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Linux/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=%s",
246                                  from_kuid(&init_user_ns, audit_get_loginuid(current)),
247                                  audit_get_sessionid(current), op);
248                 audit_log_format(ab, " path=");
249                 audit_log_untrustedstring(ab, w->path);
250                 audit_log_key(ab, r->filterkey);
251                 audit_log_format(ab, " list=%d res=1", r->listnr);
252                 audit_log_end(ab);
253         }
254 }
255 
256 /* Update inode info in audit rules based on filesystem event. */
257 static void audit_update_watch(struct audit_parent *parent,
258                                const char *dname, dev_t dev,
259                                unsigned long ino, unsigned invalidating)
260 {
261         struct audit_watch *owatch, *nwatch, *nextw;
262         struct audit_krule *r, *nextr;
263         struct audit_entry *oentry, *nentry;
264 
265         mutex_lock(&audit_filter_mutex);
266         /* Run all of the watches on this parent looking for the one that
267          * matches the given dname */
268         list_for_each_entry_safe(owatch, nextw, &parent->watches, wlist) {
269                 if (audit_compare_dname_path(dname, owatch->path,
270                                              AUDIT_NAME_FULL))
271                         continue;
272 
273                 /* If the update involves invalidating rules, do the inode-based
274                  * filtering now, so we don't omit records. */
275                 if (invalidating && !audit_dummy_context())
276                         audit_filter_inodes(current, current->audit_context);
277 
278                 /* updating ino will likely change which audit_hash_list we
279                  * are on so we need a new watch for the new list */
280                 nwatch = audit_dupe_watch(owatch);
281                 if (IS_ERR(nwatch)) {
282                         mutex_unlock(&audit_filter_mutex);
283                         audit_panic("error updating watch, skipping");
284                         return;
285                 }
286                 nwatch->dev = dev;
287                 nwatch->ino = ino;
288 
289                 list_for_each_entry_safe(r, nextr, &owatch->rules, rlist) {
290 
291                         oentry = container_of(r, struct audit_entry, rule);
292                         list_del(&oentry->rule.rlist);
293                         list_del_rcu(&oentry->list);
294 
295                         nentry = audit_dupe_rule(&oentry->rule);
296                         if (IS_ERR(nentry)) {
297                                 list_del(&oentry->rule.list);
298                                 audit_panic("error updating watch, removing");
299                         } else {
300                                 int h = audit_hash_ino((u32)ino);
301 
302                                 /*
303                                  * nentry->rule.watch == oentry->rule.watch so
304                                  * we must drop that reference and set it to our
305                                  * new watch.
306                                  */
307                                 audit_put_watch(nentry->rule.watch);
308                                 audit_get_watch(nwatch);
309                                 nentry->rule.watch = nwatch;
310                                 list_add(&nentry->rule.rlist, &nwatch->rules);
311                                 list_add_rcu(&nentry->list, &audit_inode_hash[h]);
312                                 list_replace(&oentry->rule.list,
313                                              &nentry->rule.list);
314                         }
315                         if (oentry->rule.exe)
316                                 audit_remove_mark(oentry->rule.exe);
317 
318                         audit_watch_log_rule_change(r, owatch, "updated_rules");
319 
320                         call_rcu(&oentry->rcu, audit_free_rule_rcu);
321                 }
322 
323                 audit_remove_watch(owatch);
324                 goto add_watch_to_parent; /* event applies to a single watch */
325         }
326         mutex_unlock(&audit_filter_mutex);
327         return;
328 
329 add_watch_to_parent:
330         list_add(&nwatch->wlist, &parent->watches);
331         mutex_unlock(&audit_filter_mutex);
332         return;
333 }
334 
335 /* Remove all watches & rules associated with a parent that is going away. */
336 static void audit_remove_parent_watches(struct audit_parent *parent)
337 {
338         struct audit_watch *w, *nextw;
339         struct audit_krule *r, *nextr;
340         struct audit_entry *e;
341 
342         mutex_lock(&audit_filter_mutex);
343         list_for_each_entry_safe(w, nextw, &parent->watches, wlist) {
344                 list_for_each_entry_safe(r, nextr, &w->rules, rlist) {
345                         e = container_of(r, struct audit_entry, rule);
346                         audit_watch_log_rule_change(r, w, "remove_rule");
347                         if (e->rule.exe)
348                                 audit_remove_mark(e->rule.exe);
349                         list_del(&r->rlist);
350                         list_del(&r->list);
351                         list_del_rcu(&e->list);
352                         call_rcu(&e->rcu, audit_free_rule_rcu);
353                 }
354                 audit_remove_watch(w);
355         }
356         mutex_unlock(&audit_filter_mutex);
357 
358         fsnotify_destroy_mark(&parent->mark, audit_watch_group);
359 }
360 
361 /* Get path information necessary for adding watches. */
362 static int audit_get_nd(struct audit_watch *watch, struct path *parent)
363 {
364         struct dentry *d = kern_path_locked(watch->path, parent);
365         if (IS_ERR(d))
366                 return PTR_ERR(d);
367         inode_unlock(d_backing_inode(parent->dentry));
368         if (d_is_positive(d)) {
369                 /* update watch filter fields */
370                 watch->dev = d->d_sb->s_dev;
371                 watch->ino = d_backing_inode(d)->i_ino;
372         }
373         dput(d);
374         return 0;
375 }
376 
377 /* Associate the given rule with an existing parent.
378  * Caller must hold audit_filter_mutex. */
379 static void audit_add_to_parent(struct audit_krule *krule,
380                                 struct audit_parent *parent)
381 {
382         struct audit_watch *w, *watch = krule->watch;
383         int watch_found = 0;
384 
385         BUG_ON(!mutex_is_locked(&audit_filter_mutex));
386 
387         list_for_each_entry(w, &parent->watches, wlist) {
388                 if (strcmp(watch->path, w->path))
389                         continue;
390 
391                 watch_found = 1;
392 
393                 /* put krule's ref to temporary watch */
394                 audit_put_watch(watch);
395 
396                 audit_get_watch(w);
397                 krule->watch = watch = w;
398 
399                 audit_put_parent(parent);
400                 break;
401         }
402 
403         if (!watch_found) {
404                 watch->parent = parent;
405 
406                 audit_get_watch(watch);
407                 list_add(&watch->wlist, &parent->watches);
408         }
409         list_add(&krule->rlist, &watch->rules);
410 }
411 
412 /* Find a matching watch entry, or add this one.
413  * Caller must hold audit_filter_mutex. */
414 int audit_add_watch(struct audit_krule *krule, struct list_head **list)
415 {
416         struct audit_watch *watch = krule->watch;
417         struct audit_parent *parent;
418         struct path parent_path;
419         int h, ret = 0;
420 
421         mutex_unlock(&audit_filter_mutex);
422 
423         /* Avoid calling path_lookup under audit_filter_mutex. */
424         ret = audit_get_nd(watch, &parent_path);
425 
426         /* caller expects mutex locked */
427         mutex_lock(&audit_filter_mutex);
428 
429         if (ret)
430                 return ret;
431 
432         /* either find an old parent or attach a new one */
433         parent = audit_find_parent(d_backing_inode(parent_path.dentry));
434         if (!parent) {
435                 parent = audit_init_parent(&parent_path);
436                 if (IS_ERR(parent)) {
437                         ret = PTR_ERR(parent);
438                         goto error;
439                 }
440         }
441 
442         audit_add_to_parent(krule, parent);
443 
444         h = audit_hash_ino((u32)watch->ino);
445         *list = &audit_inode_hash[h];
446 error:
447         path_put(&parent_path);
448         return ret;
449 }
450 
451 void audit_remove_watch_rule(struct audit_krule *krule)
452 {
453         struct audit_watch *watch = krule->watch;
454         struct audit_parent *parent = watch->parent;
455 
456         list_del(&krule->rlist);
457 
458         if (list_empty(&watch->rules)) {
459                 audit_remove_watch(watch);
460 
461                 if (list_empty(&parent->watches)) {
462                         audit_get_parent(parent);
463                         fsnotify_destroy_mark(&parent->mark, audit_watch_group);
464                         audit_put_parent(parent);
465                 }
466         }
467 }
468 
469 /* Update watch data in audit rules based on fsnotify events. */
470 static int audit_watch_handle_event(struct fsnotify_group *group,
471                                     struct inode *to_tell,
472                                     struct fsnotify_mark *inode_mark,
473                                     struct fsnotify_mark *vfsmount_mark,
474                                     u32 mask, const void *data, int data_type,
475                                     const unsigned char *dname, u32 cookie)
476 {
477         const struct inode *inode;
478         struct audit_parent *parent;
479 
480         parent = container_of(inode_mark, struct audit_parent, mark);
481 
482         BUG_ON(group != audit_watch_group);
483 
484         switch (data_type) {
485         case (FSNOTIFY_EVENT_PATH):
486                 inode = d_backing_inode(((const struct path *)data)->dentry);
487                 break;
488         case (FSNOTIFY_EVENT_INODE):
489                 inode = (const struct inode *)data;
490                 break;
491         default:
492                 BUG();
493                 inode = NULL;
494                 break;
495         };
496 
497         if (mask & (FS_CREATE|FS_MOVED_TO) && inode)
498                 audit_update_watch(parent, dname, inode->i_sb->s_dev, inode->i_ino, 0);
499         else if (mask & (FS_DELETE|FS_MOVED_FROM))
500                 audit_update_watch(parent, dname, AUDIT_DEV_UNSET, AUDIT_INO_UNSET, 1);
501         else if (mask & (FS_DELETE_SELF|FS_UNMOUNT|FS_MOVE_SELF))
502                 audit_remove_parent_watches(parent);
503 
504         return 0;
505 }
506 
507 static const struct fsnotify_ops audit_watch_fsnotify_ops = {
508         .handle_event =         audit_watch_handle_event,
509 };
510 
511 static int __init audit_watch_init(void)
512 {
513         audit_watch_group = fsnotify_alloc_group(&audit_watch_fsnotify_ops);
514         if (IS_ERR(audit_watch_group)) {
515                 audit_watch_group = NULL;
516                 audit_panic("cannot create audit fsnotify group");
517         }
518         return 0;
519 }
520 device_initcall(audit_watch_init);
521 
522 int audit_dupe_exe(struct audit_krule *new, struct audit_krule *old)
523 {
524         struct audit_fsnotify_mark *audit_mark;
525         char *pathname;
526 
527         pathname = kstrdup(audit_mark_path(old->exe), GFP_KERNEL);
528         if (!pathname)
529                 return -ENOMEM;
530 
531         audit_mark = audit_alloc_mark(new, pathname, strlen(pathname));
532         if (IS_ERR(audit_mark)) {
533                 kfree(pathname);
534                 return PTR_ERR(audit_mark);
535         }
536         new->exe = audit_mark;
537 
538         return 0;
539 }
540 
541 int audit_exe_compare(struct task_struct *tsk, struct audit_fsnotify_mark *mark)
542 {
543         struct file *exe_file;
544         unsigned long ino;
545         dev_t dev;
546 
547         exe_file = get_task_exe_file(tsk);
548         if (!exe_file)
549                 return 0;
550         ino = file_inode(exe_file)->i_ino;
551         dev = file_inode(exe_file)->i_sb->s_dev;
552         fput(exe_file);
553         return audit_mark_compare(mark, ino, dev);
554 }
555 

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