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

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