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 };
  57
  58 static 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 */
  88 static 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
 106 static 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
 117 static 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
 123 static inline int positive(struct dentry *dentry)
 124 {
 125         return dentry->d_inode && !d_unhashed(dentry);
 126 }
 127
 128 static 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
 135 static 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
 142 static 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
 149 static 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  */
 215 struct 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         }
 243 exit:
 244         return dentry;
 245 }
 246 EXPORT_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  */
 269 struct 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 }
 275 EXPORT_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  */
 290 void 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 }
 314 EXPORT_SYMBOL_GPL(securityfs_remove);
 315
 316 static struct kobject *security_kobj;
 317
 318 static 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
 332 core_initcall(securityfs_init);
 333 MODULE_LICENSE("GPL");
 334