inode.c

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/*
 *  inode.c - securityfs
 *
 *  Copyright (C) 2005 Greg Kroah-Hartman <[email protected]>
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License version
 *  2 as published by the Free Software Foundation.
 *
 *  Based on fs/debugfs/inode.c which had the following copyright notice:
 *    Copyright (C) 2004 Greg Kroah-Hartman <[email protected]>
 *    Copyright (C) 2004 IBM Inc.
 */

/* #define DEBUG */
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/mount.h>
#include <linux/pagemap.h>
#include <linux/init.h>
#include <linux/namei.h>
#include <linux/security.h>
#include <linux/magic.h>

static struct vfsmount *mount;
static int mount_count;

static inline int positive(struct dentry *dentry)
{
    return dentry->d_inode && !d_unhashed(dentry);
}

static int fill_super(struct super_block *sb, void *data, int silent)
{
    static struct tree_descr files[] = {{""}};

    return simple_fill_super(sb, SECURITYFS_MAGIC, files);
}

static struct dentry *get_sb(struct file_system_type *fs_type,
          int flags, const char *dev_name,
          void *data)
{
    return mount_single(fs_type, flags, data, fill_super);
}

static struct file_system_type fs_type = {
    .owner =    THIS_MODULE,
    .name =     "securityfs",
    .mount =    get_sb,
    .kill_sb =  kill_litter_super,
};

struct dentry *securityfs_create_file(const char *name, umode_t mode,
                   struct dentry *parent, void *data,
                   const struct file_operations *fops)
{
    struct dentry *dentry;
    int is_dir = S_ISDIR(mode);
    struct inode *dir, *inode;
    int error;

    if (!is_dir) {
        BUG_ON(!fops);
        mode = (mode & S_IALLUGO) | S_IFREG;
    }

    pr_debug("securityfs: creating file '%s'\n",name);

    error = simple_pin_fs(&fs_type, &mount, &mount_count);
    if (error)
        return ERR_PTR(error);

    if (!parent)
        parent = mount->mnt_root;

    dir = parent->d_inode;

    mutex_lock(&dir->i_mutex);
    dentry = lookup_one_len(name, parent, strlen(name));
    if (IS_ERR(dentry))
        goto out;

    if (dentry->d_inode) {
        error = -EEXIST;
        goto out1;
    }

    inode = new_inode(dir->i_sb);
    if (!inode) {
        error = -ENOMEM;
        goto out1;
    }

    inode->i_ino = get_next_ino();
    inode->i_mode = mode;
    inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
    inode->i_private = data;
    if (is_dir) {
        inode->i_op = &simple_dir_inode_operations;
        inode->i_fop = &simple_dir_operations;
        inc_nlink(inode);
        inc_nlink(dir);
    } else {
        inode->i_fop = fops;
    }
    d_instantiate(dentry, inode);
    dget(dentry);
    mutex_unlock(&dir->i_mutex);
    return dentry;

out1:
    dput(dentry);
    dentry = ERR_PTR(error);
out:
    mutex_unlock(&dir->i_mutex);
    simple_release_fs(&mount, &mount_count);
    return dentry;
}
EXPORT_SYMBOL_GPL(securityfs_create_file);

struct dentry *securityfs_create_dir(const char *name, struct dentry *parent)
{
    return securityfs_create_file(name,
                      S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
                      parent, NULL, NULL);
}
EXPORT_SYMBOL_GPL(securityfs_create_dir);

void securityfs_remove(struct dentry *dentry)
{
    struct dentry *parent;

    if (!dentry || IS_ERR(dentry))
        return;

    parent = dentry->d_parent;
    if (!parent || !parent->d_inode)
        return;

    mutex_lock(&parent->d_inode->i_mutex);
    if (positive(dentry)) {
        if (dentry->d_inode) {
            if (S_ISDIR(dentry->d_inode->i_mode))
                simple_rmdir(parent->d_inode, dentry);
            else
                simple_unlink(parent->d_inode, dentry);
            dput(dentry);
        }
    }
    mutex_unlock(&parent->d_inode->i_mutex);
    simple_release_fs(&mount, &mount_count);
}
EXPORT_SYMBOL_GPL(securityfs_remove);

static struct kobject *security_kobj;

static int __init securityfs_init(void)
{
    int retval;

    security_kobj = kobject_create_and_add("security", kernel_kobj);
    if (!security_kobj)
        return -EINVAL;

    retval = register_filesystem(&fs_type);
    if (retval)
        kobject_put(security_kobj);
    return retval;
}

core_initcall(securityfs_init);
MODULE_LICENSE("GPL");