/* 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/namei.h>
#include <linux/netlink.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/inotify.h>
#include <linux/security.h>
#include "audit.h"

/*
 * Reference counting:
 *
 * audit_parent: lifetime is from audit_init_parent() to receipt of an IN_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;  /* associated rules */
};

struct audit_parent {
        struct list_head        ilist;  /* entry in inotify registration list */
        struct list_head        watches; /* associated watches */
        struct inotify_watch    wdata;  /* inotify watch data */
        unsigned                flags;  /* status flags */
};

/* Inotify handle. */
struct inotify_handle *audit_ih;

/*
 * audit_parent status flags:
 *
 * AUDIT_PARENT_INVALID - set anytime rules/watches are auto-removed due to
 * a filesystem event to ensure we're adding audit watches to a valid parent.
 * Technically not needed for IN_DELETE_SELF or IN_UNMOUNT events, as we cannot
 * receive them while we have nameidata, but must be used for IN_MOVE_SELF which
 * we can receive while holding nameidata.
 */
#define AUDIT_PARENT_INVALID    0x001

/* Inotify events we care about. */
#define AUDIT_IN_WATCH IN_MOVE|IN_CREATE|IN_DELETE|IN_DELETE_SELF|IN_MOVE_SELF

static void audit_free_parent(struct inotify_watch *i_watch)
{
        struct audit_parent *parent;

        parent = container_of(i_watch, struct audit_parent, wdata);
        WARN_ON(!list_empty(&parent->watches));
        kfree(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);
        }
}

void audit_remove_watch(struct audit_watch *watch)
{
        list_del(&watch->wlist);
        put_inotify_watch(&watch->parent->wdata);
        watch->parent = NULL;
        audit_put_watch(watch); /* match initial get */
}

char *audit_watch_path(struct audit_watch *watch)
{
        return watch->path;
}

struct list_head *audit_watch_rules(struct audit_watch *watch)
{
        return &watch->rules;
}

unsigned long audit_watch_inode(struct audit_watch *watch)
{
        return watch->ino;
}

dev_t audit_watch_dev(struct audit_watch *watch)
{
        return watch->dev;
}

/* Initialize a parent watch entry. */
static struct audit_parent *audit_init_parent(struct nameidata *ndp)
{
        struct audit_parent *parent;
        s32 wd;

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

        INIT_LIST_HEAD(&parent->watches);
        parent->flags = 0;

        inotify_init_watch(&parent->wdata);
        /* grab a ref so inotify watch hangs around until we take audit_filter_mutex */
        get_inotify_watch(&parent->wdata);
        wd = inotify_add_watch(audit_ih, &parent->wdata,
                               ndp->path.dentry->d_inode, AUDIT_IN_WATCH);
        if (wd < 0) {
                audit_free_parent(&parent->wdata);
                return ERR_PTR(wd);
        }

        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_ih)
                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;
        get_inotify_watch(&old->parent->wdata);
        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);
        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 && current->audit_context)
                        audit_filter_inodes(current, current->audit_context);

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

/* Unregister inotify watches for parents on in_list.
 * Generates an IN_IGNORED event. */
void audit_inotify_unregister(struct list_head *in_list)
{
        struct audit_parent *p, *n;

        list_for_each_entry_safe(p, n, in_list, ilist) {
                list_del(&p->ilist);
                inotify_rm_watch(audit_ih, &p->wdata);
                /* the unpin matching the pin in audit_do_del_rule() */
                unpin_inotify_watch(&p->wdata);
        }
}

/* Get path information necessary for adding watches. */
static int audit_get_nd(char *path, struct nameidata **ndp, struct nameidata **ndw)
{
        struct nameidata *ndparent, *ndwatch;
        int err;

        ndparent = kmalloc(sizeof(*ndparent), GFP_KERNEL);
        if (unlikely(!ndparent))
                return -ENOMEM;

        ndwatch = kmalloc(sizeof(*ndwatch), GFP_KERNEL);
        if (unlikely(!ndwatch)) {
                kfree(ndparent);
                return -ENOMEM;
        }

        err = path_lookup(path, LOOKUP_PARENT, ndparent);
        if (err) {
                kfree(ndparent);
                kfree(ndwatch);
                return err;
        }

        err = path_lookup(path, 0, ndwatch);
        if (err) {
                kfree(ndwatch);
                ndwatch = NULL;
        }

        *ndp = ndparent;
        *ndw = ndwatch;

        return 0;
}

/* Release resources used for watch path information. */
static void audit_put_nd(struct nameidata *ndp, struct nameidata *ndw)
{
        if (ndp) {
                path_put(&ndp->path);
                kfree(ndp);
        }
        if (ndw) {
                path_put(&ndw->path);
                kfree(ndw);
        }
}

/* Associate the given rule with an existing parent inotify_watch.
 * 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;

        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) {
                get_inotify_watch(&parent->wdata);
                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 audit_watch *watch = krule->watch;
        struct inotify_watch *i_watch;
        struct audit_parent *parent;
        struct nameidata *ndp = NULL, *ndw = NULL;
        int ret = 0;

        mutex_unlock(&audit_filter_mutex);

        /* Avoid calling path_lookup under audit_filter_mutex. */
        ret = audit_get_nd(watch->path, &ndp, &ndw);
        if (ret) {
                /* caller expects mutex locked */
                mutex_lock(&audit_filter_mutex);
                goto error;
        }

        /* update watch filter fields */
        if (ndw) {
                watch->dev = ndw->path.dentry->d_inode->i_sb->s_dev;
                watch->ino = ndw->path.dentry->d_inode->i_ino;
        }

        /* The audit_filter_mutex must not be held during inotify calls because
         * we hold it during inotify event callback processing.  If an existing
         * inotify watch is found, inotify_find_watch() grabs a reference before
         * returning.
         */
        if (inotify_find_watch(audit_ih, ndp->path.dentry->d_inode,
                               &i_watch) < 0) {
                parent = audit_init_parent(ndp);
                if (IS_ERR(parent)) {
                        /* caller expects mutex locked */
                        mutex_lock(&audit_filter_mutex);
                        ret = PTR_ERR(parent);
                        goto error;
                }
        } else
                parent = container_of(i_watch, struct audit_parent, wdata);

        mutex_lock(&audit_filter_mutex);

        /* parent was moved before we took audit_filter_mutex */
        if (parent->flags & AUDIT_PARENT_INVALID)
                ret = -ENOENT;
        else
                audit_add_to_parent(krule, parent);

        /* match get in audit_init_parent or inotify_find_watch */
        put_inotify_watch(&parent->wdata);

error:
        audit_put_nd(ndp, ndw);         /* NULL args OK */
        return ret;

}

void audit_remove_watch_rule(struct audit_krule *krule, struct list_head *list)
{
        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)) {
                        /* Put parent on the inotify un-registration
                         * list.  Grab a reference before releasing
                         * audit_filter_mutex, to be released in
                         * audit_inotify_unregister().
                         * If filesystem is going away, just leave
                         * the sucker alone, eviction will take
                         * care of it. */
                        if (pin_inotify_watch(&parent->wdata))
                                list_add(&parent->ilist, list);
                }
        }
}

/* Update watch data in audit rules based on inotify events. */
static void audit_handle_ievent(struct inotify_watch *i_watch, u32 wd, u32 mask,
                         u32 cookie, const char *dname, struct inode *inode)
{
        struct audit_parent *parent;

        parent = container_of(i_watch, struct audit_parent, wdata);

        if (mask & (IN_CREATE|IN_MOVED_TO) && inode)
                audit_update_watch(parent, dname, inode->i_sb->s_dev,
                                   inode->i_ino, 0);
        else if (mask & (IN_DELETE|IN_MOVED_FROM))
                audit_update_watch(parent, dname, (dev_t)-1, (unsigned long)-1, 1);
        /* inotify automatically removes the watch and sends IN_IGNORED */
        else if (mask & (IN_DELETE_SELF|IN_UNMOUNT))
                audit_remove_parent_watches(parent);
        /* inotify does not remove the watch, so remove it manually */
        else if(mask & IN_MOVE_SELF) {
                audit_remove_parent_watches(parent);
                inotify_remove_watch_locked(audit_ih, i_watch);
        } else if (mask & IN_IGNORED)
                put_inotify_watch(i_watch);
}

static const struct inotify_operations audit_inotify_ops = {
        .handle_event   = audit_handle_ievent,
        .destroy_watch  = audit_free_parent,
};

static int __init audit_watch_init(void)
{
        audit_ih = inotify_init(&audit_inotify_ops);
        if (IS_ERR(audit_ih))
                audit_panic("cannot initialize inotify handle");
        return 0;
}
subsys_initcall(audit_watch_init);