fs/btrfs/xattr.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2007 Red Hat.  All rights reserved.
   4  */
   5
   6 #include <linux/init.h>
   7 #include <linux/fs.h>
   8 #include <linux/slab.h>
   9 #include <linux/rwsem.h>
  10 #include <linux/xattr.h>
  11 #include <linux/security.h>
  12 #include <linux/posix_acl_xattr.h>
  13 #include <linux/iversion.h>
  14 #include "ctree.h"
  15 #include "btrfs_inode.h"
  16 #include "transaction.h"
  17 #include "xattr.h"
  18 #include "disk-io.h"
  19 #include "props.h"
  20 #include "locking.h"
  21
  22 int btrfs_getxattr(struct inode *inode, const char *name,
  23                                 void *buffer, size_t size)
  24 {
  25         struct btrfs_dir_item *di;
  26         struct btrfs_root *root = BTRFS_I(inode)->root;
  27         struct btrfs_path *path;
  28         struct extent_buffer *leaf;
  29         int ret = 0;
  30         unsigned long data_ptr;
  31
  32         path = btrfs_alloc_path();
  33         if (!path)
  34                 return -ENOMEM;
  35
  36         /* lookup the xattr by name */
  37         di = btrfs_lookup_xattr(NULL, root, path, btrfs_ino(BTRFS_I(inode)),
  38                         name, strlen(name), 0);
  39         if (!di) {
  40                 ret = -ENODATA;
  41                 goto out;
  42         } else if (IS_ERR(di)) {
  43                 ret = PTR_ERR(di);
  44                 goto out;
  45         }
  46
  47         leaf = path->nodes[0];
  48         /* if size is 0, that means we want the size of the attr */
  49         if (!size) {
  50                 ret = btrfs_dir_data_len(leaf, di);
  51                 goto out;
  52         }
  53
  54         /* now get the data out of our dir_item */
  55         if (btrfs_dir_data_len(leaf, di) > size) {
  56                 ret = -ERANGE;
  57                 goto out;
  58         }
  59
  60         /*
  61          * The way things are packed into the leaf is like this
  62          * |struct btrfs_dir_item|name|data|
  63          * where name is the xattr name, so security.foo, and data is the
  64          * content of the xattr.  data_ptr points to the location in memory
  65          * where the data starts in the in memory leaf
  66          */
  67         data_ptr = (unsigned long)((char *)(di + 1) +
  68                                    btrfs_dir_name_len(leaf, di));
  69         read_extent_buffer(leaf, buffer, data_ptr,
  70                            btrfs_dir_data_len(leaf, di));
  71         ret = btrfs_dir_data_len(leaf, di);
  72
  73 out:
  74         btrfs_free_path(path);
  75         return ret;
  76 }
  77
  78 static int do_setxattr(struct btrfs_trans_handle *trans,
  79                        struct inode *inode, const char *name,
  80                        const void *value, size_t size, int flags)
  81 {
  82         struct btrfs_dir_item *di = NULL;
  83         struct btrfs_root *root = BTRFS_I(inode)->root;
  84         struct btrfs_fs_info *fs_info = root->fs_info;
  85         struct btrfs_path *path;
  86         size_t name_len = strlen(name);
  87         int ret = 0;
  88
  89         if (name_len + size > BTRFS_MAX_XATTR_SIZE(root->fs_info))
  90                 return -ENOSPC;
  91
  92         path = btrfs_alloc_path();
  93         if (!path)
  94                 return -ENOMEM;
  95         path->skip_release_on_error = 1;
  96
  97         if (!value) {
  98                 di = btrfs_lookup_xattr(trans, root, path,
  99                                 btrfs_ino(BTRFS_I(inode)), name, name_len, -1);
 100                 if (!di && (flags & XATTR_REPLACE))
 101                         ret = -ENODATA;
 102                 else if (IS_ERR(di))
 103                         ret = PTR_ERR(di);
 104                 else if (di)
 105                         ret = btrfs_delete_one_dir_name(trans, root, path, di);
 106                 goto out;
 107         }
 108
 109         /*
 110          * For a replace we can't just do the insert blindly.
 111          * Do a lookup first (read-only btrfs_search_slot), and return if xattr
 112          * doesn't exist. If it exists, fall down below to the insert/replace
 113          * path - we can't race with a concurrent xattr delete, because the VFS
 114          * locks the inode's i_mutex before calling setxattr or removexattr.
 115          */
 116         if (flags & XATTR_REPLACE) {
 117                 ASSERT(inode_is_locked(inode));
 118                 di = btrfs_lookup_xattr(NULL, root, path,
 119                                 btrfs_ino(BTRFS_I(inode)), name, name_len, 0);
 120                 if (!di)
 121                         ret = -ENODATA;
 122                 else if (IS_ERR(di))
 123                         ret = PTR_ERR(di);
 124                 if (ret)
 125                         goto out;
 126                 btrfs_release_path(path);
 127                 di = NULL;
 128         }
 129
 130         ret = btrfs_insert_xattr_item(trans, root, path, btrfs_ino(BTRFS_I(inode)),
 131                                       name, name_len, value, size);
 132         if (ret == -EOVERFLOW) {
 133                 /*
 134                  * We have an existing item in a leaf, split_leaf couldn't
 135                  * expand it. That item might have or not a dir_item that
 136                  * matches our target xattr, so lets check.
 137                  */
 138                 ret = 0;
 139                 btrfs_assert_tree_locked(path->nodes[0]);
 140                 di = btrfs_match_dir_item_name(fs_info, path, name, name_len);
 141                 if (!di && !(flags & XATTR_REPLACE)) {
 142                         ret = -ENOSPC;
 143                         goto out;
 144                 }
 145         } else if (ret == -EEXIST) {
 146                 ret = 0;
 147                 di = btrfs_match_dir_item_name(fs_info, path, name, name_len);
 148                 ASSERT(di); /* logic error */
 149         } else if (ret) {
 150                 goto out;
 151         }
 152
 153         if (di && (flags & XATTR_CREATE)) {
 154                 ret = -EEXIST;
 155                 goto out;
 156         }
 157
 158         if (di) {
 159                 /*
 160                  * We're doing a replace, and it must be atomic, that is, at
 161                  * any point in time we have either the old or the new xattr
 162                  * value in the tree. We don't want readers (getxattr and
 163                  * listxattrs) to miss a value, this is specially important
 164                  * for ACLs.
 165                  */
 166                 const int slot = path->slots[0];
 167                 struct extent_buffer *leaf = path->nodes[0];
 168                 const u16 old_data_len = btrfs_dir_data_len(leaf, di);
 169                 const u32 item_size = btrfs_item_size_nr(leaf, slot);
 170                 const u32 data_size = sizeof(*di) + name_len + size;
 171                 struct btrfs_item *item;
 172                 unsigned long data_ptr;
 173                 char *ptr;
 174
 175                 if (size > old_data_len) {
 176                         if (btrfs_leaf_free_space(fs_info, leaf) <
 177                             (size - old_data_len)) {
 178                                 ret = -ENOSPC;
 179                                 goto out;
 180                         }
 181                 }
 182
 183                 if (old_data_len + name_len + sizeof(*di) == item_size) {
 184                         /* No other xattrs packed in the same leaf item. */
 185                         if (size > old_data_len)
 186                                 btrfs_extend_item(fs_info, path,
 187                                                   size - old_data_len);
 188                         else if (size < old_data_len)
 189                                 btrfs_truncate_item(fs_info, path,
 190                                                     data_size, 1);
 191                 } else {
 192                         /* There are other xattrs packed in the same item. */
 193                         ret = btrfs_delete_one_dir_name(trans, root, path, di);
 194                         if (ret)
 195                                 goto out;
 196                         btrfs_extend_item(fs_info, path, data_size);
 197                 }
 198
 199                 item = btrfs_item_nr(slot);
 200                 ptr = btrfs_item_ptr(leaf, slot, char);
 201                 ptr += btrfs_item_size(leaf, item) - data_size;
 202                 di = (struct btrfs_dir_item *)ptr;
 203                 btrfs_set_dir_data_len(leaf, di, size);
 204                 data_ptr = ((unsigned long)(di + 1)) + name_len;
 205                 write_extent_buffer(leaf, value, data_ptr, size);
 206                 btrfs_mark_buffer_dirty(leaf);
 207         } else {
 208                 /*
 209                  * Insert, and we had space for the xattr, so path->slots[0] is
 210                  * where our xattr dir_item is and btrfs_insert_xattr_item()
 211                  * filled it.
 212                  */
 213         }
 214 out:
 215         btrfs_free_path(path);
 216         return ret;
 217 }
 218
 219 /*
 220  * @value: "" makes the attribute to empty, NULL removes it
 221  */
 222 int btrfs_setxattr(struct btrfs_trans_handle *trans,
 223                      struct inode *inode, const char *name,
 224                      const void *value, size_t size, int flags)
 225 {
 226         struct btrfs_root *root = BTRFS_I(inode)->root;
 227         int ret;
 228
 229         if (btrfs_root_readonly(root))
 230                 return -EROFS;
 231
 232         if (trans)
 233                 return do_setxattr(trans, inode, name, value, size, flags);
 234
 235         trans = btrfs_start_transaction(root, 2);
 236         if (IS_ERR(trans))
 237                 return PTR_ERR(trans);
 238
 239         ret = do_setxattr(trans, inode, name, value, size, flags);
 240         if (ret)
 241                 goto out;
 242
 243         inode_inc_iversion(inode);
 244         inode->i_ctime = current_time(inode);
 245         set_bit(BTRFS_INODE_COPY_EVERYTHING, &BTRFS_I(inode)->runtime_flags);
 246         ret = btrfs_update_inode(trans, root, inode);
 247         BUG_ON(ret);
 248 out:
 249         btrfs_end_transaction(trans);
 250         return ret;
 251 }
 252
 253 ssize_t btrfs_listxattr(struct dentry *dentry, char *buffer, size_t size)
 254 {
 255         struct btrfs_key key;
 256         struct inode *inode = d_inode(dentry);
 257         struct btrfs_root *root = BTRFS_I(inode)->root;
 258         struct btrfs_path *path;
 259         int ret = 0;
 260         size_t total_size = 0, size_left = size;
 261
 262         /*
 263          * ok we want all objects associated with this id.
 264          * NOTE: we set key.offset = 0; because we want to start with the
 265          * first xattr that we find and walk forward
 266          */
 267         key.objectid = btrfs_ino(BTRFS_I(inode));
 268         key.type = BTRFS_XATTR_ITEM_KEY;
 269         key.offset = 0;
 270
 271         path = btrfs_alloc_path();
 272         if (!path)
 273                 return -ENOMEM;
 274         path->reada = READA_FORWARD;
 275
 276         /* search for our xattrs */
 277         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
 278         if (ret < 0)
 279                 goto err;
 280
 281         while (1) {
 282                 struct extent_buffer *leaf;
 283                 int slot;
 284                 struct btrfs_dir_item *di;
 285                 struct btrfs_key found_key;
 286                 u32 item_size;
 287                 u32 cur;
 288
 289                 leaf = path->nodes[0];
 290                 slot = path->slots[0];
 291
 292                 /* this is where we start walking through the path */
 293                 if (slot >= btrfs_header_nritems(leaf)) {
 294                         /*
 295                          * if we've reached the last slot in this leaf we need
 296                          * to go to the next leaf and reset everything
 297                          */
 298                         ret = btrfs_next_leaf(root, path);
 299                         if (ret < 0)
 300                                 goto err;
 301                         else if (ret > 0)
 302                                 break;
 303                         continue;
 304                 }
 305
 306                 btrfs_item_key_to_cpu(leaf, &found_key, slot);
 307
 308                 /* check to make sure this item is what we want */
 309                 if (found_key.objectid != key.objectid)
 310                         break;
 311                 if (found_key.type > BTRFS_XATTR_ITEM_KEY)
 312                         break;
 313                 if (found_key.type < BTRFS_XATTR_ITEM_KEY)
 314                         goto next_item;
 315
 316                 di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
 317                 item_size = btrfs_item_size_nr(leaf, slot);
 318                 cur = 0;
 319                 while (cur < item_size) {
 320                         u16 name_len = btrfs_dir_name_len(leaf, di);
 321                         u16 data_len = btrfs_dir_data_len(leaf, di);
 322                         u32 this_len = sizeof(*di) + name_len + data_len;
 323                         unsigned long name_ptr = (unsigned long)(di + 1);
 324
 325                         total_size += name_len + 1;
 326                         /*
 327                          * We are just looking for how big our buffer needs to
 328                          * be.
 329                          */
 330                         if (!size)
 331                                 goto next;
 332
 333                         if (!buffer || (name_len + 1) > size_left) {
 334                                 ret = -ERANGE;
 335                                 goto err;
 336                         }
 337
 338                         read_extent_buffer(leaf, buffer, name_ptr, name_len);
 339                         buffer[name_len] = '\0';
 340
 341                         size_left -= name_len + 1;
 342                         buffer += name_len + 1;
 343 next:
 344                         cur += this_len;
 345                         di = (struct btrfs_dir_item *)((char *)di + this_len);
 346                 }
 347 next_item:
 348                 path->slots[0]++;
 349         }
 350         ret = total_size;
 351
 352 err:
 353         btrfs_free_path(path);
 354
 355         return ret;
 356 }
 357
 358 static int btrfs_xattr_handler_get(const struct xattr_handler *handler,
 359                                    struct dentry *unused, struct inode *inode,
 360                                    const char *name, void *buffer, size_t size)
 361 {
 362         name = xattr_full_name(handler, name);
 363         return btrfs_getxattr(inode, name, buffer, size);
 364 }
 365
 366 static int btrfs_xattr_handler_set(const struct xattr_handler *handler,
 367                                    struct dentry *unused, struct inode *inode,
 368                                    const char *name, const void *buffer,
 369                                    size_t size, int flags)
 370 {
 371         name = xattr_full_name(handler, name);
 372         return btrfs_setxattr(NULL, inode, name, buffer, size, flags);
 373 }
 374
 375 static int btrfs_xattr_handler_set_prop(const struct xattr_handler *handler,
 376                                         struct dentry *unused, struct inode *inode,
 377                                         const char *name, const void *value,
 378                                         size_t size, int flags)
 379 {
 380         name = xattr_full_name(handler, name);
 381         return btrfs_set_prop(inode, name, value, size, flags);
 382 }
 383
 384 static const struct xattr_handler btrfs_security_xattr_handler = {
 385         .prefix = XATTR_SECURITY_PREFIX,
 386         .get = btrfs_xattr_handler_get,
 387         .set = btrfs_xattr_handler_set,
 388 };
 389
 390 static const struct xattr_handler btrfs_trusted_xattr_handler = {
 391         .prefix = XATTR_TRUSTED_PREFIX,
 392         .get = btrfs_xattr_handler_get,
 393         .set = btrfs_xattr_handler_set,
 394 };
 395
 396 static const struct xattr_handler btrfs_user_xattr_handler = {
 397         .prefix = XATTR_USER_PREFIX,
 398         .get = btrfs_xattr_handler_get,
 399         .set = btrfs_xattr_handler_set,
 400 };
 401
 402 static const struct xattr_handler btrfs_btrfs_xattr_handler = {
 403         .prefix = XATTR_BTRFS_PREFIX,
 404         .get = btrfs_xattr_handler_get,
 405         .set = btrfs_xattr_handler_set_prop,
 406 };
 407
 408 const struct xattr_handler *btrfs_xattr_handlers[] = {
 409         &btrfs_security_xattr_handler,
 410 #ifdef CONFIG_BTRFS_FS_POSIX_ACL
 411         &posix_acl_access_xattr_handler,
 412         &posix_acl_default_xattr_handler,
 413 #endif
 414         &btrfs_trusted_xattr_handler,
 415         &btrfs_user_xattr_handler,
 416         &btrfs_btrfs_xattr_handler,
 417         NULL,
 418 };
 419
 420 static int btrfs_initxattrs(struct inode *inode,
 421                             const struct xattr *xattr_array, void *fs_info)
 422 {
 423         const struct xattr *xattr;
 424         struct btrfs_trans_handle *trans = fs_info;
 425         char *name;
 426         int err = 0;
 427
 428         for (xattr = xattr_array; xattr->name != NULL; xattr++) {
 429                 name = kmalloc(XATTR_SECURITY_PREFIX_LEN +
 430                                strlen(xattr->name) + 1, GFP_KERNEL);
 431                 if (!name) {
 432                         err = -ENOMEM;
 433                         break;
 434                 }
 435                 strcpy(name, XATTR_SECURITY_PREFIX);
 436                 strcpy(name + XATTR_SECURITY_PREFIX_LEN, xattr->name);
 437                 err = btrfs_setxattr(trans, inode, name, xattr->value,
 438                                 xattr->value_len, 0);
 439                 kfree(name);
 440                 if (err < 0)
 441                         break;
 442         }
 443         return err;
 444 }
 445
 446 int btrfs_xattr_security_init(struct btrfs_trans_handle *trans,
 447                               struct inode *inode, struct inode *dir,
 448                               const struct qstr *qstr)
 449 {
 450         return security_inode_init_security(inode, dir, qstr,
 451                                             &btrfs_initxattrs, trans);
 452 }