/* audit_watch.c -- watching inodes
   *
   * Copyright 2003-2009 Red Hat, Inc.
   * Copyright 2005 Hewlett-Packard Development Company, L.P.
   * Copyright 2005 IBM Corporation
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   */
  
  #include <linux/kernel.h>
  #include <linux/audit.h>
  #include <linux/kthread.h>
  #include <linux/mutex.h>
  #include <linux/fs.h>

  #include <linux/fsnotify_backend.h>

  #include <linux/namei.h>
  #include <linux/netlink.h>
  #include <linux/sched.h>

  #include <linux/slab.h>

  #include <linux/security.h>
  #include "audit.h"
  
  /*
   * Reference counting:
   *

   * audit_parent: lifetime is from audit_init_parent() to receipt of an FS_IGNORED

   * 	event.  Each audit_watch holds a reference to its associated parent.
   *
   * audit_watch: if added to lists, lifetime is from audit_init_watch() to
   * 	audit_remove_watch().  Additionally, an audit_watch may exist
   * 	temporarily to assist in searching existing filter data.  Each
   * 	audit_krule holds a reference to its associated watch.
   */
  
  struct audit_watch {
  	atomic_t		count;	/* reference count */

  	dev_t			dev;	/* associated superblock device */

  	char			*path;	/* insertion path */

  	unsigned long		ino;	/* associated inode number */
  	struct audit_parent	*parent; /* associated parent */
  	struct list_head	wlist;	/* entry in parent->watches list */

  	struct list_head	rules;	/* anchor for krule->rlist */

  };
  
  struct audit_parent {

  	struct list_head	watches; /* anchor for audit_watch->wlist */

  	struct fsnotify_mark mark; /* fsnotify mark on the inode */

  };

  /* fsnotify handle. */

  static struct fsnotify_group *audit_watch_group;

  /* fsnotify events we care about. */
  #define AUDIT_FS_WATCH (FS_MOVE | FS_CREATE | FS_DELETE | FS_DELETE_SELF |\
  			FS_MOVE_SELF | FS_EVENT_ON_CHILD)

  static void audit_free_parent(struct audit_parent *parent)
  {
  	WARN_ON(!list_empty(&parent->watches));
  	kfree(parent);
  }

  static void audit_watch_free_mark(struct fsnotify_mark *entry)

  {
  	struct audit_parent *parent;

  	parent = container_of(entry, struct audit_parent, mark);

  	audit_free_parent(parent);

  }

  static void audit_get_parent(struct audit_parent *parent)
  {
  	if (likely(parent))
  		fsnotify_get_mark(&parent->mark);
  }
  
  static void audit_put_parent(struct audit_parent *parent)
  {
  	if (likely(parent))
  		fsnotify_put_mark(&parent->mark);
  }
  
  /*
   * Find and return the audit_parent on the given inode.  If found a reference
   * is taken on this parent.
   */
  static inline struct audit_parent *audit_find_parent(struct inode *inode)
  {
  	struct audit_parent *parent = NULL;

  	struct fsnotify_mark *entry;

  	entry = fsnotify_find_inode_mark(audit_watch_group, inode);

  	if (entry)
  		parent = container_of(entry, struct audit_parent, mark);
  
  	return parent;
  }

  void audit_get_watch(struct audit_watch *watch)
  {
  	atomic_inc(&watch->count);
  }
  
  void audit_put_watch(struct audit_watch *watch)
  {
  	if (atomic_dec_and_test(&watch->count)) {
  		WARN_ON(watch->parent);
  		WARN_ON(!list_empty(&watch->rules));
  		kfree(watch->path);
  		kfree(watch);
  	}
  }

  static void audit_remove_watch(struct audit_watch *watch)

  {
  	list_del(&watch->wlist);

  	audit_put_parent(watch->parent);

  	watch->parent = NULL;
  	audit_put_watch(watch); /* match initial get */
  }
  
  char *audit_watch_path(struct audit_watch *watch)
  {
  	return watch->path;
  }

  int audit_watch_compare(struct audit_watch *watch, unsigned long ino, dev_t dev)

  {

  	return (watch->ino != (unsigned long)-1) &&
  		(watch->ino == ino) &&
  		(watch->dev == dev);

  }
  
  /* Initialize a parent watch entry. */

  static struct audit_parent *audit_init_parent(struct path *path)

  {

  	struct inode *inode = path->dentry->d_inode;

  	struct audit_parent *parent;

  	int ret;

  
  	parent = kzalloc(sizeof(*parent), GFP_KERNEL);
  	if (unlikely(!parent))
  		return ERR_PTR(-ENOMEM);
  
  	INIT_LIST_HEAD(&parent->watches);

  	fsnotify_init_mark(&parent->mark, audit_watch_free_mark);
  	parent->mark.mask = AUDIT_FS_WATCH;

  	ret = fsnotify_add_mark(&parent->mark, audit_watch_group, inode, NULL, 0);

  	if (ret < 0) {

  		audit_free_parent(parent);

  		return ERR_PTR(ret);

  	}
  
  	return parent;
  }
  
  /* Initialize a watch entry. */
  static struct audit_watch *audit_init_watch(char *path)
  {
  	struct audit_watch *watch;
  
  	watch = kzalloc(sizeof(*watch), GFP_KERNEL);
  	if (unlikely(!watch))
  		return ERR_PTR(-ENOMEM);
  
  	INIT_LIST_HEAD(&watch->rules);
  	atomic_set(&watch->count, 1);
  	watch->path = path;
  	watch->dev = (dev_t)-1;
  	watch->ino = (unsigned long)-1;
  
  	return watch;
  }
  
  /* Translate a watch string to kernel respresentation. */
  int audit_to_watch(struct audit_krule *krule, char *path, int len, u32 op)
  {
  	struct audit_watch *watch;

  	if (!audit_watch_group)

  		return -EOPNOTSUPP;
  
  	if (path[0] != '/' || path[len-1] == '/' ||
  	    krule->listnr != AUDIT_FILTER_EXIT ||
  	    op != Audit_equal ||
  	    krule->inode_f || krule->watch || krule->tree)
  		return -EINVAL;
  
  	watch = audit_init_watch(path);
  	if (IS_ERR(watch))
  		return PTR_ERR(watch);
  
  	audit_get_watch(watch);
  	krule->watch = watch;
  
  	return 0;
  }
  
  /* Duplicate the given audit watch.  The new watch's rules list is initialized
   * to an empty list and wlist is undefined. */
  static struct audit_watch *audit_dupe_watch(struct audit_watch *old)
  {
  	char *path;
  	struct audit_watch *new;
  
  	path = kstrdup(old->path, GFP_KERNEL);
  	if (unlikely(!path))
  		return ERR_PTR(-ENOMEM);
  
  	new = audit_init_watch(path);
  	if (IS_ERR(new)) {
  		kfree(path);
  		goto out;
  	}
  
  	new->dev = old->dev;
  	new->ino = old->ino;

  	audit_get_parent(old->parent);

  	new->parent = old->parent;
  
  out:
  	return new;
  }
  
  static void audit_watch_log_rule_change(struct audit_krule *r, struct audit_watch *w, char *op)
  {
  	if (audit_enabled) {
  		struct audit_buffer *ab;
  		ab = audit_log_start(NULL, GFP_NOFS, AUDIT_CONFIG_CHANGE);

  		if (unlikely(!ab))
  			return;

  		audit_log_format(ab, "auid=%u ses=%u op=",

  				 from_kuid(&init_user_ns, audit_get_loginuid(current)),

  				 audit_get_sessionid(current));
  		audit_log_string(ab, op);
  		audit_log_format(ab, " path=");
  		audit_log_untrustedstring(ab, w->path);

  		audit_log_key(ab, r->filterkey);

  		audit_log_format(ab, " list=%d res=1", r->listnr);
  		audit_log_end(ab);
  	}
  }
  
  /* Update inode info in audit rules based on filesystem event. */
  static void audit_update_watch(struct audit_parent *parent,
  			       const char *dname, dev_t dev,
  			       unsigned long ino, unsigned invalidating)
  {
  	struct audit_watch *owatch, *nwatch, *nextw;
  	struct audit_krule *r, *nextr;
  	struct audit_entry *oentry, *nentry;
  
  	mutex_lock(&audit_filter_mutex);

  	/* Run all of the watches on this parent looking for the one that
  	 * matches the given dname */

  	list_for_each_entry_safe(owatch, nextw, &parent->watches, wlist) {

  		if (audit_compare_dname_path(dname, owatch->path,
  					     AUDIT_NAME_FULL))

  			continue;
  
  		/* If the update involves invalidating rules, do the inode-based
  		 * filtering now, so we don't omit records. */

  		if (invalidating && !audit_dummy_context())

  			audit_filter_inodes(current, current->audit_context);

  		/* updating ino will likely change which audit_hash_list we
  		 * are on so we need a new watch for the new list */

  		nwatch = audit_dupe_watch(owatch);
  		if (IS_ERR(nwatch)) {
  			mutex_unlock(&audit_filter_mutex);
  			audit_panic("error updating watch, skipping");
  			return;
  		}
  		nwatch->dev = dev;
  		nwatch->ino = ino;
  
  		list_for_each_entry_safe(r, nextr, &owatch->rules, rlist) {
  
  			oentry = container_of(r, struct audit_entry, rule);
  			list_del(&oentry->rule.rlist);
  			list_del_rcu(&oentry->list);

  			nentry = audit_dupe_rule(&oentry->rule);

  			if (IS_ERR(nentry)) {
  				list_del(&oentry->rule.list);
  				audit_panic("error updating watch, removing");
  			} else {
  				int h = audit_hash_ino((u32)ino);

  
  				/*
  				 * nentry->rule.watch == oentry->rule.watch so
  				 * we must drop that reference and set it to our
  				 * new watch.
  				 */
  				audit_put_watch(nentry->rule.watch);
  				audit_get_watch(nwatch);
  				nentry->rule.watch = nwatch;

  				list_add(&nentry->rule.rlist, &nwatch->rules);
  				list_add_rcu(&nentry->list, &audit_inode_hash[h]);
  				list_replace(&oentry->rule.list,
  					     &nentry->rule.list);
  			}

  			audit_watch_log_rule_change(r, owatch, "updated_rules");

  
  			call_rcu(&oentry->rcu, audit_free_rule_rcu);
  		}
  
  		audit_remove_watch(owatch);
  		goto add_watch_to_parent; /* event applies to a single watch */
  	}
  	mutex_unlock(&audit_filter_mutex);
  	return;
  
  add_watch_to_parent:
  	list_add(&nwatch->wlist, &parent->watches);
  	mutex_unlock(&audit_filter_mutex);
  	return;
  }
  
  /* Remove all watches & rules associated with a parent that is going away. */
  static void audit_remove_parent_watches(struct audit_parent *parent)
  {
  	struct audit_watch *w, *nextw;
  	struct audit_krule *r, *nextr;
  	struct audit_entry *e;
  
  	mutex_lock(&audit_filter_mutex);

  	list_for_each_entry_safe(w, nextw, &parent->watches, wlist) {
  		list_for_each_entry_safe(r, nextr, &w->rules, rlist) {
  			e = container_of(r, struct audit_entry, rule);

  			audit_watch_log_rule_change(r, w, "remove_rule");

  			list_del(&r->rlist);
  			list_del(&r->list);
  			list_del_rcu(&e->list);
  			call_rcu(&e->rcu, audit_free_rule_rcu);
  		}
  		audit_remove_watch(w);
  	}
  	mutex_unlock(&audit_filter_mutex);

  	fsnotify_destroy_mark(&parent->mark, audit_watch_group);

  }

  /* Get path information necessary for adding watches. */

  static int audit_get_nd(struct audit_watch *watch, struct path *parent)

  {

  	struct dentry *d = kern_path_locked(watch->path, parent);
  	if (IS_ERR(d))

  		return PTR_ERR(d);

  	mutex_unlock(&parent->dentry->d_inode->i_mutex);

  	if (d->d_inode) {
  		/* update watch filter fields */
  		watch->dev = d->d_inode->i_sb->s_dev;
  		watch->ino = d->d_inode->i_ino;

  	}

  	dput(d);

  	return 0;
  }

  /* Associate the given rule with an existing parent.

   * Caller must hold audit_filter_mutex. */
  static void audit_add_to_parent(struct audit_krule *krule,
  				struct audit_parent *parent)
  {
  	struct audit_watch *w, *watch = krule->watch;
  	int watch_found = 0;

  	BUG_ON(!mutex_is_locked(&audit_filter_mutex));

  	list_for_each_entry(w, &parent->watches, wlist) {
  		if (strcmp(watch->path, w->path))
  			continue;
  
  		watch_found = 1;
  
  		/* put krule's and initial refs to temporary watch */
  		audit_put_watch(watch);
  		audit_put_watch(watch);
  
  		audit_get_watch(w);
  		krule->watch = watch = w;
  		break;
  	}
  
  	if (!watch_found) {

  		audit_get_parent(parent);

  		watch->parent = parent;
  
  		list_add(&watch->wlist, &parent->watches);
  	}
  	list_add(&krule->rlist, &watch->rules);
  }
  
  /* Find a matching watch entry, or add this one.
   * Caller must hold audit_filter_mutex. */

  int audit_add_watch(struct audit_krule *krule, struct list_head **list)

  {
  	struct audit_watch *watch = krule->watch;

  	struct audit_parent *parent;

  	struct path parent_path;

  	int h, ret = 0;

  	mutex_unlock(&audit_filter_mutex);
  
  	/* Avoid calling path_lookup under audit_filter_mutex. */

  	ret = audit_get_nd(watch, &parent_path);

  	/* caller expects mutex locked */

  	mutex_lock(&audit_filter_mutex);

  	if (ret)
  		return ret;

  	/* either find an old parent or attach a new one */

  	parent = audit_find_parent(parent_path.dentry->d_inode);

  	if (!parent) {

  		parent = audit_init_parent(&parent_path);

  		if (IS_ERR(parent)) {

  			ret = PTR_ERR(parent);
  			goto error;

  		}

  	}

  	audit_add_to_parent(krule, parent);

  	/* match get in audit_find_parent or audit_init_parent */
  	audit_put_parent(parent);

  	h = audit_hash_ino((u32)watch->ino);
  	*list = &audit_inode_hash[h];

  error:

  	path_put(&parent_path);

  	return ret;
  }

  void audit_remove_watch_rule(struct audit_krule *krule)

  {
  	struct audit_watch *watch = krule->watch;
  	struct audit_parent *parent = watch->parent;
  
  	list_del(&krule->rlist);
  
  	if (list_empty(&watch->rules)) {
  		audit_remove_watch(watch);
  
  		if (list_empty(&parent->watches)) {

  			audit_get_parent(parent);

  			fsnotify_destroy_mark(&parent->mark, audit_watch_group);

  			audit_put_parent(parent);

  		}
  	}
  }

  /* Update watch data in audit rules based on fsnotify events. */

  static int audit_watch_handle_event(struct fsnotify_group *group,

  				    struct inode *to_tell,

  				    struct fsnotify_mark *inode_mark,
  				    struct fsnotify_mark *vfsmount_mark,

  				    u32 mask, void *data, int data_type,

  				    const unsigned char *dname, u32 cookie)

  {
  	struct inode *inode;

  	struct audit_parent *parent;

  	parent = container_of(inode_mark, struct audit_parent, mark);

  	BUG_ON(group != audit_watch_group);

  	switch (data_type) {

  	case (FSNOTIFY_EVENT_PATH):

  		inode = ((struct path *)data)->dentry->d_inode;

  		break;
  	case (FSNOTIFY_EVENT_INODE):

  		inode = (struct inode *)data;

  		break;
  	default:
  		BUG();
  		inode = NULL;
  		break;
  	};

  	if (mask & (FS_CREATE|FS_MOVED_TO) && inode)

  		audit_update_watch(parent, dname, inode->i_sb->s_dev, inode->i_ino, 0);

  	else if (mask & (FS_DELETE|FS_MOVED_FROM))

  		audit_update_watch(parent, dname, (dev_t)-1, (unsigned long)-1, 1);

  	else if (mask & (FS_DELETE_SELF|FS_UNMOUNT|FS_MOVE_SELF))

  		audit_remove_parent_watches(parent);

  
  	return 0;
  }

  static const struct fsnotify_ops audit_watch_fsnotify_ops = {

  	.handle_event = 	audit_watch_handle_event,

  };
  
  static int __init audit_watch_init(void)
  {

  	audit_watch_group = fsnotify_alloc_group(&audit_watch_fsnotify_ops);

  	if (IS_ERR(audit_watch_group)) {
  		audit_watch_group = NULL;
  		audit_panic("cannot create audit fsnotify group");
  	}

  	return 0;
  }

  device_initcall(audit_watch_init);