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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/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         if (audit_enabled) {
242                 struct audit_buffer *ab;
243                 ab = audit_log_start(NULL, GFP_NOFS, AUDIT_CONFIG_CHANGE);
244                 if (unlikely(!ab))
245                         return;
246                 audit_log_format(ab, "auid=%u ses=%u op=%s",
247                                  from_kuid(&init_user_ns, audit_get_loginuid(current)),
248                                  audit_get_sessionid(current), 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, 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         inode_unlock(d_backing_inode(parent->dentry));
369         if (d_is_positive(d)) {
370                 /* update watch filter fields */
371                 watch->dev = d->d_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                                     u32 mask, const void *data, int data_type,
486                                     const unsigned char *dname, u32 cookie,
487                                     struct fsnotify_iter_info *iter_info)
488 {
489         struct fsnotify_mark *inode_mark = fsnotify_iter_inode_mark(iter_info);
490         const 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(((const struct path *)data)->dentry);
500                 break;
501         case (FSNOTIFY_EVENT_INODE):
502                 inode = (const 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         .free_mark =            audit_watch_free_mark,
523 };
524 
525 static int __init audit_watch_init(void)
526 {
527         audit_watch_group = fsnotify_alloc_group(&audit_watch_fsnotify_ops);
528         if (IS_ERR(audit_watch_group)) {
529                 audit_watch_group = NULL;
530                 audit_panic("cannot create audit fsnotify group");
531         }
532         return 0;
533 }
534 device_initcall(audit_watch_init);
535 
536 int audit_dupe_exe(struct audit_krule *new, struct audit_krule *old)
537 {
538         struct audit_fsnotify_mark *audit_mark;
539         char *pathname;
540 
541         pathname = kstrdup(audit_mark_path(old->exe), GFP_KERNEL);
542         if (!pathname)
543                 return -ENOMEM;
544 
545         audit_mark = audit_alloc_mark(new, pathname, strlen(pathname));
546         if (IS_ERR(audit_mark)) {
547                 kfree(pathname);
548                 return PTR_ERR(audit_mark);
549         }
550         new->exe = audit_mark;
551 
552         return 0;
553 }
554 
555 int audit_exe_compare(struct task_struct *tsk, struct audit_fsnotify_mark *mark)
556 {
557         struct file *exe_file;
558         unsigned long ino;
559         dev_t dev;
560 
561         exe_file = get_task_exe_file(tsk);
562         if (!exe_file)
563                 return 0;
564         ino = file_inode(exe_file)->i_ino;
565         dev = file_inode(exe_file)->i_sb->s_dev;
566         fput(exe_file);
567         return audit_mark_compare(mark, ino, dev);
568 }
569 

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