xref: /linux/kernel/audit_watch.c (revision b889fcf63cb62e7fdb7816565e28f44dbe4a76a5)
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 path *path)
148 {
149 	struct inode *inode = 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 				 from_kuid(&init_user_ns, 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,
269 					     AUDIT_NAME_FULL))
270 			continue;
271 
272 		/* If the update involves invalidating rules, do the inode-based
273 		 * filtering now, so we don't omit records. */
274 		if (invalidating && !audit_dummy_context())
275 			audit_filter_inodes(current, current->audit_context);
276 
277 		/* updating ino will likely change which audit_hash_list we
278 		 * are on so we need a new watch for the new list */
279 		nwatch = audit_dupe_watch(owatch);
280 		if (IS_ERR(nwatch)) {
281 			mutex_unlock(&audit_filter_mutex);
282 			audit_panic("error updating watch, skipping");
283 			return;
284 		}
285 		nwatch->dev = dev;
286 		nwatch->ino = ino;
287 
288 		list_for_each_entry_safe(r, nextr, &owatch->rules, rlist) {
289 
290 			oentry = container_of(r, struct audit_entry, rule);
291 			list_del(&oentry->rule.rlist);
292 			list_del_rcu(&oentry->list);
293 
294 			nentry = audit_dupe_rule(&oentry->rule);
295 			if (IS_ERR(nentry)) {
296 				list_del(&oentry->rule.list);
297 				audit_panic("error updating watch, removing");
298 			} else {
299 				int h = audit_hash_ino((u32)ino);
300 
301 				/*
302 				 * nentry->rule.watch == oentry->rule.watch so
303 				 * we must drop that reference and set it to our
304 				 * new watch.
305 				 */
306 				audit_put_watch(nentry->rule.watch);
307 				audit_get_watch(nwatch);
308 				nentry->rule.watch = nwatch;
309 				list_add(&nentry->rule.rlist, &nwatch->rules);
310 				list_add_rcu(&nentry->list, &audit_inode_hash[h]);
311 				list_replace(&oentry->rule.list,
312 					     &nentry->rule.list);
313 			}
314 
315 			audit_watch_log_rule_change(r, owatch, "updated rules");
316 
317 			call_rcu(&oentry->rcu, audit_free_rule_rcu);
318 		}
319 
320 		audit_remove_watch(owatch);
321 		goto add_watch_to_parent; /* event applies to a single watch */
322 	}
323 	mutex_unlock(&audit_filter_mutex);
324 	return;
325 
326 add_watch_to_parent:
327 	list_add(&nwatch->wlist, &parent->watches);
328 	mutex_unlock(&audit_filter_mutex);
329 	return;
330 }
331 
332 /* Remove all watches & rules associated with a parent that is going away. */
333 static void audit_remove_parent_watches(struct audit_parent *parent)
334 {
335 	struct audit_watch *w, *nextw;
336 	struct audit_krule *r, *nextr;
337 	struct audit_entry *e;
338 
339 	mutex_lock(&audit_filter_mutex);
340 	list_for_each_entry_safe(w, nextw, &parent->watches, wlist) {
341 		list_for_each_entry_safe(r, nextr, &w->rules, rlist) {
342 			e = container_of(r, struct audit_entry, rule);
343 			audit_watch_log_rule_change(r, w, "remove rule");
344 			list_del(&r->rlist);
345 			list_del(&r->list);
346 			list_del_rcu(&e->list);
347 			call_rcu(&e->rcu, audit_free_rule_rcu);
348 		}
349 		audit_remove_watch(w);
350 	}
351 	mutex_unlock(&audit_filter_mutex);
352 
353 	fsnotify_destroy_mark(&parent->mark);
354 }
355 
356 /* Get path information necessary for adding watches. */
357 static int audit_get_nd(struct audit_watch *watch, struct path *parent)
358 {
359 	struct dentry *d = kern_path_locked(watch->path, parent);
360 	if (IS_ERR(d))
361 		return PTR_ERR(d);
362 	mutex_unlock(&parent->dentry->d_inode->i_mutex);
363 	if (d->d_inode) {
364 		/* update watch filter fields */
365 		watch->dev = d->d_inode->i_sb->s_dev;
366 		watch->ino = d->d_inode->i_ino;
367 	}
368 	dput(d);
369 	return 0;
370 }
371 
372 /* Associate the given rule with an existing parent.
373  * Caller must hold audit_filter_mutex. */
374 static void audit_add_to_parent(struct audit_krule *krule,
375 				struct audit_parent *parent)
376 {
377 	struct audit_watch *w, *watch = krule->watch;
378 	int watch_found = 0;
379 
380 	BUG_ON(!mutex_is_locked(&audit_filter_mutex));
381 
382 	list_for_each_entry(w, &parent->watches, wlist) {
383 		if (strcmp(watch->path, w->path))
384 			continue;
385 
386 		watch_found = 1;
387 
388 		/* put krule's and initial refs to temporary watch */
389 		audit_put_watch(watch);
390 		audit_put_watch(watch);
391 
392 		audit_get_watch(w);
393 		krule->watch = watch = w;
394 		break;
395 	}
396 
397 	if (!watch_found) {
398 		audit_get_parent(parent);
399 		watch->parent = parent;
400 
401 		list_add(&watch->wlist, &parent->watches);
402 	}
403 	list_add(&krule->rlist, &watch->rules);
404 }
405 
406 /* Find a matching watch entry, or add this one.
407  * Caller must hold audit_filter_mutex. */
408 int audit_add_watch(struct audit_krule *krule, struct list_head **list)
409 {
410 	struct audit_watch *watch = krule->watch;
411 	struct audit_parent *parent;
412 	struct path parent_path;
413 	int h, ret = 0;
414 
415 	mutex_unlock(&audit_filter_mutex);
416 
417 	/* Avoid calling path_lookup under audit_filter_mutex. */
418 	ret = audit_get_nd(watch, &parent_path);
419 
420 	/* caller expects mutex locked */
421 	mutex_lock(&audit_filter_mutex);
422 
423 	if (ret)
424 		return ret;
425 
426 	/* either find an old parent or attach a new one */
427 	parent = audit_find_parent(parent_path.dentry->d_inode);
428 	if (!parent) {
429 		parent = audit_init_parent(&parent_path);
430 		if (IS_ERR(parent)) {
431 			ret = PTR_ERR(parent);
432 			goto error;
433 		}
434 	}
435 
436 	audit_add_to_parent(krule, parent);
437 
438 	/* match get in audit_find_parent or audit_init_parent */
439 	audit_put_parent(parent);
440 
441 	h = audit_hash_ino((u32)watch->ino);
442 	*list = &audit_inode_hash[h];
443 error:
444 	path_put(&parent_path);
445 	return ret;
446 }
447 
448 void audit_remove_watch_rule(struct audit_krule *krule)
449 {
450 	struct audit_watch *watch = krule->watch;
451 	struct audit_parent *parent = watch->parent;
452 
453 	list_del(&krule->rlist);
454 
455 	if (list_empty(&watch->rules)) {
456 		audit_remove_watch(watch);
457 
458 		if (list_empty(&parent->watches)) {
459 			audit_get_parent(parent);
460 			fsnotify_destroy_mark(&parent->mark);
461 			audit_put_parent(parent);
462 		}
463 	}
464 }
465 
466 static bool audit_watch_should_send_event(struct fsnotify_group *group, struct inode *inode,
467 					  struct fsnotify_mark *inode_mark,
468 					  struct fsnotify_mark *vfsmount_mark,
469 					  __u32 mask, void *data, int data_type)
470 {
471        return true;
472 }
473 
474 /* Update watch data in audit rules based on fsnotify events. */
475 static int audit_watch_handle_event(struct fsnotify_group *group,
476 				    struct fsnotify_mark *inode_mark,
477 				    struct fsnotify_mark *vfsmount_mark,
478 				    struct fsnotify_event *event)
479 {
480 	struct inode *inode;
481 	__u32 mask = event->mask;
482 	const char *dname = event->file_name;
483 	struct audit_parent *parent;
484 
485 	parent = container_of(inode_mark, struct audit_parent, mark);
486 
487 	BUG_ON(group != audit_watch_group);
488 
489 	switch (event->data_type) {
490 	case (FSNOTIFY_EVENT_PATH):
491 		inode = event->path.dentry->d_inode;
492 		break;
493 	case (FSNOTIFY_EVENT_INODE):
494 		inode = event->inode;
495 		break;
496 	default:
497 		BUG();
498 		inode = NULL;
499 		break;
500 	};
501 
502 	if (mask & (FS_CREATE|FS_MOVED_TO) && inode)
503 		audit_update_watch(parent, dname, inode->i_sb->s_dev, inode->i_ino, 0);
504 	else if (mask & (FS_DELETE|FS_MOVED_FROM))
505 		audit_update_watch(parent, dname, (dev_t)-1, (unsigned long)-1, 1);
506 	else if (mask & (FS_DELETE_SELF|FS_UNMOUNT|FS_MOVE_SELF))
507 		audit_remove_parent_watches(parent);
508 
509 	return 0;
510 }
511 
512 static const struct fsnotify_ops audit_watch_fsnotify_ops = {
513 	.should_send_event = 	audit_watch_should_send_event,
514 	.handle_event = 	audit_watch_handle_event,
515 	.free_group_priv = 	NULL,
516 	.freeing_mark = 	NULL,
517 	.free_event_priv = 	NULL,
518 };
519 
520 static int __init audit_watch_init(void)
521 {
522 	audit_watch_group = fsnotify_alloc_group(&audit_watch_fsnotify_ops);
523 	if (IS_ERR(audit_watch_group)) {
524 		audit_watch_group = NULL;
525 		audit_panic("cannot create audit fsnotify group");
526 	}
527 	return 0;
528 }
529 device_initcall(audit_watch_init);
530