summaryrefslogtreecommitdiffstats
path: root/kernel/audit_watch.c
blob: 8df43696f4ba6edff44f194398dd1baf59f4af92 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
/* audit_watch.c -- watching inodes
 *
 * Copyright 2003-2009 Red Hat, Inc.
 * Copyright 2005 Hewlett-Packard Development Company, L.P.
 * Copyright 2005 IBM Corporation
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <linux/kernel.h>
#include <linux/audit.h>
#include <linux/kthread.h>
#include <linux/mutex.h>
#include <linux/fs.h>
#include <linux/namei.h>
#include <linux/netlink.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/inotify.h>
#include <linux/security.h>
#include "audit.h"

/*
 * Reference counting:
 *
 * audit_parent: lifetime is from audit_init_parent() to receipt of an IN_IGNORED
 * 	event.  Each audit_watch holds a reference to its associated parent.
 *
 * audit_watch: if added to lists, lifetime is from audit_init_watch() to
 * 	audit_remove_watch().  Additionally, an audit_watch may exist
 * 	temporarily to assist in searching existing filter data.  Each
 * 	audit_krule holds a reference to its associated watch.
 */

struct audit_watch {
	atomic_t		count;	/* reference count */
	dev_t			dev;	/* associated superblock device */
	char			*path;	/* insertion path */
	unsigned long		ino;	/* associated inode number */
	struct audit_parent	*parent; /* associated parent */
	struct list_head	wlist;	/* entry in parent->watches list */
	struct list_head	rules;	/* associated rules */
};

struct audit_parent {
	struct list_head	ilist;	/* entry in inotify registration list */
	struct list_head	watches; /* associated watches */
	struct inotify_watch	wdata;	/* inotify watch data */
	unsigned		flags;	/* status flags */
};

/* Inotify handle. */
struct inotify_handle *audit_ih;

/*
 * audit_parent status flags:
 *
 * AUDIT_PARENT_INVALID - set anytime rules/watches are auto-removed due to
 * a filesystem event to ensure we're adding audit watches to a valid parent.
 * Technically not needed for IN_DELETE_SELF or IN_UNMOUNT events, as we cannot
 * receive them while we have nameidata, but must be used for IN_MOVE_SELF which
 * we can receive while holding nameidata.
 */
#define AUDIT_PARENT_INVALID	0x001

/* Inotify events we care about. */
#define AUDIT_IN_WATCH IN_MOVE|IN_CREATE|IN_DELETE|IN_DELETE_SELF|IN_MOVE_SELF

static void audit_free_parent(struct inotify_watch *i_watch)
{
	struct audit_parent *parent;

	parent = container_of(i_watch, struct audit_parent, wdata);
	WARN_ON(!list_empty(&parent->watches));
	kfree(parent);
}

void audit_get_watch(struct audit_watch *watch)
{
	atomic_inc(&watch->count);
}

void audit_put_watch(struct audit_watch *watch)
{
	if (atomic_dec_and_test(&watch->count)) {
		WARN_ON(watch->parent);
		WARN_ON(!list_empty(&watch->rules));
		kfree(watch->path);
		kfree(watch);
	}
}

void audit_remove_watch(struct audit_watch *watch)
{
	list_del(&watch->wlist);
	put_inotify_watch(&watch->parent->wdata);
	watch->parent = NULL;
	audit_put_watch(watch); /* match initial get */
}

char *audit_watch_path(struct audit_watch *watch)
{
	return watch->path;
}

struct list_head *audit_watch_rules(struct audit_watch *watch)
{
	return &watch->rules;
}

unsigned long audit_watch_inode(struct audit_watch *watch)
{
	return watch->ino;
}

dev_t audit_watch_dev(struct audit_watch *watch)
{
	return watch->dev;
}

/* Initialize a parent watch entry. */
static struct audit_parent *audit_init_parent(struct nameidata *ndp)
{
	struct audit_parent *parent;
	s32 wd;

	parent = kzalloc(sizeof(*parent), GFP_KERNEL);
	if (unlikely(!parent))
		return ERR_PTR(-ENOMEM);

	INIT_LIST_HEAD(&parent->watches);
	parent->flags = 0;

	inotify_init_watch(&parent->wdata);
	/* grab a ref so inotify watch hangs around until we take audit_filter_mutex */
	get_inotify_watch(&parent->wdata);
	wd = inotify_add_watch(audit_ih, &parent->wdata,
			       ndp->path.dentry->d_inode, AUDIT_IN_WATCH);
	if (wd < 0) {
		audit_free_parent(&parent->wdata);
		return ERR_PTR(wd);
	}

	return parent;
}

/* Initialize a watch entry. */
static struct audit_watch *audit_init_watch(char *path)
{
	struct audit_watch *watch;

	watch = kzalloc(sizeof(*watch), GFP_KERNEL);
	if (unlikely(!watch))
		return ERR_PTR(-ENOMEM);

	INIT_LIST_HEAD(&watch->rules);
	atomic_set(&watch->count, 1);
	watch->path = path;
	watch->dev = (dev_t)-1;
	watch->ino = (unsigned long)-1;

	return watch;
}

/* Translate a watch string to kernel respresentation. */
int audit_to_watch(struct audit_krule *krule, char *path, int len, u32 op)
{
	struct audit_watch *watch;

	if (!audit_ih)
		return -EOPNOTSUPP;

	if (path[0] != '/' || path[len-1] == '/' ||
	    krule->listnr != AUDIT_FILTER_EXIT ||
	    op != Audit_equal ||
	    krule->inode_f || krule->watch || krule->tree)
		return -EINVAL;

	watch = audit_init_watch(path);
	if (IS_ERR(watch))
		return PTR_ERR(watch);

	audit_get_watch(watch);
	krule->watch = watch;

	return 0;
}

/* Duplicate the given audit watch.  The new watch's rules list is initialized
 * to an empty list and wlist is undefined. */
static struct audit_watch *audit_dupe_watch(struct audit_watch *old)
{
	char *path;
	struct audit_watch *new;

	path = kstrdup(old->path, GFP_KERNEL);
	if (unlikely(!path))
		return ERR_PTR(-ENOMEM);

	new = audit_init_watch(path);
	if (IS_ERR(new)) {
		kfree(path);
		goto out;
	}

	new->dev = old->dev;
	new->ino = old->ino;
	get_inotify_watch(&old->parent->wdata);
	new->parent = old->parent;

out:
	return new;
}

static void audit_watch_log_rule_change(struct audit_krule *r, struct audit_watch *w, char *op)
{
	if (audit_enabled) {
		struct audit_buffer *ab;
		ab = audit_log_start(NULL, GFP_NOFS, AUDIT_CONFIG_CHANGE);
		audit_log_format(ab, "auid=%u ses=%u op=",
				 audit_get_loginuid(current),
				 audit_get_sessionid(current));
		audit_log_string(ab, op);
		audit_log_format(ab, " path=");
		audit_log_untrustedstring(ab, w->path);
		audit_log_key(ab, r->filterkey);
		audit_log_format(ab, " list=%d res=1", r->listnr);
		audit_log_end(ab);
	}
}

/* Update inode info in audit rules based on filesystem event. */
static void audit_update_watch(struct audit_parent *parent,
			       const char *dname, dev_t dev,
			       unsigned long ino, unsigned invalidating)
{
	struct audit_watch *owatch, *nwatch, *nextw;
	struct audit_krule *r, *nextr;
	struct audit_entry *oentry, *nentry;

	mutex_lock(&audit_filter_mutex);
	list_for_each_entry_safe(owatch, nextw, &parent->watches, wlist) {
		if (audit_compare_dname_path(dname, owatch->path, NULL))
			continue;

		/* If the update involves invalidating rules, do the inode-based
		 * filtering now, so we don't omit records. */
		if (invalidating && current->audit_context)
			audit_filter_inodes(current, current->audit_context);

		nwatch = audit_dupe_watch(owatch);
		if (IS_ERR(nwatch)) {
			mutex_unlock(&audit_filter_mutex);
			audit_panic("error updating watch, skipping");
			return;
		}
		nwatch->dev = dev;
		nwatch->ino = ino;

		list_for_each_entry_safe(r, nextr, &owatch->rules, rlist) {

			oentry = container_of(r, struct audit_entry, rule);
			list_del(&oentry->rule.rlist);
			list_del_rcu(&oentry->list);

			nentry = audit_dupe_rule(&oentry->rule, nwatch);
			if (IS_ERR(nentry)) {
				list_del(&oentry->rule.list);
				audit_panic("error updating watch, removing");
			} else {
				int h = audit_hash_ino((u32)ino);
				list_add(&nentry->rule.rlist, &nwatch->rules);
				list_add_rcu(&nentry->list, &audit_inode_hash[h]);
				list_replace(&oentry->rule.list,
					     &nentry->rule.list);
			}

			audit_watch_log_rule_change(r, owatch, "updated rules");

			call_rcu(&oentry->rcu, audit_free_rule_rcu);
		}

		audit_remove_watch(owatch);
		goto add_watch_to_parent; /* event applies to a single watch */
	}
	mutex_unlock(&audit_filter_mutex);
	return;

add_watch_to_parent:
	list_add(&nwatch->wlist, &parent->watches);
	mutex_unlock(&audit_filter_mutex);
	return;
}

/* Remove all watches & rules associated with a parent that is going away. */
static void audit_remove_parent_watches(struct audit_parent *parent)
{
	struct audit_watch *w, *nextw;
	struct audit_krule *r, *nextr;
	struct audit_entry *e;

	mutex_lock(&audit_filter_mutex);
	parent->flags |= AUDIT_PARENT_INVALID;
	list_for_each_entry_safe(w, nextw, &parent->watches, wlist) {
		list_for_each_entry_safe(r, nextr, &w->rules, rlist) {
			e = container_of(r, struct audit_entry, rule);
			audit_watch_log_rule_change(r, w, "remove rule");
			list_del(&r->rlist);
			list_del(&r->list);
			list_del_rcu(&e->list);
			call_rcu(&e->rcu, audit_free_rule_rcu);
		}
		audit_remove_watch(w);
	}
	mutex_unlock(&audit_filter_mutex);
}

/* Unregister inotify watches for parents on in_list.
 * Generates an IN_IGNORED event. */
void audit_inotify_unregister(struct list_head *in_list)
{
	struct audit_parent *p, *n;

	list_for_each_entry_safe(p, n, in_list, ilist) {
		list_del(&p->ilist);
		inotify_rm_watch(audit_ih, &p->wdata);
		/* the unpin matching the pin in audit_do_del_rule() */
		unpin_inotify_watch(&p->wdata);
	}
}

/* Get path information necessary for adding watches. */
static int audit_get_nd(char *path, struct nameidata **ndp, struct nameidata **ndw)
{
	struct nameidata *ndparent, *ndwatch;
	int err;

	ndparent = kmalloc(sizeof(*ndparent), GFP_KERNEL);
	if (unlikely(!ndparent))
		return -ENOMEM;

	ndwatch = kmalloc(sizeof(*ndwatch), GFP_KERNEL);
	if (unlikely(!ndwatch)) {
		kfree(ndparent);
		return -ENOMEM;
	}

	err = path_lookup(path, LOOKUP_PARENT, ndparent);
	if (err) {
		kfree(ndparent);
		kfree(ndwatch);
		return err;
	}

	err = path_lookup(path, 0, ndwatch);
	if (err) {
		kfree(ndwatch);
		ndwatch = NULL;
	}

	*ndp = ndparent;
	*ndw = ndwatch;

	return 0;
}

/* Release resources used for watch path information. */
static void audit_put_nd(struct nameidata *ndp, struct nameidata *ndw)
{
	if (ndp) {
		path_put(&ndp->path);
		kfree(ndp);
	}
	if (ndw) {
		path_put(&ndw->path);
		kfree(ndw);
	}
}

/* Associate the given rule with an existing parent inotify_watch.
 * Caller must hold audit_filter_mutex. */
static void audit_add_to_parent(struct audit_krule *krule,
				struct audit_parent *parent)
{
	struct audit_watch *w, *watch = krule->watch;
	int watch_found = 0;

	list_for_each_entry(w, &parent->watches, wlist) {
		if (strcmp(watch->path, w->path))
			continue;

		watch_found = 1;

		/* put krule's and initial refs to temporary watch */
		audit_put_watch(watch);
		audit_put_watch(watch);

		audit_get_watch(w);
		krule->watch = watch = w;
		break;
	}

	if (!watch_found) {
		get_inotify_watch(&parent->wdata);
		watch->parent = parent;

		list_add(&watch->wlist, &parent->watches);
	}
	list_add(&krule->rlist, &watch->rules);
}

/* Find a matching watch entry, or add this one.
 * Caller must hold audit_filter_mutex. */
int audit_add_watch(struct audit_krule *krule)
{
	struct audit_watch *watch = krule->watch;
	struct inotify_watch *i_watch;
	struct audit_parent *parent;
	struct nameidata *ndp = NULL, *ndw = NULL;
	int ret = 0;

	mutex_unlock(&audit_filter_mutex);

	/* Avoid calling path_lookup under audit_filter_mutex. */
	ret = audit_get_nd(watch->path, &ndp, &ndw);
	if (ret) {
		/* caller expects mutex locked */
		mutex_lock(&audit_filter_mutex);
		goto error;
	}

	/* update watch filter fields */
	if (ndw) {
		watch->dev = ndw->path.dentry->d_inode->i_sb->s_dev;
		watch->ino = ndw->path.dentry->d_inode->i_ino;
	}

	/* The audit_filter_mutex must not be held during inotify calls because
	 * we hold it during inotify event callback processing.  If an existing
	 * inotify watch is found, inotify_find_watch() grabs a reference before
	 * returning.
	 */
	if (inotify_find_watch(audit_ih, ndp->path.dentry->d_inode,
			       &i_watch) < 0) {
		parent = audit_init_parent(ndp);
		if (IS_ERR(parent)) {
			/* caller expects mutex locked */
			mutex_lock(&audit_filter_mutex);
			ret = PTR_ERR(parent);
			goto error;
		}
	} else
		parent = container_of(i_watch, struct audit_parent, wdata);

	mutex_lock(&audit_filter_mutex);

	/* parent was moved before we took audit_filter_mutex */
	if (parent->flags & AUDIT_PARENT_INVALID)
		ret = -ENOENT;
	else
		audit_add_to_parent(krule, parent);

	/* match get in audit_init_parent or inotify_find_watch */
	put_inotify_watch(&parent->wdata);

error:
	audit_put_nd(ndp, ndw);		/* NULL args OK */
	return ret;

}

void audit_remove_watch_rule(struct audit_krule *krule, struct list_head *list)
{
	struct audit_watch *watch = krule->watch;
	struct audit_parent *parent = watch->parent;

	list_del(&krule->rlist);

	if (list_empty(&watch->rules)) {
		audit_remove_watch(watch);

		if (list_empty(&parent->watches)) {
			/* Put parent on the inotify un-registration
			 * list.  Grab a reference before releasing
			 * audit_filter_mutex, to be released in
			 * audit_inotify_unregister().
			 * If filesystem is going away, just leave
			 * the sucker alone, eviction will take
			 * care of it. */
			if (pin_inotify_watch(&parent->wdata))
				list_add(&parent->ilist, list);
		}
	}
}

/* Update watch data in audit rules based on inotify events. */
static void audit_handle_ievent(struct inotify_watch *i_watch, u32 wd, u32 mask,
			 u32 cookie, const char *dname, struct inode *inode)
{
	struct audit_parent *parent;

	parent = container_of(i_watch, struct audit_parent, wdata);

	if (mask & (IN_CREATE|IN_MOVED_TO) && inode)
		audit_update_watch(parent, dname, inode->i_sb->s_dev,
				   inode->i_ino, 0);
	else if (mask & (IN_DELETE|IN_MOVED_FROM))
		audit_update_watch(parent, dname, (dev_t)-1, (unsigned long)-1, 1);
	/* inotify automatically removes the watch and sends IN_IGNORED */
	else if (mask & (IN_DELETE_SELF|IN_UNMOUNT))
		audit_remove_parent_watches(parent);
	/* inotify does not remove the watch, so remove it manually */
	else if(mask & IN_MOVE_SELF) {
		audit_remove_parent_watches(parent);
		inotify_remove_watch_locked(audit_ih, i_watch);
	} else if (mask & IN_IGNORED)
		put_inotify_watch(i_watch);
}

static const struct inotify_operations audit_inotify_ops = {
	.handle_event   = audit_handle_ievent,
	.destroy_watch  = audit_free_parent,
};

static int __init audit_watch_init(void)
{
	audit_ih = inotify_init(&audit_inotify_ops);
	if (IS_ERR(audit_ih))
		audit_panic("cannot initialize inotify handle");
	return 0;
}
subsys_initcall(audit_watch_init);
OpenPOWER on IntegriCloud