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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         }
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->i_ctime = CURRENT_TIME;
200         ret = btrfs_update_inode(trans, root, inode);
201         BUG_ON(ret);
202 out:
203         btrfs_end_transaction(trans, root);
204         return ret;
205 }
206 
207 ssize_t btrfs_listxattr(struct dentry *dentry, char *buffer, size_t size)
208 {
209         struct btrfs_key key, found_key;
210         struct inode *inode = dentry->d_inode;
211         struct btrfs_root *root = BTRFS_I(inode)->root;
212         struct btrfs_path *path;
213         struct extent_buffer *leaf;
214         struct btrfs_dir_item *di;
215         int ret = 0, slot;
216         size_t total_size = 0, size_left = size;
217         unsigned long name_ptr;
218         size_t name_len;
219 
220         /*
221          * ok we want all objects associated with this id.
222          * NOTE: we set key.offset = 0; because we want to start with the
223          * first xattr that we find and walk forward
224          */
225         key.objectid = btrfs_ino(inode);
226         btrfs_set_key_type(&key, BTRFS_XATTR_ITEM_KEY);
227         key.offset = 0;
228 
229         path = btrfs_alloc_path();
230         if (!path)
231                 return -ENOMEM;
232         path->reada = 2;
233 
234         /* search for our xattrs */
235         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
236         if (ret < 0)
237                 goto err;
238 
239         while (1) {
240                 leaf = path->nodes[0];
241                 slot = path->slots[0];
242 
243                 /* this is where we start walking through the path */
244                 if (slot >= btrfs_header_nritems(leaf)) {
245                         /*
246                          * if we've reached the last slot in this leaf we need
247                          * to go to the next leaf and reset everything
248                          */
249                         ret = btrfs_next_leaf(root, path);
250                         if (ret < 0)
251                                 goto err;
252                         else if (ret > 0)
253                                 break;
254                         continue;
255                 }
256 
257                 btrfs_item_key_to_cpu(leaf, &found_key, slot);
258 
259                 /* check to make sure this item is what we want */
260                 if (found_key.objectid != key.objectid)
261                         break;
262                 if (btrfs_key_type(&found_key) != BTRFS_XATTR_ITEM_KEY)
263                         break;
264 
265                 di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
266                 if (verify_dir_item(root, leaf, di))
267                         continue;
268 
269                 name_len = btrfs_dir_name_len(leaf, di);
270                 total_size += name_len + 1;
271 
272                 /* we are just looking for how big our buffer needs to be */
273                 if (!size)
274                         goto next;
275 
276                 if (!buffer || (name_len + 1) > size_left) {
277                         ret = -ERANGE;
278                         goto err;
279                 }
280 
281                 name_ptr = (unsigned long)(di + 1);
282                 read_extent_buffer(leaf, buffer, name_ptr, name_len);
283                 buffer[name_len] = '\0';
284 
285                 size_left -= name_len + 1;
286                 buffer += name_len + 1;
287 next:
288                 path->slots[0]++;
289         }
290         ret = total_size;
291 
292 err:
293         btrfs_free_path(path);
294 
295         return ret;
296 }
297 
298 /*
299  * List of handlers for synthetic system.* attributes.  All real ondisk
300  * attributes are handled directly.
301  */
302 const struct xattr_handler *btrfs_xattr_handlers[] = {
303 #ifdef CONFIG_BTRFS_FS_POSIX_ACL
304         &btrfs_xattr_acl_access_handler,
305         &btrfs_xattr_acl_default_handler,
306 #endif
307         NULL,
308 };
309 
310 /*
311  * Check if the attribute is in a supported namespace.
312  *
313  * This is applied after the check for the synthetic attributes in the system
314  * namespace.
315  */
316 static int btrfs_is_valid_xattr(const char *name)
317 {
318         int len = strlen(name);
319         int prefixlen = 0;
320 
321         if (!strncmp(name, XATTR_SECURITY_PREFIX,
322                         XATTR_SECURITY_PREFIX_LEN))
323                 prefixlen = XATTR_SECURITY_PREFIX_LEN;
324         else if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
325                 prefixlen = XATTR_SYSTEM_PREFIX_LEN;
326         else if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN))
327                 prefixlen = XATTR_TRUSTED_PREFIX_LEN;
328         else if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN))
329                 prefixlen = XATTR_USER_PREFIX_LEN;
330         else
331                 return -EOPNOTSUPP;
332 
333         /*
334          * The name cannot consist of just prefix
335          */
336         if (len <= prefixlen)
337                 return -EINVAL;
338 
339         return 0;
340 }
341 
342 ssize_t btrfs_getxattr(struct dentry *dentry, const char *name,
343                        void *buffer, size_t size)
344 {
345         int ret;
346 
347         /*
348          * If this is a request for a synthetic attribute in the system.*
349          * namespace use the generic infrastructure to resolve a handler
350          * for it via sb->s_xattr.
351          */
352         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
353                 return generic_getxattr(dentry, name, buffer, size);
354 
355         ret = btrfs_is_valid_xattr(name);
356         if (ret)
357                 return ret;
358         return __btrfs_getxattr(dentry->d_inode, name, buffer, size);
359 }
360 
361 int btrfs_setxattr(struct dentry *dentry, const char *name, const void *value,
362                    size_t size, int flags)
363 {
364         struct btrfs_root *root = BTRFS_I(dentry->d_inode)->root;
365         int ret;
366 
367         /*
368          * The permission on security.* and system.* is not checked
369          * in permission().
370          */
371         if (btrfs_root_readonly(root))
372                 return -EROFS;
373 
374         /*
375          * If this is a request for a synthetic attribute in the system.*
376          * namespace use the generic infrastructure to resolve a handler
377          * for it via sb->s_xattr.
378          */
379         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
380                 return generic_setxattr(dentry, name, value, size, flags);
381 
382         ret = btrfs_is_valid_xattr(name);
383         if (ret)
384                 return ret;
385 
386         if (size == 0)
387                 value = "";  /* empty EA, do not remove */
388 
389         return __btrfs_setxattr(NULL, dentry->d_inode, name, value, size,
390                                 flags);
391 }
392 
393 int btrfs_removexattr(struct dentry *dentry, const char *name)
394 {
395         struct btrfs_root *root = BTRFS_I(dentry->d_inode)->root;
396         int ret;
397 
398         /*
399          * The permission on security.* and system.* is not checked
400          * in permission().
401          */
402         if (btrfs_root_readonly(root))
403                 return -EROFS;
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_removexattr(dentry, name);
412 
413         ret = btrfs_is_valid_xattr(name);
414         if (ret)
415                 return ret;
416 
417         return __btrfs_setxattr(NULL, dentry->d_inode, name, NULL, 0,
418                                 XATTR_REPLACE);
419 }
420 
421 int btrfs_initxattrs(struct inode *inode, const struct xattr *xattr_array,
422                      void *fs_info)
423 {
424         const struct xattr *xattr;
425         struct btrfs_trans_handle *trans = fs_info;
426         char *name;
427         int err = 0;
428 
429         for (xattr = xattr_array; xattr->name != NULL; xattr++) {
430                 name = kmalloc(XATTR_SECURITY_PREFIX_LEN +
431                                strlen(xattr->name) + 1, GFP_NOFS);
432                 if (!name) {
433                         err = -ENOMEM;
434                         break;
435                 }
436                 strcpy(name, XATTR_SECURITY_PREFIX);
437                 strcpy(name + XATTR_SECURITY_PREFIX_LEN, xattr->name);
438                 err = __btrfs_setxattr(trans, inode, name,
439                                        xattr->value, xattr->value_len, 0);
440                 kfree(name);
441                 if (err < 0)
442                         break;
443         }
444         return err;
445 }
446 
447 int btrfs_xattr_security_init(struct btrfs_trans_handle *trans,
448                               struct inode *inode, struct inode *dir,
449                               const struct qstr *qstr)
450 {
451         return security_inode_init_security(inode, dir, qstr,
452                                             &btrfs_initxattrs, trans);
453 }
454 

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