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_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 */
  85 static int mknod(struct inode *dir, struct dentry *dentry,
  86                          int mode, dev_t dev)
  87 {
  88         struct inode *inode;
  89         int error = -ENOMEM;
  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
 103 static 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
 114 static 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
 120 static inline int positive(struct dentry *dentry)
 121 {
 122         return dentry->d_inode && !d_unhashed(dentry);
 123 }
 124
 125 static 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
 132 static 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
 139 static 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
 146 static 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                 parent = mount->mnt_sb->s_root;
 161
 162         mutex_lock(&parent->d_inode->i_mutex);
 163         *dentry = lookup_one_len(name, parent, strlen(name));
 164         if (!IS_ERR(*dentry)) {
 165                 if ((mode & S_IFMT) == S_IFDIR)
 166                         error = mkdir(parent->d_inode, *dentry, mode);
 167                 else
 168                         error = create(parent->d_inode, *dentry, mode);
 169                 if (error)
 170                         dput(*dentry);
 171         } else
 172                 error = PTR_ERR(*dentry);
 173         mutex_unlock(&parent->d_inode->i_mutex);
 174
 175         return error;
 176 }
 177
 178 /**
 179  * securityfs_create_file - create a file in the securityfs filesystem
 180  *
 181  * @name: a pointer to a string containing the name of the file to create.
 182  * @mode: the permission that the file should have
 183  * @parent: a pointer to the parent dentry for this file.  This should be a
 184  *          directory dentry if set.  If this parameter is %NULL, then the
 185  *          file will be created in the root of the securityfs filesystem.
 186  * @data: a pointer to something that the caller will want to get to later
 187  *        on.  The inode.i_private pointer will point to this value on
 188  *        the open() call.
 189  * @fops: a pointer to a struct file_operations that should be used for
 190  *        this file.
 191  *
 192  * This is the basic "create a file" function for securityfs.  It allows for a
 193  * wide range of flexibility in creating a file, or a directory (if you
 194  * want to create a directory, the securityfs_create_dir() function is
 195  * recommended to be used instead).
 196  *
 197  * This function returns a pointer to a dentry if it succeeds.  This
 198  * pointer must be passed to the securityfs_remove() function when the file is
 199  * to be removed (no automatic cleanup happens if your module is unloaded,
 200  * you are responsible here).  If an error occurs, the function will return
 201  * the erorr value (via ERR_PTR).
 202  *
 203  * If securityfs is not enabled in the kernel, the value %-ENODEV is
 204  * returned.
 205  */
 206 struct dentry *securityfs_create_file(const char *name, mode_t mode,
 207                                    struct dentry *parent, void *data,
 208                                    const struct file_operations *fops)
 209 {
 210         struct dentry *dentry = NULL;
 211         int error;
 212
 213         pr_debug("securityfs: creating file '%s'\n",name);
 214
 215         error = simple_pin_fs(&fs_type, &mount, &mount_count);
 216         if (error) {
 217                 dentry = ERR_PTR(error);
 218                 goto exit;
 219         }
 220
 221         error = create_by_name(name, mode, parent, &dentry);
 222         if (error) {
 223                 dentry = ERR_PTR(error);
 224                 simple_release_fs(&mount, &mount_count);
 225                 goto exit;
 226         }
 227
 228         if (dentry->d_inode) {
 229                 if (fops)
 230                         dentry->d_inode->i_fop = fops;
 231                 if (data)
 232                         dentry->d_inode->i_private = data;
 233         }
 234 exit:
 235         return dentry;
 236 }
 237 EXPORT_SYMBOL_GPL(securityfs_create_file);
 238
 239 /**
 240  * securityfs_create_dir - create a directory in the securityfs filesystem
 241  *
 242  * @name: a pointer to a string containing the name of the directory to
 243  *        create.
 244  * @parent: a pointer to the parent dentry for this file.  This should be a
 245  *          directory dentry if set.  If this parameter is %NULL, then the
 246  *          directory will be created in the root of the securityfs filesystem.
 247  *
 248  * This function creates a directory in securityfs with the given @name.
 249  *
 250  * This function returns a pointer to a dentry if it succeeds.  This
 251  * pointer must be passed to the securityfs_remove() function when the file is
 252  * to be removed (no automatic cleanup happens if your module is unloaded,
 253  * you are responsible here).  If an error occurs, %NULL will be returned.
 254  *
 255  * If securityfs is not enabled in the kernel, the value %-ENODEV is
 256  * returned.  It is not wise to check for this value, but rather, check for
 257  * %NULL or !%NULL instead as to eliminate the need for #ifdef in the calling
 258  * code.
 259  */
 260 struct dentry *securityfs_create_dir(const char *name, struct dentry *parent)
 261 {
 262         return securityfs_create_file(name,
 263                                       S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
 264                                       parent, NULL, NULL);
 265 }
 266 EXPORT_SYMBOL_GPL(securityfs_create_dir);
 267
 268 /**
 269  * securityfs_remove - removes a file or directory from the securityfs filesystem
 270  *
 271  * @dentry: a pointer to a the dentry of the file or directory to be removed.
 272  *
 273  * This function removes a file or directory in securityfs that was previously
 274  * created with a call to another securityfs function (like
 275  * securityfs_create_file() or variants thereof.)
 276  *
 277  * This function is required to be called in order for the file to be
 278  * removed. No automatic cleanup of files will happen when a module is
 279  * removed; you are responsible here.
 280  */
 281 void securityfs_remove(struct dentry *dentry)
 282 {
 283         struct dentry *parent;
 284
 285         if (!dentry || IS_ERR(dentry))
 286                 return;
 287
 288         parent = dentry->d_parent;
 289         if (!parent || !parent->d_inode)
 290                 return;
 291
 292         mutex_lock(&parent->d_inode->i_mutex);
 293         if (positive(dentry)) {
 294                 if (dentry->d_inode) {
 295                         if (S_ISDIR(dentry->d_inode->i_mode))
 296                                 simple_rmdir(parent->d_inode, dentry);
 297                         else
 298                                 simple_unlink(parent->d_inode, dentry);
 299                         dput(dentry);
 300                 }
 301         }
 302         mutex_unlock(&parent->d_inode->i_mutex);
 303         simple_release_fs(&mount, &mount_count);
 304 }
 305 EXPORT_SYMBOL_GPL(securityfs_remove);
 306
 307 static struct kobject *security_kobj;
 308
 309 static int __init securityfs_init(void)
 310 {
 311         int retval;
 312
 313         security_kobj = kobject_create_and_add("security", kernel_kobj);
 314         if (!security_kobj)
 315                 return -EINVAL;
 316
 317         retval = register_filesystem(&fs_type);
 318         if (retval)
 319                 kobject_put(security_kobj);
 320         return retval;
 321 }
 322
 323 core_initcall(securityfs_init);
 324 MODULE_LICENSE("GPL");
 325