Root/kernel/audit_watch.c

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 = 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        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(&parent->dentry->d_inode->i_mutex);
365    if (d->d_inode) {
366        /* update watch filter fields */
367        watch->dev = d->d_inode->i_sb->s_dev;
368        watch->ino = d->d_inode->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(parent_path.dentry->d_inode);
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 = ((struct path *)data)->dentry->d_inode;
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

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