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_uid = 0;
  65                inode->i_gid = 0;
  66                inode->i_blocks = 0;
  67                inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  68                switch (mode & S_IFMT) {
  69                default:
  70                        init_special_inode(inode, mode, dev);
  71                        break;
  72                case S_IFREG:
  73                        inode->i_fop = &default_file_ops;
  74                        break;
  75                case S_IFDIR:
  76                        inode->i_op = &simple_dir_inode_operations;
  77                        inode->i_fop = &simple_dir_operations;
  78
  79                        /* directory inodes start off with i_nlink == 2 (for "." entry) */
  80                        inc_nlink(inode);
  81                        break;
  82                }
  83        }
  84        return inode;
  85}
  86
  87/* SMP-safe */
  88static int mknod(struct inode *dir, struct dentry *dentry,
  89                         int mode, dev_t dev)
  90{
  91        struct inode *inode;
  92        int error = -EPERM;
  93
  94        if (dentry->d_inode)
  95                return -EEXIST;
  96
  97        inode = get_inode(dir->i_sb, mode, dev);
  98        if (inode) {
  99                d_instantiate(dentry, inode);
 100                dget(dentry);
 101                error = 0;
 102        }
 103        return error;
 104}
 105
 106static int mkdir(struct inode *dir, struct dentry *dentry, int mode)
 107{
 108        int res;
 109
 110        mode = (mode & (S_IRWXUGO | S_ISVTX)) | S_IFDIR;
 111        res = mknod(dir, dentry, mode, 0);
 112        if (!res)
 113                inc_nlink(dir);
 114        return res;
 115}
 116
 117static int create(struct inode *dir, struct dentry *dentry, int mode)
 118{
 119        mode = (mode & S_IALLUGO) | S_IFREG;
 120        return mknod(dir, dentry, mode, 0);
 121}
 122
 123static inline int positive(struct dentry *dentry)
 124{
 125        return dentry->d_inode && !d_unhashed(dentry);
 126}
 127
 128static int fill_super(struct super_block *sb, void *data, int silent)
 129{
 130        static struct tree_descr files[] = {{""}};
 131
 132        return simple_fill_super(sb, SECURITYFS_MAGIC, files);
 133}
 134
 135static int get_sb(struct file_system_type *fs_type,
 136                  int flags, const char *dev_name,
 137                  void *data, struct vfsmount *mnt)
 138{
 139        return get_sb_single(fs_type, flags, data, fill_super, mnt);
 140}
 141
 142static struct file_system_type fs_type = {
 143        .owner =        THIS_MODULE,
 144        .name =         "securityfs",
 145        .get_sb =       get_sb,
 146        .kill_sb =      kill_litter_super,
 147};
 148
 149static int create_by_name(const char *name, mode_t mode,
 150                          struct dentry *parent,
 151                          struct dentry **dentry)
 152{
 153        int error = 0;
 154
 155        *dentry = NULL;
 156
 157        /* If the parent is not specified, we create it in the root.
 158         * We need the root dentry to do this, which is in the super
 159         * block. A pointer to that is in the struct vfsmount that we
 160         * have around.
 161         */
 162        if (!parent ) {
 163                if (mount && mount->mnt_sb) {
 164                        parent = mount->mnt_sb->s_root;
 165                }
 166        }
 167        if (!parent) {
 168                pr_debug("securityfs: Ah! can not find a parent!\n");
 169                return -EFAULT;
 170        }
 171
 172        mutex_lock(&parent->d_inode->i_mutex);
 173        *dentry = lookup_one_len(name, parent, strlen(name));
 174        if (!IS_ERR(dentry)) {
 175                if ((mode & S_IFMT) == S_IFDIR)
 176                        error = mkdir(parent->d_inode, *dentry, mode);
 177                else
 178                        error = create(parent->d_inode, *dentry, mode);
 179        } else
 180                error = PTR_ERR(dentry);
 181        mutex_unlock(&parent->d_inode->i_mutex);
 182
 183        return error;
 184}
 185
 186/**
 187 * securityfs_create_file - create a file in the securityfs filesystem
 188 *
 189 * @name: a pointer to a string containing the name of the file to create.
 190 * @mode: the permission that the file should have
 191 * @parent: a pointer to the parent dentry for this file.  This should be a
 192 *          directory dentry if set.  If this parameter is %NULL, then the
 193 *          file will be created in the root of the securityfs filesystem.
 194 * @data: a pointer to something that the caller will want to get to later
 195 *        on.  The inode.i_private pointer will point to this value on
 196 *        the open() call.
 197 * @fops: a pointer to a struct file_operations that should be used for
 198 *        this file.
 199 *
 200 * This is the basic "create a file" function for securityfs.  It allows for a
 201 * wide range of flexibility in creating a file, or a directory (if you
 202 * want to create a directory, the securityfs_create_dir() function is
 203 * recommended to be used instead).
 204 *
 205 * This function returns a pointer to a dentry if it succeeds.  This
 206 * pointer must be passed to the securityfs_remove() function when the file is
 207 * to be removed (no automatic cleanup happens if your module is unloaded,
 208 * you are responsible here).  If an error occurs, %NULL is returned.
 209 *
 210 * If securityfs is not enabled in the kernel, the value %-ENODEV is
 211 * returned.  It is not wise to check for this value, but rather, check for
 212 * %NULL or !%NULL instead as to eliminate the need for #ifdef in the calling
 213 * code.
 214 */
 215struct dentry *securityfs_create_file(const char *name, mode_t mode,
 216                                   struct dentry *parent, void *data,
 217                                   const struct file_operations *fops)
 218{
 219        struct dentry *dentry = NULL;
 220        int error;
 221
 222        pr_debug("securityfs: creating file '%s'\n",name);
 223
 224        error = simple_pin_fs(&fs_type, &mount, &mount_count);
 225        if (error) {
 226                dentry = ERR_PTR(error);
 227                goto exit;
 228        }
 229
 230        error = create_by_name(name, mode, parent, &dentry);
 231        if (error) {
 232                dentry = ERR_PTR(error);
 233                simple_release_fs(&mount, &mount_count);
 234                goto exit;
 235        }
 236
 237        if (dentry->d_inode) {
 238                if (fops)
 239                        dentry->d_inode->i_fop = fops;
 240                if (data)
 241                        dentry->d_inode->i_private = data;
 242        }
 243exit:
 244        return dentry;
 245}
 246EXPORT_SYMBOL_GPL(securityfs_create_file);
 247
 248/**
 249 * securityfs_create_dir - create a directory in the securityfs filesystem
 250 *
 251 * @name: a pointer to a string containing the name of the directory to
 252 *        create.
 253 * @parent: a pointer to the parent dentry for this file.  This should be a
 254 *          directory dentry if set.  If this parameter is %NULL, then the
 255 *          directory will be created in the root of the securityfs filesystem.
 256 *
 257 * This function creates a directory in securityfs with the given @name.
 258 *
 259 * This function returns a pointer to a dentry if it succeeds.  This
 260 * pointer must be passed to the securityfs_remove() function when the file is
 261 * to be removed (no automatic cleanup happens if your module is unloaded,
 262 * you are responsible here).  If an error occurs, %NULL will be returned.
 263 *
 264 * If securityfs is not enabled in the kernel, the value %-ENODEV is
 265 * returned.  It is not wise to check for this value, but rather, check for
 266 * %NULL or !%NULL instead as to eliminate the need for #ifdef in the calling
 267 * code.
 268 */
 269struct dentry *securityfs_create_dir(const char *name, struct dentry *parent)
 270{
 271        return securityfs_create_file(name,
 272                                      S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
 273                                      parent, NULL, NULL);
 274}
 275EXPORT_SYMBOL_GPL(securityfs_create_dir);
 276
 277/**
 278 * securityfs_remove - removes a file or directory from the securityfs filesystem
 279 *
 280 * @dentry: a pointer to a the dentry of the file or directory to be removed.
 281 *
 282 * This function removes a file or directory in securityfs that was previously
 283 * created with a call to another securityfs function (like
 284 * securityfs_create_file() or variants thereof.)
 285 *
 286 * This function is required to be called in order for the file to be
 287 * removed. No automatic cleanup of files will happen when a module is
 288 * removed; you are responsible here.
 289 */
 290void securityfs_remove(struct dentry *dentry)
 291{
 292        struct dentry *parent;
 293
 294        if (!dentry)
 295                return;
 296
 297        parent = dentry->d_parent;
 298        if (!parent || !parent->d_inode)
 299                return;
 300
 301        mutex_lock(&parent->d_inode->i_mutex);
 302        if (positive(dentry)) {
 303                if (dentry->d_inode) {
 304                        if (S_ISDIR(dentry->d_inode->i_mode))
 305                                simple_rmdir(parent->d_inode, dentry);
 306                        else
 307                                simple_unlink(parent->d_inode, dentry);
 308                        dput(dentry);
 309                }
 310        }
 311        mutex_unlock(&parent->d_inode->i_mutex);
 312        simple_release_fs(&mount, &mount_count);
 313}
 314EXPORT_SYMBOL_GPL(securityfs_remove);
 315
 316static struct kobject *security_kobj;
 317
 318static int __init securityfs_init(void)
 319{
 320        int retval;
 321
 322        security_kobj = kobject_create_and_add("security", kernel_kobj);
 323        if (!security_kobj)
 324                return -EINVAL;
 325
 326        retval = register_filesystem(&fs_type);
 327        if (retval)
 328                kobject_put(security_kobj);
 329        return retval;
 330}
 331
 332core_initcall(securityfs_init);
 333MODULE_LICENSE("GPL");
 334
 335