projects/linux·blob v5.19 · refs

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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(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 exe_file = get_task_exe_file(tsk);
531 if (!exe_file)
532 return 0;
533 ino = file_inode(exe_file)->i_ino;
534 dev = file_inode(exe_file)->i_sb->s_dev;
535 fput(exe_file);
536 return audit_mark_compare(mark, ino, dev);
537}