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 representation. */
 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                         call_rcu(&oentry->rcu, audit_free_rule_rcu);
 320                 }
 321
 322                 audit_remove_watch(owatch);
 323                 goto add_watch_to_parent; /* event applies to a single watch */
 324         }
 325         mutex_unlock(&audit_filter_mutex);
 326         return;
 327
 328 add_watch_to_parent:
 329         list_add(&nwatch->wlist, &parent->watches);
 330         mutex_unlock(&audit_filter_mutex);
 331         return;
 332 }
 333
 334 /* Remove all watches & rules associated with a parent that is going away. */
 335 static void audit_remove_parent_watches(struct audit_parent *parent)
 336 {
 337         struct audit_watch *w, *nextw;
 338         struct audit_krule *r, *nextr;
 339         struct audit_entry *e;
 340
 341         mutex_lock(&audit_filter_mutex);
 342         list_for_each_entry_safe(w, nextw, &parent->watches, wlist) {
 343                 list_for_each_entry_safe(r, nextr, &w->rules, rlist) {
 344                         e = container_of(r, struct audit_entry, rule);
 345                         audit_watch_log_rule_change(r, w, "remove_rule");
 346                         if (e->rule.exe)
 347                                 audit_remove_mark(e->rule.exe);
 348                         list_del(&r->rlist);
 349                         list_del(&r->list);
 350                         list_del_rcu(&e->list);
 351                         call_rcu(&e->rcu, audit_free_rule_rcu);
 352                 }
 353                 audit_remove_watch(w);
 354         }
 355         mutex_unlock(&audit_filter_mutex);
 356
 357         fsnotify_destroy_mark(&parent->mark, audit_watch_group);
 358 }
 359
 360 /* Get path information necessary for adding watches. */
 361 static int audit_get_nd(struct audit_watch *watch, struct path *parent)
 362 {
 363         struct dentry *d = kern_path_locked(watch->path, parent);
 364         if (IS_ERR(d))
 365                 return PTR_ERR(d);
 366         if (d_is_positive(d)) {
 367                 /* update watch filter fields */
 368                 watch->dev = d->d_sb->s_dev;
 369                 watch->ino = d_backing_inode(d)->i_ino;
 370         }
 371         inode_unlock(d_backing_inode(parent->dentry));
 372         dput(d);
 373         return 0;
 374 }
 375
 376 /* Associate the given rule with an existing parent.
 377  * Caller must hold audit_filter_mutex. */
 378 static void audit_add_to_parent(struct audit_krule *krule,
 379                                 struct audit_parent *parent)
 380 {
 381         struct audit_watch *w, *watch = krule->watch;
 382         int watch_found = 0;
 383
 384         BUG_ON(!mutex_is_locked(&audit_filter_mutex));
 385
 386         list_for_each_entry(w, &parent->watches, wlist) {
 387                 if (strcmp(watch->path, w->path))
 388                         continue;
 389
 390                 watch_found = 1;
 391
 392                 /* put krule's ref to temporary watch */
 393                 audit_put_watch(watch);
 394
 395                 audit_get_watch(w);
 396                 krule->watch = watch = w;
 397
 398                 audit_put_parent(parent);
 399                 break;
 400         }
 401
 402         if (!watch_found) {
 403                 watch->parent = parent;
 404
 405                 audit_get_watch(watch);
 406                 list_add(&watch->wlist, &parent->watches);
 407         }
 408         list_add(&krule->rlist, &watch->rules);
 409 }
 410
 411 /* Find a matching watch entry, or add this one.
 412  * Caller must hold audit_filter_mutex. */
 413 int audit_add_watch(struct audit_krule *krule, struct list_head **list)
 414 {
 415         struct audit_watch *watch = krule->watch;
 416         struct audit_parent *parent;
 417         struct path parent_path;
 418         int h, ret = 0;
 419
 420         /*
 421          * When we will be calling audit_add_to_parent, krule->watch might have
 422          * been updated and watch might have been freed.
 423          * So we need to keep a reference of watch.
 424          */
 425         audit_get_watch(watch);
 426
 427         mutex_unlock(&audit_filter_mutex);
 428
 429         /* Avoid calling path_lookup under audit_filter_mutex. */
 430         ret = audit_get_nd(watch, &parent_path);
 431
 432         /* caller expects mutex locked */
 433         mutex_lock(&audit_filter_mutex);
 434
 435         if (ret) {
 436                 audit_put_watch(watch);
 437                 return ret;
 438         }
 439
 440         /* either find an old parent or attach a new one */
 441         parent = audit_find_parent(d_backing_inode(parent_path.dentry));
 442         if (!parent) {
 443                 parent = audit_init_parent(&parent_path);
 444                 if (IS_ERR(parent)) {
 445                         ret = PTR_ERR(parent);
 446                         goto error;
 447                 }
 448         }
 449
 450         audit_add_to_parent(krule, parent);
 451
 452         h = audit_hash_ino((u32)watch->ino);
 453         *list = &audit_inode_hash[h];
 454 error:
 455         path_put(&parent_path);
 456         audit_put_watch(watch);
 457         return ret;
 458 }
 459
 460 void audit_remove_watch_rule(struct audit_krule *krule)
 461 {
 462         struct audit_watch *watch = krule->watch;
 463         struct audit_parent *parent = watch->parent;
 464
 465         list_del(&krule->rlist);
 466
 467         if (list_empty(&watch->rules)) {
 468                 /*
 469                  * audit_remove_watch() drops our reference to 'parent' which
 470                  * can get freed. Grab our own reference to be safe.
 471                  */
 472                 audit_get_parent(parent);
 473                 audit_remove_watch(watch);
 474                 if (list_empty(&parent->watches))
 475                         fsnotify_destroy_mark(&parent->mark, audit_watch_group);
 476                 audit_put_parent(parent);
 477         }
 478 }
 479
 480 /* Update watch data in audit rules based on fsnotify events. */
 481 static int audit_watch_handle_event(struct fsnotify_group *group,
 482                                     struct inode *to_tell,
 483                                     struct fsnotify_mark *inode_mark,
 484                                     struct fsnotify_mark *vfsmount_mark,
 485                                     u32 mask, void *data, int data_type,
 486                                     const unsigned char *dname, u32 cookie)
 487 {
 488         struct inode *inode;
 489         struct audit_parent *parent;
 490
 491         parent = container_of(inode_mark, struct audit_parent, mark);
 492
 493         BUG_ON(group != audit_watch_group);
 494
 495         switch (data_type) {
 496         case (FSNOTIFY_EVENT_PATH):
 497                 inode = d_backing_inode(((struct path *)data)->dentry);
 498                 break;
 499         case (FSNOTIFY_EVENT_INODE):
 500                 inode = (struct inode *)data;
 501                 break;
 502         default:
 503                 BUG();
 504                 inode = NULL;
 505                 break;
 506         };
 507
 508         if (mask & (FS_CREATE|FS_MOVED_TO) && inode)
 509                 audit_update_watch(parent, dname, inode->i_sb->s_dev, inode->i_ino, 0);
 510         else if (mask & (FS_DELETE|FS_MOVED_FROM))
 511                 audit_update_watch(parent, dname, AUDIT_DEV_UNSET, AUDIT_INO_UNSET, 1);
 512         else if (mask & (FS_DELETE_SELF|FS_UNMOUNT|FS_MOVE_SELF))
 513                 audit_remove_parent_watches(parent);
 514
 515         return 0;
 516 }
 517
 518 static const struct fsnotify_ops audit_watch_fsnotify_ops = {
 519         .handle_event =         audit_watch_handle_event,
 520 };
 521
 522 static int __init audit_watch_init(void)
 523 {
 524         audit_watch_group = fsnotify_alloc_group(&audit_watch_fsnotify_ops);
 525         if (IS_ERR(audit_watch_group)) {
 526                 audit_watch_group = NULL;
 527                 audit_panic("cannot create audit fsnotify group");
 528         }
 529         return 0;
 530 }
 531 device_initcall(audit_watch_init);
 532
 533 int audit_dupe_exe(struct audit_krule *new, struct audit_krule *old)
 534 {
 535         struct audit_fsnotify_mark *audit_mark;
 536         char *pathname;
 537
 538         pathname = kstrdup(audit_mark_path(old->exe), GFP_KERNEL);
 539         if (!pathname)
 540                 return -ENOMEM;
 541
 542         audit_mark = audit_alloc_mark(new, pathname, strlen(pathname));
 543         if (IS_ERR(audit_mark)) {
 544                 kfree(pathname);
 545                 return PTR_ERR(audit_mark);
 546         }
 547         new->exe = audit_mark;
 548
 549         return 0;
 550 }
 551
 552 int audit_exe_compare(struct task_struct *tsk, struct audit_fsnotify_mark *mark)
 553 {
 554         struct file *exe_file;
 555         unsigned long ino;
 556         dev_t dev;
 557
 558         exe_file = get_task_exe_file(tsk);
 559         if (!exe_file)
 560                 return 0;
 561         ino = exe_file->f_inode->i_ino;
 562         dev = exe_file->f_inode->i_sb->s_dev;
 563         fput(exe_file);
 564         return audit_mark_compare(mark, ino, dev);
 565 }