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 <linux/posix_acl_xattr.h>
  26 #include <linux/iversion.h>
  27 #include "ctree.h"
  28 #include "btrfs_inode.h"
  29 #include "transaction.h"
  30 #include "xattr.h"
  31 #include "disk-io.h"
  32 #include "props.h"
  33 #include "locking.h"
  34
  35
  36 ssize_t __btrfs_getxattr(struct inode *inode, const char *name,
  37                                 void *buffer, size_t size)
  38 {
  39         struct btrfs_dir_item *di;
  40         struct btrfs_root *root = BTRFS_I(inode)->root;
  41         struct btrfs_path *path;
  42         struct extent_buffer *leaf;
  43         int ret = 0;
  44         unsigned long data_ptr;
  45
  46         path = btrfs_alloc_path();
  47         if (!path)
  48                 return -ENOMEM;
  49
  50         /* lookup the xattr by name */
  51         di = btrfs_lookup_xattr(NULL, root, path, btrfs_ino(BTRFS_I(inode)),
  52                         name, strlen(name), 0);
  53         if (!di) {
  54                 ret = -ENODATA;
  55                 goto out;
  56         } else if (IS_ERR(di)) {
  57                 ret = PTR_ERR(di);
  58                 goto out;
  59         }
  60
  61         leaf = path->nodes[0];
  62         /* if size is 0, that means we want the size of the attr */
  63         if (!size) {
  64                 ret = btrfs_dir_data_len(leaf, di);
  65                 goto out;
  66         }
  67
  68         /* now get the data out of our dir_item */
  69         if (btrfs_dir_data_len(leaf, di) > size) {
  70                 ret = -ERANGE;
  71                 goto out;
  72         }
  73
  74         /*
  75          * The way things are packed into the leaf is like this
  76          * |struct btrfs_dir_item|name|data|
  77          * where name is the xattr name, so security.foo, and data is the
  78          * content of the xattr.  data_ptr points to the location in memory
  79          * where the data starts in the in memory leaf
  80          */
  81         data_ptr = (unsigned long)((char *)(di + 1) +
  82                                    btrfs_dir_name_len(leaf, di));
  83         read_extent_buffer(leaf, buffer, data_ptr,
  84                            btrfs_dir_data_len(leaf, di));
  85         ret = btrfs_dir_data_len(leaf, di);
  86
  87 out:
  88         btrfs_free_path(path);
  89         return ret;
  90 }
  91
  92 static int do_setxattr(struct btrfs_trans_handle *trans,
  93                        struct inode *inode, const char *name,
  94                        const void *value, size_t size, int flags)
  95 {
  96         struct btrfs_dir_item *di = NULL;
  97         struct btrfs_root *root = BTRFS_I(inode)->root;
  98         struct btrfs_fs_info *fs_info = root->fs_info;
  99         struct btrfs_path *path;
 100         size_t name_len = strlen(name);
 101         int ret = 0;
 102
 103         if (name_len + size > BTRFS_MAX_XATTR_SIZE(root->fs_info))
 104                 return -ENOSPC;
 105
 106         path = btrfs_alloc_path();
 107         if (!path)
 108                 return -ENOMEM;
 109         path->skip_release_on_error = 1;
 110
 111         if (!value) {
 112                 di = btrfs_lookup_xattr(trans, root, path,
 113                                 btrfs_ino(BTRFS_I(inode)), name, name_len, -1);
 114                 if (!di && (flags & XATTR_REPLACE))
 115                         ret = -ENODATA;
 116                 else if (IS_ERR(di))
 117                         ret = PTR_ERR(di);
 118                 else if (di)
 119                         ret = btrfs_delete_one_dir_name(trans, root, path, di);
 120                 goto out;
 121         }
 122
 123         /*
 124          * For a replace we can't just do the insert blindly.
 125          * Do a lookup first (read-only btrfs_search_slot), and return if xattr
 126          * doesn't exist. If it exists, fall down below to the insert/replace
 127          * path - we can't race with a concurrent xattr delete, because the VFS
 128          * locks the inode's i_mutex before calling setxattr or removexattr.
 129          */
 130         if (flags & XATTR_REPLACE) {
 131                 ASSERT(inode_is_locked(inode));
 132                 di = btrfs_lookup_xattr(NULL, root, path,
 133                                 btrfs_ino(BTRFS_I(inode)), name, name_len, 0);
 134                 if (!di)
 135                         ret = -ENODATA;
 136                 else if (IS_ERR(di))
 137                         ret = PTR_ERR(di);
 138                 if (ret)
 139                         goto out;
 140                 btrfs_release_path(path);
 141                 di = NULL;
 142         }
 143
 144         ret = btrfs_insert_xattr_item(trans, root, path, btrfs_ino(BTRFS_I(inode)),
 145                                       name, name_len, value, size);
 146         if (ret == -EOVERFLOW) {
 147                 /*
 148                  * We have an existing item in a leaf, split_leaf couldn't
 149                  * expand it. That item might have or not a dir_item that
 150                  * matches our target xattr, so lets check.
 151                  */
 152                 ret = 0;
 153                 btrfs_assert_tree_locked(path->nodes[0]);
 154                 di = btrfs_match_dir_item_name(fs_info, path, name, name_len);
 155                 if (!di && !(flags & XATTR_REPLACE)) {
 156                         ret = -ENOSPC;
 157                         goto out;
 158                 }
 159         } else if (ret == -EEXIST) {
 160                 ret = 0;
 161                 di = btrfs_match_dir_item_name(fs_info, path, name, name_len);
 162                 ASSERT(di); /* logic error */
 163         } else if (ret) {
 164                 goto out;
 165         }
 166
 167         if (di && (flags & XATTR_CREATE)) {
 168                 ret = -EEXIST;
 169                 goto out;
 170         }
 171
 172         if (di) {
 173                 /*
 174                  * We're doing a replace, and it must be atomic, that is, at
 175                  * any point in time we have either the old or the new xattr
 176                  * value in the tree. We don't want readers (getxattr and
 177                  * listxattrs) to miss a value, this is specially important
 178                  * for ACLs.
 179                  */
 180                 const int slot = path->slots[0];
 181                 struct extent_buffer *leaf = path->nodes[0];
 182                 const u16 old_data_len = btrfs_dir_data_len(leaf, di);
 183                 const u32 item_size = btrfs_item_size_nr(leaf, slot);
 184                 const u32 data_size = sizeof(*di) + name_len + size;
 185                 struct btrfs_item *item;
 186                 unsigned long data_ptr;
 187                 char *ptr;
 188
 189                 if (size > old_data_len) {
 190                         if (btrfs_leaf_free_space(fs_info, leaf) <
 191                             (size - old_data_len)) {
 192                                 ret = -ENOSPC;
 193                                 goto out;
 194                         }
 195                 }
 196
 197                 if (old_data_len + name_len + sizeof(*di) == item_size) {
 198                         /* No other xattrs packed in the same leaf item. */
 199                         if (size > old_data_len)
 200                                 btrfs_extend_item(fs_info, path,
 201                                                   size - old_data_len);
 202                         else if (size < old_data_len)
 203                                 btrfs_truncate_item(fs_info, path,
 204                                                     data_size, 1);
 205                 } else {
 206                         /* There are other xattrs packed in the same item. */
 207                         ret = btrfs_delete_one_dir_name(trans, root, path, di);
 208                         if (ret)
 209                                 goto out;
 210                         btrfs_extend_item(fs_info, path, data_size);
 211                 }
 212
 213                 item = btrfs_item_nr(slot);
 214                 ptr = btrfs_item_ptr(leaf, slot, char);
 215                 ptr += btrfs_item_size(leaf, item) - data_size;
 216                 di = (struct btrfs_dir_item *)ptr;
 217                 btrfs_set_dir_data_len(leaf, di, size);
 218                 data_ptr = ((unsigned long)(di + 1)) + name_len;
 219                 write_extent_buffer(leaf, value, data_ptr, size);
 220                 btrfs_mark_buffer_dirty(leaf);
 221         } else {
 222                 /*
 223                  * Insert, and we had space for the xattr, so path->slots[0] is
 224                  * where our xattr dir_item is and btrfs_insert_xattr_item()
 225                  * filled it.
 226                  */
 227         }
 228 out:
 229         btrfs_free_path(path);
 230         return ret;
 231 }
 232
 233 /*
 234  * @value: "" makes the attribute to empty, NULL removes it
 235  */
 236 int __btrfs_setxattr(struct btrfs_trans_handle *trans,
 237                      struct inode *inode, const char *name,
 238                      const void *value, size_t size, int flags)
 239 {
 240         struct btrfs_root *root = BTRFS_I(inode)->root;
 241         int ret;
 242
 243         if (btrfs_root_readonly(root))
 244                 return -EROFS;
 245
 246         if (trans)
 247                 return do_setxattr(trans, inode, name, value, size, flags);
 248
 249         trans = btrfs_start_transaction(root, 2);
 250         if (IS_ERR(trans))
 251                 return PTR_ERR(trans);
 252
 253         ret = do_setxattr(trans, inode, name, value, size, flags);
 254         if (ret)
 255                 goto out;
 256
 257         inode_inc_iversion(inode);
 258         inode->i_ctime = current_time(inode);
 259         set_bit(BTRFS_INODE_COPY_EVERYTHING, &BTRFS_I(inode)->runtime_flags);
 260         ret = btrfs_update_inode(trans, root, inode);
 261         BUG_ON(ret);
 262 out:
 263         btrfs_end_transaction(trans);
 264         return ret;
 265 }
 266
 267 ssize_t btrfs_listxattr(struct dentry *dentry, char *buffer, size_t size)
 268 {
 269         struct btrfs_key key;
 270         struct inode *inode = d_inode(dentry);
 271         struct btrfs_root *root = BTRFS_I(inode)->root;
 272         struct btrfs_path *path;
 273         int ret = 0;
 274         size_t total_size = 0, size_left = size;
 275
 276         /*
 277          * ok we want all objects associated with this id.
 278          * NOTE: we set key.offset = 0; because we want to start with the
 279          * first xattr that we find and walk forward
 280          */
 281         key.objectid = btrfs_ino(BTRFS_I(inode));
 282         key.type = BTRFS_XATTR_ITEM_KEY;
 283         key.offset = 0;
 284
 285         path = btrfs_alloc_path();
 286         if (!path)
 287                 return -ENOMEM;
 288         path->reada = READA_FORWARD;
 289
 290         /* search for our xattrs */
 291         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
 292         if (ret < 0)
 293                 goto err;
 294
 295         while (1) {
 296                 struct extent_buffer *leaf;
 297                 int slot;
 298                 struct btrfs_dir_item *di;
 299                 struct btrfs_key found_key;
 300                 u32 item_size;
 301                 u32 cur;
 302
 303                 leaf = path->nodes[0];
 304                 slot = path->slots[0];
 305
 306                 /* this is where we start walking through the path */
 307                 if (slot >= btrfs_header_nritems(leaf)) {
 308                         /*
 309                          * if we've reached the last slot in this leaf we need
 310                          * to go to the next leaf and reset everything
 311                          */
 312                         ret = btrfs_next_leaf(root, path);
 313                         if (ret < 0)
 314                                 goto err;
 315                         else if (ret > 0)
 316                                 break;
 317                         continue;
 318                 }
 319
 320                 btrfs_item_key_to_cpu(leaf, &found_key, slot);
 321
 322                 /* check to make sure this item is what we want */
 323                 if (found_key.objectid != key.objectid)
 324                         break;
 325                 if (found_key.type > BTRFS_XATTR_ITEM_KEY)
 326                         break;
 327                 if (found_key.type < BTRFS_XATTR_ITEM_KEY)
 328                         goto next_item;
 329
 330                 di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
 331                 item_size = btrfs_item_size_nr(leaf, slot);
 332                 cur = 0;
 333                 while (cur < item_size) {
 334                         u16 name_len = btrfs_dir_name_len(leaf, di);
 335                         u16 data_len = btrfs_dir_data_len(leaf, di);
 336                         u32 this_len = sizeof(*di) + name_len + data_len;
 337                         unsigned long name_ptr = (unsigned long)(di + 1);
 338
 339                         total_size += name_len + 1;
 340                         /*
 341                          * We are just looking for how big our buffer needs to
 342                          * be.
 343                          */
 344                         if (!size)
 345                                 goto next;
 346
 347                         if (!buffer || (name_len + 1) > size_left) {
 348                                 ret = -ERANGE;
 349                                 goto err;
 350                         }
 351
 352                         read_extent_buffer(leaf, buffer, name_ptr, name_len);
 353                         buffer[name_len] = '\0';
 354
 355                         size_left -= name_len + 1;
 356                         buffer += name_len + 1;
 357 next:
 358                         cur += this_len;
 359                         di = (struct btrfs_dir_item *)((char *)di + this_len);
 360                 }
 361 next_item:
 362                 path->slots[0]++;
 363         }
 364         ret = total_size;
 365
 366 err:
 367         btrfs_free_path(path);
 368
 369         return ret;
 370 }
 371
 372 static int btrfs_xattr_handler_get(const struct xattr_handler *handler,
 373                                    struct dentry *unused, struct inode *inode,
 374                                    const char *name, void *buffer, size_t size)
 375 {
 376         name = xattr_full_name(handler, name);
 377         return __btrfs_getxattr(inode, name, buffer, size);
 378 }
 379
 380 static int btrfs_xattr_handler_set(const struct xattr_handler *handler,
 381                                    struct dentry *unused, struct inode *inode,
 382                                    const char *name, const void *buffer,
 383                                    size_t size, int flags)
 384 {
 385         name = xattr_full_name(handler, name);
 386         return __btrfs_setxattr(NULL, inode, name, buffer, size, flags);
 387 }
 388
 389 static int btrfs_xattr_handler_set_prop(const struct xattr_handler *handler,
 390                                         struct dentry *unused, struct inode *inode,
 391                                         const char *name, const void *value,
 392                                         size_t size, int flags)
 393 {
 394         name = xattr_full_name(handler, name);
 395         return btrfs_set_prop(inode, name, value, size, flags);
 396 }
 397
 398 static const struct xattr_handler btrfs_security_xattr_handler = {
 399         .prefix = XATTR_SECURITY_PREFIX,
 400         .get = btrfs_xattr_handler_get,
 401         .set = btrfs_xattr_handler_set,
 402 };
 403
 404 static const struct xattr_handler btrfs_trusted_xattr_handler = {
 405         .prefix = XATTR_TRUSTED_PREFIX,
 406         .get = btrfs_xattr_handler_get,
 407         .set = btrfs_xattr_handler_set,
 408 };
 409
 410 static const struct xattr_handler btrfs_user_xattr_handler = {
 411         .prefix = XATTR_USER_PREFIX,
 412         .get = btrfs_xattr_handler_get,
 413         .set = btrfs_xattr_handler_set,
 414 };
 415
 416 static const struct xattr_handler btrfs_btrfs_xattr_handler = {
 417         .prefix = XATTR_BTRFS_PREFIX,
 418         .get = btrfs_xattr_handler_get,
 419         .set = btrfs_xattr_handler_set_prop,
 420 };
 421
 422 const struct xattr_handler *btrfs_xattr_handlers[] = {
 423         &btrfs_security_xattr_handler,
 424 #ifdef CONFIG_BTRFS_FS_POSIX_ACL
 425         &posix_acl_access_xattr_handler,
 426         &posix_acl_default_xattr_handler,
 427 #endif
 428         &btrfs_trusted_xattr_handler,
 429         &btrfs_user_xattr_handler,
 430         &btrfs_btrfs_xattr_handler,
 431         NULL,
 432 };
 433
 434 static int btrfs_initxattrs(struct inode *inode,
 435                             const struct xattr *xattr_array, void *fs_info)
 436 {
 437         const struct xattr *xattr;
 438         struct btrfs_trans_handle *trans = fs_info;
 439         char *name;
 440         int err = 0;
 441
 442         for (xattr = xattr_array; xattr->name != NULL; xattr++) {
 443                 name = kmalloc(XATTR_SECURITY_PREFIX_LEN +
 444                                strlen(xattr->name) + 1, GFP_KERNEL);
 445                 if (!name) {
 446                         err = -ENOMEM;
 447                         break;
 448                 }
 449                 strcpy(name, XATTR_SECURITY_PREFIX);
 450                 strcpy(name + XATTR_SECURITY_PREFIX_LEN, xattr->name);
 451                 err = __btrfs_setxattr(trans, inode, name,
 452                                        xattr->value, xattr->value_len, 0);
 453                 kfree(name);
 454                 if (err < 0)
 455                         break;
 456         }
 457         return err;
 458 }
 459
 460 int btrfs_xattr_security_init(struct btrfs_trans_handle *trans,
 461                               struct inode *inode, struct inode *dir,
 462                               const struct qstr *qstr)
 463 {
 464         return security_inode_init_security(inode, dir, qstr,
 465                                             &btrfs_initxattrs, trans);
 466 }