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
  28/*
  29 * TODO:
  30 *   I think I can get rid of these default_file_ops, but not quite sure...
  31 */
  32static ssize_t default_read_file(struct file *file, char __user *buf,
  33                                 size_t count, loff_t *ppos)
  34{
  35        return 0;
  36}
  37
  38static ssize_t default_write_file(struct file *file, const char __user *buf,
  39                                   size_t count, loff_t *ppos)
  40{
  41        return count;
  42}
  43
  44static int default_open(struct inode *inode, struct file *file)
  45{
  46        if (inode->i_private)
  47                file->private_data = inode->i_private;
  48
  49        return 0;
  50}
  51
  52static const struct file_operations default_file_ops = {
  53        .read =         default_read_file,
  54        .write =        default_write_file,
  55        .open =         default_open,
  56        .llseek =       noop_llseek,
  57};
  58
  59static struct inode *get_inode(struct super_block *sb, int mode, dev_t dev)
  60{
  61        struct inode *inode = new_inode(sb);
  62
  63        if (inode) {
  64                inode->i_ino = get_next_ino();
  65                inode->i_mode = mode;
  66                inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  67                switch (mode & S_IFMT) {
  68                default:
  69                        init_special_inode(inode, mode, dev);
  70                        break;
  71                case S_IFREG:
  72                        inode->i_fop = &default_file_ops;
  73                        break;
  74                case S_IFDIR:
  75                        inode->i_op = &simple_dir_inode_operations;
  76                        inode->i_fop = &simple_dir_operations;
  77
  78                        /* directory inodes start off with i_nlink == 2 (for "." entry) */
  79                        inc_nlink(inode);
  80                        break;
  81                }
  82        }
  83        return inode;
  84}
  85
  86/* SMP-safe */
  87static int mknod(struct inode *dir, struct dentry *dentry,
  88                         int mode, dev_t dev)
  89{
  90        struct inode *inode;
  91        int error = -ENOMEM;
  92
  93        if (dentry->d_inode)
  94                return -EEXIST;
  95
  96        inode = get_inode(dir->i_sb, mode, dev);
  97        if (inode) {
  98                d_instantiate(dentry, inode);
  99                dget(dentry);
 100                error = 0;
 101        }
 102        return error;
 103}
 104
 105static int mkdir(struct inode *dir, struct dentry *dentry, int mode)
 106{
 107        int res;
 108
 109        mode = (mode & (S_IRWXUGO | S_ISVTX)) | S_IFDIR;
 110        res = mknod(dir, dentry, mode, 0);
 111        if (!res)
 112                inc_nlink(dir);
 113        return res;
 114}
 115
 116static int create(struct inode *dir, struct dentry *dentry, int mode)
 117{
 118        mode = (mode & S_IALLUGO) | S_IFREG;
 119        return mknod(dir, dentry, mode, 0);
 120}
 121
 122static inline int positive(struct dentry *dentry)
 123{
 124        return dentry->d_inode && !d_unhashed(dentry);
 125}
 126
 127static int fill_super(struct super_block *sb, void *data, int silent)
 128{
 129        static struct tree_descr files[] = {{""}};
 130
 131        return simple_fill_super(sb, SECURITYFS_MAGIC, files);
 132}
 133
 134static struct dentry *get_sb(struct file_system_type *fs_type,
 135                  int flags, const char *dev_name,
 136                  void *data)
 137{
 138        return mount_single(fs_type, flags, data, fill_super);
 139}
 140
 141static struct file_system_type fs_type = {
 142        .owner =        THIS_MODULE,
 143        .name =         "securityfs",
 144        .mount =        get_sb,
 145        .kill_sb =      kill_litter_super,
 146};
 147
 148static int create_by_name(const char *name, mode_t mode,
 149                          struct dentry *parent,
 150                          struct dentry **dentry)
 151{
 152        int error = 0;
 153
 154        *dentry = NULL;
 155
 156        /* If the parent is not specified, we create it in the root.
 157         * We need the root dentry to do this, which is in the super
 158         * block. A pointer to that is in the struct vfsmount that we
 159         * have around.
 160         */
 161        if (!parent)
 162                parent = mount->mnt_sb->s_root;
 163
 164        mutex_lock(&parent->d_inode->i_mutex);
 165        *dentry = lookup_one_len(name, parent, strlen(name));
 166        if (!IS_ERR(*dentry)) {
 167                if ((mode & S_IFMT) == S_IFDIR)
 168                        error = mkdir(parent->d_inode, *dentry, mode);
 169                else
 170                        error = create(parent->d_inode, *dentry, mode);
 171                if (error)
 172                        dput(*dentry);
 173        } else
 174                error = PTR_ERR(*dentry);
 175        mutex_unlock(&parent->d_inode->i_mutex);
 176
 177        return error;
 178}
 179
 180/**
 181 * securityfs_create_file - create a file in the securityfs filesystem
 182 *
 183 * @name: a pointer to a string containing the name of the file to create.
 184 * @mode: the permission that the file should have
 185 * @parent: a pointer to the parent dentry for this file.  This should be a
 186 *          directory dentry if set.  If this parameter is %NULL, then the
 187 *          file will be created in the root of the securityfs filesystem.
 188 * @data: a pointer to something that the caller will want to get to later
 189 *        on.  The inode.i_private pointer will point to this value on
 190 *        the open() call.
 191 * @fops: a pointer to a struct file_operations that should be used for
 192 *        this file.
 193 *
 194 * This is the basic "create a file" function for securityfs.  It allows for a
 195 * wide range of flexibility in creating a file, or a directory (if you
 196 * want to create a directory, the securityfs_create_dir() function is
 197 * recommended to be used instead).
 198 *
 199 * This function returns a pointer to a dentry if it succeeds.  This
 200 * pointer must be passed to the securityfs_remove() function when the file is
 201 * to be removed (no automatic cleanup happens if your module is unloaded,
 202 * you are responsible here).  If an error occurs, the function will return
 203 * the erorr value (via ERR_PTR).
 204 *
 205 * If securityfs is not enabled in the kernel, the value %-ENODEV is
 206 * returned.
 207 */
 208struct dentry *securityfs_create_file(const char *name, mode_t mode,
 209                                   struct dentry *parent, void *data,
 210                                   const struct file_operations *fops)
 211{
 212        struct dentry *dentry = NULL;
 213        int error;
 214
 215        pr_debug("securityfs: creating file '%s'\n",name);
 216
 217        error = simple_pin_fs(&fs_type, &mount, &mount_count);
 218        if (error) {
 219                dentry = ERR_PTR(error);
 220                goto exit;
 221        }
 222
 223        error = create_by_name(name, mode, parent, &dentry);
 224        if (error) {
 225                dentry = ERR_PTR(error);
 226                simple_release_fs(&mount, &mount_count);
 227                goto exit;
 228        }
 229
 230        if (dentry->d_inode) {
 231                if (fops)
 232                        dentry->d_inode->i_fop = fops;
 233                if (data)
 234                        dentry->d_inode->i_private = data;
 235        }
 236exit:
 237        return dentry;
 238}
 239EXPORT_SYMBOL_GPL(securityfs_create_file);
 240
 241/**
 242 * securityfs_create_dir - create a directory in the securityfs filesystem
 243 *
 244 * @name: a pointer to a string containing the name of the directory to
 245 *        create.
 246 * @parent: a pointer to the parent dentry for this file.  This should be a
 247 *          directory dentry if set.  If this parameter is %NULL, then the
 248 *          directory will be created in the root of the securityfs filesystem.
 249 *
 250 * This function creates a directory in securityfs with the given @name.
 251 *
 252 * This function returns a pointer to a dentry if it succeeds.  This
 253 * pointer must be passed to the securityfs_remove() function when the file is
 254 * to be removed (no automatic cleanup happens if your module is unloaded,
 255 * you are responsible here).  If an error occurs, %NULL will be returned.
 256 *
 257 * If securityfs is not enabled in the kernel, the value %-ENODEV is
 258 * returned.  It is not wise to check for this value, but rather, check for
 259 * %NULL or !%NULL instead as to eliminate the need for #ifdef in the calling
 260 * code.
 261 */
 262struct dentry *securityfs_create_dir(const char *name, struct dentry *parent)
 263{
 264        return securityfs_create_file(name,
 265                                      S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
 266                                      parent, NULL, NULL);
 267}
 268EXPORT_SYMBOL_GPL(securityfs_create_dir);
 269
 270/**
 271 * securityfs_remove - removes a file or directory from the securityfs filesystem
 272 *
 273 * @dentry: a pointer to a the dentry of the file or directory to be removed.
 274 *
 275 * This function removes a file or directory in securityfs that was previously
 276 * created with a call to another securityfs function (like
 277 * securityfs_create_file() or variants thereof.)
 278 *
 279 * This function is required to be called in order for the file to be
 280 * removed. No automatic cleanup of files will happen when a module is
 281 * removed; you are responsible here.
 282 */
 283void securityfs_remove(struct dentry *dentry)
 284{
 285        struct dentry *parent;
 286
 287        if (!dentry || IS_ERR(dentry))
 288                return;
 289
 290        parent = dentry->d_parent;
 291        if (!parent || !parent->d_inode)
 292                return;
 293
 294        mutex_lock(&parent->d_inode->i_mutex);
 295        if (positive(dentry)) {
 296                if (dentry->d_inode) {
 297                        if (S_ISDIR(dentry->d_inode->i_mode))
 298                                simple_rmdir(parent->d_inode, dentry);
 299                        else
 300                                simple_unlink(parent->d_inode, dentry);
 301                        dput(dentry);
 302                }
 303        }
 304        mutex_unlock(&parent->d_inode->i_mutex);
 305        simple_release_fs(&mount, &mount_count);
 306}
 307EXPORT_SYMBOL_GPL(securityfs_remove);
 308
 309static struct kobject *security_kobj;
 310
 311static int __init securityfs_init(void)
 312{
 313        int retval;
 314
 315        security_kobj = kobject_create_and_add("security", kernel_kobj);
 316        if (!security_kobj)
 317                return -EINVAL;
 318
 319        retval = register_filesystem(&fs_type);
 320        if (retval)
 321                kobject_put(security_kobj);
 322        return retval;
 323}
 324
 325core_initcall(securityfs_init);
 326MODULE_LICENSE("GPL");
 327
 328
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