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/refcount.h>
  32 #include <linux/sched.h>
  33 #include <linux/slab.h>
  34 #include <linux/security.h>
  35 #include "audit.h"
  36
  37 /*
  38  * Reference counting:
  39  *
  40  * audit_parent: lifetime is from audit_init_parent() to receipt of an FS_IGNORED
  41  *      event.  Each audit_watch holds a reference to its associated parent.
  42  *
  43  * audit_watch: if added to lists, lifetime is from audit_init_watch() to
  44  *      audit_remove_watch().  Additionally, an audit_watch may exist
  45  *      temporarily to assist in searching existing filter data.  Each
  46  *      audit_krule holds a reference to its associated watch.
  47  */
  48
  49 struct audit_watch {
  50         refcount_t              count;  /* reference count */
  51         dev_t                   dev;    /* associated superblock device */
  52         char                    *path;  /* insertion path */
  53         unsigned long           ino;    /* associated inode number */
  54         struct audit_parent     *parent; /* associated parent */
  55         struct list_head        wlist;  /* entry in parent->watches list */
  56         struct list_head        rules;  /* anchor for krule->rlist */
  57 };
  58
  59 struct audit_parent {
  60         struct list_head        watches; /* anchor for audit_watch->wlist */
  61         struct fsnotify_mark mark; /* fsnotify mark on the inode */
  62 };
  63
  64 /* fsnotify handle. */
  65 static struct fsnotify_group *audit_watch_group;
  66
  67 /* fsnotify events we care about. */
  68 #define AUDIT_FS_WATCH (FS_MOVE | FS_CREATE | FS_DELETE | FS_DELETE_SELF |\
  69                         FS_MOVE_SELF | FS_EVENT_ON_CHILD | FS_UNMOUNT)
  70
  71 static void audit_free_parent(struct audit_parent *parent)
  72 {
  73         WARN_ON(!list_empty(&parent->watches));
  74         kfree(parent);
  75 }
  76
  77 static void audit_watch_free_mark(struct fsnotify_mark *entry)
  78 {
  79         struct audit_parent *parent;
  80
  81         parent = container_of(entry, struct audit_parent, mark);
  82         audit_free_parent(parent);
  83 }
  84
  85 static void audit_get_parent(struct audit_parent *parent)
  86 {
  87         if (likely(parent))
  88                 fsnotify_get_mark(&parent->mark);
  89 }
  90
  91 static void audit_put_parent(struct audit_parent *parent)
  92 {
  93         if (likely(parent))
  94                 fsnotify_put_mark(&parent->mark);
  95 }
  96
  97 /*
  98  * Find and return the audit_parent on the given inode.  If found a reference
  99  * is taken on this parent.
 100  */
 101 static inline struct audit_parent *audit_find_parent(struct inode *inode)
 102 {
 103         struct audit_parent *parent = NULL;
 104         struct fsnotify_mark *entry;
 105
 106         entry = fsnotify_find_mark(&inode->i_fsnotify_marks, audit_watch_group);
 107         if (entry)
 108                 parent = container_of(entry, struct audit_parent, mark);
 109
 110         return parent;
 111 }
 112
 113 void audit_get_watch(struct audit_watch *watch)
 114 {
 115         refcount_inc(&watch->count);
 116 }
 117
 118 void audit_put_watch(struct audit_watch *watch)
 119 {
 120         if (refcount_dec_and_test(&watch->count)) {
 121                 WARN_ON(watch->parent);
 122                 WARN_ON(!list_empty(&watch->rules));
 123                 kfree(watch->path);
 124                 kfree(watch);
 125         }
 126 }
 127
 128 static void audit_remove_watch(struct audit_watch *watch)
 129 {
 130         list_del(&watch->wlist);
 131         audit_put_parent(watch->parent);
 132         watch->parent = NULL;
 133         audit_put_watch(watch); /* match initial get */
 134 }
 135
 136 char *audit_watch_path(struct audit_watch *watch)
 137 {
 138         return watch->path;
 139 }
 140
 141 int audit_watch_compare(struct audit_watch *watch, unsigned long ino, dev_t dev)
 142 {
 143         return (watch->ino != AUDIT_INO_UNSET) &&
 144                 (watch->ino == ino) &&
 145                 (watch->dev == dev);
 146 }
 147
 148 /* Initialize a parent watch entry. */
 149 static struct audit_parent *audit_init_parent(struct path *path)
 150 {
 151         struct inode *inode = d_backing_inode(path->dentry);
 152         struct audit_parent *parent;
 153         int ret;
 154
 155         parent = kzalloc(sizeof(*parent), GFP_KERNEL);
 156         if (unlikely(!parent))
 157                 return ERR_PTR(-ENOMEM);
 158
 159         INIT_LIST_HEAD(&parent->watches);
 160
 161         fsnotify_init_mark(&parent->mark, audit_watch_group);
 162         parent->mark.mask = AUDIT_FS_WATCH;
 163         ret = fsnotify_add_inode_mark(&parent->mark, inode, 0);
 164         if (ret < 0) {
 165                 audit_free_parent(parent);
 166                 return ERR_PTR(ret);
 167         }
 168
 169         return parent;
 170 }
 171
 172 /* Initialize a watch entry. */
 173 static struct audit_watch *audit_init_watch(char *path)
 174 {
 175         struct audit_watch *watch;
 176
 177         watch = kzalloc(sizeof(*watch), GFP_KERNEL);
 178         if (unlikely(!watch))
 179                 return ERR_PTR(-ENOMEM);
 180
 181         INIT_LIST_HEAD(&watch->rules);
 182         refcount_set(&watch->count, 1);
 183         watch->path = path;
 184         watch->dev = AUDIT_DEV_UNSET;
 185         watch->ino = AUDIT_INO_UNSET;
 186
 187         return watch;
 188 }
 189
 190 /* Translate a watch string to kernel representation. */
 191 int audit_to_watch(struct audit_krule *krule, char *path, int len, u32 op)
 192 {
 193         struct audit_watch *watch;
 194
 195         if (!audit_watch_group)
 196                 return -EOPNOTSUPP;
 197
 198         if (path[0] != '/' || path[len-1] == '/' ||
 199             krule->listnr != AUDIT_FILTER_EXIT ||
 200             op != Audit_equal ||
 201             krule->inode_f || krule->watch || krule->tree)
 202                 return -EINVAL;
 203
 204         watch = audit_init_watch(path);
 205         if (IS_ERR(watch))
 206                 return PTR_ERR(watch);
 207
 208         krule->watch = watch;
 209
 210         return 0;
 211 }
 212
 213 /* Duplicate the given audit watch.  The new watch's rules list is initialized
 214  * to an empty list and wlist is undefined. */
 215 static struct audit_watch *audit_dupe_watch(struct audit_watch *old)
 216 {
 217         char *path;
 218         struct audit_watch *new;
 219
 220         path = kstrdup(old->path, GFP_KERNEL);
 221         if (unlikely(!path))
 222                 return ERR_PTR(-ENOMEM);
 223
 224         new = audit_init_watch(path);
 225         if (IS_ERR(new)) {
 226                 kfree(path);
 227                 goto out;
 228         }
 229
 230         new->dev = old->dev;
 231         new->ino = old->ino;
 232         audit_get_parent(old->parent);
 233         new->parent = old->parent;
 234
 235 out:
 236         return new;
 237 }
 238
 239 static void audit_watch_log_rule_change(struct audit_krule *r, struct audit_watch *w, char *op)
 240 {
 241         struct audit_buffer *ab;
 242
 243         if (!audit_enabled)
 244                 return;
 245         ab = audit_log_start(NULL, GFP_NOFS, AUDIT_CONFIG_CHANGE);
 246         if (!ab)
 247                 return;
 248         audit_log_format(ab, "auid=%u ses=%u op=%s",
 249                          from_kuid(&init_user_ns, audit_get_loginuid(current)),
 250                          audit_get_sessionid(current), 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 /* Update inode info in audit rules based on filesystem event. */
 259 static void audit_update_watch(struct audit_parent *parent,
 260                                const char *dname, dev_t dev,
 261                                unsigned long ino, unsigned invalidating)
 262 {
 263         struct audit_watch *owatch, *nwatch, *nextw;
 264         struct audit_krule *r, *nextr;
 265         struct audit_entry *oentry, *nentry;
 266
 267         mutex_lock(&audit_filter_mutex);
 268         /* Run all of the watches on this parent looking for the one that
 269          * matches the given dname */
 270         list_for_each_entry_safe(owatch, nextw, &parent->watches, wlist) {
 271                 if (audit_compare_dname_path(dname, owatch->path,
 272                                              AUDIT_NAME_FULL))
 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, 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                         if (oentry->rule.exe)
 318                                 audit_remove_mark(oentry->rule.exe);
 319
 320                         audit_watch_log_rule_change(r, owatch, "updated_rules");
 321
 322                         call_rcu(&oentry->rcu, audit_free_rule_rcu);
 323                 }
 324
 325                 audit_remove_watch(owatch);
 326                 goto add_watch_to_parent; /* event applies to a single watch */
 327         }
 328         mutex_unlock(&audit_filter_mutex);
 329         return;
 330
 331 add_watch_to_parent:
 332         list_add(&nwatch->wlist, &parent->watches);
 333         mutex_unlock(&audit_filter_mutex);
 334         return;
 335 }
 336
 337 /* Remove all watches & rules associated with a parent that is going away. */
 338 static void audit_remove_parent_watches(struct audit_parent *parent)
 339 {
 340         struct audit_watch *w, *nextw;
 341         struct audit_krule *r, *nextr;
 342         struct audit_entry *e;
 343
 344         mutex_lock(&audit_filter_mutex);
 345         list_for_each_entry_safe(w, nextw, &parent->watches, wlist) {
 346                 list_for_each_entry_safe(r, nextr, &w->rules, rlist) {
 347                         e = container_of(r, struct audit_entry, rule);
 348                         audit_watch_log_rule_change(r, w, "remove_rule");
 349                         if (e->rule.exe)
 350                                 audit_remove_mark(e->rule.exe);
 351                         list_del(&r->rlist);
 352                         list_del(&r->list);
 353                         list_del_rcu(&e->list);
 354                         call_rcu(&e->rcu, audit_free_rule_rcu);
 355                 }
 356                 audit_remove_watch(w);
 357         }
 358         mutex_unlock(&audit_filter_mutex);
 359
 360         fsnotify_destroy_mark(&parent->mark, audit_watch_group);
 361 }
 362
 363 /* Get path information necessary for adding watches. */
 364 static int audit_get_nd(struct audit_watch *watch, struct path *parent)
 365 {
 366         struct dentry *d = kern_path_locked(watch->path, parent);
 367         if (IS_ERR(d))
 368                 return PTR_ERR(d);
 369         inode_unlock(d_backing_inode(parent->dentry));
 370         if (d_is_positive(d)) {
 371                 /* update watch filter fields */
 372                 watch->dev = d->d_sb->s_dev;
 373                 watch->ino = d_backing_inode(d)->i_ino;
 374         }
 375         dput(d);
 376         return 0;
 377 }
 378
 379 /* Associate the given rule with an existing parent.
 380  * Caller must hold audit_filter_mutex. */
 381 static void audit_add_to_parent(struct audit_krule *krule,
 382                                 struct audit_parent *parent)
 383 {
 384         struct audit_watch *w, *watch = krule->watch;
 385         int watch_found = 0;
 386
 387         BUG_ON(!mutex_is_locked(&audit_filter_mutex));
 388
 389         list_for_each_entry(w, &parent->watches, wlist) {
 390                 if (strcmp(watch->path, w->path))
 391                         continue;
 392
 393                 watch_found = 1;
 394
 395                 /* put krule's ref to temporary watch */
 396                 audit_put_watch(watch);
 397
 398                 audit_get_watch(w);
 399                 krule->watch = watch = w;
 400
 401                 audit_put_parent(parent);
 402                 break;
 403         }
 404
 405         if (!watch_found) {
 406                 watch->parent = parent;
 407
 408                 audit_get_watch(watch);
 409                 list_add(&watch->wlist, &parent->watches);
 410         }
 411         list_add(&krule->rlist, &watch->rules);
 412 }
 413
 414 /* Find a matching watch entry, or add this one.
 415  * Caller must hold audit_filter_mutex. */
 416 int audit_add_watch(struct audit_krule *krule, struct list_head **list)
 417 {
 418         struct audit_watch *watch = krule->watch;
 419         struct audit_parent *parent;
 420         struct path parent_path;
 421         int h, ret = 0;
 422
 423         /*
 424          * When we will be calling audit_add_to_parent, krule->watch might have
 425          * been updated and watch might have been freed.
 426          * So we need to keep a reference of watch.
 427          */
 428         audit_get_watch(watch);
 429
 430         mutex_unlock(&audit_filter_mutex);
 431
 432         /* Avoid calling path_lookup under audit_filter_mutex. */
 433         ret = audit_get_nd(watch, &parent_path);
 434
 435         /* caller expects mutex locked */
 436         mutex_lock(&audit_filter_mutex);
 437
 438         if (ret) {
 439                 audit_put_watch(watch);
 440                 return ret;
 441         }
 442
 443         /* either find an old parent or attach a new one */
 444         parent = audit_find_parent(d_backing_inode(parent_path.dentry));
 445         if (!parent) {
 446                 parent = audit_init_parent(&parent_path);
 447                 if (IS_ERR(parent)) {
 448                         ret = PTR_ERR(parent);
 449                         goto error;
 450                 }
 451         }
 452
 453         audit_add_to_parent(krule, parent);
 454
 455         h = audit_hash_ino((u32)watch->ino);
 456         *list = &audit_inode_hash[h];
 457 error:
 458         path_put(&parent_path);
 459         audit_put_watch(watch);
 460         return ret;
 461 }
 462
 463 void audit_remove_watch_rule(struct audit_krule *krule)
 464 {
 465         struct audit_watch *watch = krule->watch;
 466         struct audit_parent *parent = watch->parent;
 467
 468         list_del(&krule->rlist);
 469
 470         if (list_empty(&watch->rules)) {
 471                 /*
 472                  * audit_remove_watch() drops our reference to 'parent' which
 473                  * can get freed. Grab our own reference to be safe.
 474                  */
 475                 audit_get_parent(parent);
 476                 audit_remove_watch(watch);
 477                 if (list_empty(&parent->watches))
 478                         fsnotify_destroy_mark(&parent->mark, audit_watch_group);
 479                 audit_put_parent(parent);
 480         }
 481 }
 482
 483 /* Update watch data in audit rules based on fsnotify events. */
 484 static int audit_watch_handle_event(struct fsnotify_group *group,
 485                                     struct inode *to_tell,
 486                                     u32 mask, const void *data, int data_type,
 487                                     const unsigned char *dname, u32 cookie,
 488                                     struct fsnotify_iter_info *iter_info)
 489 {
 490         struct fsnotify_mark *inode_mark = fsnotify_iter_inode_mark(iter_info);
 491         const struct inode *inode;
 492         struct audit_parent *parent;
 493
 494         parent = container_of(inode_mark, struct audit_parent, mark);
 495
 496         BUG_ON(group != audit_watch_group);
 497
 498         switch (data_type) {
 499         case (FSNOTIFY_EVENT_PATH):
 500                 inode = d_backing_inode(((const struct path *)data)->dentry);
 501                 break;
 502         case (FSNOTIFY_EVENT_INODE):
 503                 inode = (const struct inode *)data;
 504                 break;
 505         default:
 506                 BUG();
 507                 inode = NULL;
 508                 break;
 509         }
 510
 511         if (mask & (FS_CREATE|FS_MOVED_TO) && inode)
 512                 audit_update_watch(parent, dname, inode->i_sb->s_dev, inode->i_ino, 0);
 513         else if (mask & (FS_DELETE|FS_MOVED_FROM))
 514                 audit_update_watch(parent, dname, AUDIT_DEV_UNSET, AUDIT_INO_UNSET, 1);
 515         else if (mask & (FS_DELETE_SELF|FS_UNMOUNT|FS_MOVE_SELF))
 516                 audit_remove_parent_watches(parent);
 517
 518         return 0;
 519 }
 520
 521 static const struct fsnotify_ops audit_watch_fsnotify_ops = {
 522         .handle_event =         audit_watch_handle_event,
 523         .free_mark =            audit_watch_free_mark,
 524 };
 525
 526 static int __init audit_watch_init(void)
 527 {
 528         audit_watch_group = fsnotify_alloc_group(&audit_watch_fsnotify_ops);
 529         if (IS_ERR(audit_watch_group)) {
 530                 audit_watch_group = NULL;
 531                 audit_panic("cannot create audit fsnotify group");
 532         }
 533         return 0;
 534 }
 535 device_initcall(audit_watch_init);
 536
 537 int audit_dupe_exe(struct audit_krule *new, struct audit_krule *old)
 538 {
 539         struct audit_fsnotify_mark *audit_mark;
 540         char *pathname;
 541
 542         pathname = kstrdup(audit_mark_path(old->exe), GFP_KERNEL);
 543         if (!pathname)
 544                 return -ENOMEM;
 545
 546         audit_mark = audit_alloc_mark(new, pathname, strlen(pathname));
 547         if (IS_ERR(audit_mark)) {
 548                 kfree(pathname);
 549                 return PTR_ERR(audit_mark);
 550         }
 551         new->exe = audit_mark;
 552
 553         return 0;
 554 }
 555
 556 int audit_exe_compare(struct task_struct *tsk, struct audit_fsnotify_mark *mark)
 557 {
 558         struct file *exe_file;
 559         unsigned long ino;
 560         dev_t dev;
 561
 562         exe_file = get_task_exe_file(tsk);
 563         if (!exe_file)
 564                 return 0;
 565         ino = file_inode(exe_file)->i_ino;
 566         dev = file_inode(exe_file)->i_sb->s_dev;
 567         fput(exe_file);
 568         return audit_mark_compare(mark, ino, dev);
 569 }