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TOMOYO Linux Cross Reference
Linux/kernel/audit_watch.c

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  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        watches; /* anchor for audit_watch->wlist */
 59         struct fsnotify_mark mark; /* fsnotify mark on the inode */
 60 };
 61 
 62 /* fsnotify handle. */
 63 static struct fsnotify_group *audit_watch_group;
 64 
 65 /* fsnotify events we care about. */
 66 #define AUDIT_FS_WATCH (FS_MOVE | FS_CREATE | FS_DELETE | FS_DELETE_SELF |\
 67                         FS_MOVE_SELF | FS_EVENT_ON_CHILD)
 68 
 69 static void audit_free_parent(struct audit_parent *parent)
 70 {
 71         WARN_ON(!list_empty(&parent->watches));
 72         kfree(parent);
 73 }
 74 
 75 static void audit_watch_free_mark(struct fsnotify_mark *entry)
 76 {
 77         struct audit_parent *parent;
 78 
 79         parent = container_of(entry, struct audit_parent, mark);
 80         audit_free_parent(parent);
 81 }
 82 
 83 static void audit_get_parent(struct audit_parent *parent)
 84 {
 85         if (likely(parent))
 86                 fsnotify_get_mark(&parent->mark);
 87 }
 88 
 89 static void audit_put_parent(struct audit_parent *parent)
 90 {
 91         if (likely(parent))
 92                 fsnotify_put_mark(&parent->mark);
 93 }
 94 
 95 /*
 96  * Find and return the audit_parent on the given inode.  If found a reference
 97  * is taken on this parent.
 98  */
 99 static inline struct audit_parent *audit_find_parent(struct inode *inode)
100 {
101         struct audit_parent *parent = NULL;
102         struct fsnotify_mark *entry;
103 
104         entry = fsnotify_find_inode_mark(audit_watch_group, inode);
105         if (entry)
106                 parent = container_of(entry, struct audit_parent, mark);
107 
108         return parent;
109 }
110 
111 void audit_get_watch(struct audit_watch *watch)
112 {
113         atomic_inc(&watch->count);
114 }
115 
116 void audit_put_watch(struct audit_watch *watch)
117 {
118         if (atomic_dec_and_test(&watch->count)) {
119                 WARN_ON(watch->parent);
120                 WARN_ON(!list_empty(&watch->rules));
121                 kfree(watch->path);
122                 kfree(watch);
123         }
124 }
125 
126 static void audit_remove_watch(struct audit_watch *watch)
127 {
128         list_del(&watch->wlist);
129         audit_put_parent(watch->parent);
130         watch->parent = NULL;
131         audit_put_watch(watch); /* match initial get */
132 }
133 
134 char *audit_watch_path(struct audit_watch *watch)
135 {
136         return watch->path;
137 }
138 
139 int audit_watch_compare(struct audit_watch *watch, unsigned long ino, dev_t dev)
140 {
141         return (watch->ino != (unsigned long)-1) &&
142                 (watch->ino == ino) &&
143                 (watch->dev == dev);
144 }
145 
146 /* Initialize a parent watch entry. */
147 static struct audit_parent *audit_init_parent(struct nameidata *ndp)
148 {
149         struct inode *inode = ndp->path.dentry->d_inode;
150         struct audit_parent *parent;
151         int ret;
152 
153         parent = kzalloc(sizeof(*parent), GFP_KERNEL);
154         if (unlikely(!parent))
155                 return ERR_PTR(-ENOMEM);
156 
157         INIT_LIST_HEAD(&parent->watches);
158 
159         fsnotify_init_mark(&parent->mark, audit_watch_free_mark);
160         parent->mark.mask = AUDIT_FS_WATCH;
161         ret = fsnotify_add_mark(&parent->mark, audit_watch_group, inode, NULL, 0);
162         if (ret < 0) {
163                 audit_free_parent(parent);
164                 return ERR_PTR(ret);
165         }
166 
167         return parent;
168 }
169 
170 /* Initialize a watch entry. */
171 static struct audit_watch *audit_init_watch(char *path)
172 {
173         struct audit_watch *watch;
174 
175         watch = kzalloc(sizeof(*watch), GFP_KERNEL);
176         if (unlikely(!watch))
177                 return ERR_PTR(-ENOMEM);
178 
179         INIT_LIST_HEAD(&watch->rules);
180         atomic_set(&watch->count, 1);
181         watch->path = path;
182         watch->dev = (dev_t)-1;
183         watch->ino = (unsigned long)-1;
184 
185         return watch;
186 }
187 
188 /* Translate a watch string to kernel respresentation. */
189 int audit_to_watch(struct audit_krule *krule, char *path, int len, u32 op)
190 {
191         struct audit_watch *watch;
192 
193         if (!audit_watch_group)
194                 return -EOPNOTSUPP;
195 
196         if (path[0] != '/' || path[len-1] == '/' ||
197             krule->listnr != AUDIT_FILTER_EXIT ||
198             op != Audit_equal ||
199             krule->inode_f || krule->watch || krule->tree)
200                 return -EINVAL;
201 
202         watch = audit_init_watch(path);
203         if (IS_ERR(watch))
204                 return PTR_ERR(watch);
205 
206         audit_get_watch(watch);
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                 audit_log_format(ab, "auid=%u ses=%u op=",
244                                  audit_get_loginuid(current),
245                                  audit_get_sessionid(current));
246                 audit_log_string(ab, op);
247                 audit_log_format(ab, " path=");
248                 audit_log_untrustedstring(ab, w->path);
249                 audit_log_key(ab, r->filterkey);
250                 audit_log_format(ab, " list=%d res=1", r->listnr);
251                 audit_log_end(ab);
252         }
253 }
254 
255 /* Update inode info in audit rules based on filesystem event. */
256 static void audit_update_watch(struct audit_parent *parent,
257                                const char *dname, dev_t dev,
258                                unsigned long ino, unsigned invalidating)
259 {
260         struct audit_watch *owatch, *nwatch, *nextw;
261         struct audit_krule *r, *nextr;
262         struct audit_entry *oentry, *nentry;
263 
264         mutex_lock(&audit_filter_mutex);
265         /* Run all of the watches on this parent looking for the one that
266          * matches the given dname */
267         list_for_each_entry_safe(owatch, nextw, &parent->watches, wlist) {
268                 if (audit_compare_dname_path(dname, owatch->path, NULL))
269                         continue;
270 
271                 /* If the update involves invalidating rules, do the inode-based
272                  * filtering now, so we don't omit records. */
273                 if (invalidating && !audit_dummy_context())
274                         audit_filter_inodes(current, current->audit_context);
275 
276                 /* updating ino will likely change which audit_hash_list we
277                  * are on so we need a new watch for the new list */
278                 nwatch = audit_dupe_watch(owatch);
279                 if (IS_ERR(nwatch)) {
280                         mutex_unlock(&audit_filter_mutex);
281                         audit_panic("error updating watch, skipping");
282                         return;
283                 }
284                 nwatch->dev = dev;
285                 nwatch->ino = ino;
286 
287                 list_for_each_entry_safe(r, nextr, &owatch->rules, rlist) {
288 
289                         oentry = container_of(r, struct audit_entry, rule);
290                         list_del(&oentry->rule.rlist);
291                         list_del_rcu(&oentry->list);
292 
293                         nentry = audit_dupe_rule(&oentry->rule);
294                         if (IS_ERR(nentry)) {
295                                 list_del(&oentry->rule.list);
296                                 audit_panic("error updating watch, removing");
297                         } else {
298                                 int h = audit_hash_ino((u32)ino);
299 
300                                 /*
301                                  * nentry->rule.watch == oentry->rule.watch so
302                                  * we must drop that reference and set it to our
303                                  * new watch.
304                                  */
305                                 audit_put_watch(nentry->rule.watch);
306                                 audit_get_watch(nwatch);
307                                 nentry->rule.watch = nwatch;
308                                 list_add(&nentry->rule.rlist, &nwatch->rules);
309                                 list_add_rcu(&nentry->list, &audit_inode_hash[h]);
310                                 list_replace(&oentry->rule.list,
311                                              &nentry->rule.list);
312                         }
313 
314                         audit_watch_log_rule_change(r, owatch, "updated rules");
315 
316                         call_rcu(&oentry->rcu, audit_free_rule_rcu);
317                 }
318 
319                 audit_remove_watch(owatch);
320                 goto add_watch_to_parent; /* event applies to a single watch */
321         }
322         mutex_unlock(&audit_filter_mutex);
323         return;
324 
325 add_watch_to_parent:
326         list_add(&nwatch->wlist, &parent->watches);
327         mutex_unlock(&audit_filter_mutex);
328         return;
329 }
330 
331 /* Remove all watches & rules associated with a parent that is going away. */
332 static void audit_remove_parent_watches(struct audit_parent *parent)
333 {
334         struct audit_watch *w, *nextw;
335         struct audit_krule *r, *nextr;
336         struct audit_entry *e;
337 
338         mutex_lock(&audit_filter_mutex);
339         list_for_each_entry_safe(w, nextw, &parent->watches, wlist) {
340                 list_for_each_entry_safe(r, nextr, &w->rules, rlist) {
341                         e = container_of(r, struct audit_entry, rule);
342                         audit_watch_log_rule_change(r, w, "remove rule");
343                         list_del(&r->rlist);
344                         list_del(&r->list);
345                         list_del_rcu(&e->list);
346                         call_rcu(&e->rcu, audit_free_rule_rcu);
347                 }
348                 audit_remove_watch(w);
349         }
350         mutex_unlock(&audit_filter_mutex);
351 
352         fsnotify_destroy_mark(&parent->mark);
353 }
354 
355 /* Get path information necessary for adding watches. */
356 static int audit_get_nd(char *path, struct nameidata **ndp, struct nameidata **ndw)
357 {
358         struct nameidata *ndparent, *ndwatch;
359         int err;
360 
361         ndparent = kmalloc(sizeof(*ndparent), GFP_KERNEL);
362         if (unlikely(!ndparent))
363                 return -ENOMEM;
364 
365         ndwatch = kmalloc(sizeof(*ndwatch), GFP_KERNEL);
366         if (unlikely(!ndwatch)) {
367                 kfree(ndparent);
368                 return -ENOMEM;
369         }
370 
371         err = path_lookup(path, LOOKUP_PARENT, ndparent);
372         if (err) {
373                 kfree(ndparent);
374                 kfree(ndwatch);
375                 return err;
376         }
377 
378         err = path_lookup(path, 0, ndwatch);
379         if (err) {
380                 kfree(ndwatch);
381                 ndwatch = NULL;
382         }
383 
384         *ndp = ndparent;
385         *ndw = ndwatch;
386 
387         return 0;
388 }
389 
390 /* Release resources used for watch path information. */
391 static void audit_put_nd(struct nameidata *ndp, struct nameidata *ndw)
392 {
393         if (ndp) {
394                 path_put(&ndp->path);
395                 kfree(ndp);
396         }
397         if (ndw) {
398                 path_put(&ndw->path);
399                 kfree(ndw);
400         }
401 }
402 
403 /* Associate the given rule with an existing parent.
404  * Caller must hold audit_filter_mutex. */
405 static void audit_add_to_parent(struct audit_krule *krule,
406                                 struct audit_parent *parent)
407 {
408         struct audit_watch *w, *watch = krule->watch;
409         int watch_found = 0;
410 
411         BUG_ON(!mutex_is_locked(&audit_filter_mutex));
412 
413         list_for_each_entry(w, &parent->watches, wlist) {
414                 if (strcmp(watch->path, w->path))
415                         continue;
416 
417                 watch_found = 1;
418 
419                 /* put krule's and initial refs to temporary watch */
420                 audit_put_watch(watch);
421                 audit_put_watch(watch);
422 
423                 audit_get_watch(w);
424                 krule->watch = watch = w;
425                 break;
426         }
427 
428         if (!watch_found) {
429                 audit_get_parent(parent);
430                 watch->parent = parent;
431 
432                 list_add(&watch->wlist, &parent->watches);
433         }
434         list_add(&krule->rlist, &watch->rules);
435 }
436 
437 /* Find a matching watch entry, or add this one.
438  * Caller must hold audit_filter_mutex. */
439 int audit_add_watch(struct audit_krule *krule, struct list_head **list)
440 {
441         struct audit_watch *watch = krule->watch;
442         struct audit_parent *parent;
443         struct nameidata *ndp = NULL, *ndw = NULL;
444         int h, ret = 0;
445 
446         mutex_unlock(&audit_filter_mutex);
447 
448         /* Avoid calling path_lookup under audit_filter_mutex. */
449         ret = audit_get_nd(watch->path, &ndp, &ndw);
450         if (ret) {
451                 /* caller expects mutex locked */
452                 mutex_lock(&audit_filter_mutex);
453                 goto error;
454         }
455 
456         mutex_lock(&audit_filter_mutex);
457 
458         /* update watch filter fields */
459         if (ndw) {
460                 watch->dev = ndw->path.dentry->d_inode->i_sb->s_dev;
461                 watch->ino = ndw->path.dentry->d_inode->i_ino;
462         }
463 
464         /* either find an old parent or attach a new one */
465         parent = audit_find_parent(ndp->path.dentry->d_inode);
466         if (!parent) {
467                 parent = audit_init_parent(ndp);
468                 if (IS_ERR(parent)) {
469                         ret = PTR_ERR(parent);
470                         goto error;
471                 }
472         }
473 
474         audit_add_to_parent(krule, parent);
475 
476         /* match get in audit_find_parent or audit_init_parent */
477         audit_put_parent(parent);
478 
479         h = audit_hash_ino((u32)watch->ino);
480         *list = &audit_inode_hash[h];
481 error:
482         audit_put_nd(ndp, ndw);         /* NULL args OK */
483         return ret;
484 
485 }
486 
487 void audit_remove_watch_rule(struct audit_krule *krule)
488 {
489         struct audit_watch *watch = krule->watch;
490         struct audit_parent *parent = watch->parent;
491 
492         list_del(&krule->rlist);
493 
494         if (list_empty(&watch->rules)) {
495                 audit_remove_watch(watch);
496 
497                 if (list_empty(&parent->watches)) {
498                         audit_get_parent(parent);
499                         fsnotify_destroy_mark(&parent->mark);
500                         audit_put_parent(parent);
501                 }
502         }
503 }
504 
505 static bool audit_watch_should_send_event(struct fsnotify_group *group, struct inode *inode,
506                                           struct fsnotify_mark *inode_mark,
507                                           struct fsnotify_mark *vfsmount_mark,
508                                           __u32 mask, void *data, int data_type)
509 {
510        return true;
511 }
512 
513 /* Update watch data in audit rules based on fsnotify events. */
514 static int audit_watch_handle_event(struct fsnotify_group *group,
515                                     struct fsnotify_mark *inode_mark,
516                                     struct fsnotify_mark *vfsmount_mark,
517                                     struct fsnotify_event *event)
518 {
519         struct inode *inode;
520         __u32 mask = event->mask;
521         const char *dname = event->file_name;
522         struct audit_parent *parent;
523 
524         parent = container_of(inode_mark, struct audit_parent, mark);
525 
526         BUG_ON(group != audit_watch_group);
527 
528         switch (event->data_type) {
529         case (FSNOTIFY_EVENT_PATH):
530                 inode = event->path.dentry->d_inode;
531                 break;
532         case (FSNOTIFY_EVENT_INODE):
533                 inode = event->inode;
534                 break;
535         default:
536                 BUG();
537                 inode = NULL;
538                 break;
539         };
540 
541         if (mask & (FS_CREATE|FS_MOVED_TO) && inode)
542                 audit_update_watch(parent, dname, inode->i_sb->s_dev, inode->i_ino, 0);
543         else if (mask & (FS_DELETE|FS_MOVED_FROM))
544                 audit_update_watch(parent, dname, (dev_t)-1, (unsigned long)-1, 1);
545         else if (mask & (FS_DELETE_SELF|FS_UNMOUNT|FS_MOVE_SELF))
546                 audit_remove_parent_watches(parent);
547 
548         return 0;
549 }
550 
551 static const struct fsnotify_ops audit_watch_fsnotify_ops = {
552         .should_send_event =    audit_watch_should_send_event,
553         .handle_event =         audit_watch_handle_event,
554         .free_group_priv =      NULL,
555         .freeing_mark =         NULL,
556         .free_event_priv =      NULL,
557 };
558 
559 static int __init audit_watch_init(void)
560 {
561         audit_watch_group = fsnotify_alloc_group(&audit_watch_fsnotify_ops);
562         if (IS_ERR(audit_watch_group)) {
563                 audit_watch_group = NULL;
564                 audit_panic("cannot create audit fsnotify group");
565         }
566         return 0;
567 }
568 device_initcall(audit_watch_init);
569 

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