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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 "ctree.h"
 26 #include "btrfs_inode.h"
 27 #include "transaction.h"
 28 #include "xattr.h"
 29 #include "disk-io.h"
 30 
 31 
 32 ssize_t __btrfs_getxattr(struct inode *inode, const char *name,
 33                                 void *buffer, size_t size)
 34 {
 35         struct btrfs_dir_item *di;
 36         struct btrfs_root *root = BTRFS_I(inode)->root;
 37         struct btrfs_path *path;
 38         struct extent_buffer *leaf;
 39         int ret = 0;
 40         unsigned long data_ptr;
 41 
 42         path = btrfs_alloc_path();
 43         if (!path)
 44                 return -ENOMEM;
 45 
 46         /* lookup the xattr by name */
 47         di = btrfs_lookup_xattr(NULL, root, path, btrfs_ino(inode), name,
 48                                 strlen(name), 0);
 49         if (!di) {
 50                 ret = -ENODATA;
 51                 goto out;
 52         } else if (IS_ERR(di)) {
 53                 ret = PTR_ERR(di);
 54                 goto out;
 55         }
 56 
 57         leaf = path->nodes[0];
 58         /* if size is 0, that means we want the size of the attr */
 59         if (!size) {
 60                 ret = btrfs_dir_data_len(leaf, di);
 61                 goto out;
 62         }
 63 
 64         /* now get the data out of our dir_item */
 65         if (btrfs_dir_data_len(leaf, di) > size) {
 66                 ret = -ERANGE;
 67                 goto out;
 68         }
 69 
 70         /*
 71          * The way things are packed into the leaf is like this
 72          * |struct btrfs_dir_item|name|data|
 73          * where name is the xattr name, so security.foo, and data is the
 74          * content of the xattr.  data_ptr points to the location in memory
 75          * where the data starts in the in memory leaf
 76          */
 77         data_ptr = (unsigned long)((char *)(di + 1) +
 78                                    btrfs_dir_name_len(leaf, di));
 79         read_extent_buffer(leaf, buffer, data_ptr,
 80                            btrfs_dir_data_len(leaf, di));
 81         ret = btrfs_dir_data_len(leaf, di);
 82 
 83 out:
 84         btrfs_free_path(path);
 85         return ret;
 86 }
 87 
 88 static int do_setxattr(struct btrfs_trans_handle *trans,
 89                        struct inode *inode, const char *name,
 90                        const void *value, size_t size, int flags)
 91 {
 92         struct btrfs_dir_item *di;
 93         struct btrfs_root *root = BTRFS_I(inode)->root;
 94         struct btrfs_path *path;
 95         size_t name_len = strlen(name);
 96         int ret = 0;
 97 
 98         if (name_len + size > BTRFS_MAX_XATTR_SIZE(root))
 99                 return -ENOSPC;
100 
101         path = btrfs_alloc_path();
102         if (!path)
103                 return -ENOMEM;
104 
105         if (flags & XATTR_REPLACE) {
106                 di = btrfs_lookup_xattr(trans, root, path, btrfs_ino(inode), name,
107                                         name_len, -1);
108                 if (IS_ERR(di)) {
109                         ret = PTR_ERR(di);
110                         goto out;
111                 } else if (!di) {
112                         ret = -ENODATA;
113                         goto out;
114                 }
115                 ret = btrfs_delete_one_dir_name(trans, root, path, di);
116                 if (ret)
117                         goto out;
118                 btrfs_release_path(path);
119 
120                 /*
121                  * remove the attribute
122                  */
123                 if (!value)
124                         goto out;
125         } else {
126                 di = btrfs_lookup_xattr(NULL, root, path, btrfs_ino(inode),
127                                         name, name_len, 0);
128                 if (IS_ERR(di)) {
129                         ret = PTR_ERR(di);
130                         goto out;
131                 }
132                 if (!di && !value)
133                         goto out;
134                 btrfs_release_path(path);
135         }
136 
137 again:
138         ret = btrfs_insert_xattr_item(trans, root, path, btrfs_ino(inode),
139                                       name, name_len, value, size);
140         /*
141          * If we're setting an xattr to a new value but the new value is say
142          * exactly BTRFS_MAX_XATTR_SIZE, we could end up with EOVERFLOW getting
143          * back from split_leaf.  This is because it thinks we'll be extending
144          * the existing item size, but we're asking for enough space to add the
145          * item itself.  So if we get EOVERFLOW just set ret to EEXIST and let
146          * the rest of the function figure it out.
147          */
148         if (ret == -EOVERFLOW)
149                 ret = -EEXIST;
150 
151         if (ret == -EEXIST) {
152                 if (flags & XATTR_CREATE)
153                         goto out;
154                 /*
155                  * We can't use the path we already have since we won't have the
156                  * proper locking for a delete, so release the path and
157                  * re-lookup to delete the thing.
158                  */
159                 btrfs_release_path(path);
160                 di = btrfs_lookup_xattr(trans, root, path, btrfs_ino(inode),
161                                         name, name_len, -1);
162                 if (IS_ERR(di)) {
163                         ret = PTR_ERR(di);
164                         goto out;
165                 } else if (!di) {
166                         /* Shouldn't happen but just in case... */
167                         btrfs_release_path(path);
168                         goto again;
169                 }
170 
171                 ret = btrfs_delete_one_dir_name(trans, root, path, di);
172                 if (ret)
173                         goto out;
174 
175                 /*
176                  * We have a value to set, so go back and try to insert it now.
177                  */
178                 if (value) {
179                         btrfs_release_path(path);
180                         goto again;
181                 }
182         }
183 out:
184         btrfs_free_path(path);
185         return ret;
186 }
187 
188 /*
189  * @value: "" makes the attribute to empty, NULL removes it
190  */
191 int __btrfs_setxattr(struct btrfs_trans_handle *trans,
192                      struct inode *inode, const char *name,
193                      const void *value, size_t size, int flags)
194 {
195         struct btrfs_root *root = BTRFS_I(inode)->root;
196         int ret;
197 
198         if (trans)
199                 return do_setxattr(trans, inode, name, value, size, flags);
200 
201         trans = btrfs_start_transaction(root, 2);
202         if (IS_ERR(trans))
203                 return PTR_ERR(trans);
204 
205         ret = do_setxattr(trans, inode, name, value, size, flags);
206         if (ret)
207                 goto out;
208 
209         inode_inc_iversion(inode);
210         inode->i_ctime = CURRENT_TIME;
211         set_bit(BTRFS_INODE_COPY_EVERYTHING, &BTRFS_I(inode)->runtime_flags);
212         ret = btrfs_update_inode(trans, root, inode);
213         BUG_ON(ret);
214 out:
215         btrfs_end_transaction(trans, root);
216         return ret;
217 }
218 
219 ssize_t btrfs_listxattr(struct dentry *dentry, char *buffer, size_t size)
220 {
221         struct btrfs_key key, found_key;
222         struct inode *inode = dentry->d_inode;
223         struct btrfs_root *root = BTRFS_I(inode)->root;
224         struct btrfs_path *path;
225         struct extent_buffer *leaf;
226         struct btrfs_dir_item *di;
227         int ret = 0, slot;
228         size_t total_size = 0, size_left = size;
229         unsigned long name_ptr;
230         size_t name_len;
231 
232         /*
233          * ok we want all objects associated with this id.
234          * NOTE: we set key.offset = 0; because we want to start with the
235          * first xattr that we find and walk forward
236          */
237         key.objectid = btrfs_ino(inode);
238         btrfs_set_key_type(&key, BTRFS_XATTR_ITEM_KEY);
239         key.offset = 0;
240 
241         path = btrfs_alloc_path();
242         if (!path)
243                 return -ENOMEM;
244         path->reada = 2;
245 
246         /* search for our xattrs */
247         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
248         if (ret < 0)
249                 goto err;
250 
251         while (1) {
252                 leaf = path->nodes[0];
253                 slot = path->slots[0];
254 
255                 /* this is where we start walking through the path */
256                 if (slot >= btrfs_header_nritems(leaf)) {
257                         /*
258                          * if we've reached the last slot in this leaf we need
259                          * to go to the next leaf and reset everything
260                          */
261                         ret = btrfs_next_leaf(root, path);
262                         if (ret < 0)
263                                 goto err;
264                         else if (ret > 0)
265                                 break;
266                         continue;
267                 }
268 
269                 btrfs_item_key_to_cpu(leaf, &found_key, slot);
270 
271                 /* check to make sure this item is what we want */
272                 if (found_key.objectid != key.objectid)
273                         break;
274                 if (btrfs_key_type(&found_key) != BTRFS_XATTR_ITEM_KEY)
275                         break;
276 
277                 di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
278                 if (verify_dir_item(root, leaf, di))
279                         goto next;
280 
281                 name_len = btrfs_dir_name_len(leaf, di);
282                 total_size += name_len + 1;
283 
284                 /* we are just looking for how big our buffer needs to be */
285                 if (!size)
286                         goto next;
287 
288                 if (!buffer || (name_len + 1) > size_left) {
289                         ret = -ERANGE;
290                         goto err;
291                 }
292 
293                 name_ptr = (unsigned long)(di + 1);
294                 read_extent_buffer(leaf, buffer, name_ptr, name_len);
295                 buffer[name_len] = '\0';
296 
297                 size_left -= name_len + 1;
298                 buffer += name_len + 1;
299 next:
300                 path->slots[0]++;
301         }
302         ret = total_size;
303 
304 err:
305         btrfs_free_path(path);
306 
307         return ret;
308 }
309 
310 /*
311  * List of handlers for synthetic system.* attributes.  All real ondisk
312  * attributes are handled directly.
313  */
314 const struct xattr_handler *btrfs_xattr_handlers[] = {
315 #ifdef CONFIG_BTRFS_FS_POSIX_ACL
316         &btrfs_xattr_acl_access_handler,
317         &btrfs_xattr_acl_default_handler,
318 #endif
319         NULL,
320 };
321 
322 /*
323  * Check if the attribute is in a supported namespace.
324  *
325  * This applied after the check for the synthetic attributes in the system
326  * namespace.
327  */
328 static bool btrfs_is_valid_xattr(const char *name)
329 {
330         return !strncmp(name, XATTR_SECURITY_PREFIX,
331                         XATTR_SECURITY_PREFIX_LEN) ||
332                !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN) ||
333                !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) ||
334                !strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN);
335 }
336 
337 ssize_t btrfs_getxattr(struct dentry *dentry, const char *name,
338                        void *buffer, size_t size)
339 {
340         /*
341          * If this is a request for a synthetic attribute in the system.*
342          * namespace use the generic infrastructure to resolve a handler
343          * for it via sb->s_xattr.
344          */
345         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
346                 return generic_getxattr(dentry, name, buffer, size);
347 
348         if (!btrfs_is_valid_xattr(name))
349                 return -EOPNOTSUPP;
350         return __btrfs_getxattr(dentry->d_inode, name, buffer, size);
351 }
352 
353 int btrfs_setxattr(struct dentry *dentry, const char *name, const void *value,
354                    size_t size, int flags)
355 {
356         struct btrfs_root *root = BTRFS_I(dentry->d_inode)->root;
357 
358         /*
359          * The permission on security.* and system.* is not checked
360          * in permission().
361          */
362         if (btrfs_root_readonly(root))
363                 return -EROFS;
364 
365         /*
366          * If this is a request for a synthetic attribute in the system.*
367          * namespace use the generic infrastructure to resolve a handler
368          * for it via sb->s_xattr.
369          */
370         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
371                 return generic_setxattr(dentry, name, value, size, flags);
372 
373         if (!btrfs_is_valid_xattr(name))
374                 return -EOPNOTSUPP;
375 
376         if (size == 0)
377                 value = "";  /* empty EA, do not remove */
378 
379         return __btrfs_setxattr(NULL, dentry->d_inode, name, value, size,
380                                 flags);
381 }
382 
383 int btrfs_removexattr(struct dentry *dentry, const char *name)
384 {
385         struct btrfs_root *root = BTRFS_I(dentry->d_inode)->root;
386 
387         /*
388          * The permission on security.* and system.* is not checked
389          * in permission().
390          */
391         if (btrfs_root_readonly(root))
392                 return -EROFS;
393 
394         /*
395          * If this is a request for a synthetic attribute in the system.*
396          * namespace use the generic infrastructure to resolve a handler
397          * for it via sb->s_xattr.
398          */
399         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
400                 return generic_removexattr(dentry, name);
401 
402         if (!btrfs_is_valid_xattr(name))
403                 return -EOPNOTSUPP;
404 
405         return __btrfs_setxattr(NULL, dentry->d_inode, name, NULL, 0,
406                                 XATTR_REPLACE);
407 }
408 
409 static int btrfs_initxattrs(struct inode *inode,
410                             const struct xattr *xattr_array, void *fs_info)
411 {
412         const struct xattr *xattr;
413         struct btrfs_trans_handle *trans = fs_info;
414         char *name;
415         int err = 0;
416 
417         for (xattr = xattr_array; xattr->name != NULL; xattr++) {
418                 name = kmalloc(XATTR_SECURITY_PREFIX_LEN +
419                                strlen(xattr->name) + 1, GFP_NOFS);
420                 if (!name) {
421                         err = -ENOMEM;
422                         break;
423                 }
424                 strcpy(name, XATTR_SECURITY_PREFIX);
425                 strcpy(name + XATTR_SECURITY_PREFIX_LEN, xattr->name);
426                 err = __btrfs_setxattr(trans, inode, name,
427                                        xattr->value, xattr->value_len, 0);
428                 kfree(name);
429                 if (err < 0)
430                         break;
431         }
432         return err;
433 }
434 
435 int btrfs_xattr_security_init(struct btrfs_trans_handle *trans,
436                               struct inode *inode, struct inode *dir,
437                               const struct qstr *qstr)
438 {
439         return security_inode_init_security(inode, dir, qstr,
440                                             &btrfs_initxattrs, trans);
441 }
442 

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