security/inode.c

   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
  25 static struct vfsmount *mount;
  26 static int mount_count;
  27
  28 /*
  29  * TODO:
  30  *   I think I can get rid of these default_file_ops, but not quite sure...
  31  */
  32 static ssize_t default_read_file(struct file *file, char __user *buf,
  33                                  size_t count, loff_t *ppos)
  34 {
  35         return 0;
  36 }
  37
  38 static 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
  44 static 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
  52 static 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
  59 static 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 */
  87 static 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
 105 static 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
 116 static 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
 122 static inline int positive(struct dentry *dentry)
 123 {
 124         return dentry->d_inode && !d_unhashed(dentry);
 125 }
 126
 127 static 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
 134 static 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
 141 static 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
 148 static 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  */
 208 struct 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         }
 236 exit:
 237         return dentry;
 238 }
 239 EXPORT_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  */
 262 struct 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 }
 268 EXPORT_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  */
 283 void 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 }
 307 EXPORT_SYMBOL_GPL(securityfs_remove);
 308
 309 static struct kobject *security_kobj;
 310
 311 static 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
 325 core_initcall(securityfs_init);
 326 MODULE_LICENSE("GPL");
 327