// SPDX-License-Identifier: GPL-2.0-or-later
/* audit_fsnotify.c -- tracking inodes
 *
 * Copyright 2003-2009,2014-2015 Red Hat, Inc.
 * Copyright 2005 Hewlett-Packard Development Company, L.P.
 * Copyright 2005 IBM Corporation
 */

#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"

/*
 * this mark lives on the parent directory of the inode in question.
 * but dev, ino, and path are about the child
 */
struct audit_fsnotify_mark {
        dev_t dev;              /* associated superblock device */
        unsigned long ino;      /* associated inode number */
        char *path;             /* insertion path */
        struct fsnotify_mark mark; /* fsnotify mark on the inode */
        struct audit_krule *rule;
};

/* fsnotify handle. */
static struct fsnotify_group *audit_fsnotify_group;

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

static void audit_fsnotify_mark_free(struct audit_fsnotify_mark *audit_mark)
{
        kfree(audit_mark->path);
        kfree(audit_mark);
}

static void audit_fsnotify_free_mark(struct fsnotify_mark *mark)
{
        struct audit_fsnotify_mark *audit_mark;

        audit_mark = container_of(mark, struct audit_fsnotify_mark, mark);
        audit_fsnotify_mark_free(audit_mark);
}

char *audit_mark_path(struct audit_fsnotify_mark *mark)
{
        return mark->path;
}

int audit_mark_compare(struct audit_fsnotify_mark *mark, unsigned long ino, dev_t dev)
{
        if (mark->ino == AUDIT_INO_UNSET)
                return 0;
        return (mark->ino == ino) && (mark->dev == dev);
}

static void audit_update_mark(struct audit_fsnotify_mark *audit_mark,
                             const struct inode *inode)
{
        audit_mark->dev = inode ? inode->i_sb->s_dev : AUDIT_DEV_UNSET;
        audit_mark->ino = inode ? inode->i_ino : AUDIT_INO_UNSET;
}

struct audit_fsnotify_mark *audit_alloc_mark(struct audit_krule *krule, char *pathname, int len)
{
        struct audit_fsnotify_mark *audit_mark;
        struct path path;
        struct dentry *dentry;
        int ret;

        if (pathname[0] != '/' || pathname[len-1] == '/')
                return ERR_PTR(-EINVAL);

        dentry = kern_path_parent(pathname, &path);
        if (IS_ERR(dentry))
                return ERR_CAST(dentry); /* returning an error */
        if (d_really_is_negative(dentry)) {
                audit_mark = ERR_PTR(-ENOENT);
                goto out;
        }

        audit_mark = kzalloc_obj(*audit_mark);
        if (unlikely(!audit_mark)) {
                audit_mark = ERR_PTR(-ENOMEM);
                goto out;
        }

        fsnotify_init_mark(&audit_mark->mark, audit_fsnotify_group);
        audit_mark->mark.mask = AUDIT_FS_EVENTS;
        audit_mark->path = pathname;
        audit_update_mark(audit_mark, dentry->d_inode);
        audit_mark->rule = krule;

        ret = fsnotify_add_inode_mark(&audit_mark->mark, path.dentry->d_inode, 0);
        if (ret < 0) {
                audit_mark->path = NULL;
                fsnotify_put_mark(&audit_mark->mark);
                audit_mark = ERR_PTR(ret);
        }
out:
        dput(dentry);
        path_put(&path);
        return audit_mark;
}

static void audit_mark_log_rule_change(struct audit_fsnotify_mark *audit_mark, char *op)
{
        struct audit_buffer *ab;
        struct audit_krule *rule = audit_mark->rule;

        if (!audit_enabled)
                return;
        ab = audit_log_start(audit_context(), GFP_NOFS, AUDIT_CONFIG_CHANGE);
        if (unlikely(!ab))
                return;
        audit_log_session_info(ab);
        audit_log_format(ab, " op=%s path=", op);
        audit_log_untrustedstring(ab, audit_mark->path);
        audit_log_key(ab, rule->filterkey);
        audit_log_format(ab, " list=%d res=1", rule->listnr);
        audit_log_end(ab);
}

void audit_remove_mark(struct audit_fsnotify_mark *audit_mark)
{
        fsnotify_destroy_mark(&audit_mark->mark, audit_fsnotify_group);
        fsnotify_put_mark(&audit_mark->mark);
}

void audit_remove_mark_rule(struct audit_krule *krule)
{
        struct audit_fsnotify_mark *mark = krule->exe;

        audit_remove_mark(mark);
}

static void audit_autoremove_mark_rule(struct audit_fsnotify_mark *audit_mark)
{
        struct audit_krule *rule = audit_mark->rule;
        struct audit_entry *entry = container_of(rule, struct audit_entry, rule);

        audit_mark_log_rule_change(audit_mark, "autoremove_rule");
        audit_del_rule(entry);
}

/* Update mark data in audit rules based on fsnotify events. */
static int audit_mark_handle_event(struct fsnotify_mark *inode_mark, u32 mask,
                                   struct inode *inode, struct inode *dir,
                                   const struct qstr *dname, u32 cookie)
{
        struct audit_fsnotify_mark *audit_mark;

        audit_mark = container_of(inode_mark, struct audit_fsnotify_mark, mark);

        if (WARN_ON_ONCE(inode_mark->group != audit_fsnotify_group))
                return 0;

        if (mask & (FS_CREATE|FS_MOVED_TO|FS_DELETE|FS_MOVED_FROM)) {
                if (audit_compare_dname_path(dname, audit_mark->path, AUDIT_NAME_FULL))
                        return 0;
                audit_update_mark(audit_mark, inode);
        } else if (mask & (FS_DELETE_SELF|FS_UNMOUNT|FS_MOVE_SELF)) {
                audit_autoremove_mark_rule(audit_mark);
        }

        return 0;
}

static const struct fsnotify_ops audit_mark_fsnotify_ops = {
        .handle_inode_event = audit_mark_handle_event,
        .free_mark = audit_fsnotify_free_mark,
};

static int __init audit_fsnotify_init(void)
{
        audit_fsnotify_group = fsnotify_alloc_group(&audit_mark_fsnotify_ops,
                                                    FSNOTIFY_GROUP_DUPS);
        if (IS_ERR(audit_fsnotify_group)) {
                audit_fsnotify_group = NULL;
                audit_panic("cannot create audit fsnotify group");
        }
        return 0;
}
device_initcall(audit_fsnotify_init);