fs/btrfs/xattr.c

   1 /*
   2  * Copyright (C) 2007 Red Hat.  All rights reserved.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public
   6  * License v2 as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public
  14  * License along with this program; if not, write to the
  15  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  16  * Boston, MA 021110-1307, USA.
  17  */
  18
  19 #include <linux/init.h>
  20 #include <linux/fs.h>
  21 #include <linux/slab.h>
  22 #include <linux/rwsem.h>
  23 #include <linux/xattr.h>
  24 #include <linux/security.h>
  25 #include "ctree.h"
  26 #include "btrfs_inode.h"
  27 #include "transaction.h"
  28 #include "xattr.h"
  29 #include "disk-io.h"
  30 #include "props.h"
  31
  32
  33 ssize_t __btrfs_getxattr(struct inode *inode, const char *name,
  34                                 void *buffer, size_t size)
  35 {
  36         struct btrfs_dir_item *di;
  37         struct btrfs_root *root = BTRFS_I(inode)->root;
  38         struct btrfs_path *path;
  39         struct extent_buffer *leaf;
  40         int ret = 0;
  41         unsigned long data_ptr;
  42
  43         path = btrfs_alloc_path();
  44         if (!path)
  45                 return -ENOMEM;
  46
  47         /* lookup the xattr by name */
  48         di = btrfs_lookup_xattr(NULL, root, path, btrfs_ino(inode), name,
  49                                 strlen(name), 0);
  50         if (!di) {
  51                 ret = -ENODATA;
  52                 goto out;
  53         } else if (IS_ERR(di)) {
  54                 ret = PTR_ERR(di);
  55                 goto out;
  56         }
  57
  58         leaf = path->nodes[0];
  59         /* if size is 0, that means we want the size of the attr */
  60         if (!size) {
  61                 ret = btrfs_dir_data_len(leaf, di);
  62                 goto out;
  63         }
  64
  65         /* now get the data out of our dir_item */
  66         if (btrfs_dir_data_len(leaf, di) > size) {
  67                 ret = -ERANGE;
  68                 goto out;
  69         }
  70
  71         /*
  72          * The way things are packed into the leaf is like this
  73          * |struct btrfs_dir_item|name|data|
  74          * where name is the xattr name, so security.foo, and data is the
  75          * content of the xattr.  data_ptr points to the location in memory
  76          * where the data starts in the in memory leaf
  77          */
  78         data_ptr = (unsigned long)((char *)(di + 1) +
  79                                    btrfs_dir_name_len(leaf, di));
  80         read_extent_buffer(leaf, buffer, data_ptr,
  81                            btrfs_dir_data_len(leaf, di));
  82         ret = btrfs_dir_data_len(leaf, di);
  83
  84 out:
  85         btrfs_free_path(path);
  86         return ret;
  87 }
  88
  89 static int do_setxattr(struct btrfs_trans_handle *trans,
  90                        struct inode *inode, const char *name,
  91                        const void *value, size_t size, int flags)
  92 {
  93         struct btrfs_dir_item *di;
  94         struct btrfs_root *root = BTRFS_I(inode)->root;
  95         struct btrfs_path *path;
  96         size_t name_len = strlen(name);
  97         int ret = 0;
  98
  99         if (name_len + size > BTRFS_MAX_XATTR_SIZE(root))
 100                 return -ENOSPC;
 101
 102         path = btrfs_alloc_path();
 103         if (!path)
 104                 return -ENOMEM;
 105
 106         if (flags & XATTR_REPLACE) {
 107                 di = btrfs_lookup_xattr(trans, root, path, btrfs_ino(inode), name,
 108                                         name_len, -1);
 109                 if (IS_ERR(di)) {
 110                         ret = PTR_ERR(di);
 111                         goto out;
 112                 } else if (!di) {
 113                         ret = -ENODATA;
 114                         goto out;
 115                 }
 116                 ret = btrfs_delete_one_dir_name(trans, root, path, di);
 117                 if (ret)
 118                         goto out;
 119                 btrfs_release_path(path);
 120
 121                 /*
 122                  * remove the attribute
 123                  */
 124                 if (!value)
 125                         goto out;
 126         } else {
 127                 di = btrfs_lookup_xattr(NULL, root, path, btrfs_ino(inode),
 128                                         name, name_len, 0);
 129                 if (IS_ERR(di)) {
 130                         ret = PTR_ERR(di);
 131                         goto out;
 132                 }
 133                 if (!di && !value)
 134                         goto out;
 135                 btrfs_release_path(path);
 136         }
 137
 138 again:
 139         ret = btrfs_insert_xattr_item(trans, root, path, btrfs_ino(inode),
 140                                       name, name_len, value, size);
 141         /*
 142          * If we're setting an xattr to a new value but the new value is say
 143          * exactly BTRFS_MAX_XATTR_SIZE, we could end up with EOVERFLOW getting
 144          * back from split_leaf.  This is because it thinks we'll be extending
 145          * the existing item size, but we're asking for enough space to add the
 146          * item itself.  So if we get EOVERFLOW just set ret to EEXIST and let
 147          * the rest of the function figure it out.
 148          */
 149         if (ret == -EOVERFLOW)
 150                 ret = -EEXIST;
 151
 152         if (ret == -EEXIST) {
 153                 if (flags & XATTR_CREATE)
 154                         goto out;
 155                 /*
 156                  * We can't use the path we already have since we won't have the
 157                  * proper locking for a delete, so release the path and
 158                  * re-lookup to delete the thing.
 159                  */
 160                 btrfs_release_path(path);
 161                 di = btrfs_lookup_xattr(trans, root, path, btrfs_ino(inode),
 162                                         name, name_len, -1);
 163                 if (IS_ERR(di)) {
 164                         ret = PTR_ERR(di);
 165                         goto out;
 166                 } else if (!di) {
 167                         /* Shouldn't happen but just in case... */
 168                         btrfs_release_path(path);
 169                         goto again;
 170                 }
 171
 172                 ret = btrfs_delete_one_dir_name(trans, root, path, di);
 173                 if (ret)
 174                         goto out;
 175
 176                 /*
 177                  * We have a value to set, so go back and try to insert it now.
 178                  */
 179                 if (value) {
 180                         btrfs_release_path(path);
 181                         goto again;
 182                 }
 183         }
 184 out:
 185         btrfs_free_path(path);
 186         return ret;
 187 }
 188
 189 /*
 190  * @value: "" makes the attribute to empty, NULL removes it
 191  */
 192 int __btrfs_setxattr(struct btrfs_trans_handle *trans,
 193                      struct inode *inode, const char *name,
 194                      const void *value, size_t size, int flags)
 195 {
 196         struct btrfs_root *root = BTRFS_I(inode)->root;
 197         int ret;
 198
 199         if (trans)
 200                 return do_setxattr(trans, inode, name, value, size, flags);
 201
 202         trans = btrfs_start_transaction(root, 2);
 203         if (IS_ERR(trans))
 204                 return PTR_ERR(trans);
 205
 206         ret = do_setxattr(trans, inode, name, value, size, flags);
 207         if (ret)
 208                 goto out;
 209
 210         inode_inc_iversion(inode);
 211         inode->i_ctime = CURRENT_TIME;
 212         set_bit(BTRFS_INODE_COPY_EVERYTHING, &BTRFS_I(inode)->runtime_flags);
 213         ret = btrfs_update_inode(trans, root, inode);
 214         BUG_ON(ret);
 215 out:
 216         btrfs_end_transaction(trans, root);
 217         return ret;
 218 }
 219
 220 ssize_t btrfs_listxattr(struct dentry *dentry, char *buffer, size_t size)
 221 {
 222         struct btrfs_key key, found_key;
 223         struct inode *inode = dentry->d_inode;
 224         struct btrfs_root *root = BTRFS_I(inode)->root;
 225         struct btrfs_path *path;
 226         struct extent_buffer *leaf;
 227         struct btrfs_dir_item *di;
 228         int ret = 0, slot;
 229         size_t total_size = 0, size_left = size;
 230         unsigned long name_ptr;
 231         size_t name_len;
 232
 233         /*
 234          * ok we want all objects associated with this id.
 235          * NOTE: we set key.offset = 0; because we want to start with the
 236          * first xattr that we find and walk forward
 237          */
 238         key.objectid = btrfs_ino(inode);
 239         btrfs_set_key_type(&key, BTRFS_XATTR_ITEM_KEY);
 240         key.offset = 0;
 241
 242         path = btrfs_alloc_path();
 243         if (!path)
 244                 return -ENOMEM;
 245         path->reada = 2;
 246
 247         /* search for our xattrs */
 248         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
 249         if (ret < 0)
 250                 goto err;
 251
 252         while (1) {
 253                 leaf = path->nodes[0];
 254                 slot = path->slots[0];
 255
 256                 /* this is where we start walking through the path */
 257                 if (slot >= btrfs_header_nritems(leaf)) {
 258                         /*
 259                          * if we've reached the last slot in this leaf we need
 260                          * to go to the next leaf and reset everything
 261                          */
 262                         ret = btrfs_next_leaf(root, path);
 263                         if (ret < 0)
 264                                 goto err;
 265                         else if (ret > 0)
 266                                 break;
 267                         continue;
 268                 }
 269
 270                 btrfs_item_key_to_cpu(leaf, &found_key, slot);
 271
 272                 /* check to make sure this item is what we want */
 273                 if (found_key.objectid != key.objectid)
 274                         break;
 275                 if (btrfs_key_type(&found_key) != BTRFS_XATTR_ITEM_KEY)
 276                         break;
 277
 278                 di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
 279                 if (verify_dir_item(root, leaf, di))
 280                         goto next;
 281
 282                 name_len = btrfs_dir_name_len(leaf, di);
 283                 total_size += name_len + 1;
 284
 285                 /* we are just looking for how big our buffer needs to be */
 286                 if (!size)
 287                         goto next;
 288
 289                 if (!buffer || (name_len + 1) > size_left) {
 290                         ret = -ERANGE;
 291                         goto err;
 292                 }
 293
 294                 name_ptr = (unsigned long)(di + 1);
 295                 read_extent_buffer(leaf, buffer, name_ptr, name_len);
 296                 buffer[name_len] = '\0';
 297
 298                 size_left -= name_len + 1;
 299                 buffer += name_len + 1;
 300 next:
 301                 path->slots[0]++;
 302         }
 303         ret = total_size;
 304
 305 err:
 306         btrfs_free_path(path);
 307
 308         return ret;
 309 }
 310
 311 /*
 312  * List of handlers for synthetic system.* attributes.  All real ondisk
 313  * attributes are handled directly.
 314  */
 315 const struct xattr_handler *btrfs_xattr_handlers[] = {
 316 #ifdef CONFIG_BTRFS_FS_POSIX_ACL
 317         &btrfs_xattr_acl_access_handler,
 318         &btrfs_xattr_acl_default_handler,
 319 #endif
 320         NULL,
 321 };
 322
 323 /*
 324  * Check if the attribute is in a supported namespace.
 325  *
 326  * This applied after the check for the synthetic attributes in the system
 327  * namespace.
 328  */
 329 static bool btrfs_is_valid_xattr(const char *name)
 330 {
 331         return !strncmp(name, XATTR_SECURITY_PREFIX,
 332                         XATTR_SECURITY_PREFIX_LEN) ||
 333                !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN) ||
 334                !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) ||
 335                !strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN) ||
 336                 !strncmp(name, XATTR_BTRFS_PREFIX, XATTR_BTRFS_PREFIX_LEN);
 337 }
 338
 339 ssize_t btrfs_getxattr(struct dentry *dentry, const char *name,
 340                        void *buffer, size_t size)
 341 {
 342         /*
 343          * If this is a request for a synthetic attribute in the system.*
 344          * namespace use the generic infrastructure to resolve a handler
 345          * for it via sb->s_xattr.
 346          */
 347         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
 348                 return generic_getxattr(dentry, name, buffer, size);
 349
 350         if (!btrfs_is_valid_xattr(name))
 351                 return -EOPNOTSUPP;
 352         return __btrfs_getxattr(dentry->d_inode, name, buffer, size);
 353 }
 354
 355 int btrfs_setxattr(struct dentry *dentry, const char *name, const void *value,
 356                    size_t size, int flags)
 357 {
 358         struct btrfs_root *root = BTRFS_I(dentry->d_inode)->root;
 359
 360         /*
 361          * The permission on security.* and system.* is not checked
 362          * in permission().
 363          */
 364         if (btrfs_root_readonly(root))
 365                 return -EROFS;
 366
 367         /*
 368          * If this is a request for a synthetic attribute in the system.*
 369          * namespace use the generic infrastructure to resolve a handler
 370          * for it via sb->s_xattr.
 371          */
 372         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
 373                 return generic_setxattr(dentry, name, value, size, flags);
 374
 375         if (!btrfs_is_valid_xattr(name))
 376                 return -EOPNOTSUPP;
 377
 378         if (!strncmp(name, XATTR_BTRFS_PREFIX, XATTR_BTRFS_PREFIX_LEN))
 379                 return btrfs_set_prop(dentry->d_inode, name,
 380                                       value, size, flags);
 381
 382         if (size == 0)
 383                 value = "";  /* empty EA, do not remove */
 384
 385         return __btrfs_setxattr(NULL, dentry->d_inode, name, value, size,
 386                                 flags);
 387 }
 388
 389 int btrfs_removexattr(struct dentry *dentry, const char *name)
 390 {
 391         struct btrfs_root *root = BTRFS_I(dentry->d_inode)->root;
 392
 393         /*
 394          * The permission on security.* and system.* is not checked
 395          * in permission().
 396          */
 397         if (btrfs_root_readonly(root))
 398                 return -EROFS;
 399
 400         /*
 401          * If this is a request for a synthetic attribute in the system.*
 402          * namespace use the generic infrastructure to resolve a handler
 403          * for it via sb->s_xattr.
 404          */
 405         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
 406                 return generic_removexattr(dentry, name);
 407
 408         if (!btrfs_is_valid_xattr(name))
 409                 return -EOPNOTSUPP;
 410
 411         if (!strncmp(name, XATTR_BTRFS_PREFIX, XATTR_BTRFS_PREFIX_LEN))
 412                 return btrfs_set_prop(dentry->d_inode, name,
 413                                       NULL, 0, XATTR_REPLACE);
 414
 415         return __btrfs_setxattr(NULL, dentry->d_inode, name, NULL, 0,
 416                                 XATTR_REPLACE);
 417 }
 418
 419 static int btrfs_initxattrs(struct inode *inode,
 420                             const struct xattr *xattr_array, void *fs_info)
 421 {
 422         const struct xattr *xattr;
 423         struct btrfs_trans_handle *trans = fs_info;
 424         char *name;
 425         int err = 0;
 426
 427         for (xattr = xattr_array; xattr->name != NULL; xattr++) {
 428                 name = kmalloc(XATTR_SECURITY_PREFIX_LEN +
 429                                strlen(xattr->name) + 1, GFP_NOFS);
 430                 if (!name) {
 431                         err = -ENOMEM;
 432                         break;
 433                 }
 434                 strcpy(name, XATTR_SECURITY_PREFIX);
 435                 strcpy(name + XATTR_SECURITY_PREFIX_LEN, xattr->name);
 436                 err = __btrfs_setxattr(trans, inode, name,
 437                                        xattr->value, xattr->value_len, 0);
 438                 kfree(name);
 439                 if (err < 0)
 440                         break;
 441         }
 442         return err;
 443 }
 444
 445 int btrfs_xattr_security_init(struct btrfs_trans_handle *trans,
 446                               struct inode *inode, struct inode *dir,
 447                               const struct qstr *qstr)
 448 {
 449         return security_inode_init_security(inode, dir, qstr,
 450                                             &btrfs_initxattrs, trans);
 451 }