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->u.generic_ip)
  48                 file->private_data = inode->u.generic_ip;
  49
  50         return 0;
  51 }
  52
  53 static 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_blksize = PAGE_CACHE_SIZE;
  68                 inode->i_blocks = 0;
  69                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  70                 switch (mode & S_IFMT) {
  71                 default:
  72                         init_special_inode(inode, mode, dev);
  73                         break;
  74                 case S_IFREG:
  75                         inode->i_fop = &default_file_ops;
  76                         break;
  77                 case S_IFDIR:
  78                         inode->i_op = &simple_dir_inode_operations;
  79                         inode->i_fop = &simple_dir_operations;
  80
  81                         /* directory inodes start off with i_nlink == 2 (for "." entry) */
  82                         inode->i_nlink++;
  83                         break;
  84                 }
  85         }
  86         return inode;
  87 }
  88
  89 /* SMP-safe */
  90 static int mknod(struct inode *dir, struct dentry *dentry,
  91                          int mode, dev_t dev)
  92 {
  93         struct inode *inode;
  94         int error = -EPERM;
  95
  96         if (dentry->d_inode)
  97                 return -EEXIST;
  98
  99         inode = get_inode(dir->i_sb, mode, dev);
 100         if (inode) {
 101                 d_instantiate(dentry, inode);
 102                 dget(dentry);
 103                 error = 0;
 104         }
 105         return error;
 106 }
 107
 108 static int mkdir(struct inode *dir, struct dentry *dentry, int mode)
 109 {
 110         int res;
 111
 112         mode = (mode & (S_IRWXUGO | S_ISVTX)) | S_IFDIR;
 113         res = mknod(dir, dentry, mode, 0);
 114         if (!res)
 115                 dir->i_nlink++;
 116         return res;
 117 }
 118
 119 static int create(struct inode *dir, struct dentry *dentry, int mode)
 120 {
 121         mode = (mode & S_IALLUGO) | S_IFREG;
 122         return mknod(dir, dentry, mode, 0);
 123 }
 124
 125 static inline int positive(struct dentry *dentry)
 126 {
 127         return dentry->d_inode && !d_unhashed(dentry);
 128 }
 129
 130 static int fill_super(struct super_block *sb, void *data, int silent)
 131 {
 132         static struct tree_descr files[] = {{""}};
 133
 134         return simple_fill_super(sb, SECURITYFS_MAGIC, files);
 135 }
 136
 137 static int get_sb(struct file_system_type *fs_type,
 138                   int flags, const char *dev_name,
 139                   void *data, struct vfsmount *mnt)
 140 {
 141         return get_sb_single(fs_type, flags, data, fill_super, mnt);
 142 }
 143
 144 static struct file_system_type fs_type = {
 145         .owner =        THIS_MODULE,
 146         .name =         "securityfs",
 147         .get_sb =       get_sb,
 148         .kill_sb =      kill_litter_super,
 149 };
 150
 151 static int create_by_name(const char *name, mode_t mode,
 152                           struct dentry *parent,
 153                           struct dentry **dentry)
 154 {
 155         int error = 0;
 156
 157         *dentry = NULL;
 158
 159         /* If the parent is not specified, we create it in the root.
 160          * We need the root dentry to do this, which is in the super
 161          * block. A pointer to that is in the struct vfsmount that we
 162          * have around.
 163          */
 164         if (!parent ) {
 165                 if (mount && mount->mnt_sb) {
 166                         parent = mount->mnt_sb->s_root;
 167                 }
 168         }
 169         if (!parent) {
 170                 pr_debug("securityfs: Ah! can not find a parent!\n");
 171                 return -EFAULT;
 172         }
 173
 174         mutex_lock(&parent->d_inode->i_mutex);
 175         *dentry = lookup_one_len(name, parent, strlen(name));
 176         if (!IS_ERR(dentry)) {
 177                 if ((mode & S_IFMT) == S_IFDIR)
 178                         error = mkdir(parent->d_inode, *dentry, mode);
 179                 else
 180                         error = create(parent->d_inode, *dentry, mode);
 181         } else
 182                 error = PTR_ERR(dentry);
 183         mutex_unlock(&parent->d_inode->i_mutex);
 184
 185         return error;
 186 }
 187
 188 /**
 189  * securityfs_create_file - create a file in the securityfs filesystem
 190  *
 191  * @name: a pointer to a string containing the name of the file to create.
 192  * @mode: the permission that the file should have
 193  * @parent: a pointer to the parent dentry for this file.  This should be a
 194  *          directory dentry if set.  If this paramater is NULL, then the
 195  *          file will be created in the root of the securityfs filesystem.
 196  * @data: a pointer to something that the caller will want to get to later
 197  *        on.  The inode.u.generic_ip pointer will point to this value on
 198  *        the open() call.
 199  * @fops: a pointer to a struct file_operations that should be used for
 200  *        this file.
 201  *
 202  * This is the basic "create a file" function for securityfs.  It allows for a
 203  * wide range of flexibility in createing a file, or a directory (if you
 204  * want to create a directory, the securityfs_create_dir() function is
 205  * recommended to be used instead.)
 206  *
 207  * This function will return a pointer to a dentry if it succeeds.  This
 208  * pointer must be passed to the securityfs_remove() function when the file is
 209  * to be removed (no automatic cleanup happens if your module is unloaded,
 210  * you are responsible here.)  If an error occurs, NULL will be returned.
 211  *
 212  * If securityfs is not enabled in the kernel, the value -ENODEV will be
 213  * returned.  It is not wise to check for this value, but rather, check for
 214  * NULL or !NULL instead as to eliminate the need for #ifdef in the calling
 215  * code.
 216  */
 217 struct dentry *securityfs_create_file(const char *name, mode_t mode,
 218                                    struct dentry *parent, void *data,
 219                                    struct file_operations *fops)
 220 {
 221         struct dentry *dentry = NULL;
 222         int error;
 223
 224         pr_debug("securityfs: creating file '%s'\n",name);
 225
 226         error = simple_pin_fs(&fs_type, &mount, &mount_count);
 227         if (error) {
 228                 dentry = ERR_PTR(error);
 229                 goto exit;
 230         }
 231
 232         error = create_by_name(name, mode, parent, &dentry);
 233         if (error) {
 234                 dentry = ERR_PTR(error);
 235                 simple_release_fs(&mount, &mount_count);
 236                 goto exit;
 237         }
 238
 239         if (dentry->d_inode) {
 240                 if (fops)
 241                         dentry->d_inode->i_fop = fops;
 242                 if (data)
 243                         dentry->d_inode->u.generic_ip = data;
 244         }
 245 exit:
 246         return dentry;
 247 }
 248 EXPORT_SYMBOL_GPL(securityfs_create_file);
 249
 250 /**
 251  * securityfs_create_dir - create a directory in the securityfs filesystem
 252  *
 253  * @name: a pointer to a string containing the name of the directory to
 254  *        create.
 255  * @parent: a pointer to the parent dentry for this file.  This should be a
 256  *          directory dentry if set.  If this paramater is NULL, then the
 257  *          directory will be created in the root of the securityfs filesystem.
 258  *
 259  * This function creates a directory in securityfs with the given name.
 260  *
 261  * This function will return a pointer to a dentry if it succeeds.  This
 262  * pointer must be passed to the securityfs_remove() function when the file is
 263  * to be removed (no automatic cleanup happens if your module is unloaded,
 264  * you are responsible here.)  If an error occurs, NULL will be returned.
 265  *
 266  * If securityfs is not enabled in the kernel, the value -ENODEV will be
 267  * returned.  It is not wise to check for this value, but rather, check for
 268  * NULL or !NULL instead as to eliminate the need for #ifdef in the calling
 269  * code.
 270  */
 271 struct dentry *securityfs_create_dir(const char *name, struct dentry *parent)
 272 {
 273         return securityfs_create_file(name,
 274                                       S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
 275                                       parent, NULL, NULL);
 276 }
 277 EXPORT_SYMBOL_GPL(securityfs_create_dir);
 278
 279 /**
 280  * securityfs_remove - removes a file or directory from the securityfs filesystem
 281  *
 282  * @dentry: a pointer to a the dentry of the file or directory to be
 283  *          removed.
 284  *
 285  * This function removes a file or directory in securityfs that was previously
 286  * created with a call to another securityfs function (like
 287  * securityfs_create_file() or variants thereof.)
 288  *
 289  * This function is required to be called in order for the file to be
 290  * removed, no automatic cleanup of files will happen when a module is
 291  * removed, you are responsible here.
 292  */
 293 void securityfs_remove(struct dentry *dentry)
 294 {
 295         struct dentry *parent;
 296
 297         if (!dentry)
 298                 return;
 299
 300         parent = dentry->d_parent;
 301         if (!parent || !parent->d_inode)
 302                 return;
 303
 304         mutex_lock(&parent->d_inode->i_mutex);
 305         if (positive(dentry)) {
 306                 if (dentry->d_inode) {
 307                         if (S_ISDIR(dentry->d_inode->i_mode))
 308                                 simple_rmdir(parent->d_inode, dentry);
 309                         else
 310                                 simple_unlink(parent->d_inode, dentry);
 311                         dput(dentry);
 312                 }
 313         }
 314         mutex_unlock(&parent->d_inode->i_mutex);
 315         simple_release_fs(&mount, &mount_count);
 316 }
 317 EXPORT_SYMBOL_GPL(securityfs_remove);
 318
 319 static decl_subsys(security, NULL, NULL);
 320
 321 static int __init securityfs_init(void)
 322 {
 323         int retval;
 324
 325         kset_set_kset_s(&security_subsys, kernel_subsys);
 326         retval = subsystem_register(&security_subsys);
 327         if (retval)
 328                 return retval;
 329
 330         retval = register_filesystem(&fs_type);
 331         if (retval)
 332                 subsystem_unregister(&security_subsys);
 333         return retval;
 334 }
 335
 336 static void __exit securityfs_exit(void)
 337 {
 338         simple_release_fs(&mount, &mount_count);
 339         unregister_filesystem(&fs_type);
 340         subsystem_unregister(&security_subsys);
 341 }
 342
 343 core_initcall(securityfs_init);
 344 module_exit(securityfs_exit);
 345 MODULE_LICENSE("GPL");
 346