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};
  57
  58static struct inode *get_inode(struct super_block *sb, int mode, dev_t dev)
  59{
  60        struct inode *inode = new_inode(sb);
  61
  62        if (inode) {
  63                inode->i_mode = mode;
  64                inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  65                switch (mode & S_IFMT) {
  66                default:
  67                        init_special_inode(inode, mode, dev);
  68                        break;
  69                case S_IFREG:
  70                        inode->i_fop = &default_file_ops;
  71                        break;
  72                case S_IFDIR:
  73                        inode->i_op = &simple_dir_inode_operations;
  74                        inode->i_fop = &simple_dir_operations;
  75
  76                        /* directory inodes start off with i_nlink == 2 (for "." entry) */
  77                        inc_nlink(inode);
  78                        break;
  79                }
  80        }
  81        return inode;
  82}
  83
  84/* SMP-safe */
  85static int mknod(struct inode *dir, struct dentry *dentry,
  86                         int mode, dev_t dev)
  87{
  88        struct inode *inode;
  89        int error = -EPERM;
  90
  91        if (dentry->d_inode)
  92                return -EEXIST;
  93
  94        inode = get_inode(dir->i_sb, mode, dev);
  95        if (inode) {
  96                d_instantiate(dentry, inode);
  97                dget(dentry);
  98                error = 0;
  99        }
 100        return error;
 101}
 102
 103static int mkdir(struct inode *dir, struct dentry *dentry, int mode)
 104{
 105        int res;
 106
 107        mode = (mode & (S_IRWXUGO | S_ISVTX)) | S_IFDIR;
 108        res = mknod(dir, dentry, mode, 0);
 109        if (!res)
 110                inc_nlink(dir);
 111        return res;
 112}
 113
 114static int create(struct inode *dir, struct dentry *dentry, int mode)
 115{
 116        mode = (mode & S_IALLUGO) | S_IFREG;
 117        return mknod(dir, dentry, mode, 0);
 118}
 119
 120static inline int positive(struct dentry *dentry)
 121{
 122        return dentry->d_inode && !d_unhashed(dentry);
 123}
 124
 125static int fill_super(struct super_block *sb, void *data, int silent)
 126{
 127        static struct tree_descr files[] = {{""}};
 128
 129        return simple_fill_super(sb, SECURITYFS_MAGIC, files);
 130}
 131
 132static int get_sb(struct file_system_type *fs_type,
 133                  int flags, const char *dev_name,
 134                  void *data, struct vfsmount *mnt)
 135{
 136        return get_sb_single(fs_type, flags, data, fill_super, mnt);
 137}
 138
 139static struct file_system_type fs_type = {
 140        .owner =        THIS_MODULE,
 141        .name =         "securityfs",
 142        .get_sb =       get_sb,
 143        .kill_sb =      kill_litter_super,
 144};
 145
 146static int create_by_name(const char *name, mode_t mode,
 147                          struct dentry *parent,
 148                          struct dentry **dentry)
 149{
 150        int error = 0;
 151
 152        *dentry = NULL;
 153
 154        /* If the parent is not specified, we create it in the root.
 155         * We need the root dentry to do this, which is in the super
 156         * block. A pointer to that is in the struct vfsmount that we
 157         * have around.
 158         */
 159        if (!parent ) {
 160                if (mount && mount->mnt_sb) {
 161                        parent = mount->mnt_sb->s_root;
 162                }
 163        }
 164        if (!parent) {
 165                pr_debug("securityfs: Ah! can not find a parent!\n");
 166                return -EFAULT;
 167        }
 168
 169        mutex_lock(&parent->d_inode->i_mutex);
 170        *dentry = lookup_one_len(name, parent, strlen(name));
 171        if (!IS_ERR(dentry)) {
 172                if ((mode & S_IFMT) == S_IFDIR)
 173                        error = mkdir(parent->d_inode, *dentry, mode);
 174                else
 175                        error = create(parent->d_inode, *dentry, mode);
 176        } else
 177                error = PTR_ERR(dentry);
 178        mutex_unlock(&parent->d_inode->i_mutex);
 179
 180        return error;
 181}
 182
 183/**
 184 * securityfs_create_file - create a file in the securityfs filesystem
 185 *
 186 * @name: a pointer to a string containing the name of the file to create.
 187 * @mode: the permission that the file should have
 188 * @parent: a pointer to the parent dentry for this file.  This should be a
 189 *          directory dentry if set.  If this parameter is %NULL, then the
 190 *          file will be created in the root of the securityfs filesystem.
 191 * @data: a pointer to something that the caller will want to get to later
 192 *        on.  The inode.i_private pointer will point to this value on
 193 *        the open() call.
 194 * @fops: a pointer to a struct file_operations that should be used for
 195 *        this file.
 196 *
 197 * This is the basic "create a file" function for securityfs.  It allows for a
 198 * wide range of flexibility in creating a file, or a directory (if you
 199 * want to create a directory, the securityfs_create_dir() function is
 200 * recommended to be used instead).
 201 *
 202 * This function returns a pointer to a dentry if it succeeds.  This
 203 * pointer must be passed to the securityfs_remove() function when the file is
 204 * to be removed (no automatic cleanup happens if your module is unloaded,
 205 * you are responsible here).  If an error occurs, the function will return
 206 * the erorr value (via ERR_PTR).
 207 *
 208 * If securityfs is not enabled in the kernel, the value %-ENODEV is
 209 * returned.
 210 */
 211struct dentry *securityfs_create_file(const char *name, mode_t mode,
 212                                   struct dentry *parent, void *data,
 213                                   const struct file_operations *fops)
 214{
 215        struct dentry *dentry = NULL;
 216        int error;
 217
 218        pr_debug("securityfs: creating file '%s'\n",name);
 219
 220        error = simple_pin_fs(&fs_type, &mount, &mount_count);
 221        if (error) {
 222                dentry = ERR_PTR(error);
 223                goto exit;
 224        }
 225
 226        error = create_by_name(name, mode, parent, &dentry);
 227        if (error) {
 228                dentry = ERR_PTR(error);
 229                simple_release_fs(&mount, &mount_count);
 230                goto exit;
 231        }
 232
 233        if (dentry->d_inode) {
 234                if (fops)
 235                        dentry->d_inode->i_fop = fops;
 236                if (data)
 237                        dentry->d_inode->i_private = data;
 238        }
 239exit:
 240        return dentry;
 241}
 242EXPORT_SYMBOL_GPL(securityfs_create_file);
 243
 244/**
 245 * securityfs_create_dir - create a directory in the securityfs filesystem
 246 *
 247 * @name: a pointer to a string containing the name of the directory to
 248 *        create.
 249 * @parent: a pointer to the parent dentry for this file.  This should be a
 250 *          directory dentry if set.  If this parameter is %NULL, then the
 251 *          directory will be created in the root of the securityfs filesystem.
 252 *
 253 * This function creates a directory in securityfs with the given @name.
 254 *
 255 * This function returns a pointer to a dentry if it succeeds.  This
 256 * pointer must be passed to the securityfs_remove() function when the file is
 257 * to be removed (no automatic cleanup happens if your module is unloaded,
 258 * you are responsible here).  If an error occurs, %NULL will be returned.
 259 *
 260 * If securityfs is not enabled in the kernel, the value %-ENODEV is
 261 * returned.  It is not wise to check for this value, but rather, check for
 262 * %NULL or !%NULL instead as to eliminate the need for #ifdef in the calling
 263 * code.
 264 */
 265struct dentry *securityfs_create_dir(const char *name, struct dentry *parent)
 266{
 267        return securityfs_create_file(name,
 268                                      S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
 269                                      parent, NULL, NULL);
 270}
 271EXPORT_SYMBOL_GPL(securityfs_create_dir);
 272
 273/**
 274 * securityfs_remove - removes a file or directory from the securityfs filesystem
 275 *
 276 * @dentry: a pointer to a the dentry of the file or directory to be removed.
 277 *
 278 * This function removes a file or directory in securityfs that was previously
 279 * created with a call to another securityfs function (like
 280 * securityfs_create_file() or variants thereof.)
 281 *
 282 * This function is required to be called in order for the file to be
 283 * removed. No automatic cleanup of files will happen when a module is
 284 * removed; you are responsible here.
 285 */
 286void securityfs_remove(struct dentry *dentry)
 287{
 288        struct dentry *parent;
 289
 290        if (!dentry)
 291                return;
 292
 293        parent = dentry->d_parent;
 294        if (!parent || !parent->d_inode)
 295                return;
 296
 297        mutex_lock(&parent->d_inode->i_mutex);
 298        if (positive(dentry)) {
 299                if (dentry->d_inode) {
 300                        if (S_ISDIR(dentry->d_inode->i_mode))
 301                                simple_rmdir(parent->d_inode, dentry);
 302                        else
 303                                simple_unlink(parent->d_inode, dentry);
 304                        dput(dentry);
 305                }
 306        }
 307        mutex_unlock(&parent->d_inode->i_mutex);
 308        simple_release_fs(&mount, &mount_count);
 309}
 310EXPORT_SYMBOL_GPL(securityfs_remove);
 311
 312static struct kobject *security_kobj;
 313
 314static int __init securityfs_init(void)
 315{
 316        int retval;
 317
 318        security_kobj = kobject_create_and_add("security", kernel_kobj);
 319        if (!security_kobj)
 320                return -EINVAL;
 321
 322        retval = register_filesystem(&fs_type);
 323        if (retval)
 324                kobject_put(security_kobj);
 325        return retval;
 326}
 327
 328core_initcall(securityfs_init);
 329MODULE_LICENSE("GPL");
 330
 331