linux/kernel/audit_watch.c at master · fabgithub/linux · GitHub

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/* audit_watch.c -- watching inodes

* 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_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);

}

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);

linux/kernel/audit_watch.c at master · fabgithub/linux · GitHub

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