&parent->mark);
  94 }
  95
  96 /*
  97  * Find and return the audit_parent on the given inode.  If found a reference
  98  * is taken on this parent.
  99  */
 100 static inline struct audit_parent *audit_find_parent(struct inode *inode)
 101 {
 102         struct audit_parent *parent = NULL;
 103         struct fsnotify_mark_entry *entry;
 104
 105         spin_lock(&inode->i_lock);
 106         entry = fsnotify_find_mark_entry(audit_watch_group, inode);
 107         spin_unlock(&inode->i_lock);
 108
 109         if (entry)
 110                 parent = container_of(entry, struct audit_parent, mark);
 111
 112         return parent;
 113 }
 114
 115 void audit_get_watch(struct audit_watch *watch)
 116 {
 117         atomic_inc(&watch->count);
 118 }
 119
 120 void audit_put_watch(struct audit_watch *watch)
 121 {
 122         if (atomic_dec_and_test(&watch->count)) {
 123                 WARN_ON(watch->parent);
 124                 WARN_ON(!list_empty(&watch->rules));
 125                 kfree(watch->path);
 126                 kfree(watch);
 127         }
 128 }
 129
 130 void audit_remove_watch(struct audit_watch *watch)
 131 {
 132         list_del(&watch->wlist);
 133         audit_put_parent(watch->parent);
 134         watch->parent = NULL;
 135         audit_put_watch(watch); /* match initial get */
 136 }
 137
 138 char *audit_watch_path(struct audit_watch *watch)
 139 {
 140         return watch->path;
 141 }
 142
 143 int audit_watch_compare(struct audit_watch *watch, unsigned long ino, dev_t dev)
 144 {
 145         return (watch->ino != (unsigned long)-1) &&
 146                 (watch->ino == ino) &&
 147                 (watch->dev == dev);
 148 }
 149
 150 /* Initialize a parent watch entry. */
 151 static struct audit_parent *audit_init_parent(struct nameidata *ndp)
 152 {
 153         struct inode *inode = ndp->path.dentry->d_inode;
 154         struct audit_parent *parent;
 155         int ret;
 156
 157         parent = kzalloc(sizeof(*parent), GFP_KERNEL);
 158         if (unlikely(!parent))
 159                 return ERR_PTR(-ENOMEM);
 160
 161         INIT_LIST_HEAD(&parent->watches);
 162
 163         fsnotify_init_mark(&parent->mark, audit_watch_free_mark);
 164         parent->mark.mask = AUDIT_FS_WATCH;
 165         ret = fsnotify_add_mark(&parent->mark, audit_watch_group, inode);
 166         if (ret < 0) {
 167                 audit_free_parent(parent);
 168                 return ERR_PTR(ret);
 169         }
 170
 171         return parent;
 172 }
 173
 174 /* Initialize a watch entry. */
 175 static struct audit_watch *audit_init_watch(char *path)
 176 {
 177         struct audit_watch *watch;
 178
 179         watch = kzalloc(sizeof(*watch), GFP_KERNEL);
 180         if (unlikely(!watch))
 181                 return ERR_PTR(-ENOMEM);
 182
 183         INIT_LIST_HEAD(&watch->rules);
 184         atomic_set(&watch->count, 1);
 185         watch->path = path;
 186         watch->dev = (dev_t)-1;
 187         watch->ino = (unsigned long)-1;
 188
 189         return watch;
 190 }
 191
 192 /* Translate a watch string to kernel respresentation. */
 193 int audit_to_watch(struct audit_krule *krule, char *path, int len, u32 op)
 194 {
 195         struct audit_watch *watch;
 196
 197         if (!audit_watch_group)
 198                 return -EOPNOTSUPP;
 199
 200         if (path[0] != '/' || path[len-1] == '/' ||
 201             krule->listnr != AUDIT_FILTER_EXIT ||
 202             op != Audit_equal ||
 203             krule->inode_f || krule->watch || krule->tree)
 204                 return -EINVAL;
 205
 206         watch = audit_init_watch(path);
 207         if (IS_ERR(watch))
 208                 return PTR_ERR(watch);
 209
 210         audit_get_watch(watch);
 211         krule->watch = watch;
 212
 213         return 0;
 214 }
 215
 216 /* Duplicate the given audit watch.  The new watch's rules list is initialized
 217  * to an empty list and wlist is undefined. */
 218 static struct audit_watch *audit_dupe_watch(struct audit_watch *old)
 219 {
 220         char *path;
 221         struct audit_watch *new;
 222
 223         path = kstrdup(old->path, GFP_KERNEL);
 224         if (unlikely(!path))
 225                 return ERR_PTR(-ENOMEM);
 226
 227         new = audit_init_watch(path);
 228         if (IS_ERR(new)) {
 229                 kfree(path);
 230                 goto out;
 231         }
 232
 233         new->dev = old->dev;
 234         new->ino = old->ino;
 235         audit_get_parent(old->parent);
 236         new->parent = old->parent;
 237
 238 out:
 239         return new;
 240 }
 241
 242 static void audit_watch_log_rule_change(struct audit_krule *r, struct audit_watch *w, char *op)
 243 {
 244         if (audit_enabled) {
 245                 struct audit_buffer *ab;
 246                 ab = audit_log_start(NULL, GFP_NOFS, AUDIT_CONFIG_CHANGE);
 247                 audit_log_format(ab, "auid=%u ses=%u op=",
 248                                  audit_get_loginuid(current),
 249                                  audit_get_sessionid(current));
 250                 audit_log_string(ab, op);
 251                 audit_log_format(ab, " path=");
 252                 audit_log_untrustedstring(ab, w->path);
 253                 audit_log_key(ab, r->filterkey);
 254                 audit_log_format(ab, " list=%d res=1", r->listnr);
 255                 audit_log_end(ab);
 256         }
 257 }
 258
 259 /* Update inode info in audit rules based on filesystem event. */
 260 static void audit_update_watch(struct audit_parent *parent,
 261                                const char *dname, dev_t dev,
 262                                unsigned long ino, unsigned invalidating)
 263 {
 264         struct audit_watch *owatch, *nwatch, *nextw;
 265         struct audit_krule *r, *nextr;
 266         struct audit_entry *oentry, *nentry;
 267
 268         mutex_lock(&audit_filter_mutex);
 269         /* Run all of the watches on this parent looking for the one that
 270          * matches the given dname */
 271         list_for_each_entry_safe(owatch, nextw, &parent->watches, wlist) {
 272                 if (audit_compare_dname_path(dname, owatch->path, NULL))
 273                         continue;
 274
 275                 /* If the update involves invalidating rules, do the inode-based
 276                  * filtering now, so we don't omit records. */
 277                 if (invalidating && !audit_dummy_context())
 278                         audit_filter_inodes(current, current->audit_context);
 279
 280                 /* updating ino will likely change which audit_hash_list we
 281                  * are on so we need a new watch for the new list */
 282                 nwatch = audit_dupe_watch(owatch);
 283                 if (IS_ERR(nwatch)) {
 284                         mutex_unlock(&audit_filter_mutex);
 285                         audit_panic("error updating watch, skipping");
 286                         return;
 287                 }
 288                 nwatch->dev = dev;
 289                 nwatch->ino = ino;
 290
 291                 list_for_each_entry_safe(r, nextr, &owatch->rules, rlist) {
 292
 293                         oentry = container_of(r, struct audit_entry, rule);
 294                         list_del(&oentry->rule.rlist);
 295                         list_del_rcu(&oentry->list);
 296
 297                         nentry = audit_dupe_rule(&oentry->rule);
 298                         if (IS_ERR(nentry)) {
 299                                 list_del(&oentry->rule.list);
 300                                 audit_panic("error updating watch, removing");
 301                         } else {
 302                                 int h = audit_hash_ino((u32)ino);
 303
 304                                 /*
 305                                  * nentry->rule.watch == oentry->rule.watch so
 306                                  * we must drop that reference and set it to our
 307                                  * new watch.
 308                                  */
 309                                 audit_put_watch(nentry->rule.watch);
 310                                 audit_get_watch(nwatch);
 311                                 nentry->rule.watch = nwatch;
 312                                 list_add(&nentry->rule.rlist, &nwatch->rules);
 313                                 list_add_rcu(&nentry->list, &audit_inode_hash[h]);
 314                                 list_replace(&oentry->rule.list,
 315                                              &nentry->rule.list);
 316                         }
 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                         list_del(&r->rlist);
 348                         list_del(&r->list);
 349                         list_del_rcu(&e->list);
 350                         call_rcu(&e->rcu, audit_free_rule_rcu);
 351                 }
 352                 audit_remove_watch(w);
 353         }
 354         mutex_unlock(&audit_filter_mutex);
 355
 356         fsnotify_destroy_mark_by_entry(&parent->mark);
 357 }
 358
 359 /* Unregister inotify watches for parents on in_list.
 360  * Generates an FS_IGNORED event. */
 361 void audit_watch_inotify_unregister(struct list_head *in_list)
 362 {
 363         struct audit_parent *p, *n;
 364
 365         list_for_each_entry_safe(p, n, in_list, ilist) {
 366                 list_del(&p->ilist);
 367                 fsnotify_destroy_mark_by_entry(&p->mark);
 368                 /* matches the get in audit_remove_watch_rule() */
 369                 audit_put_parent(p);
 370         }
 371 }
 372
 373 /* Get path information necessary for adding watches. */
 374 static int audit_get_nd(char *path, struct nameidata **ndp, struct nameidata **ndw)
 375 {
 376         struct nameidata *ndparent, *ndwatch;
 377         int err;
 378
 379         ndparent = kmalloc(sizeof(*ndparent), GFP_KERNEL);
 380         if (unlikely(!ndparent))
 381                 return -ENOMEM;
 382
 383         ndwatch = kmalloc(sizeof(*ndwatch), GFP_KERNEL);
 384         if (unlikely(!ndwatch)) {
 385                 kfree(ndparent);
 386                 return -ENOMEM;
 387         }
 388
 389         err = path_lookup(path, LOOKUP_PARENT, ndparent);
 390         if (err) {
 391                 kfree(ndparent);
 392                 kfree(ndwatch);
 393                 return err;
 394         }
 395
 396         err = path_lookup(path, 0, ndwatch);
 397         if (err) {
 398                 kfree(ndwatch);
 399                 ndwatch = NULL;
 400         }
 401
 402         *ndp = ndparent;
 403         *ndw = ndwatch;
 404
 405         return 0;
 406 }
 407
 408 /* Release resources used for watch path information. */
 409 static void audit_put_nd(struct nameidata *ndp, struct nameidata *ndw)
 410 {
 411         if (ndp) {
 412                 path_put(&ndp->path);
 413                 kfree(ndp);
 414         }
 415         if (ndw) {
 416                 path_put(&ndw->path);
 417                 kfree(ndw);
 418         }
 419 }
 420
 421 /* Associate the given rule with an existing parent.
 422  * Caller must hold audit_filter_mutex. */
 423 static void audit_add_to_parent(struct audit_krule *krule,
 424                                 struct audit_parent *parent)
 425 {
 426         struct audit_watch *w, *watch = krule->watch;
 427         int watch_found = 0;
 428
 429         BUG_ON(!mutex_is_locked(&audit_filter_mutex));
 430
 431         list_for_each_entry(w, &parent->watches, wlist) {
 432                 if (strcmp(watch->path, w->path))
 433                         continue;
 434
 435                 watch_found = 1;
 436
 437                 /* put krule's and initial refs to temporary watch */
 438                 audit_put_watch(watch);
 439                 audit_put_watch(watch);
 440
 441                 audit_get_watch(w);
 442                 krule->watch = watch = w;
 443                 break;
 444         }
 445
 446         if (!watch_found) {
 447                 audit_get_parent(parent);
 448                 watch->parent = parent;
 449
 450                 list_add(&watch->wlist, &parent->watches);
 451         }
 452         list_add(&krule->rlist, &watch->rules);
 453 }
 454
 455 /* Find a matching watch entry, or add this one.
 456  * Caller must hold audit_filter_mutex. */
 457 int audit_add_watch(struct audit_krule *krule, struct list_head **list)
 458 {
 459         struct audit_watch *watch = krule->watch;
 460         struct audit_parent *parent;
 461         struct nameidata *ndp = NULL, *ndw = NULL;
 462         int h, ret = 0;
 463
 464         mutex_unlock(&audit_filter_mutex);
 465
 466         /* Avoid calling path_lookup under audit_filter_mutex. */
 467         ret = audit_get_nd(watch->path, &ndp, &ndw);
 468         if (ret) {
 469                 /* caller expects mutex locked */
 470                 mutex_lock(&audit_filter_mutex);
 471                 goto error;
 472         }
 473
 474         mutex_lock(&audit_filter_mutex);
 475
 476         /* update watch filter fields */
 477         if (ndw) {
 478                 watch->dev = ndw->path.dentry->d_inode->i_sb->s_dev;
 479                 watch->ino = ndw->path.dentry->d_inode->i_ino;
 480         }
 481
 482         /* either find an old parent or attach a new one */
 483         parent = audit_find_parent(ndp->path.dentry->d_inode);
 484         if (!parent) {
 485                 parent = audit_init_parent(ndp);
 486                 if (IS_ERR(parent)) {
 487                         ret = PTR_ERR(parent);
 488                         goto error;
 489                 }
 490         }
 491
 492         audit_add_to_parent(krule, parent);
 493
 494         /* match get in audit_find_parent or audit_init_parent */
 495         audit_put_parent(parent);
 496
 497         h = audit_hash_ino((u32)watch->ino);
 498         *list = &audit_inode_hash[h];
 499 error:
 500         audit_put_nd(ndp, ndw);         /* NULL args OK */
 501         return ret;
 502
 503 }
 504
 505 void audit_remove_watch_rule(struct audit_krule *krule, struct list_head *list)
 506 {
 507         struct audit_watch *watch = krule->watch;
 508         struct audit_parent *parent = watch->parent;
 509
 510         list_del(&krule->rlist);
 511
 512         if (list_empty(&watch->rules)) {
 513                 audit_remove_watch(watch);
 514
 515                 if (list_empty(&parent->watches)) {
 516                         /* Put parent on the un-registration list.
 517                          * Grab a reference before releasing
 518                          * audit_filter_mutex, to be released in
 519                          * audit_watch_inotify_unregister().
 520                          * If filesystem is going away, just leave
 521                          * the sucker alone, eviction will take
 522                          * care of it. */
 523                         audit_get_parent(parent);
 524                         list_add(&parent->ilist, list);
 525                 }
 526         }
 527 }
 528
 529 static bool audit_watch_should_send_event(struct fsnotify_group *group, struct inode *inode, __u32 mask)
 530 {
 531         struct fsnotify_mark_entry *entry;
 532         bool send;
 533
 534         spin_lock(&inode->i_lock);
 535         entry = fsnotify_find_mark_entry(group, inode);
 536         spin_unlock(&inode->i_lock);
 537         if (!entry)
 538                 return false;
 539
 540         mask = (mask & ~FS_EVENT_ON_CHILD);
 541         send = (entry->mask & mask);
 542
 543         /* find took a reference */
 544         fsnotify_put_mark(entry);
 545
 546         return send;
 547 }
 548
 549 /* Update watch data in audit rules based on fsnotify events. */
 550 static int audit_watch_handle_event(struct fsnotify_group *group, struct fsnotify_event *event)
 551 {
 552         struct inode *inode;
 553         __u32 mask = event->mask;
 554         const char *dname = event->file_name;
 555         struct audit_parent *parent;
 556
 557         BUG_ON(group != audit_watch_group);
 558
 559         parent = audit_find_parent(event->to_tell);
 560         if (unlikely(!parent))
 561                 return 0;
 562
 563         switch (event->data_type) {
 564         case (FSNOTIFY_EVENT_PATH):
 565                 inode = event->path.dentry->d_inode;
 566                 break;
 567         case (FSNOTIFY_EVENT_INODE):
 568                 inode = event->inode;
 569                 break;
 570         default:
 571                 BUG();
 572                 inode = NULL;
 573                 break;
 574         };
 575
 576         if (mask & (FS_CREATE|FS_MOVED_TO) && inode)
 577                 audit_update_watch(parent, dname, inode->i_sb->s_dev, inode->i_ino, 0);
 578         else if (mask & (FS_DELETE|FS_MOVED_FROM))
 579                 audit_update_watch(parent, dname, (dev_t)-1, (unsigned long)-1, 1);
 580         else if (mask & (FS_DELETE_SELF|FS_UNMOUNT|FS_MOVE_SELF))
 581                 audit_remove_parent_watches(parent);
 582         /* moved put_inotify_watch to freeing mark */
 583
 584         /* matched the ref taken by audit_find_parent */
 585         audit_put_parent(parent);
 586
 587         return 0;
 588 }
 589
 590 static const struct fsnotify_ops audit_watch_fsnotify_ops = {
 591         .should_send_event =    audit_watch_should_send_event,
 592         .handle_event =         audit_watch_handle_event,
 593         .free_group_priv =      NULL,
 594         .freeing_mark =         NULL,
 595         .free_event_priv =      NULL,
 596 };
 597
 598 static int __init audit_watch_init(void)
 599 {
 600         audit_watch_group = fsnotify_obtain_group(AUDIT_WATCH_GROUP_NUM, AUDIT_FS_WATCH,
 601                                                   &audit_watch_fsnotify_ops);
 602         if (IS_ERR(audit_watch_group)) {
 603                 audit_watch_group = NULL;
 604                 audit_panic("cannot create audit fsnotify group");
 605         }
 606         return 0;
 607 }
 608 subsys_initcall(audit_watch_init);