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/sched.h>
  32 #include <linux/slab.h>
  33 #include <linux/security.h>
  34 #include "audit.h"
  35
  36 /*
  37  * Reference counting:
  38  *
  39  * audit_parent: lifetime is from audit_init_parent() to receipt of an FS_IGNORED
  40  *      event.  Each audit_watch holds a reference to its associated parent.
  41  *
  42  * audit_watch: if added to lists, lifetime is from audit_init_watch() to
  43  *      audit_remove_watch().  Additionally, an audit_watch may exist
  44  *      temporarily to assist in searching existing filter data.  Each
  45  *      audit_krule holds a reference to its associated watch.
  46  */
  47
  48 struct audit_watch {
  49         atomic_t                count;  /* reference count */
  50         dev_t                   dev;    /* associated superblock device */
  51         char                    *path;  /* insertion path */
  52         unsigned long           ino;    /* associated inode number */
  53         struct audit_parent     *parent; /* associated parent */
  54         struct list_head        wlist;  /* entry in parent->watches list */
  55         struct list_head        rules;  /* anchor for krule->rlist */
  56 };
  57
  58 struct audit_parent {
  59         struct list_head        watches; /* anchor for audit_watch->wlist */
  60         struct fsnotify_mark mark; /* fsnotify mark on the inode */
  61 };
  62
  63 /* fsnotify handle. */
  64 static 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)
  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;
 104
 105         entry = fsnotify_find_inode_mark(audit_watch_group, inode);
 106         if (entry)
 107                 parent = container_of(entry, struct audit_parent, mark);
 108
 109         return parent;
 110 }
 111
 112 void audit_get_watch(struct audit_watch *watch)
 113 {
 114         atomic_inc(&watch->count);
 115 }
 116
 117 void audit_put_watch(struct audit_watch *watch)
 118 {
 119         if (atomic_dec_and_test(&watch->count)) {
 120                 WARN_ON(watch->parent);
 121                 WARN_ON(!list_empty(&watch->rules));
 122                 kfree(watch->path);
 123                 kfree(watch);
 124         }
 125 }
 126
 127 static void audit_remove_watch(struct audit_watch *watch)
 128 {
 129         list_del(&watch->wlist);
 130         audit_put_parent(watch->parent);
 131         watch->parent = NULL;
 132         audit_put_watch(watch); /* match initial get */
 133 }
 134
 135 char *audit_watch_path(struct audit_watch *watch)
 136 {
 137         return watch->path;
 138 }
 139
 140 int audit_watch_compare(struct audit_watch *watch, unsigned long ino, dev_t dev)
 141 {
 142         return (watch->ino != AUDIT_INO_UNSET) &&
 143                 (watch->ino == ino) &&
 144                 (watch->dev == dev);
 145 }
 146
 147 /* Initialize a parent watch entry. */
 148 static struct audit_parent *audit_init_parent(struct path *path)
 149 {
 150         struct inode *inode = d_backing_inode(path->dentry);
 151         struct audit_parent *parent;
 152         int ret;
 153
 154         parent = kzalloc(sizeof(*parent), GFP_KERNEL);
 155         if (unlikely(!parent))
 156                 return ERR_PTR(-ENOMEM);
 157
 158         INIT_LIST_HEAD(&parent->watches);
 159
 160         fsnotify_init_mark(&parent->mark, audit_watch_free_mark);
 161         parent->mark.mask = AUDIT_FS_WATCH;
 162         ret = fsnotify_add_mark(&parent->mark, audit_watch_group, inode, NULL, 0);
 163         if (ret < 0) {
 164                 audit_free_parent(parent);
 165                 return ERR_PTR(ret);
 166         }
 167
 168         return parent;
 169 }
 170
 171 /* Initialize a watch entry. */
 172 static struct audit_watch *audit_init_watch(char *path)
 173 {
 174         struct audit_watch *watch;
 175
 176         watch = kzalloc(sizeof(*watch), GFP_KERNEL);
 177         if (unlikely(!watch))
 178                 return ERR_PTR(-ENOMEM);
 179
 180         INIT_LIST_HEAD(&watch->rules);
 181         atomic_set(&watch->count, 1);
 182         watch->path = path;
 183         watch->dev = AUDIT_DEV_UNSET;
 184         watch->ino = AUDIT_INO_UNSET;
 185
 186         return watch;
 187 }
 188
 189 /* Translate a watch string to kernel respresentation. */
 190 int audit_to_watch(struct audit_krule *krule, char *path, int len, u32 op)
 191 {
 192         struct audit_watch *watch;
 193
 194         if (!audit_watch_group)
 195                 return -EOPNOTSUPP;
 196
 197         if (path[0] != '/' || path[len-1] == '/' ||
 198             krule->listnr != AUDIT_FILTER_EXIT ||
 199             op != Audit_equal ||
 200             krule->inode_f || krule->watch || krule->tree)
 201                 return -EINVAL;
 202
 203         watch = audit_init_watch(path);
 204         if (IS_ERR(watch))
 205                 return PTR_ERR(watch);
 206
 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                         if (oentry->rule.exe)
 317                                 audit_remove_mark(oentry->rule.exe);
 318
 319                         audit_watch_log_rule_change(r, owatch, "updated_rules");
 320
 321                         call_rcu(&oentry->rcu, audit_free_rule_rcu);
 322                 }
 323
 324                 audit_remove_watch(owatch);
 325                 goto add_watch_to_parent; /* event applies to a single watch */
 326         }
 327         mutex_unlock(&audit_filter_mutex);
 328         return;
 329
 330 add_watch_to_parent:
 331         list_add(&nwatch->wlist, &parent->watches);
 332         mutex_unlock(&audit_filter_mutex);
 333         return;
 334 }
 335
 336 /* Remove all watches & rules associated with a parent that is going away. */
 337 static void audit_remove_parent_watches(struct audit_parent *parent)
 338 {
 339         struct audit_watch *w, *nextw;
 340         struct audit_krule *r, *nextr;
 341         struct audit_entry *e;
 342
 343         mutex_lock(&audit_filter_mutex);
 344         list_for_each_entry_safe(w, nextw, &parent->watches, wlist) {
 345                 list_for_each_entry_safe(r, nextr, &w->rules, rlist) {
 346                         e = container_of(r, struct audit_entry, rule);
 347                         audit_watch_log_rule_change(r, w, "remove_rule");
 348                         if (e->rule.exe)
 349                                 audit_remove_mark(e->rule.exe);
 350                         list_del(&r->rlist);
 351                         list_del(&r->list);
 352                         list_del_rcu(&e->list);
 353                         call_rcu(&e->rcu, audit_free_rule_rcu);
 354                 }
 355                 audit_remove_watch(w);
 356         }
 357         mutex_unlock(&audit_filter_mutex);
 358
 359         fsnotify_destroy_mark(&parent->mark, audit_watch_group);
 360 }
 361
 362 /* Get path information necessary for adding watches. */
 363 static int audit_get_nd(struct audit_watch *watch, struct path *parent)
 364 {
 365         struct dentry *d = kern_path_locked(watch->path, parent);
 366         if (IS_ERR(d))
 367                 return PTR_ERR(d);
 368         mutex_unlock(&d_backing_inode(parent->dentry)->i_mutex);
 369         if (d_is_positive(d)) {
 370                 /* update watch filter fields */
 371                 watch->dev = d_backing_inode(d)->i_sb->s_dev;
 372                 watch->ino = d_backing_inode(d)->i_ino;
 373         }
 374         dput(d);
 375         return 0;
 376 }
 377
 378 /* Associate the given rule with an existing parent.
 379  * Caller must hold audit_filter_mutex. */
 380 static void audit_add_to_parent(struct audit_krule *krule,
 381                                 struct audit_parent *parent)
 382 {
 383         struct audit_watch *w, *watch = krule->watch;
 384         int watch_found = 0;
 385
 386         BUG_ON(!mutex_is_locked(&audit_filter_mutex));
 387
 388         list_for_each_entry(w, &parent->watches, wlist) {
 389                 if (strcmp(watch->path, w->path))
 390                         continue;
 391
 392                 watch_found = 1;
 393
 394                 /* put krule's ref to temporary watch */
 395                 audit_put_watch(watch);
 396
 397                 audit_get_watch(w);
 398                 krule->watch = watch = w;
 399
 400                 audit_put_parent(parent);
 401                 break;
 402         }
 403
 404         if (!watch_found) {
 405                 watch->parent = parent;
 406
 407                 audit_get_watch(watch);
 408                 list_add(&watch->wlist, &parent->watches);
 409         }
 410         list_add(&krule->rlist, &watch->rules);
 411 }
 412
 413 /* Find a matching watch entry, or add this one.
 414  * Caller must hold audit_filter_mutex. */
 415 int audit_add_watch(struct audit_krule *krule, struct list_head **list)
 416 {
 417         struct audit_watch *watch = krule->watch;
 418         struct audit_parent *parent;
 419         struct path parent_path;
 420         int h, ret = 0;
 421
 422         /*
 423          * When we will be calling audit_add_to_parent, krule->watch might have
 424          * been updated and watch might have been freed.
 425          * So we need to keep a reference of watch.
 426          */
 427         audit_get_watch(watch);
 428
 429         mutex_unlock(&audit_filter_mutex);
 430
 431         /* Avoid calling path_lookup under audit_filter_mutex. */
 432         ret = audit_get_nd(watch, &parent_path);
 433
 434         /* caller expects mutex locked */
 435         mutex_lock(&audit_filter_mutex);
 436
 437         if (ret) {
 438                 audit_put_watch(watch);
 439                 return ret;
 440         }
 441
 442         /* either find an old parent or attach a new one */
 443         parent = audit_find_parent(d_backing_inode(parent_path.dentry));
 444         if (!parent) {
 445                 parent = audit_init_parent(&parent_path);
 446                 if (IS_ERR(parent)) {
 447                         ret = PTR_ERR(parent);
 448                         goto error;
 449                 }
 450         }
 451
 452         audit_add_to_parent(krule, parent);
 453
 454         h = audit_hash_ino((u32)watch->ino);
 455         *list = &audit_inode_hash[h];
 456 error:
 457         path_put(&parent_path);
 458         audit_put_watch(watch);
 459         return ret;
 460 }
 461
 462 void audit_remove_watch_rule(struct audit_krule *krule)
 463 {
 464         struct audit_watch *watch = krule->watch;
 465         struct audit_parent *parent = watch->parent;
 466
 467         list_del(&krule->rlist);
 468
 469         if (list_empty(&watch->rules)) {
 470                 /*
 471                  * audit_remove_watch() drops our reference to 'parent' which
 472                  * can get freed. Grab our own reference to be safe.
 473                  */
 474                 audit_get_parent(parent);
 475                 audit_remove_watch(watch);
 476                 if (list_empty(&parent->watches))
 477                         fsnotify_destroy_mark(&parent->mark, audit_watch_group);
 478                 audit_put_parent(parent);
 479         }
 480 }
 481
 482 /* Update watch data in audit rules based on fsnotify events. */
 483 static int audit_watch_handle_event(struct fsnotify_group *group,
 484                                     struct inode *to_tell,
 485                                     struct fsnotify_mark *inode_mark,
 486                                     struct fsnotify_mark *vfsmount_mark,
 487                                     u32 mask, void *data, int data_type,
 488                                     const unsigned char *dname, u32 cookie)
 489 {
 490         struct inode *inode;
 491         struct audit_parent *parent;
 492
 493         parent = container_of(inode_mark, struct audit_parent, mark);
 494
 495         BUG_ON(group != audit_watch_group);
 496
 497         switch (data_type) {
 498         case (FSNOTIFY_EVENT_PATH):
 499                 inode = d_backing_inode(((struct path *)data)->dentry);
 500                 break;
 501         case (FSNOTIFY_EVENT_INODE):
 502                 inode = (struct inode *)data;
 503                 break;
 504         default:
 505                 BUG();
 506                 inode = NULL;
 507                 break;
 508         };
 509
 510         if (mask & (FS_CREATE|FS_MOVED_TO) && inode)
 511                 audit_update_watch(parent, dname, inode->i_sb->s_dev, inode->i_ino, 0);
 512         else if (mask & (FS_DELETE|FS_MOVED_FROM))
 513                 audit_update_watch(parent, dname, AUDIT_DEV_UNSET, AUDIT_INO_UNSET, 1);
 514         else if (mask & (FS_DELETE_SELF|FS_UNMOUNT|FS_MOVE_SELF))
 515                 audit_remove_parent_watches(parent);
 516
 517         return 0;
 518 }
 519
 520 static const struct fsnotify_ops audit_watch_fsnotify_ops = {
 521         .handle_event =         audit_watch_handle_event,
 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 = exe_file->f_inode->i_ino;
 564         dev = exe_file->f_inode->i_sb->s_dev;
 565         fput(exe_file);
 566         return audit_mark_compare(mark, ino, dev);
 567 }