linux/security/inode.c
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   1/*
   2 *  inode.c - securityfs
   3 *
   4 *  Copyright (C) 2005 Greg Kroah-Hartman <gregkh@suse.de>
   5 *
   6 *      This program is free software; you can redistribute it and/or
   7 *      modify it under the terms of the GNU General Public License version
   8 *      2 as published by the Free Software Foundation.
   9 *
  10 *  Based on fs/debugfs/inode.c which had the following copyright notice:
  11 *    Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com>
  12 *    Copyright (C) 2004 IBM Inc.
  13 */
  14
  15/* #define DEBUG */
  16#include <linux/module.h>
  17#include <linux/fs.h>
  18#include <linux/mount.h>
  19#include <linux/pagemap.h>
  20#include <linux/init.h>
  21#include <linux/namei.h>
  22#include <linux/security.h>
  23#include <linux/magic.h>
  24
  25static struct vfsmount *mount;
  26static int mount_count;
  27
  28static inline int positive(struct dentry *dentry)
  29{
  30        return dentry->d_inode && !d_unhashed(dentry);
  31}
  32
  33static int fill_super(struct super_block *sb, void *data, int silent)
  34{
  35        static struct tree_descr files[] = {{""}};
  36
  37        return simple_fill_super(sb, SECURITYFS_MAGIC, files);
  38}
  39
  40static struct dentry *get_sb(struct file_system_type *fs_type,
  41                  int flags, const char *dev_name,
  42                  void *data)
  43{
  44        return mount_single(fs_type, flags, data, fill_super);
  45}
  46
  47static struct file_system_type fs_type = {
  48        .owner =        THIS_MODULE,
  49        .name =         "securityfs",
  50        .mount =        get_sb,
  51        .kill_sb =      kill_litter_super,
  52};
  53
  54/**
  55 * securityfs_create_file - create a file in the securityfs filesystem
  56 *
  57 * @name: a pointer to a string containing the name of the file to create.
  58 * @mode: the permission that the file should have
  59 * @parent: a pointer to the parent dentry for this file.  This should be a
  60 *          directory dentry if set.  If this parameter is %NULL, then the
  61 *          file will be created in the root of the securityfs filesystem.
  62 * @data: a pointer to something that the caller will want to get to later
  63 *        on.  The inode.i_private pointer will point to this value on
  64 *        the open() call.
  65 * @fops: a pointer to a struct file_operations that should be used for
  66 *        this file.
  67 *
  68 * This is the basic "create a file" function for securityfs.  It allows for a
  69 * wide range of flexibility in creating a file, or a directory (if you
  70 * want to create a directory, the securityfs_create_dir() function is
  71 * recommended to be used instead).
  72 *
  73 * This function returns a pointer to a dentry if it succeeds.  This
  74 * pointer must be passed to the securityfs_remove() function when the file is
  75 * to be removed (no automatic cleanup happens if your module is unloaded,
  76 * you are responsible here).  If an error occurs, the function will return
  77 * the erorr value (via ERR_PTR).
  78 *
  79 * If securityfs is not enabled in the kernel, the value %-ENODEV is
  80 * returned.
  81 */
  82struct dentry *securityfs_create_file(const char *name, umode_t mode,
  83                                   struct dentry *parent, void *data,
  84                                   const struct file_operations *fops)
  85{
  86        struct dentry *dentry;
  87        int is_dir = S_ISDIR(mode);
  88        struct inode *dir, *inode;
  89        int error;
  90
  91        if (!is_dir) {
  92                BUG_ON(!fops);
  93                mode = (mode & S_IALLUGO) | S_IFREG;
  94        }
  95
  96        pr_debug("securityfs: creating file '%s'\n",name);
  97
  98        error = simple_pin_fs(&fs_type, &mount, &mount_count);
  99        if (error)
 100                return ERR_PTR(error);
 101
 102        if (!parent)
 103                parent = mount->mnt_root;
 104
 105        dir = parent->d_inode;
 106
 107        mutex_lock(&dir->i_mutex);
 108        dentry = lookup_one_len(name, parent, strlen(name));
 109        if (IS_ERR(dentry))
 110                goto out;
 111
 112        if (dentry->d_inode) {
 113                error = -EEXIST;
 114                goto out1;
 115        }
 116
 117        inode = new_inode(dir->i_sb);
 118        if (!inode) {
 119                error = -ENOMEM;
 120                goto out1;
 121        }
 122
 123        inode->i_ino = get_next_ino();
 124        inode->i_mode = mode;
 125        inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 126        inode->i_private = data;
 127        if (is_dir) {
 128                inode->i_op = &simple_dir_inode_operations;
 129                inode->i_fop = &simple_dir_operations;
 130                inc_nlink(inode);
 131                inc_nlink(dir);
 132        } else {
 133                inode->i_fop = fops;
 134        }
 135        d_instantiate(dentry, inode);
 136        dget(dentry);
 137        mutex_unlock(&dir->i_mutex);
 138        return dentry;
 139
 140out1:
 141        dput(dentry);
 142        dentry = ERR_PTR(error);
 143out:
 144        mutex_unlock(&dir->i_mutex);
 145        simple_release_fs(&mount, &mount_count);
 146        return dentry;
 147}
 148EXPORT_SYMBOL_GPL(securityfs_create_file);
 149
 150/**
 151 * securityfs_create_dir - create a directory in the securityfs filesystem
 152 *
 153 * @name: a pointer to a string containing the name of the directory to
 154 *        create.
 155 * @parent: a pointer to the parent dentry for this file.  This should be a
 156 *          directory dentry if set.  If this parameter is %NULL, then the
 157 *          directory will be created in the root of the securityfs filesystem.
 158 *
 159 * This function creates a directory in securityfs with the given @name.
 160 *
 161 * This function returns a pointer to a dentry if it succeeds.  This
 162 * pointer must be passed to the securityfs_remove() function when the file is
 163 * to be removed (no automatic cleanup happens if your module is unloaded,
 164 * you are responsible here).  If an error occurs, %NULL will be returned.
 165 *
 166 * If securityfs is not enabled in the kernel, the value %-ENODEV is
 167 * returned.  It is not wise to check for this value, but rather, check for
 168 * %NULL or !%NULL instead as to eliminate the need for #ifdef in the calling
 169 * code.
 170 */
 171struct dentry *securityfs_create_dir(const char *name, struct dentry *parent)
 172{
 173        return securityfs_create_file(name,
 174                                      S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
 175                                      parent, NULL, NULL);
 176}
 177EXPORT_SYMBOL_GPL(securityfs_create_dir);
 178
 179/**
 180 * securityfs_remove - removes a file or directory from the securityfs filesystem
 181 *
 182 * @dentry: a pointer to a the dentry of the file or directory to be removed.
 183 *
 184 * This function removes a file or directory in securityfs that was previously
 185 * created with a call to another securityfs function (like
 186 * securityfs_create_file() or variants thereof.)
 187 *
 188 * This function is required to be called in order for the file to be
 189 * removed. No automatic cleanup of files will happen when a module is
 190 * removed; you are responsible here.
 191 */
 192void securityfs_remove(struct dentry *dentry)
 193{
 194        struct dentry *parent;
 195
 196        if (!dentry || IS_ERR(dentry))
 197                return;
 198
 199        parent = dentry->d_parent;
 200        if (!parent || !parent->d_inode)
 201                return;
 202
 203        mutex_lock(&parent->d_inode->i_mutex);
 204        if (positive(dentry)) {
 205                if (dentry->d_inode) {
 206                        if (S_ISDIR(dentry->d_inode->i_mode))
 207                                simple_rmdir(parent->d_inode, dentry);
 208                        else
 209                                simple_unlink(parent->d_inode, dentry);
 210                        dput(dentry);
 211                }
 212        }
 213        mutex_unlock(&parent->d_inode->i_mutex);
 214        simple_release_fs(&mount, &mount_count);
 215}
 216EXPORT_SYMBOL_GPL(securityfs_remove);
 217
 218static struct kobject *security_kobj;
 219
 220static int __init securityfs_init(void)
 221{
 222        int retval;
 223
 224        security_kobj = kobject_create_and_add("security", kernel_kobj);
 225        if (!security_kobj)
 226                return -EINVAL;
 227
 228        retval = register_filesystem(&fs_type);
 229        if (retval)
 230                kobject_put(security_kobj);
 231        return retval;
 232}
 233
 234core_initcall(securityfs_init);
 235MODULE_LICENSE("GPL");
 236
 237
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