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
47struct 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
57struct 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. */
63static 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
69static void audit_free_parent(struct audit_parent *parent)
70{
71	WARN_ON(!list_empty(&parent->watches));
72	kfree(parent);
73}
74
75static 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
83static void audit_get_parent(struct audit_parent *parent)
84{
85	if (likely(parent))
86		fsnotify_get_mark(&parent->mark);
87}
88
89static 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 */
99static 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
111void audit_get_watch(struct audit_watch *watch)
112{
113	atomic_inc(&watch->count);
114}
115
116void 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
126static 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
134char *audit_watch_path(struct audit_watch *watch)
135{
136	return watch->path;
137}
138
139int 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. */
147static struct audit_parent *audit_init_parent(struct path *path)
148{
149	struct inode *inode = d_backing_inode(path->dentry);
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. */
171static 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. */
189int 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. */
214static 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
234out:
235	return new;
236}
237
238static 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=",
246				 from_kuid(&init_user_ns, audit_get_loginuid(current)),
247				 audit_get_sessionid(current));
248		audit_log_string(ab, 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. */
258static 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, 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
317			audit_watch_log_rule_change(r, owatch, "updated_rules");
318
319			call_rcu(&oentry->rcu, audit_free_rule_rcu);
320		}
321
322		audit_remove_watch(owatch);
323		goto add_watch_to_parent; /* event applies to a single watch */
324	}
325	mutex_unlock(&audit_filter_mutex);
326	return;
327
328add_watch_to_parent:
329	list_add(&nwatch->wlist, &parent->watches);
330	mutex_unlock(&audit_filter_mutex);
331	return;
332}
333
334/* Remove all watches & rules associated with a parent that is going away. */
335static void audit_remove_parent_watches(struct audit_parent *parent)
336{
337	struct audit_watch *w, *nextw;
338	struct audit_krule *r, *nextr;
339	struct audit_entry *e;
340
341	mutex_lock(&audit_filter_mutex);
342	list_for_each_entry_safe(w, nextw, &parent->watches, wlist) {
343		list_for_each_entry_safe(r, nextr, &w->rules, rlist) {
344			e = container_of(r, struct audit_entry, rule);
345			audit_watch_log_rule_change(r, w, "remove_rule");
346			list_del(&r->rlist);
347			list_del(&r->list);
348			list_del_rcu(&e->list);
349			call_rcu(&e->rcu, audit_free_rule_rcu);
350		}
351		audit_remove_watch(w);
352	}
353	mutex_unlock(&audit_filter_mutex);
354
355	fsnotify_destroy_mark(&parent->mark, audit_watch_group);
356}
357
358/* Get path information necessary for adding watches. */
359static int audit_get_nd(struct audit_watch *watch, struct path *parent)
360{
361	struct dentry *d = kern_path_locked(watch->path, parent);
362	if (IS_ERR(d))
363		return PTR_ERR(d);
364	mutex_unlock(&d_backing_inode(parent->dentry)->i_mutex);
365	if (d_is_positive(d)) {
366		/* update watch filter fields */
367		watch->dev = d_backing_inode(d)->i_sb->s_dev;
368		watch->ino = d_backing_inode(d)->i_ino;
369	}
370	dput(d);
371	return 0;
372}
373
374/* Associate the given rule with an existing parent.
375 * Caller must hold audit_filter_mutex. */
376static void audit_add_to_parent(struct audit_krule *krule,
377				struct audit_parent *parent)
378{
379	struct audit_watch *w, *watch = krule->watch;
380	int watch_found = 0;
381
382	BUG_ON(!mutex_is_locked(&audit_filter_mutex));
383
384	list_for_each_entry(w, &parent->watches, wlist) {
385		if (strcmp(watch->path, w->path))
386			continue;
387
388		watch_found = 1;
389
390		/* put krule's and initial refs to temporary watch */
391		audit_put_watch(watch);
392		audit_put_watch(watch);
393
394		audit_get_watch(w);
395		krule->watch = watch = w;
396		break;
397	}
398
399	if (!watch_found) {
400		audit_get_parent(parent);
401		watch->parent = parent;
402
403		list_add(&watch->wlist, &parent->watches);
404	}
405	list_add(&krule->rlist, &watch->rules);
406}
407
408/* Find a matching watch entry, or add this one.
409 * Caller must hold audit_filter_mutex. */
410int audit_add_watch(struct audit_krule *krule, struct list_head **list)
411{
412	struct audit_watch *watch = krule->watch;
413	struct audit_parent *parent;
414	struct path parent_path;
415	int h, ret = 0;
416
417	mutex_unlock(&audit_filter_mutex);
418
419	/* Avoid calling path_lookup under audit_filter_mutex. */
420	ret = audit_get_nd(watch, &parent_path);
421
422	/* caller expects mutex locked */
423	mutex_lock(&audit_filter_mutex);
424
425	if (ret)
426		return ret;
427
428	/* either find an old parent or attach a new one */
429	parent = audit_find_parent(d_backing_inode(parent_path.dentry));
430	if (!parent) {
431		parent = audit_init_parent(&parent_path);
432		if (IS_ERR(parent)) {
433			ret = PTR_ERR(parent);
434			goto error;
435		}
436	}
437
438	audit_add_to_parent(krule, parent);
439
440	/* match get in audit_find_parent or audit_init_parent */
441	audit_put_parent(parent);
442
443	h = audit_hash_ino((u32)watch->ino);
444	*list = &audit_inode_hash[h];
445error:
446	path_put(&parent_path);
447	return ret;
448}
449
450void audit_remove_watch_rule(struct audit_krule *krule)
451{
452	struct audit_watch *watch = krule->watch;
453	struct audit_parent *parent = watch->parent;
454
455	list_del(&krule->rlist);
456
457	if (list_empty(&watch->rules)) {
458		audit_remove_watch(watch);
459
460		if (list_empty(&parent->watches)) {
461			audit_get_parent(parent);
462			fsnotify_destroy_mark(&parent->mark, audit_watch_group);
463			audit_put_parent(parent);
464		}
465	}
466}
467
468/* Update watch data in audit rules based on fsnotify events. */
469static int audit_watch_handle_event(struct fsnotify_group *group,
470				    struct inode *to_tell,
471				    struct fsnotify_mark *inode_mark,
472				    struct fsnotify_mark *vfsmount_mark,
473				    u32 mask, void *data, int data_type,
474				    const unsigned char *dname, u32 cookie)
475{
476	struct inode *inode;
477	struct audit_parent *parent;
478
479	parent = container_of(inode_mark, struct audit_parent, mark);
480
481	BUG_ON(group != audit_watch_group);
482
483	switch (data_type) {
484	case (FSNOTIFY_EVENT_PATH):
485		inode = d_backing_inode(((struct path *)data)->dentry);
486		break;
487	case (FSNOTIFY_EVENT_INODE):
488		inode = (struct inode *)data;
489		break;
490	default:
491		BUG();
492		inode = NULL;
493		break;
494	};
495
496	if (mask & (FS_CREATE|FS_MOVED_TO) && inode)
497		audit_update_watch(parent, dname, inode->i_sb->s_dev, inode->i_ino, 0);
498	else if (mask & (FS_DELETE|FS_MOVED_FROM))
499		audit_update_watch(parent, dname, (dev_t)-1, (unsigned long)-1, 1);
500	else if (mask & (FS_DELETE_SELF|FS_UNMOUNT|FS_MOVE_SELF))
501		audit_remove_parent_watches(parent);
502
503	return 0;
504}
505
506static const struct fsnotify_ops audit_watch_fsnotify_ops = {
507	.handle_event = 	audit_watch_handle_event,
508};
509
510static int __init audit_watch_init(void)
511{
512	audit_watch_group = fsnotify_alloc_group(&audit_watch_fsnotify_ops);
513	if (IS_ERR(audit_watch_group)) {
514		audit_watch_group = NULL;
515		audit_panic("cannot create audit fsnotify group");
516	}
517	return 0;
518}
519device_initcall(audit_watch_init);
520