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 
   47 struct 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 
   57 struct 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. */
   63 static 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 
   69 static void audit_free_parent(struct audit_parent *parent)
   70 {
   71         WARN_ON(!list_empty(&parent->watches));
   72         kfree(parent);
   73 }
   74 
   75 static 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 
   83 static void audit_get_parent(struct audit_parent *parent)
   84 {
   85         if (likely(parent))
   86                 fsnotify_get_mark(&parent->mark);
   87 }
   88 
   89 static 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  */
   99 static 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 
  111 void audit_get_watch(struct audit_watch *watch)
  112 {
  113         atomic_inc(&watch->count);
  114 }
  115 
  116 void 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 
  126 static 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 
  134 char *audit_watch_path(struct audit_watch *watch)
  135 {
  136         return watch->path;
  137 }
  138 
  139 int 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. */
  147 static 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. */
  171 static 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. */
  189 int 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. */
  214 static 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 
  234 out:
  235         return new;
  236 }
  237 
  238 static 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. */
  258 static 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 
  328 add_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. */
  335 static 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. */
  359 static 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. */
  376 static 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. */
  410 int 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];
  445 error:
  446         path_put(&parent_path);
  447         return ret;
  448 }
  449 
  450 void 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 static bool audit_watch_should_send_event(struct fsnotify_group *group, struct inode *inode,
  469                                           struct fsnotify_mark *inode_mark,
  470                                           struct fsnotify_mark *vfsmount_mark,
  471                                           __u32 mask, void *data, int data_type)
  472 {
  473        return true;
  474 }
  475 
  476 /* Update watch data in audit rules based on fsnotify events. */
  477 static int audit_watch_handle_event(struct fsnotify_group *group,
  478                                     struct fsnotify_mark *inode_mark,
  479                                     struct fsnotify_mark *vfsmount_mark,
  480                                     struct fsnotify_event *event)
  481 {
  482         struct inode *inode;
  483         __u32 mask = event->mask;
  484         const char *dname = event->file_name;
  485         struct audit_parent *parent;
  486 
  487         parent = container_of(inode_mark, struct audit_parent, mark);
  488 
  489         BUG_ON(group != audit_watch_group);
  490 
  491         switch (event->data_type) {
  492         case (FSNOTIFY_EVENT_PATH):
  493                 inode = event->path.dentry->d_inode;
  494                 break;
  495         case (FSNOTIFY_EVENT_INODE):
  496                 inode = event->inode;
  497                 break;
  498         default:
  499                 BUG();
  500                 inode = NULL;
  501                 break;
  502         };
  503 
  504         if (mask & (FS_CREATE|FS_MOVED_TO) && inode)
  505                 audit_update_watch(parent, dname, inode->i_sb->s_dev, inode->i_ino, 0);
  506         else if (mask & (FS_DELETE|FS_MOVED_FROM))
  507                 audit_update_watch(parent, dname, (dev_t)-1, (unsigned long)-1, 1);
  508         else if (mask & (FS_DELETE_SELF|FS_UNMOUNT|FS_MOVE_SELF))
  509                 audit_remove_parent_watches(parent);
  510 
  511         return 0;
  512 }
  513 
  514 static const struct fsnotify_ops audit_watch_fsnotify_ops = {
  515         .should_send_event =    audit_watch_should_send_event,
  516         .handle_event =         audit_watch_handle_event,
  517         .free_group_priv =      NULL,
  518         .freeing_mark =         NULL,
  519         .free_event_priv =      NULL,
  520 };
  521 
  522 static int __init audit_watch_init(void)
  523 {
  524         audit_watch_group = fsnotify_alloc_group(&audit_watch_fsnotify_ops);
  525         if (IS_ERR(audit_watch_group)) {
  526                 audit_watch_group = NULL;
  527                 audit_panic("cannot create audit fsnotify group");
  528         }
  529         return 0;
  530 }
  531 device_initcall(audit_watch_init);
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FreeBSD/Linux Kernel Cross Reference sys/kernel/audit_watch.c

FreeBSD/Linux Kernel Cross Reference
sys/kernel/audit_watch.c
