linux/kernel/audit_watch.c
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   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                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(struct audit_watch *watch, struct path *parent)
 357{
 358        struct dentry *d = kern_path_locked(watch->path, parent);
 359        if (IS_ERR(d))
 360                return PTR_ERR(d);
 361        mutex_unlock(&parent->dentry->d_inode->i_mutex);
 362        if (d->d_inode) {
 363                /* update watch filter fields */
 364                watch->dev = d->d_inode->i_sb->s_dev;
 365                watch->ino = d->d_inode->i_ino;
 366        }
 367        dput(d);
 368        return 0;
 369}
 370
 371/* Associate the given rule with an existing parent.
 372 * Caller must hold audit_filter_mutex. */
 373static void audit_add_to_parent(struct audit_krule *krule,
 374                                struct audit_parent *parent)
 375{
 376        struct audit_watch *w, *watch = krule->watch;
 377        int watch_found = 0;
 378
 379        BUG_ON(!mutex_is_locked(&audit_filter_mutex));
 380
 381        list_for_each_entry(w, &parent->watches, wlist) {
 382                if (strcmp(watch->path, w->path))
 383                        continue;
 384
 385                watch_found = 1;
 386
 387                /* put krule's and initial refs to temporary watch */
 388                audit_put_watch(watch);
 389                audit_put_watch(watch);
 390
 391                audit_get_watch(w);
 392                krule->watch = watch = w;
 393                break;
 394        }
 395
 396        if (!watch_found) {
 397                audit_get_parent(parent);
 398                watch->parent = parent;
 399
 400                list_add(&watch->wlist, &parent->watches);
 401        }
 402        list_add(&krule->rlist, &watch->rules);
 403}
 404
 405/* Find a matching watch entry, or add this one.
 406 * Caller must hold audit_filter_mutex. */
 407int audit_add_watch(struct audit_krule *krule, struct list_head **list)
 408{
 409        struct audit_watch *watch = krule->watch;
 410        struct audit_parent *parent;
 411        struct path parent_path;
 412        int h, ret = 0;
 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                return ret;
 424
 425        /* either find an old parent or attach a new one */
 426        parent = audit_find_parent(parent_path.dentry->d_inode);
 427        if (!parent) {
 428                parent = audit_init_parent(&parent_path);
 429                if (IS_ERR(parent)) {
 430                        ret = PTR_ERR(parent);
 431                        goto error;
 432                }
 433        }
 434
 435        audit_add_to_parent(krule, parent);
 436
 437        /* match get in audit_find_parent or audit_init_parent */
 438        audit_put_parent(parent);
 439
 440        h = audit_hash_ino((u32)watch->ino);
 441        *list = &audit_inode_hash[h];
 442error:
 443        path_put(&parent_path);
 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                audit_remove_watch(watch);
 456
 457                if (list_empty(&parent->watches)) {
 458                        audit_get_parent(parent);
 459                        fsnotify_destroy_mark(&parent->mark);
 460                        audit_put_parent(parent);
 461                }
 462        }
 463}
 464
 465static bool audit_watch_should_send_event(struct fsnotify_group *group, struct inode *inode,
 466                                          struct fsnotify_mark *inode_mark,
 467                                          struct fsnotify_mark *vfsmount_mark,
 468                                          __u32 mask, void *data, int data_type)
 469{
 470       return true;
 471}
 472
 473/* Update watch data in audit rules based on fsnotify events. */
 474static int audit_watch_handle_event(struct fsnotify_group *group,
 475                                    struct fsnotify_mark *inode_mark,
 476                                    struct fsnotify_mark *vfsmount_mark,
 477                                    struct fsnotify_event *event)
 478{
 479        struct inode *inode;
 480        __u32 mask = event->mask;
 481        const char *dname = event->file_name;
 482        struct audit_parent *parent;
 483
 484        parent = container_of(inode_mark, struct audit_parent, mark);
 485
 486        BUG_ON(group != audit_watch_group);
 487
 488        switch (event->data_type) {
 489        case (FSNOTIFY_EVENT_PATH):
 490                inode = event->path.dentry->d_inode;
 491                break;
 492        case (FSNOTIFY_EVENT_INODE):
 493                inode = event->inode;
 494                break;
 495        default:
 496                BUG();
 497                inode = NULL;
 498                break;
 499        };
 500
 501        if (mask & (FS_CREATE|FS_MOVED_TO) && inode)
 502                audit_update_watch(parent, dname, inode->i_sb->s_dev, inode->i_ino, 0);
 503        else if (mask & (FS_DELETE|FS_MOVED_FROM))
 504                audit_update_watch(parent, dname, (dev_t)-1, (unsigned long)-1, 1);
 505        else if (mask & (FS_DELETE_SELF|FS_UNMOUNT|FS_MOVE_SELF))
 506                audit_remove_parent_watches(parent);
 507
 508        return 0;
 509}
 510
 511static const struct fsnotify_ops audit_watch_fsnotify_ops = {
 512        .should_send_event =    audit_watch_should_send_event,
 513        .handle_event =         audit_watch_handle_event,
 514        .free_group_priv =      NULL,
 515        .freeing_mark =         NULL,
 516        .free_event_priv =      NULL,
 517};
 518
 519static int __init audit_watch_init(void)
 520{
 521        audit_watch_group = fsnotify_alloc_group(&audit_watch_fsnotify_ops);
 522        if (IS_ERR(audit_watch_group)) {
 523                audit_watch_group = NULL;
 524                audit_panic("cannot create audit fsnotify group");
 525        }
 526        return 0;
 527}
 528device_initcall(audit_watch_init);
 529
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