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/* 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);
audit_log_format(ab, "auid=%u ses=%u op=",
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, NULL))
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);
}

/* Get path information necessary for adding watches. */
static int audit_get_nd(struct audit_watch *watch, struct path *parent)
{
struct nameidata nd;
struct dentry *d;
int err;

err = kern_path_parent(watch->path, &nd);
if (err)
return err;

if (nd.last_type != LAST_NORM) {
path_put(&nd.path);
return -EINVAL;
}

mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
d = lookup_one_len(nd.last.name, nd.path.dentry, nd.last.len);
if (IS_ERR(d)) {
mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
path_put(&nd.path);
return PTR_ERR(d);
}
if (d->d_inode) {
/* update watch filter fields */
watch->dev = d->d_inode->i_sb->s_dev;
watch->ino = d->d_inode->i_ino;
}
mutex_unlock(&nd.path.dentry->d_inode->i_mutex);

*parent = nd.path;
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_put_parent(parent);
}
}
}

static bool audit_watch_should_send_event(struct fsnotify_group *group, struct inode *inode,
struct fsnotify_mark *inode_mark,
struct fsnotify_mark *vfsmount_mark,
__u32 mask, void *data, int data_type)
{
       return true;
}

/* Update watch data in audit rules based on fsnotify events. */
static int audit_watch_handle_event(struct fsnotify_group *group,
struct fsnotify_mark *inode_mark,
struct fsnotify_mark *vfsmount_mark,
struct fsnotify_event *event)
{
struct inode *inode;
__u32 mask = event->mask;
const char *dname = event->file_name;
struct audit_parent *parent;

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

BUG_ON(group != audit_watch_group);

switch (event->data_type) {
case (FSNOTIFY_EVENT_PATH):
inode = event->path.dentry->d_inode;
break;
case (FSNOTIFY_EVENT_INODE):
inode = event->inode;
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 = {
.should_send_event = audit_watch_should_send_event,
.handle_event = audit_watch_handle_event,
.free_group_priv = NULL,
.freeing_mark = NULL,
.free_event_priv = NULL,
};

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);
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