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