kernel/audit_watch.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* audit_watch.c -- watching inodes
   3  *
   4  * Copyright 2003-2009 Red Hat, Inc.
   5  * Copyright 2005 Hewlett-Packard Development Company, L.P.
   6  * Copyright 2005 IBM Corporation
   7  */
   8
   9 #include <linux/file.h>
  10 #include <linux/kernel.h>
  11 #include <linux/audit.h>
  12 #include <linux/kthread.h>
  13 #include <linux/mutex.h>
  14 #include <linux/fs.h>
  15 #include <linux/fsnotify_backend.h>
  16 #include <linux/namei.h>
  17 #include <linux/netlink.h>
  18 #include <linux/refcount.h>
  19 #include <linux/sched.h>
  20 #include <linux/slab.h>
  21 #include <linux/security.h>
  22 #include "audit.h"
  23
  24 /*
  25  * Reference counting:
  26  *
  27  * audit_parent: lifetime is from audit_init_parent() to receipt of an FS_IGNORED
  28  *      event.  Each audit_watch holds a reference to its associated parent.
  29  *
  30  * audit_watch: if added to lists, lifetime is from audit_init_watch() to
  31  *      audit_remove_watch().  Additionally, an audit_watch may exist
  32  *      temporarily to assist in searching existing filter data.  Each
  33  *      audit_krule holds a reference to its associated watch.
  34  */
  35
  36 struct audit_watch {
  37         refcount_t              count;  /* reference count */
  38         dev_t                   dev;    /* associated superblock device */
  39         char                    *path;  /* insertion path */
  40         unsigned long           ino;    /* associated inode number */
  41         struct audit_parent     *parent; /* associated parent */
  42         struct list_head        wlist;  /* entry in parent->watches list */
  43         struct list_head        rules;  /* anchor for krule->rlist */
  44 };
  45
  46 struct audit_parent {
  47         struct list_head        watches; /* anchor for audit_watch->wlist */
  48         struct fsnotify_mark mark; /* fsnotify mark on the inode */
  49 };
  50
  51 /* fsnotify handle. */
  52 static struct fsnotify_group *audit_watch_group;
  53
  54 /* fsnotify events we care about. */
  55 #define AUDIT_FS_WATCH (FS_MOVE | FS_CREATE | FS_DELETE | FS_DELETE_SELF |\
  56                         FS_MOVE_SELF | FS_UNMOUNT)
  57
  58 static void audit_free_parent(struct audit_parent *parent)
  59 {
  60         WARN_ON(!list_empty(&parent->watches));
  61         kfree(parent);
  62 }
  63
  64 static void audit_watch_free_mark(struct fsnotify_mark *entry)
  65 {
  66         struct audit_parent *parent;
  67
  68         parent = container_of(entry, struct audit_parent, mark);
  69         audit_free_parent(parent);
  70 }
  71
  72 static void audit_get_parent(struct audit_parent *parent)
  73 {
  74         if (likely(parent))
  75                 fsnotify_get_mark(&parent->mark);
  76 }
  77
  78 static void audit_put_parent(struct audit_parent *parent)
  79 {
  80         if (likely(parent))
  81                 fsnotify_put_mark(&parent->mark);
  82 }
  83
  84 /*
  85  * Find and return the audit_parent on the given inode.  If found a reference
  86  * is taken on this parent.
  87  */
  88 static inline struct audit_parent *audit_find_parent(struct inode *inode)
  89 {
  90         struct audit_parent *parent = NULL;
  91         struct fsnotify_mark *entry;
  92
  93         entry = fsnotify_find_inode_mark(inode, audit_watch_group);
  94         if (entry)
  95                 parent = container_of(entry, struct audit_parent, mark);
  96
  97         return parent;
  98 }
  99
 100 void audit_get_watch(struct audit_watch *watch)
 101 {
 102         refcount_inc(&watch->count);
 103 }
 104
 105 void audit_put_watch(struct audit_watch *watch)
 106 {
 107         if (refcount_dec_and_test(&watch->count)) {
 108                 WARN_ON(watch->parent);
 109                 WARN_ON(!list_empty(&watch->rules));
 110                 kfree(watch->path);
 111                 kfree(watch);
 112         }
 113 }
 114
 115 static void audit_remove_watch(struct audit_watch *watch)
 116 {
 117         list_del(&watch->wlist);
 118         audit_put_parent(watch->parent);
 119         watch->parent = NULL;
 120         audit_put_watch(watch); /* match initial get */
 121 }
 122
 123 char *audit_watch_path(struct audit_watch *watch)
 124 {
 125         return watch->path;
 126 }
 127
 128 int audit_watch_compare(struct audit_watch *watch, unsigned long ino, dev_t dev)
 129 {
 130         return (watch->ino != AUDIT_INO_UNSET) &&
 131                 (watch->ino == ino) &&
 132                 (watch->dev == dev);
 133 }
 134
 135 /* Initialize a parent watch entry. */
 136 static struct audit_parent *audit_init_parent(const struct path *path)
 137 {
 138         struct inode *inode = d_backing_inode(path->dentry);
 139         struct audit_parent *parent;
 140         int ret;
 141
 142         parent = kzalloc(sizeof(*parent), GFP_KERNEL);
 143         if (unlikely(!parent))
 144                 return ERR_PTR(-ENOMEM);
 145
 146         INIT_LIST_HEAD(&parent->watches);
 147
 148         fsnotify_init_mark(&parent->mark, audit_watch_group);
 149         parent->mark.mask = AUDIT_FS_WATCH;
 150         ret = fsnotify_add_inode_mark(&parent->mark, inode, 0);
 151         if (ret < 0) {
 152                 audit_free_parent(parent);
 153                 return ERR_PTR(ret);
 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         refcount_set(&watch->count, 1);
 170         watch->path = path;
 171         watch->dev = AUDIT_DEV_UNSET;
 172         watch->ino = AUDIT_INO_UNSET;
 173
 174         return watch;
 175 }
 176
 177 /* Translate a watch string to kernel representation. */
 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_watch_group)
 183                 return -EOPNOTSUPP;
 184
 185         if (path[0] != '/' || path[len-1] == '/' ||
 186             (krule->listnr != AUDIT_FILTER_EXIT &&
 187              krule->listnr != AUDIT_FILTER_URING_EXIT) ||
 188             op != Audit_equal ||
 189             krule->inode_f || krule->watch || krule->tree)
 190                 return -EINVAL;
 191
 192         watch = audit_init_watch(path);
 193         if (IS_ERR(watch))
 194                 return PTR_ERR(watch);
 195
 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         audit_get_parent(old->parent);
 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         struct audit_buffer *ab;
 230
 231         if (!audit_enabled)
 232                 return;
 233         ab = audit_log_start(audit_context(), GFP_NOFS, AUDIT_CONFIG_CHANGE);
 234         if (!ab)
 235                 return;
 236         audit_log_session_info(ab);
 237         audit_log_format(ab, "op=%s path=", op);
 238         audit_log_untrustedstring(ab, w->path);
 239         audit_log_key(ab, r->filterkey);
 240         audit_log_format(ab, " list=%d res=1", r->listnr);
 241         audit_log_end(ab);
 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 struct qstr *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         /* Run all of the watches on this parent looking for the one that
 255          * matches the given dname */
 256         list_for_each_entry_safe(owatch, nextw, &parent->watches, wlist) {
 257                 if (audit_compare_dname_path(dname, owatch->path,
 258                                              AUDIT_NAME_FULL))
 259                         continue;
 260
 261                 /* If the update involves invalidating rules, do the inode-based
 262                  * filtering now, so we don't omit records. */
 263                 if (invalidating && !audit_dummy_context())
 264                         audit_filter_inodes(current, audit_context());
 265
 266                 /* updating ino will likely change which audit_hash_list we
 267                  * are on so we need a new watch for the new list */
 268                 nwatch = audit_dupe_watch(owatch);
 269                 if (IS_ERR(nwatch)) {
 270                         mutex_unlock(&audit_filter_mutex);
 271                         audit_panic("error updating watch, skipping");
 272                         return;
 273                 }
 274                 nwatch->dev = dev;
 275                 nwatch->ino = ino;
 276
 277                 list_for_each_entry_safe(r, nextr, &owatch->rules, rlist) {
 278
 279                         oentry = container_of(r, struct audit_entry, rule);
 280                         list_del(&oentry->rule.rlist);
 281                         list_del_rcu(&oentry->list);
 282
 283                         nentry = audit_dupe_rule(&oentry->rule);
 284                         if (IS_ERR(nentry)) {
 285                                 list_del(&oentry->rule.list);
 286                                 audit_panic("error updating watch, removing");
 287                         } else {
 288                                 int h = audit_hash_ino((u32)ino);
 289
 290                                 /*
 291                                  * nentry->rule.watch == oentry->rule.watch so
 292                                  * we must drop that reference and set it to our
 293                                  * new watch.
 294                                  */
 295                                 audit_put_watch(nentry->rule.watch);
 296                                 audit_get_watch(nwatch);
 297                                 nentry->rule.watch = nwatch;
 298                                 list_add(&nentry->rule.rlist, &nwatch->rules);
 299                                 list_add_rcu(&nentry->list, &audit_inode_hash[h]);
 300                                 list_replace(&oentry->rule.list,
 301                                              &nentry->rule.list);
 302                         }
 303                         if (oentry->rule.exe)
 304                                 audit_remove_mark(oentry->rule.exe);
 305
 306                         call_rcu(&oentry->rcu, audit_free_rule_rcu);
 307                 }
 308
 309                 audit_remove_watch(owatch);
 310                 goto add_watch_to_parent; /* event applies to a single watch */
 311         }
 312         mutex_unlock(&audit_filter_mutex);
 313         return;
 314
 315 add_watch_to_parent:
 316         list_add(&nwatch->wlist, &parent->watches);
 317         mutex_unlock(&audit_filter_mutex);
 318         return;
 319 }
 320
 321 /* Remove all watches & rules associated with a parent that is going away. */
 322 static void audit_remove_parent_watches(struct audit_parent *parent)
 323 {
 324         struct audit_watch *w, *nextw;
 325         struct audit_krule *r, *nextr;
 326         struct audit_entry *e;
 327
 328         mutex_lock(&audit_filter_mutex);
 329         list_for_each_entry_safe(w, nextw, &parent->watches, wlist) {
 330                 list_for_each_entry_safe(r, nextr, &w->rules, rlist) {
 331                         e = container_of(r, struct audit_entry, rule);
 332                         audit_watch_log_rule_change(r, w, "remove_rule");
 333                         if (e->rule.exe)
 334                                 audit_remove_mark(e->rule.exe);
 335                         list_del(&r->rlist);
 336                         list_del(&r->list);
 337                         list_del_rcu(&e->list);
 338                         call_rcu(&e->rcu, audit_free_rule_rcu);
 339                 }
 340                 audit_remove_watch(w);
 341         }
 342         mutex_unlock(&audit_filter_mutex);
 343
 344         fsnotify_destroy_mark(&parent->mark, audit_watch_group);
 345 }
 346
 347 /* Get path information necessary for adding watches. */
 348 static int audit_get_nd(struct audit_watch *watch, struct path *parent)
 349 {
 350         struct dentry *d = kern_path_locked(watch->path, parent);
 351         if (IS_ERR(d))
 352                 return PTR_ERR(d);
 353         if (d_is_positive(d)) {
 354                 /* update watch filter fields */
 355                 watch->dev = d->d_sb->s_dev;
 356                 watch->ino = d_backing_inode(d)->i_ino;
 357         }
 358         inode_unlock(d_backing_inode(parent->dentry));
 359         dput(d);
 360         return 0;
 361 }
 362
 363 /* Associate the given rule with an existing parent.
 364  * Caller must hold audit_filter_mutex. */
 365 static void audit_add_to_parent(struct audit_krule *krule,
 366                                 struct audit_parent *parent)
 367 {
 368         struct audit_watch *w, *watch = krule->watch;
 369         int watch_found = 0;
 370
 371         BUG_ON(!mutex_is_locked(&audit_filter_mutex));
 372
 373         list_for_each_entry(w, &parent->watches, wlist) {
 374                 if (strcmp(watch->path, w->path))
 375                         continue;
 376
 377                 watch_found = 1;
 378
 379                 /* put krule's ref to temporary watch */
 380                 audit_put_watch(watch);
 381
 382                 audit_get_watch(w);
 383                 krule->watch = watch = w;
 384
 385                 audit_put_parent(parent);
 386                 break;
 387         }
 388
 389         if (!watch_found) {
 390                 watch->parent = parent;
 391
 392                 audit_get_watch(watch);
 393                 list_add(&watch->wlist, &parent->watches);
 394         }
 395         list_add(&krule->rlist, &watch->rules);
 396 }
 397
 398 /* Find a matching watch entry, or add this one.
 399  * Caller must hold audit_filter_mutex. */
 400 int audit_add_watch(struct audit_krule *krule, struct list_head **list)
 401 {
 402         struct audit_watch *watch = krule->watch;
 403         struct audit_parent *parent;
 404         struct path parent_path;
 405         int h, ret = 0;
 406
 407         /*
 408          * When we will be calling audit_add_to_parent, krule->watch might have
 409          * been updated and watch might have been freed.
 410          * So we need to keep a reference of watch.
 411          */
 412         audit_get_watch(watch);
 413
 414         mutex_unlock(&audit_filter_mutex);
 415
 416         /* Avoid calling path_lookup under audit_filter_mutex. */
 417         ret = audit_get_nd(watch, &parent_path);
 418
 419         /* caller expects mutex locked */
 420         mutex_lock(&audit_filter_mutex);
 421
 422         if (ret) {
 423                 audit_put_watch(watch);
 424                 return ret;
 425         }
 426
 427         /* either find an old parent or attach a new one */
 428         parent = audit_find_parent(d_backing_inode(parent_path.dentry));
 429         if (!parent) {
 430                 parent = audit_init_parent(&parent_path);
 431                 if (IS_ERR(parent)) {
 432                         ret = PTR_ERR(parent);
 433                         goto error;
 434                 }
 435         }
 436
 437         audit_add_to_parent(krule, parent);
 438
 439         h = audit_hash_ino((u32)watch->ino);
 440         *list = &audit_inode_hash[h];
 441 error:
 442         path_put(&parent_path);
 443         audit_put_watch(watch);
 444         return ret;
 445 }
 446
 447 void audit_remove_watch_rule(struct audit_krule *krule)
 448 {
 449         struct audit_watch *watch = krule->watch;
 450         struct audit_parent *parent = watch->parent;
 451
 452         list_del(&krule->rlist);
 453
 454         if (list_empty(&watch->rules)) {
 455                 /*
 456                  * audit_remove_watch() drops our reference to 'parent' which
 457                  * can get freed. Grab our own reference to be safe.
 458                  */
 459                 audit_get_parent(parent);
 460                 audit_remove_watch(watch);
 461                 if (list_empty(&parent->watches))
 462                         fsnotify_destroy_mark(&parent->mark, audit_watch_group);
 463                 audit_put_parent(parent);
 464         }
 465 }
 466
 467 /* Update watch data in audit rules based on fsnotify events. */
 468 static int audit_watch_handle_event(struct fsnotify_mark *inode_mark, u32 mask,
 469                                     struct inode *inode, struct inode *dir,
 470                                     const struct qstr *dname, u32 cookie)
 471 {
 472         struct audit_parent *parent;
 473
 474         parent = container_of(inode_mark, struct audit_parent, mark);
 475
 476         if (WARN_ON_ONCE(inode_mark->group != audit_watch_group))
 477                 return 0;
 478
 479         if (mask & (FS_CREATE|FS_MOVED_TO) && inode)
 480                 audit_update_watch(parent, dname, inode->i_sb->s_dev, inode->i_ino, 0);
 481         else if (mask & (FS_DELETE|FS_MOVED_FROM))
 482                 audit_update_watch(parent, dname, AUDIT_DEV_UNSET, AUDIT_INO_UNSET, 1);
 483         else if (mask & (FS_DELETE_SELF|FS_UNMOUNT|FS_MOVE_SELF))
 484                 audit_remove_parent_watches(parent);
 485
 486         return 0;
 487 }
 488
 489 static const struct fsnotify_ops audit_watch_fsnotify_ops = {
 490         .handle_inode_event =   audit_watch_handle_event,
 491         .free_mark =            audit_watch_free_mark,
 492 };
 493
 494 static int __init audit_watch_init(void)
 495 {
 496         audit_watch_group = fsnotify_alloc_group(&audit_watch_fsnotify_ops, 0);
 497         if (IS_ERR(audit_watch_group)) {
 498                 audit_watch_group = NULL;
 499                 audit_panic("cannot create audit fsnotify group");
 500         }
 501         return 0;
 502 }
 503 device_initcall(audit_watch_init);
 504
 505 int audit_dupe_exe(struct audit_krule *new, struct audit_krule *old)
 506 {
 507         struct audit_fsnotify_mark *audit_mark;
 508         char *pathname;
 509
 510         pathname = kstrdup(audit_mark_path(old->exe), GFP_KERNEL);
 511         if (!pathname)
 512                 return -ENOMEM;
 513
 514         audit_mark = audit_alloc_mark(new, pathname, strlen(pathname));
 515         if (IS_ERR(audit_mark)) {
 516                 kfree(pathname);
 517                 return PTR_ERR(audit_mark);
 518         }
 519         new->exe = audit_mark;
 520
 521         return 0;
 522 }
 523
 524 int audit_exe_compare(struct task_struct *tsk, struct audit_fsnotify_mark *mark)
 525 {
 526         struct file *exe_file;
 527         unsigned long ino;
 528         dev_t dev;
 529
 530         /* only do exe filtering if we are recording @current events/records */
 531         if (tsk != current)
 532                 return 0;
 533
 534         if (!current->mm)
 535                 return 0;
 536         exe_file = get_mm_exe_file(current->mm);
 537         if (!exe_file)
 538                 return 0;
 539         ino = file_inode(exe_file)->i_ino;
 540         dev = file_inode(exe_file)->i_sb->s_dev;
 541         fput(exe_file);
 542
 543         return audit_mark_compare(mark, ino, dev);
 544 }