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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 = dentry->d_inode;
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 
319                 di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
320                 if (verify_dir_item(root, leaf, di))
321                         goto next;
322 
323                 name_len = btrfs_dir_name_len(leaf, di);
324                 total_size += name_len + 1;
325 
326                 /* we are just looking for how big our buffer needs to be */
327                 if (!size)
328                         goto next;
329 
330                 if (!buffer || (name_len + 1) > size_left) {
331                         ret = -ERANGE;
332                         goto err;
333                 }
334 
335                 name_ptr = (unsigned long)(di + 1);
336                 read_extent_buffer(leaf, buffer, name_ptr, name_len);
337                 buffer[name_len] = '\0';
338 
339                 size_left -= name_len + 1;
340                 buffer += name_len + 1;
341 next:
342                 path->slots[0]++;
343         }
344         ret = total_size;
345 
346 err:
347         btrfs_free_path(path);
348 
349         return ret;
350 }
351 
352 /*
353  * List of handlers for synthetic system.* attributes.  All real ondisk
354  * attributes are handled directly.
355  */
356 const struct xattr_handler *btrfs_xattr_handlers[] = {
357 #ifdef CONFIG_BTRFS_FS_POSIX_ACL
358         &posix_acl_access_xattr_handler,
359         &posix_acl_default_xattr_handler,
360 #endif
361         NULL,
362 };
363 
364 /*
365  * Check if the attribute is in a supported namespace.
366  *
367  * This is applied after the check for the synthetic attributes in the system
368  * namespace.
369  */
370 static int btrfs_is_valid_xattr(const char *name)
371 {
372         int len = strlen(name);
373         int prefixlen = 0;
374 
375         if (!strncmp(name, XATTR_SECURITY_PREFIX,
376                         XATTR_SECURITY_PREFIX_LEN))
377                 prefixlen = XATTR_SECURITY_PREFIX_LEN;
378         else if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
379                 prefixlen = XATTR_SYSTEM_PREFIX_LEN;
380         else if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN))
381                 prefixlen = XATTR_TRUSTED_PREFIX_LEN;
382         else if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN))
383                 prefixlen = XATTR_USER_PREFIX_LEN;
384         else if (!strncmp(name, XATTR_BTRFS_PREFIX, XATTR_BTRFS_PREFIX_LEN))
385                 prefixlen = XATTR_BTRFS_PREFIX_LEN;
386         else
387                 return -EOPNOTSUPP;
388 
389         /*
390          * The name cannot consist of just prefix
391          */
392         if (len <= prefixlen)
393                 return -EINVAL;
394 
395         return 0;
396 }
397 
398 ssize_t btrfs_getxattr(struct dentry *dentry, const char *name,
399                        void *buffer, size_t size)
400 {
401         int ret;
402 
403         /*
404          * If this is a request for a synthetic attribute in the system.*
405          * namespace use the generic infrastructure to resolve a handler
406          * for it via sb->s_xattr.
407          */
408         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
409                 return generic_getxattr(dentry, name, buffer, size);
410 
411         ret = btrfs_is_valid_xattr(name);
412         if (ret)
413                 return ret;
414         return __btrfs_getxattr(dentry->d_inode, name, buffer, size);
415 }
416 
417 int btrfs_setxattr(struct dentry *dentry, const char *name, const void *value,
418                    size_t size, int flags)
419 {
420         struct btrfs_root *root = BTRFS_I(dentry->d_inode)->root;
421         int ret;
422 
423         /*
424          * The permission on security.* and system.* is not checked
425          * in permission().
426          */
427         if (btrfs_root_readonly(root))
428                 return -EROFS;
429 
430         /*
431          * If this is a request for a synthetic attribute in the system.*
432          * namespace use the generic infrastructure to resolve a handler
433          * for it via sb->s_xattr.
434          */
435         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
436                 return generic_setxattr(dentry, name, value, size, flags);
437 
438         ret = btrfs_is_valid_xattr(name);
439         if (ret)
440                 return ret;
441 
442         if (!strncmp(name, XATTR_BTRFS_PREFIX, XATTR_BTRFS_PREFIX_LEN))
443                 return btrfs_set_prop(dentry->d_inode, name,
444                                       value, size, flags);
445 
446         if (size == 0)
447                 value = "";  /* empty EA, do not remove */
448 
449         return __btrfs_setxattr(NULL, dentry->d_inode, name, value, size,
450                                 flags);
451 }
452 
453 int btrfs_removexattr(struct dentry *dentry, const char *name)
454 {
455         struct btrfs_root *root = BTRFS_I(dentry->d_inode)->root;
456         int ret;
457 
458         /*
459          * The permission on security.* and system.* is not checked
460          * in permission().
461          */
462         if (btrfs_root_readonly(root))
463                 return -EROFS;
464 
465         /*
466          * If this is a request for a synthetic attribute in the system.*
467          * namespace use the generic infrastructure to resolve a handler
468          * for it via sb->s_xattr.
469          */
470         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
471                 return generic_removexattr(dentry, name);
472 
473         ret = btrfs_is_valid_xattr(name);
474         if (ret)
475                 return ret;
476 
477         if (!strncmp(name, XATTR_BTRFS_PREFIX, XATTR_BTRFS_PREFIX_LEN))
478                 return btrfs_set_prop(dentry->d_inode, name,
479                                       NULL, 0, XATTR_REPLACE);
480 
481         return __btrfs_setxattr(NULL, dentry->d_inode, name, NULL, 0,
482                                 XATTR_REPLACE);
483 }
484 
485 static int btrfs_initxattrs(struct inode *inode,
486                             const struct xattr *xattr_array, void *fs_info)
487 {
488         const struct xattr *xattr;
489         struct btrfs_trans_handle *trans = fs_info;
490         char *name;
491         int err = 0;
492 
493         for (xattr = xattr_array; xattr->name != NULL; xattr++) {
494                 name = kmalloc(XATTR_SECURITY_PREFIX_LEN +
495                                strlen(xattr->name) + 1, GFP_NOFS);
496                 if (!name) {
497                         err = -ENOMEM;
498                         break;
499                 }
500                 strcpy(name, XATTR_SECURITY_PREFIX);
501                 strcpy(name + XATTR_SECURITY_PREFIX_LEN, xattr->name);
502                 err = __btrfs_setxattr(trans, inode, name,
503                                        xattr->value, xattr->value_len, 0);
504                 kfree(name);
505                 if (err < 0)
506                         break;
507         }
508         return err;
509 }
510 
511 int btrfs_xattr_security_init(struct btrfs_trans_handle *trans,
512                               struct inode *inode, struct inode *dir,
513                               const struct qstr *qstr)
514 {
515         return security_inode_init_security(inode, dir, qstr,
516                                             &btrfs_initxattrs, trans);
517 }
518 

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