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Linux/fs/btrfs/xattr.c

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  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 "ctree.h"
 27 #include "btrfs_inode.h"
 28 #include "transaction.h"
 29 #include "xattr.h"
 30 #include "disk-io.h"
 31 #include "props.h"
 32 #include "locking.h"
 33 
 34 
 35 ssize_t __btrfs_getxattr(struct inode *inode, const char *name,
 36                                 void *buffer, size_t size)
 37 {
 38         struct btrfs_dir_item *di;
 39         struct btrfs_root *root = BTRFS_I(inode)->root;
 40         struct btrfs_path *path;
 41         struct extent_buffer *leaf;
 42         int ret = 0;
 43         unsigned long data_ptr;
 44 
 45         path = btrfs_alloc_path();
 46         if (!path)
 47                 return -ENOMEM;
 48 
 49         /* lookup the xattr by name */
 50         di = btrfs_lookup_xattr(NULL, root, path, btrfs_ino(inode), name,
 51                                 strlen(name), 0);
 52         if (!di) {
 53                 ret = -ENODATA;
 54                 goto out;
 55         } else if (IS_ERR(di)) {
 56                 ret = PTR_ERR(di);
 57                 goto out;
 58         }
 59 
 60         leaf = path->nodes[0];
 61         /* if size is 0, that means we want the size of the attr */
 62         if (!size) {
 63                 ret = btrfs_dir_data_len(leaf, di);
 64                 goto out;
 65         }
 66 
 67         /* now get the data out of our dir_item */
 68         if (btrfs_dir_data_len(leaf, di) > size) {
 69                 ret = -ERANGE;
 70                 goto out;
 71         }
 72 
 73         /*
 74          * The way things are packed into the leaf is like this
 75          * |struct btrfs_dir_item|name|data|
 76          * where name is the xattr name, so security.foo, and data is the
 77          * content of the xattr.  data_ptr points to the location in memory
 78          * where the data starts in the in memory leaf
 79          */
 80         data_ptr = (unsigned long)((char *)(di + 1) +
 81                                    btrfs_dir_name_len(leaf, di));
 82         read_extent_buffer(leaf, buffer, data_ptr,
 83                            btrfs_dir_data_len(leaf, di));
 84         ret = btrfs_dir_data_len(leaf, di);
 85 
 86 out:
 87         btrfs_free_path(path);
 88         return ret;
 89 }
 90 
 91 static int do_setxattr(struct btrfs_trans_handle *trans,
 92                        struct inode *inode, const char *name,
 93                        const void *value, size_t size, int flags)
 94 {
 95         struct btrfs_dir_item *di = NULL;
 96         struct btrfs_root *root = BTRFS_I(inode)->root;
 97         struct btrfs_path *path;
 98         size_t name_len = strlen(name);
 99         int ret = 0;
100 
101         if (name_len + size > BTRFS_MAX_XATTR_SIZE(root))
102                 return -ENOSPC;
103 
104         path = btrfs_alloc_path();
105         if (!path)
106                 return -ENOMEM;
107         path->skip_release_on_error = 1;
108 
109         if (!value) {
110                 di = btrfs_lookup_xattr(trans, root, path, btrfs_ino(inode),
111                                         name, name_len, -1);
112                 if (!di && (flags & XATTR_REPLACE))
113                         ret = -ENODATA;
114                 else if (IS_ERR(di))
115                         ret = PTR_ERR(di);
116                 else if (di)
117                         ret = btrfs_delete_one_dir_name(trans, root, path, di);
118                 goto out;
119         }
120 
121         /*
122          * For a replace we can't just do the insert blindly.
123          * Do a lookup first (read-only btrfs_search_slot), and return if xattr
124          * doesn't exist. If it exists, fall down below to the insert/replace
125          * path - we can't race with a concurrent xattr delete, because the VFS
126          * locks the inode's i_mutex before calling setxattr or removexattr.
127          */
128         if (flags & XATTR_REPLACE) {
129                 ASSERT(mutex_is_locked(&inode->i_mutex));
130                 di = btrfs_lookup_xattr(NULL, root, path, btrfs_ino(inode),
131                                         name, name_len, 0);
132                 if (!di)
133                         ret = -ENODATA;
134                 else if (IS_ERR(di))
135                         ret = PTR_ERR(di);
136                 if (ret)
137                         goto out;
138                 btrfs_release_path(path);
139                 di = NULL;
140         }
141 
142         ret = btrfs_insert_xattr_item(trans, root, path, btrfs_ino(inode),
143                                       name, name_len, value, size);
144         if (ret == -EOVERFLOW) {
145                 /*
146                  * We have an existing item in a leaf, split_leaf couldn't
147                  * expand it. That item might have or not a dir_item that
148                  * matches our target xattr, so lets check.
149                  */
150                 ret = 0;
151                 btrfs_assert_tree_locked(path->nodes[0]);
152                 di = btrfs_match_dir_item_name(root, path, name, name_len);
153                 if (!di && !(flags & XATTR_REPLACE)) {
154                         ret = -ENOSPC;
155                         goto out;
156                 }
157         } else if (ret == -EEXIST) {
158                 ret = 0;
159                 di = btrfs_match_dir_item_name(root, path, name, name_len);
160                 ASSERT(di); /* logic error */
161         } else if (ret) {
162                 goto out;
163         }
164 
165         if (di && (flags & XATTR_CREATE)) {
166                 ret = -EEXIST;
167                 goto out;
168         }
169 
170         if (di) {
171                 /*
172                  * We're doing a replace, and it must be atomic, that is, at
173                  * any point in time we have either the old or the new xattr
174                  * value in the tree. We don't want readers (getxattr and
175                  * listxattrs) to miss a value, this is specially important
176                  * for ACLs.
177                  */
178                 const int slot = path->slots[0];
179                 struct extent_buffer *leaf = path->nodes[0];
180                 const u16 old_data_len = btrfs_dir_data_len(leaf, di);
181                 const u32 item_size = btrfs_item_size_nr(leaf, slot);
182                 const u32 data_size = sizeof(*di) + name_len + size;
183                 struct btrfs_item *item;
184                 unsigned long data_ptr;
185                 char *ptr;
186 
187                 if (size > old_data_len) {
188                         if (btrfs_leaf_free_space(root, leaf) <
189                             (size - old_data_len)) {
190                                 ret = -ENOSPC;
191                                 goto out;
192                         }
193                 }
194 
195                 if (old_data_len + name_len + sizeof(*di) == item_size) {
196                         /* No other xattrs packed in the same leaf item. */
197                         if (size > old_data_len)
198                                 btrfs_extend_item(root, path,
199                                                   size - old_data_len);
200                         else if (size < old_data_len)
201                                 btrfs_truncate_item(root, path, data_size, 1);
202                 } else {
203                         /* There are other xattrs packed in the same item. */
204                         ret = btrfs_delete_one_dir_name(trans, root, path, di);
205                         if (ret)
206                                 goto out;
207                         btrfs_extend_item(root, path, data_size);
208                 }
209 
210                 item = btrfs_item_nr(slot);
211                 ptr = btrfs_item_ptr(leaf, slot, char);
212                 ptr += btrfs_item_size(leaf, item) - data_size;
213                 di = (struct btrfs_dir_item *)ptr;
214                 btrfs_set_dir_data_len(leaf, di, size);
215                 data_ptr = ((unsigned long)(di + 1)) + name_len;
216                 write_extent_buffer(leaf, value, data_ptr, size);
217                 btrfs_mark_buffer_dirty(leaf);
218         } else {
219                 /*
220                  * Insert, and we had space for the xattr, so path->slots[0] is
221                  * where our xattr dir_item is and btrfs_insert_xattr_item()
222                  * filled it.
223                  */
224         }
225 out:
226         btrfs_free_path(path);
227         return ret;
228 }
229 
230 /*
231  * @value: "" makes the attribute to empty, NULL removes it
232  */
233 int __btrfs_setxattr(struct btrfs_trans_handle *trans,
234                      struct inode *inode, const char *name,
235                      const void *value, size_t size, int flags)
236 {
237         struct btrfs_root *root = BTRFS_I(inode)->root;
238         int ret;
239 
240         if (trans)
241                 return do_setxattr(trans, inode, name, value, size, flags);
242 
243         trans = btrfs_start_transaction(root, 2);
244         if (IS_ERR(trans))
245                 return PTR_ERR(trans);
246 
247         ret = do_setxattr(trans, inode, name, value, size, flags);
248         if (ret)
249                 goto out;
250 
251         inode_inc_iversion(inode);
252         inode->i_ctime = CURRENT_TIME;
253         set_bit(BTRFS_INODE_COPY_EVERYTHING, &BTRFS_I(inode)->runtime_flags);
254         ret = btrfs_update_inode(trans, root, inode);
255         BUG_ON(ret);
256 out:
257         btrfs_end_transaction(trans, root);
258         return ret;
259 }
260 
261 ssize_t btrfs_listxattr(struct dentry *dentry, char *buffer, size_t size)
262 {
263         struct btrfs_key key, found_key;
264         struct inode *inode = d_inode(dentry);
265         struct btrfs_root *root = BTRFS_I(inode)->root;
266         struct btrfs_path *path;
267         struct extent_buffer *leaf;
268         struct btrfs_dir_item *di;
269         int ret = 0, slot;
270         size_t total_size = 0, size_left = size;
271         unsigned long name_ptr;
272         size_t name_len;
273 
274         /*
275          * ok we want all objects associated with this id.
276          * NOTE: we set key.offset = 0; because we want to start with the
277          * first xattr that we find and walk forward
278          */
279         key.objectid = btrfs_ino(inode);
280         key.type = BTRFS_XATTR_ITEM_KEY;
281         key.offset = 0;
282 
283         path = btrfs_alloc_path();
284         if (!path)
285                 return -ENOMEM;
286         path->reada = 2;
287 
288         /* search for our xattrs */
289         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
290         if (ret < 0)
291                 goto err;
292 
293         while (1) {
294                 leaf = path->nodes[0];
295                 slot = path->slots[0];
296 
297                 /* this is where we start walking through the path */
298                 if (slot >= btrfs_header_nritems(leaf)) {
299                         /*
300                          * if we've reached the last slot in this leaf we need
301                          * to go to the next leaf and reset everything
302                          */
303                         ret = btrfs_next_leaf(root, path);
304                         if (ret < 0)
305                                 goto err;
306                         else if (ret > 0)
307                                 break;
308                         continue;
309                 }
310 
311                 btrfs_item_key_to_cpu(leaf, &found_key, slot);
312 
313                 /* check to make sure this item is what we want */
314                 if (found_key.objectid != key.objectid)
315                         break;
316                 if (found_key.type > BTRFS_XATTR_ITEM_KEY)
317                         break;
318                 if (found_key.type < BTRFS_XATTR_ITEM_KEY)
319                         goto next;
320 
321                 di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
322                 if (verify_dir_item(root, leaf, di))
323                         goto next;
324 
325                 name_len = btrfs_dir_name_len(leaf, di);
326                 total_size += name_len + 1;
327 
328                 /* we are just looking for how big our buffer needs to be */
329                 if (!size)
330                         goto next;
331 
332                 if (!buffer || (name_len + 1) > size_left) {
333                         ret = -ERANGE;
334                         goto err;
335                 }
336 
337                 name_ptr = (unsigned long)(di + 1);
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                 path->slots[0]++;
345         }
346         ret = total_size;
347 
348 err:
349         btrfs_free_path(path);
350 
351         return ret;
352 }
353 
354 /*
355  * List of handlers for synthetic system.* attributes.  All real ondisk
356  * attributes are handled directly.
357  */
358 const struct xattr_handler *btrfs_xattr_handlers[] = {
359 #ifdef CONFIG_BTRFS_FS_POSIX_ACL
360         &posix_acl_access_xattr_handler,
361         &posix_acl_default_xattr_handler,
362 #endif
363         NULL,
364 };
365 
366 /*
367  * Check if the attribute is in a supported namespace.
368  *
369  * This is applied after the check for the synthetic attributes in the system
370  * namespace.
371  */
372 static int btrfs_is_valid_xattr(const char *name)
373 {
374         int len = strlen(name);
375         int prefixlen = 0;
376 
377         if (!strncmp(name, XATTR_SECURITY_PREFIX,
378                         XATTR_SECURITY_PREFIX_LEN))
379                 prefixlen = XATTR_SECURITY_PREFIX_LEN;
380         else if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
381                 prefixlen = XATTR_SYSTEM_PREFIX_LEN;
382         else if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN))
383                 prefixlen = XATTR_TRUSTED_PREFIX_LEN;
384         else if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN))
385                 prefixlen = XATTR_USER_PREFIX_LEN;
386         else if (!strncmp(name, XATTR_BTRFS_PREFIX, XATTR_BTRFS_PREFIX_LEN))
387                 prefixlen = XATTR_BTRFS_PREFIX_LEN;
388         else
389                 return -EOPNOTSUPP;
390 
391         /*
392          * The name cannot consist of just prefix
393          */
394         if (len <= prefixlen)
395                 return -EINVAL;
396 
397         return 0;
398 }
399 
400 ssize_t btrfs_getxattr(struct dentry *dentry, const char *name,
401                        void *buffer, size_t size)
402 {
403         int ret;
404 
405         /*
406          * If this is a request for a synthetic attribute in the system.*
407          * namespace use the generic infrastructure to resolve a handler
408          * for it via sb->s_xattr.
409          */
410         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
411                 return generic_getxattr(dentry, name, buffer, size);
412 
413         ret = btrfs_is_valid_xattr(name);
414         if (ret)
415                 return ret;
416         return __btrfs_getxattr(d_inode(dentry), name, buffer, size);
417 }
418 
419 int btrfs_setxattr(struct dentry *dentry, const char *name, const void *value,
420                    size_t size, int flags)
421 {
422         struct btrfs_root *root = BTRFS_I(d_inode(dentry))->root;
423         int ret;
424 
425         /*
426          * The permission on security.* and system.* is not checked
427          * in permission().
428          */
429         if (btrfs_root_readonly(root))
430                 return -EROFS;
431 
432         /*
433          * If this is a request for a synthetic attribute in the system.*
434          * namespace use the generic infrastructure to resolve a handler
435          * for it via sb->s_xattr.
436          */
437         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
438                 return generic_setxattr(dentry, name, value, size, flags);
439 
440         ret = btrfs_is_valid_xattr(name);
441         if (ret)
442                 return ret;
443 
444         if (!strncmp(name, XATTR_BTRFS_PREFIX, XATTR_BTRFS_PREFIX_LEN))
445                 return btrfs_set_prop(d_inode(dentry), name,
446                                       value, size, flags);
447 
448         if (size == 0)
449                 value = "";  /* empty EA, do not remove */
450 
451         return __btrfs_setxattr(NULL, d_inode(dentry), name, value, size,
452                                 flags);
453 }
454 
455 int btrfs_removexattr(struct dentry *dentry, const char *name)
456 {
457         struct btrfs_root *root = BTRFS_I(d_inode(dentry))->root;
458         int ret;
459 
460         /*
461          * The permission on security.* and system.* is not checked
462          * in permission().
463          */
464         if (btrfs_root_readonly(root))
465                 return -EROFS;
466 
467         /*
468          * If this is a request for a synthetic attribute in the system.*
469          * namespace use the generic infrastructure to resolve a handler
470          * for it via sb->s_xattr.
471          */
472         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
473                 return generic_removexattr(dentry, name);
474 
475         ret = btrfs_is_valid_xattr(name);
476         if (ret)
477                 return ret;
478 
479         if (!strncmp(name, XATTR_BTRFS_PREFIX, XATTR_BTRFS_PREFIX_LEN))
480                 return btrfs_set_prop(d_inode(dentry), name,
481                                       NULL, 0, XATTR_REPLACE);
482 
483         return __btrfs_setxattr(NULL, d_inode(dentry), name, NULL, 0,
484                                 XATTR_REPLACE);
485 }
486 
487 static int btrfs_initxattrs(struct inode *inode,
488                             const struct xattr *xattr_array, void *fs_info)
489 {
490         const struct xattr *xattr;
491         struct btrfs_trans_handle *trans = fs_info;
492         char *name;
493         int err = 0;
494 
495         for (xattr = xattr_array; xattr->name != NULL; xattr++) {
496                 name = kmalloc(XATTR_SECURITY_PREFIX_LEN +
497                                strlen(xattr->name) + 1, GFP_NOFS);
498                 if (!name) {
499                         err = -ENOMEM;
500                         break;
501                 }
502                 strcpy(name, XATTR_SECURITY_PREFIX);
503                 strcpy(name + XATTR_SECURITY_PREFIX_LEN, xattr->name);
504                 err = __btrfs_setxattr(trans, inode, name,
505                                        xattr->value, xattr->value_len, 0);
506                 kfree(name);
507                 if (err < 0)
508                         break;
509         }
510         return err;
511 }
512 
513 int btrfs_xattr_security_init(struct btrfs_trans_handle *trans,
514                               struct inode *inode, struct inode *dir,
515                               const struct qstr *qstr)
516 {
517         return security_inode_init_security(inode, dir, qstr,
518                                             &btrfs_initxattrs, trans);
519 }
520 

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