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. */
63struct 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
126void 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 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. */
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		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. */
256static 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
325add_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. */
332static 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. */
356static 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. */
391static 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. */
405static 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. */
439int 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];
481error:
482	audit_put_nd(ndp, ndw);		/* NULL args OK */
483	return ret;
484
485}
486
487void 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
505static 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. */
514static 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
551static 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
559static 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}
568device_initcall(audit_watch_init);
569