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
  24 #define SECURITYFS_MAGIC        0x73636673
  25
  26 static struct vfsmount *mount;
  27 static int mount_count;
  28
  29 /*
  30  * TODO:
  31  *   I think I can get rid of these default_file_ops, but not quite sure...
  32  */
  33 static ssize_t default_read_file(struct file *file, char __user *buf,
  34                                  size_t count, loff_t *ppos)
  35 {
  36         return 0;
  37 }
  38
  39 static ssize_t default_write_file(struct file *file, const char __user *buf,
  40                                    size_t count, loff_t *ppos)
  41 {
  42         return count;
  43 }
  44
  45 static int default_open(struct inode *inode, struct file *file)
  46 {
  47         if (inode->i_private)
  48                 file->private_data = inode->i_private;
  49
  50         return 0;
  51 }
  52
  53 static const struct file_operations default_file_ops = {
  54         .read =         default_read_file,
  55         .write =        default_write_file,
  56         .open =         default_open,
  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_mode = mode;
  65                 inode->i_uid = 0;
  66                 inode->i_gid = 0;
  67                 inode->i_blocks = 0;
  68                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  69                 switch (mode & S_IFMT) {
  70                 default:
  71                         init_special_inode(inode, mode, dev);
  72                         break;
  73                 case S_IFREG:
  74                         inode->i_fop = &default_file_ops;
  75                         break;
  76                 case S_IFDIR:
  77                         inode->i_op = &simple_dir_inode_operations;
  78                         inode->i_fop = &simple_dir_operations;
  79
  80                         /* directory inodes start off with i_nlink == 2 (for "." entry) */
  81                         inc_nlink(inode);
  82                         break;
  83                 }
  84         }
  85         return inode;
  86 }
  87
  88 /* SMP-safe */
  89 static int mknod(struct inode *dir, struct dentry *dentry,
  90                          int mode, dev_t dev)
  91 {
  92         struct inode *inode;
  93         int error = -EPERM;
  94
  95         if (dentry->d_inode)
  96                 return -EEXIST;
  97
  98         inode = get_inode(dir->i_sb, mode, dev);
  99         if (inode) {
 100                 d_instantiate(dentry, inode);
 101                 dget(dentry);
 102                 error = 0;
 103         }
 104         return error;
 105 }
 106
 107 static int mkdir(struct inode *dir, struct dentry *dentry, int mode)
 108 {
 109         int res;
 110
 111         mode = (mode & (S_IRWXUGO | S_ISVTX)) | S_IFDIR;
 112         res = mknod(dir, dentry, mode, 0);
 113         if (!res)
 114                 inc_nlink(dir);
 115         return res;
 116 }
 117
 118 static int create(struct inode *dir, struct dentry *dentry, int mode)
 119 {
 120         mode = (mode & S_IALLUGO) | S_IFREG;
 121         return mknod(dir, dentry, mode, 0);
 122 }
 123
 124 static inline int positive(struct dentry *dentry)
 125 {
 126         return dentry->d_inode && !d_unhashed(dentry);
 127 }
 128
 129 static int fill_super(struct super_block *sb, void *data, int silent)
 130 {
 131         static struct tree_descr files[] = {{""}};
 132
 133         return simple_fill_super(sb, SECURITYFS_MAGIC, files);
 134 }
 135
 136 static int get_sb(struct file_system_type *fs_type,
 137                   int flags, const char *dev_name,
 138                   void *data, struct vfsmount *mnt)
 139 {
 140         return get_sb_single(fs_type, flags, data, fill_super, mnt);
 141 }
 142
 143 static struct file_system_type fs_type = {
 144         .owner =        THIS_MODULE,
 145         .name =         "securityfs",
 146         .get_sb =       get_sb,
 147         .kill_sb =      kill_litter_super,
 148 };
 149
 150 static int create_by_name(const char *name, mode_t mode,
 151                           struct dentry *parent,
 152                           struct dentry **dentry)
 153 {
 154         int error = 0;
 155
 156         *dentry = NULL;
 157
 158         /* If the parent is not specified, we create it in the root.
 159          * We need the root dentry to do this, which is in the super
 160          * block. A pointer to that is in the struct vfsmount that we
 161          * have around.
 162          */
 163         if (!parent ) {
 164                 if (mount && mount->mnt_sb) {
 165                         parent = mount->mnt_sb->s_root;
 166                 }
 167         }
 168         if (!parent) {
 169                 pr_debug("securityfs: Ah! can not find a parent!\n");
 170                 return -EFAULT;
 171         }
 172
 173         mutex_lock(&parent->d_inode->i_mutex);
 174         *dentry = lookup_one_len(name, parent, strlen(name));
 175         if (!IS_ERR(dentry)) {
 176                 if ((mode & S_IFMT) == S_IFDIR)
 177                         error = mkdir(parent->d_inode, *dentry, mode);
 178                 else
 179                         error = create(parent->d_inode, *dentry, mode);
 180         } else
 181                 error = PTR_ERR(dentry);
 182         mutex_unlock(&parent->d_inode->i_mutex);
 183
 184         return error;
 185 }
 186
 187 /**
 188  * securityfs_create_file - create a file in the securityfs filesystem
 189  *
 190  * @name: a pointer to a string containing the name of the file to create.
 191  * @mode: the permission that the file should have
 192  * @parent: a pointer to the parent dentry for this file.  This should be a
 193  *          directory dentry if set.  If this paramater is NULL, then the
 194  *          file will be created in the root of the securityfs filesystem.
 195  * @data: a pointer to something that the caller will want to get to later
 196  *        on.  The inode.i_private pointer will point to this value on
 197  *        the open() call.
 198  * @fops: a pointer to a struct file_operations that should be used for
 199  *        this file.
 200  *
 201  * This is the basic "create a file" function for securityfs.  It allows for a
 202  * wide range of flexibility in createing a file, or a directory (if you
 203  * want to create a directory, the securityfs_create_dir() function is
 204  * recommended to be used instead.)
 205  *
 206  * This function will return a pointer to a dentry if it succeeds.  This
 207  * pointer must be passed to the securityfs_remove() function when the file is
 208  * to be removed (no automatic cleanup happens if your module is unloaded,
 209  * you are responsible here.)  If an error occurs, NULL will be returned.
 210  *
 211  * If securityfs is not enabled in the kernel, the value -ENODEV will be
 212  * returned.  It is not wise to check for this value, but rather, check for
 213  * NULL or !NULL instead as to eliminate the need for #ifdef in the calling
 214  * code.
 215  */
 216 struct dentry *securityfs_create_file(const char *name, mode_t mode,
 217                                    struct dentry *parent, void *data,
 218                                    const struct file_operations *fops)
 219 {
 220         struct dentry *dentry = NULL;
 221         int error;
 222
 223         pr_debug("securityfs: creating file '%s'\n",name);
 224
 225         error = simple_pin_fs(&fs_type, &mount, &mount_count);
 226         if (error) {
 227                 dentry = ERR_PTR(error);
 228                 goto exit;
 229         }
 230
 231         error = create_by_name(name, mode, parent, &dentry);
 232         if (error) {
 233                 dentry = ERR_PTR(error);
 234                 simple_release_fs(&mount, &mount_count);
 235                 goto exit;
 236         }
 237
 238         if (dentry->d_inode) {
 239                 if (fops)
 240                         dentry->d_inode->i_fop = fops;
 241                 if (data)
 242                         dentry->d_inode->i_private = data;
 243         }
 244 exit:
 245         return dentry;
 246 }
 247 EXPORT_SYMBOL_GPL(securityfs_create_file);
 248
 249 /**
 250  * securityfs_create_dir - create a directory in the securityfs filesystem
 251  *
 252  * @name: a pointer to a string containing the name of the directory to
 253  *        create.
 254  * @parent: a pointer to the parent dentry for this file.  This should be a
 255  *          directory dentry if set.  If this paramater is NULL, then the
 256  *          directory will be created in the root of the securityfs filesystem.
 257  *
 258  * This function creates a directory in securityfs with the given name.
 259  *
 260  * This function will return a pointer to a dentry if it succeeds.  This
 261  * pointer must be passed to the securityfs_remove() function when the file is
 262  * to be removed (no automatic cleanup happens if your module is unloaded,
 263  * you are responsible here.)  If an error occurs, NULL will be returned.
 264  *
 265  * If securityfs is not enabled in the kernel, the value -ENODEV will be
 266  * returned.  It is not wise to check for this value, but rather, check for
 267  * NULL or !NULL instead as to eliminate the need for #ifdef in the calling
 268  * code.
 269  */
 270 struct dentry *securityfs_create_dir(const char *name, struct dentry *parent)
 271 {
 272         return securityfs_create_file(name,
 273                                       S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
 274                                       parent, NULL, NULL);
 275 }
 276 EXPORT_SYMBOL_GPL(securityfs_create_dir);
 277
 278 /**
 279  * securityfs_remove - removes a file or directory from the securityfs filesystem
 280  *
 281  * @dentry: a pointer to a the dentry of the file or directory to be
 282  *          removed.
 283  *
 284  * This function removes a file or directory in securityfs that was previously
 285  * created with a call to another securityfs function (like
 286  * securityfs_create_file() or variants thereof.)
 287  *
 288  * This function is required to be called in order for the file to be
 289  * removed, no automatic cleanup of files will happen when a module is
 290  * removed, you are responsible here.
 291  */
 292 void securityfs_remove(struct dentry *dentry)
 293 {
 294         struct dentry *parent;
 295
 296         if (!dentry)
 297                 return;
 298
 299         parent = dentry->d_parent;
 300         if (!parent || !parent->d_inode)
 301                 return;
 302
 303         mutex_lock(&parent->d_inode->i_mutex);
 304         if (positive(dentry)) {
 305                 if (dentry->d_inode) {
 306                         if (S_ISDIR(dentry->d_inode->i_mode))
 307                                 simple_rmdir(parent->d_inode, dentry);
 308                         else
 309                                 simple_unlink(parent->d_inode, dentry);
 310                         dput(dentry);
 311                 }
 312         }
 313         mutex_unlock(&parent->d_inode->i_mutex);
 314         simple_release_fs(&mount, &mount_count);
 315 }
 316 EXPORT_SYMBOL_GPL(securityfs_remove);
 317
 318 static decl_subsys(security, NULL, NULL);
 319
 320 static int __init securityfs_init(void)
 321 {
 322         int retval;
 323
 324         kobj_set_kset_s(&security_subsys, kernel_subsys);
 325         retval = subsystem_register(&security_subsys);
 326         if (retval)
 327                 return retval;
 328
 329         retval = register_filesystem(&fs_type);
 330         if (retval)
 331                 subsystem_unregister(&security_subsys);
 332         return retval;
 333 }
 334
 335 core_initcall(securityfs_init);
 336 MODULE_LICENSE("GPL");
 337