1// SPDX-License-Identifier: GPL-2.0-or-later
2/* audit_watch.c -- watching inodes
3 *
4 * Copyright 2003-2009 Red Hat, Inc.
5 * Copyright 2005 Hewlett-Packard Development Company, L.P.
6 * Copyright 2005 IBM Corporation
7 */
8
9#include <linux/file.h>
10#include <linux/kernel.h>
11#include <linux/audit.h>
12#include <linux/kthread.h>
13#include <linux/mutex.h>
14#include <linux/fs.h>
15#include <linux/fsnotify_backend.h>
16#include <linux/namei.h>
17#include <linux/netlink.h>
18#include <linux/refcount.h>
19#include <linux/sched.h>
20#include <linux/slab.h>
21#include <linux/security.h>
22#include "audit.h"
23
24/*
25 * Reference counting:
26 *
27 * audit_parent: lifetime is from audit_init_parent() to receipt of an FS_IGNORED
28 * 	event.  Each audit_watch holds a reference to its associated parent.
29 *
30 * audit_watch: if added to lists, lifetime is from audit_init_watch() to
31 * 	audit_remove_watch().  Additionally, an audit_watch may exist
32 * 	temporarily to assist in searching existing filter data.  Each
33 * 	audit_krule holds a reference to its associated watch.
34 */
35
36struct audit_watch {
37	refcount_t		count;	/* reference count */
38	dev_t			dev;	/* associated superblock device */
39	char			*path;	/* insertion path */
40	unsigned long		ino;	/* associated inode number */
41	struct audit_parent	*parent; /* associated parent */
42	struct list_head	wlist;	/* entry in parent->watches list */
43	struct list_head	rules;	/* anchor for krule->rlist */
44};
45
46struct audit_parent {
47	struct list_head	watches; /* anchor for audit_watch->wlist */
48	struct fsnotify_mark mark; /* fsnotify mark on the inode */
49};
50
51/* fsnotify handle. */
52static struct fsnotify_group *audit_watch_group;
53
54/* fsnotify events we care about. */
55#define AUDIT_FS_WATCH (FS_MOVE | FS_CREATE | FS_DELETE | FS_DELETE_SELF |\
56			FS_MOVE_SELF | FS_UNMOUNT)
57
58static void audit_free_parent(struct audit_parent *parent)
59{
60	WARN_ON(!list_empty(&parent->watches));
61	kfree(parent);
62}
63
64static void audit_watch_free_mark(struct fsnotify_mark *entry)
65{
66	struct audit_parent *parent;
67
68	parent = container_of(entry, struct audit_parent, mark);
69	audit_free_parent(parent);
70}
71
72static void audit_get_parent(struct audit_parent *parent)
73{
74	if (likely(parent))
75		fsnotify_get_mark(&parent->mark);
76}
77
78static void audit_put_parent(struct audit_parent *parent)
79{
80	if (likely(parent))
81		fsnotify_put_mark(&parent->mark);
82}
83
84/*
85 * Find and return the audit_parent on the given inode.  If found a reference
86 * is taken on this parent.
87 */
88static inline struct audit_parent *audit_find_parent(struct inode *inode)
89{
90	struct audit_parent *parent = NULL;
91	struct fsnotify_mark *entry;
92
93	entry = fsnotify_find_mark(&inode->i_fsnotify_marks, audit_watch_group);
94	if (entry)
95		parent = container_of(entry, struct audit_parent, mark);
96
97	return parent;
98}
99
100void audit_get_watch(struct audit_watch *watch)
101{
102	refcount_inc(&watch->count);
103}
104
105void audit_put_watch(struct audit_watch *watch)
106{
107	if (refcount_dec_and_test(&watch->count)) {
108		WARN_ON(watch->parent);
109		WARN_ON(!list_empty(&watch->rules));
110		kfree(watch->path);
111		kfree(watch);
112	}
113}
114
115static void audit_remove_watch(struct audit_watch *watch)
116{
117	list_del(&watch->wlist);
118	audit_put_parent(watch->parent);
119	watch->parent = NULL;
120	audit_put_watch(watch); /* match initial get */
121}
122
123char *audit_watch_path(struct audit_watch *watch)
124{
125	return watch->path;
126}
127
128int audit_watch_compare(struct audit_watch *watch, unsigned long ino, dev_t dev)
129{
130	return (watch->ino != AUDIT_INO_UNSET) &&
131		(watch->ino == ino) &&
132		(watch->dev == dev);
133}
134
135/* Initialize a parent watch entry. */
136static struct audit_parent *audit_init_parent(const struct path *path)
137{
138	struct inode *inode = d_backing_inode(path->dentry);
139	struct audit_parent *parent;
140	int ret;
141
142	parent = kzalloc(sizeof(*parent), GFP_KERNEL);
143	if (unlikely(!parent))
144		return ERR_PTR(-ENOMEM);
145
146	INIT_LIST_HEAD(&parent->watches);
147
148	fsnotify_init_mark(&parent->mark, audit_watch_group);
149	parent->mark.mask = AUDIT_FS_WATCH;
150	ret = fsnotify_add_inode_mark(&parent->mark, inode, 0);
151	if (ret < 0) {
152		audit_free_parent(parent);
153		return ERR_PTR(ret);
154	}
155
156	return parent;
157}
158
159/* Initialize a watch entry. */
160static struct audit_watch *audit_init_watch(char *path)
161{
162	struct audit_watch *watch;
163
164	watch = kzalloc(sizeof(*watch), GFP_KERNEL);
165	if (unlikely(!watch))
166		return ERR_PTR(-ENOMEM);
167
168	INIT_LIST_HEAD(&watch->rules);
169	refcount_set(&watch->count, 1);
170	watch->path = path;
171	watch->dev = AUDIT_DEV_UNSET;
172	watch->ino = AUDIT_INO_UNSET;
173
174	return watch;
175}
176
177/* Translate a watch string to kernel representation. */
178int audit_to_watch(struct audit_krule *krule, char *path, int len, u32 op)
179{
180	struct audit_watch *watch;
181
182	if (!audit_watch_group)
183		return -EOPNOTSUPP;
184
185	if (path[0] != '/' || path[len-1] == '/' ||
186	    (krule->listnr != AUDIT_FILTER_EXIT &&
187	     krule->listnr != AUDIT_FILTER_URING_EXIT) ||
188	    op != Audit_equal ||
189	    krule->inode_f || krule->watch || krule->tree)
190		return -EINVAL;
191
192	watch = audit_init_watch(path);
193	if (IS_ERR(watch))
194		return PTR_ERR(watch);
195
196	krule->watch = watch;
197
198	return 0;
199}
200
201/* Duplicate the given audit watch.  The new watch's rules list is initialized
202 * to an empty list and wlist is undefined. */
203static struct audit_watch *audit_dupe_watch(struct audit_watch *old)
204{
205	char *path;
206	struct audit_watch *new;
207
208	path = kstrdup(old->path, GFP_KERNEL);
209	if (unlikely(!path))
210		return ERR_PTR(-ENOMEM);
211
212	new = audit_init_watch(path);
213	if (IS_ERR(new)) {
214		kfree(path);
215		goto out;
216	}
217
218	new->dev = old->dev;
219	new->ino = old->ino;
220	audit_get_parent(old->parent);
221	new->parent = old->parent;
222
223out:
224	return new;
225}
226
227static void audit_watch_log_rule_change(struct audit_krule *r, struct audit_watch *w, char *op)
228{
229	struct audit_buffer *ab;
230
231	if (!audit_enabled)
232		return;
233	ab = audit_log_start(audit_context(), GFP_NOFS, AUDIT_CONFIG_CHANGE);
234	if (!ab)
235		return;
236	audit_log_session_info(ab);
237	audit_log_format(ab, "op=%s path=", op);
238	audit_log_untrustedstring(ab, w->path);
239	audit_log_key(ab, r->filterkey);
240	audit_log_format(ab, " list=%d res=1", r->listnr);
241	audit_log_end(ab);
242}
243
244/* Update inode info in audit rules based on filesystem event. */
245static void audit_update_watch(struct audit_parent *parent,
246			       const struct qstr *dname, dev_t dev,
247			       unsigned long ino, unsigned invalidating)
248{
249	struct audit_watch *owatch, *nwatch, *nextw;
250	struct audit_krule *r, *nextr;
251	struct audit_entry *oentry, *nentry;
252
253	mutex_lock(&audit_filter_mutex);
254	/* Run all of the watches on this parent looking for the one that
255	 * matches the given dname */
256	list_for_each_entry_safe(owatch, nextw, &parent->watches, wlist) {
257		if (audit_compare_dname_path(dname, owatch->path,
258					     AUDIT_NAME_FULL))
259			continue;
260
261		/* If the update involves invalidating rules, do the inode-based
262		 * filtering now, so we don't omit records. */
263		if (invalidating && !audit_dummy_context())
264			audit_filter_inodes(current, audit_context());
265
266		/* updating ino will likely change which audit_hash_list we
267		 * are on so we need a new watch for the new list */
268		nwatch = audit_dupe_watch(owatch);
269		if (IS_ERR(nwatch)) {
270			mutex_unlock(&audit_filter_mutex);
271			audit_panic("error updating watch, skipping");
272			return;
273		}
274		nwatch->dev = dev;
275		nwatch->ino = ino;
276
277		list_for_each_entry_safe(r, nextr, &owatch->rules, rlist) {
278
279			oentry = container_of(r, struct audit_entry, rule);
280			list_del(&oentry->rule.rlist);
281			list_del_rcu(&oentry->list);
282
283			nentry = audit_dupe_rule(&oentry->rule);
284			if (IS_ERR(nentry)) {
285				list_del(&oentry->rule.list);
286				audit_panic("error updating watch, removing");
287			} else {
288				int h = audit_hash_ino((u32)ino);
289
290				/*
291				 * nentry->rule.watch == oentry->rule.watch so
292				 * we must drop that reference and set it to our
293				 * new watch.
294				 */
295				audit_put_watch(nentry->rule.watch);
296				audit_get_watch(nwatch);
297				nentry->rule.watch = nwatch;
298				list_add(&nentry->rule.rlist, &nwatch->rules);
299				list_add_rcu(&nentry->list, &audit_inode_hash[h]);
300				list_replace(&oentry->rule.list,
301					     &nentry->rule.list);
302			}
303			if (oentry->rule.exe)
304				audit_remove_mark(oentry->rule.exe);
305
306			call_rcu(&oentry->rcu, audit_free_rule_rcu);
307		}
308
309		audit_remove_watch(owatch);
310		goto add_watch_to_parent; /* event applies to a single watch */
311	}
312	mutex_unlock(&audit_filter_mutex);
313	return;
314
315add_watch_to_parent:
316	list_add(&nwatch->wlist, &parent->watches);
317	mutex_unlock(&audit_filter_mutex);
318	return;
319}
320
321/* Remove all watches & rules associated with a parent that is going away. */
322static void audit_remove_parent_watches(struct audit_parent *parent)
323{
324	struct audit_watch *w, *nextw;
325	struct audit_krule *r, *nextr;
326	struct audit_entry *e;
327
328	mutex_lock(&audit_filter_mutex);
329	list_for_each_entry_safe(w, nextw, &parent->watches, wlist) {
330		list_for_each_entry_safe(r, nextr, &w->rules, rlist) {
331			e = container_of(r, struct audit_entry, rule);
332			audit_watch_log_rule_change(r, w, "remove_rule");
333			if (e->rule.exe)
334				audit_remove_mark(e->rule.exe);
335			list_del(&r->rlist);
336			list_del(&r->list);
337			list_del_rcu(&e->list);
338			call_rcu(&e->rcu, audit_free_rule_rcu);
339		}
340		audit_remove_watch(w);
341	}
342	mutex_unlock(&audit_filter_mutex);
343
344	fsnotify_destroy_mark(&parent->mark, audit_watch_group);
345}
346
347/* Get path information necessary for adding watches. */
348static int audit_get_nd(struct audit_watch *watch, struct path *parent)
349{
350	struct dentry *d = kern_path_locked(watch->path, parent);
351	if (IS_ERR(d))
352		return PTR_ERR(d);
353	if (d_is_positive(d)) {
354		/* update watch filter fields */
355		watch->dev = d->d_sb->s_dev;
356		watch->ino = d_backing_inode(d)->i_ino;
357	}
358	inode_unlock(d_backing_inode(parent->dentry));
359	dput(d);
360	return 0;
361}
362
363/* Associate the given rule with an existing parent.
364 * Caller must hold audit_filter_mutex. */
365static void audit_add_to_parent(struct audit_krule *krule,
366				struct audit_parent *parent)
367{
368	struct audit_watch *w, *watch = krule->watch;
369	int watch_found = 0;
370
371	BUG_ON(!mutex_is_locked(&audit_filter_mutex));
372
373	list_for_each_entry(w, &parent->watches, wlist) {
374		if (strcmp(watch->path, w->path))
375			continue;
376
377		watch_found = 1;
378
379		/* put krule's ref to temporary watch */
380		audit_put_watch(watch);
381
382		audit_get_watch(w);
383		krule->watch = watch = w;
384
385		audit_put_parent(parent);
386		break;
387	}
388
389	if (!watch_found) {
390		watch->parent = parent;
391
392		audit_get_watch(watch);
393		list_add(&watch->wlist, &parent->watches);
394	}
395	list_add(&krule->rlist, &watch->rules);
396}
397
398/* Find a matching watch entry, or add this one.
399 * Caller must hold audit_filter_mutex. */
400int audit_add_watch(struct audit_krule *krule, struct list_head **list)
401{
402	struct audit_watch *watch = krule->watch;
403	struct audit_parent *parent;
404	struct path parent_path;
405	int h, ret = 0;
406
407	/*
408	 * When we will be calling audit_add_to_parent, krule->watch might have
409	 * been updated and watch might have been freed.
410	 * So we need to keep a reference of watch.
411	 */
412	audit_get_watch(watch);
413
414	mutex_unlock(&audit_filter_mutex);
415
416	/* Avoid calling path_lookup under audit_filter_mutex. */
417	ret = audit_get_nd(watch, &parent_path);
418
419	/* caller expects mutex locked */
420	mutex_lock(&audit_filter_mutex);
421
422	if (ret) {
423		audit_put_watch(watch);
424		return ret;
425	}
426
427	/* either find an old parent or attach a new one */
428	parent = audit_find_parent(d_backing_inode(parent_path.dentry));
429	if (!parent) {
430		parent = audit_init_parent(&parent_path);
431		if (IS_ERR(parent)) {
432			ret = PTR_ERR(parent);
433			goto error;
434		}
435	}
436
437	audit_add_to_parent(krule, parent);
438
439	h = audit_hash_ino((u32)watch->ino);
440	*list = &audit_inode_hash[h];
441error:
442	path_put(&parent_path);
443	audit_put_watch(watch);
444	return ret;
445}
446
447void audit_remove_watch_rule(struct audit_krule *krule)
448{
449	struct audit_watch *watch = krule->watch;
450	struct audit_parent *parent = watch->parent;
451
452	list_del(&krule->rlist);
453
454	if (list_empty(&watch->rules)) {
455		/*
456		 * audit_remove_watch() drops our reference to 'parent' which
457		 * can get freed. Grab our own reference to be safe.
458		 */
459		audit_get_parent(parent);
460		audit_remove_watch(watch);
461		if (list_empty(&parent->watches))
462			fsnotify_destroy_mark(&parent->mark, audit_watch_group);
463		audit_put_parent(parent);
464	}
465}
466
467/* Update watch data in audit rules based on fsnotify events. */
468static int audit_watch_handle_event(struct fsnotify_mark *inode_mark, u32 mask,
469				    struct inode *inode, struct inode *dir,
470				    const struct qstr *dname, u32 cookie)
471{
472	struct audit_parent *parent;
473
474	parent = container_of(inode_mark, struct audit_parent, mark);
475
476	if (WARN_ON_ONCE(inode_mark->group != audit_watch_group))
477		return 0;
478
479	if (mask & (FS_CREATE|FS_MOVED_TO) && inode)
480		audit_update_watch(parent, dname, inode->i_sb->s_dev, inode->i_ino, 0);
481	else if (mask & (FS_DELETE|FS_MOVED_FROM))
482		audit_update_watch(parent, dname, AUDIT_DEV_UNSET, AUDIT_INO_UNSET, 1);
483	else if (mask & (FS_DELETE_SELF|FS_UNMOUNT|FS_MOVE_SELF))
484		audit_remove_parent_watches(parent);
485
486	return 0;
487}
488
489static const struct fsnotify_ops audit_watch_fsnotify_ops = {
490	.handle_inode_event =	audit_watch_handle_event,
491	.free_mark =		audit_watch_free_mark,
492};
493
494static int __init audit_watch_init(void)
495{
496	audit_watch_group = fsnotify_alloc_group(&audit_watch_fsnotify_ops, 0);
497	if (IS_ERR(audit_watch_group)) {
498		audit_watch_group = NULL;
499		audit_panic("cannot create audit fsnotify group");
500	}
501	return 0;
502}
503device_initcall(audit_watch_init);
504
505int audit_dupe_exe(struct audit_krule *new, struct audit_krule *old)
506{
507	struct audit_fsnotify_mark *audit_mark;
508	char *pathname;
509
510	pathname = kstrdup(audit_mark_path(old->exe), GFP_KERNEL);
511	if (!pathname)
512		return -ENOMEM;
513
514	audit_mark = audit_alloc_mark(new, pathname, strlen(pathname));
515	if (IS_ERR(audit_mark)) {
516		kfree(pathname);
517		return PTR_ERR(audit_mark);
518	}
519	new->exe = audit_mark;
520
521	return 0;
522}
523
524int audit_exe_compare(struct task_struct *tsk, struct audit_fsnotify_mark *mark)
525{
526	struct file *exe_file;
527	unsigned long ino;
528	dev_t dev;
529
530	/* only do exe filtering if we are recording @current events/records */
531	if (tsk != current)
532		return 0;
533
534	if (!current->mm)
535		return 0;
536	exe_file = get_mm_exe_file(current->mm);
537	if (!exe_file)
538		return 0;
539	ino = file_inode(exe_file)->i_ino;
540	dev = file_inode(exe_file)->i_sb->s_dev;
541	fput(exe_file);
542
543	return audit_mark_compare(mark, ino, dev);
544}
545