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 <linux/sched/mm.h>
  15 #include "ctree.h"
  16 #include "btrfs_inode.h"
  17 #include "transaction.h"
  18 #include "xattr.h"
  19 #include "disk-io.h"
  20 #include "props.h"
  21 #include "locking.h"
  22
  23 int btrfs_getxattr(struct inode *inode, const char *name,
  24                                 void *buffer, size_t size)
  25 {
  26         struct btrfs_dir_item *di;
  27         struct btrfs_root *root = BTRFS_I(inode)->root;
  28         struct btrfs_path *path;
  29         struct extent_buffer *leaf;
  30         int ret = 0;
  31         unsigned long data_ptr;
  32
  33         path = btrfs_alloc_path();
  34         if (!path)
  35                 return -ENOMEM;
  36
  37         /* lookup the xattr by name */
  38         di = btrfs_lookup_xattr(NULL, root, path, btrfs_ino(BTRFS_I(inode)),
  39                         name, strlen(name), 0);
  40         if (!di) {
  41                 ret = -ENODATA;
  42                 goto out;
  43         } else if (IS_ERR(di)) {
  44                 ret = PTR_ERR(di);
  45                 goto out;
  46         }
  47
  48         leaf = path->nodes[0];
  49         /* if size is 0, that means we want the size of the attr */
  50         if (!size) {
  51                 ret = btrfs_dir_data_len(leaf, di);
  52                 goto out;
  53         }
  54
  55         /* now get the data out of our dir_item */
  56         if (btrfs_dir_data_len(leaf, di) > size) {
  57                 ret = -ERANGE;
  58                 goto out;
  59         }
  60
  61         /*
  62          * The way things are packed into the leaf is like this
  63          * |struct btrfs_dir_item|name|data|
  64          * where name is the xattr name, so security.foo, and data is the
  65          * content of the xattr.  data_ptr points to the location in memory
  66          * where the data starts in the in memory leaf
  67          */
  68         data_ptr = (unsigned long)((char *)(di + 1) +
  69                                    btrfs_dir_name_len(leaf, di));
  70         read_extent_buffer(leaf, buffer, data_ptr,
  71                            btrfs_dir_data_len(leaf, di));
  72         ret = btrfs_dir_data_len(leaf, di);
  73
  74 out:
  75         btrfs_free_path(path);
  76         return ret;
  77 }
  78
  79 static int do_setxattr(struct btrfs_trans_handle *trans,
  80                        struct inode *inode, const char *name,
  81                        const void *value, size_t size, int flags)
  82 {
  83         struct btrfs_dir_item *di = NULL;
  84         struct btrfs_root *root = BTRFS_I(inode)->root;
  85         struct btrfs_fs_info *fs_info = root->fs_info;
  86         struct btrfs_path *path;
  87         size_t name_len = strlen(name);
  88         int ret = 0;
  89
  90         if (name_len + size > BTRFS_MAX_XATTR_SIZE(root->fs_info))
  91                 return -ENOSPC;
  92
  93         path = btrfs_alloc_path();
  94         if (!path)
  95                 return -ENOMEM;
  96         path->skip_release_on_error = 1;
  97
  98         if (!value) {
  99                 di = btrfs_lookup_xattr(trans, root, path,
 100                                 btrfs_ino(BTRFS_I(inode)), name, name_len, -1);
 101                 if (!di && (flags & XATTR_REPLACE))
 102                         ret = -ENODATA;
 103                 else if (IS_ERR(di))
 104                         ret = PTR_ERR(di);
 105                 else if (di)
 106                         ret = btrfs_delete_one_dir_name(trans, root, path, di);
 107                 goto out;
 108         }
 109
 110         /*
 111          * For a replace we can't just do the insert blindly.
 112          * Do a lookup first (read-only btrfs_search_slot), and return if xattr
 113          * doesn't exist. If it exists, fall down below to the insert/replace
 114          * path - we can't race with a concurrent xattr delete, because the VFS
 115          * locks the inode's i_mutex before calling setxattr or removexattr.
 116          */
 117         if (flags & XATTR_REPLACE) {
 118                 ASSERT(inode_is_locked(inode));
 119                 di = btrfs_lookup_xattr(NULL, root, path,
 120                                 btrfs_ino(BTRFS_I(inode)), name, name_len, 0);
 121                 if (!di)
 122                         ret = -ENODATA;
 123                 else if (IS_ERR(di))
 124                         ret = PTR_ERR(di);
 125                 if (ret)
 126                         goto out;
 127                 btrfs_release_path(path);
 128                 di = NULL;
 129         }
 130
 131         ret = btrfs_insert_xattr_item(trans, root, path, btrfs_ino(BTRFS_I(inode)),
 132                                       name, name_len, value, size);
 133         if (ret == -EOVERFLOW) {
 134                 /*
 135                  * We have an existing item in a leaf, split_leaf couldn't
 136                  * expand it. That item might have or not a dir_item that
 137                  * matches our target xattr, so lets check.
 138                  */
 139                 ret = 0;
 140                 btrfs_assert_tree_locked(path->nodes[0]);
 141                 di = btrfs_match_dir_item_name(fs_info, path, name, name_len);
 142                 if (!di && !(flags & XATTR_REPLACE)) {
 143                         ret = -ENOSPC;
 144                         goto out;
 145                 }
 146         } else if (ret == -EEXIST) {
 147                 ret = 0;
 148                 di = btrfs_match_dir_item_name(fs_info, path, name, name_len);
 149                 ASSERT(di); /* logic error */
 150         } else if (ret) {
 151                 goto out;
 152         }
 153
 154         if (di && (flags & XATTR_CREATE)) {
 155                 ret = -EEXIST;
 156                 goto out;
 157         }
 158
 159         if (di) {
 160                 /*
 161                  * We're doing a replace, and it must be atomic, that is, at
 162                  * any point in time we have either the old or the new xattr
 163                  * value in the tree. We don't want readers (getxattr and
 164                  * listxattrs) to miss a value, this is specially important
 165                  * for ACLs.
 166                  */
 167                 const int slot = path->slots[0];
 168                 struct extent_buffer *leaf = path->nodes[0];
 169                 const u16 old_data_len = btrfs_dir_data_len(leaf, di);
 170                 const u32 item_size = btrfs_item_size_nr(leaf, slot);
 171                 const u32 data_size = sizeof(*di) + name_len + size;
 172                 struct btrfs_item *item;
 173                 unsigned long data_ptr;
 174                 char *ptr;
 175
 176                 if (size > old_data_len) {
 177                         if (btrfs_leaf_free_space(fs_info, leaf) <
 178                             (size - old_data_len)) {
 179                                 ret = -ENOSPC;
 180                                 goto out;
 181                         }
 182                 }
 183
 184                 if (old_data_len + name_len + sizeof(*di) == item_size) {
 185                         /* No other xattrs packed in the same leaf item. */
 186                         if (size > old_data_len)
 187                                 btrfs_extend_item(fs_info, path,
 188                                                   size - old_data_len);
 189                         else if (size < old_data_len)
 190                                 btrfs_truncate_item(fs_info, path,
 191                                                     data_size, 1);
 192                 } else {
 193                         /* There are other xattrs packed in the same item. */
 194                         ret = btrfs_delete_one_dir_name(trans, root, path, di);
 195                         if (ret)
 196                                 goto out;
 197                         btrfs_extend_item(fs_info, path, data_size);
 198                 }
 199
 200                 item = btrfs_item_nr(slot);
 201                 ptr = btrfs_item_ptr(leaf, slot, char);
 202                 ptr += btrfs_item_size(leaf, item) - data_size;
 203                 di = (struct btrfs_dir_item *)ptr;
 204                 btrfs_set_dir_data_len(leaf, di, size);
 205                 data_ptr = ((unsigned long)(di + 1)) + name_len;
 206                 write_extent_buffer(leaf, value, data_ptr, size);
 207                 btrfs_mark_buffer_dirty(leaf);
 208         } else {
 209                 /*
 210                  * Insert, and we had space for the xattr, so path->slots[0] is
 211                  * where our xattr dir_item is and btrfs_insert_xattr_item()
 212                  * filled it.
 213                  */
 214         }
 215 out:
 216         btrfs_free_path(path);
 217         return ret;
 218 }
 219
 220 /*
 221  * @value: "" makes the attribute to empty, NULL removes it
 222  */
 223 int btrfs_setxattr(struct btrfs_trans_handle *trans,
 224                      struct inode *inode, const char *name,
 225                      const void *value, size_t size, int flags)
 226 {
 227         struct btrfs_root *root = BTRFS_I(inode)->root;
 228         int ret;
 229
 230         if (btrfs_root_readonly(root))
 231                 return -EROFS;
 232
 233         if (trans)
 234                 return do_setxattr(trans, inode, name, value, size, flags);
 235
 236         trans = btrfs_start_transaction(root, 2);
 237         if (IS_ERR(trans))
 238                 return PTR_ERR(trans);
 239
 240         ret = do_setxattr(trans, inode, name, value, size, flags);
 241         if (ret)
 242                 goto out;
 243
 244         inode_inc_iversion(inode);
 245         inode->i_ctime = current_time(inode);
 246         set_bit(BTRFS_INODE_COPY_EVERYTHING, &BTRFS_I(inode)->runtime_flags);
 247         ret = btrfs_update_inode(trans, root, inode);
 248         BUG_ON(ret);
 249 out:
 250         btrfs_end_transaction(trans);
 251         return ret;
 252 }
 253
 254 ssize_t btrfs_listxattr(struct dentry *dentry, char *buffer, size_t size)
 255 {
 256         struct btrfs_key key;
 257         struct inode *inode = d_inode(dentry);
 258         struct btrfs_root *root = BTRFS_I(inode)->root;
 259         struct btrfs_path *path;
 260         int ret = 0;
 261         size_t total_size = 0, size_left = size;
 262
 263         /*
 264          * ok we want all objects associated with this id.
 265          * NOTE: we set key.offset = 0; because we want to start with the
 266          * first xattr that we find and walk forward
 267          */
 268         key.objectid = btrfs_ino(BTRFS_I(inode));
 269         key.type = BTRFS_XATTR_ITEM_KEY;
 270         key.offset = 0;
 271
 272         path = btrfs_alloc_path();
 273         if (!path)
 274                 return -ENOMEM;
 275         path->reada = READA_FORWARD;
 276
 277         /* search for our xattrs */
 278         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
 279         if (ret < 0)
 280                 goto err;
 281
 282         while (1) {
 283                 struct extent_buffer *leaf;
 284                 int slot;
 285                 struct btrfs_dir_item *di;
 286                 struct btrfs_key found_key;
 287                 u32 item_size;
 288                 u32 cur;
 289
 290                 leaf = path->nodes[0];
 291                 slot = path->slots[0];
 292
 293                 /* this is where we start walking through the path */
 294                 if (slot >= btrfs_header_nritems(leaf)) {
 295                         /*
 296                          * if we've reached the last slot in this leaf we need
 297                          * to go to the next leaf and reset everything
 298                          */
 299                         ret = btrfs_next_leaf(root, path);
 300                         if (ret < 0)
 301                                 goto err;
 302                         else if (ret > 0)
 303                                 break;
 304                         continue;
 305                 }
 306
 307                 btrfs_item_key_to_cpu(leaf, &found_key, slot);
 308
 309                 /* check to make sure this item is what we want */
 310                 if (found_key.objectid != key.objectid)
 311                         break;
 312                 if (found_key.type > BTRFS_XATTR_ITEM_KEY)
 313                         break;
 314                 if (found_key.type < BTRFS_XATTR_ITEM_KEY)
 315                         goto next_item;
 316
 317                 di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
 318                 item_size = btrfs_item_size_nr(leaf, slot);
 319                 cur = 0;
 320                 while (cur < item_size) {
 321                         u16 name_len = btrfs_dir_name_len(leaf, di);
 322                         u16 data_len = btrfs_dir_data_len(leaf, di);
 323                         u32 this_len = sizeof(*di) + name_len + data_len;
 324                         unsigned long name_ptr = (unsigned long)(di + 1);
 325
 326                         total_size += name_len + 1;
 327                         /*
 328                          * We are just looking for how big our buffer needs to
 329                          * be.
 330                          */
 331                         if (!size)
 332                                 goto next;
 333
 334                         if (!buffer || (name_len + 1) > size_left) {
 335                                 ret = -ERANGE;
 336                                 goto err;
 337                         }
 338
 339                         read_extent_buffer(leaf, buffer, name_ptr, name_len);
 340                         buffer[name_len] = '\0';
 341
 342                         size_left -= name_len + 1;
 343                         buffer += name_len + 1;
 344 next:
 345                         cur += this_len;
 346                         di = (struct btrfs_dir_item *)((char *)di + this_len);
 347                 }
 348 next_item:
 349                 path->slots[0]++;
 350         }
 351         ret = total_size;
 352
 353 err:
 354         btrfs_free_path(path);
 355
 356         return ret;
 357 }
 358
 359 static int btrfs_xattr_handler_get(const struct xattr_handler *handler,
 360                                    struct dentry *unused, struct inode *inode,
 361                                    const char *name, void *buffer, size_t size)
 362 {
 363         name = xattr_full_name(handler, name);
 364         return btrfs_getxattr(inode, name, buffer, size);
 365 }
 366
 367 static int btrfs_xattr_handler_set(const struct xattr_handler *handler,
 368                                    struct dentry *unused, struct inode *inode,
 369                                    const char *name, const void *buffer,
 370                                    size_t size, int flags)
 371 {
 372         name = xattr_full_name(handler, name);
 373         return btrfs_setxattr(NULL, inode, name, buffer, size, flags);
 374 }
 375
 376 static int btrfs_xattr_handler_set_prop(const struct xattr_handler *handler,
 377                                         struct dentry *unused, struct inode *inode,
 378                                         const char *name, const void *value,
 379                                         size_t size, int flags)
 380 {
 381         name = xattr_full_name(handler, name);
 382         return btrfs_set_prop(inode, name, value, size, flags);
 383 }
 384
 385 static const struct xattr_handler btrfs_security_xattr_handler = {
 386         .prefix = XATTR_SECURITY_PREFIX,
 387         .get = btrfs_xattr_handler_get,
 388         .set = btrfs_xattr_handler_set,
 389 };
 390
 391 static const struct xattr_handler btrfs_trusted_xattr_handler = {
 392         .prefix = XATTR_TRUSTED_PREFIX,
 393         .get = btrfs_xattr_handler_get,
 394         .set = btrfs_xattr_handler_set,
 395 };
 396
 397 static const struct xattr_handler btrfs_user_xattr_handler = {
 398         .prefix = XATTR_USER_PREFIX,
 399         .get = btrfs_xattr_handler_get,
 400         .set = btrfs_xattr_handler_set,
 401 };
 402
 403 static const struct xattr_handler btrfs_btrfs_xattr_handler = {
 404         .prefix = XATTR_BTRFS_PREFIX,
 405         .get = btrfs_xattr_handler_get,
 406         .set = btrfs_xattr_handler_set_prop,
 407 };
 408
 409 const struct xattr_handler *btrfs_xattr_handlers[] = {
 410         &btrfs_security_xattr_handler,
 411 #ifdef CONFIG_BTRFS_FS_POSIX_ACL
 412         &posix_acl_access_xattr_handler,
 413         &posix_acl_default_xattr_handler,
 414 #endif
 415         &btrfs_trusted_xattr_handler,
 416         &btrfs_user_xattr_handler,
 417         &btrfs_btrfs_xattr_handler,
 418         NULL,
 419 };
 420
 421 static int btrfs_initxattrs(struct inode *inode,
 422                             const struct xattr *xattr_array, void *fs_info)
 423 {
 424         const struct xattr *xattr;
 425         struct btrfs_trans_handle *trans = fs_info;
 426         unsigned int nofs_flag;
 427         char *name;
 428         int err = 0;
 429
 430         /*
 431          * We're holding a transaction handle, so use a NOFS memory allocation
 432          * context to avoid deadlock if reclaim happens.
 433          */
 434         nofs_flag = memalloc_nofs_save();
 435         for (xattr = xattr_array; xattr->name != NULL; xattr++) {
 436                 name = kmalloc(XATTR_SECURITY_PREFIX_LEN +
 437                                strlen(xattr->name) + 1, GFP_KERNEL);
 438                 if (!name) {
 439                         err = -ENOMEM;
 440                         break;
 441                 }
 442                 strcpy(name, XATTR_SECURITY_PREFIX);
 443                 strcpy(name + XATTR_SECURITY_PREFIX_LEN, xattr->name);
 444                 err = btrfs_setxattr(trans, inode, name, xattr->value,
 445                                 xattr->value_len, 0);
 446                 kfree(name);
 447                 if (err < 0)
 448                         break;
 449         }
 450         memalloc_nofs_restore(nofs_flag);
 451         return err;
 452 }
 453
 454 int btrfs_xattr_security_init(struct btrfs_trans_handle *trans,
 455                               struct inode *inode, struct inode *dir,
 456                               const struct qstr *qstr)
 457 {
 458         return security_inode_init_security(inode, dir, qstr,
 459                                             &btrfs_initxattrs, trans);
 460 }