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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 
 33 
 34 ssize_t __btrfs_getxattr(struct inode *inode, const char *name,
 35                                 void *buffer, size_t size)
 36 {
 37         struct btrfs_dir_item *di;
 38         struct btrfs_root *root = BTRFS_I(inode)->root;
 39         struct btrfs_path *path;
 40         struct extent_buffer *leaf;
 41         int ret = 0;
 42         unsigned long data_ptr;
 43 
 44         path = btrfs_alloc_path();
 45         if (!path)
 46                 return -ENOMEM;
 47 
 48         /* lookup the xattr by name */
 49         di = btrfs_lookup_xattr(NULL, root, path, btrfs_ino(inode), name,
 50                                 strlen(name), 0);
 51         if (!di) {
 52                 ret = -ENODATA;
 53                 goto out;
 54         } else if (IS_ERR(di)) {
 55                 ret = PTR_ERR(di);
 56                 goto out;
 57         }
 58 
 59         leaf = path->nodes[0];
 60         /* if size is 0, that means we want the size of the attr */
 61         if (!size) {
 62                 ret = btrfs_dir_data_len(leaf, di);
 63                 goto out;
 64         }
 65 
 66         /* now get the data out of our dir_item */
 67         if (btrfs_dir_data_len(leaf, di) > size) {
 68                 ret = -ERANGE;
 69                 goto out;
 70         }
 71 
 72         /*
 73          * The way things are packed into the leaf is like this
 74          * |struct btrfs_dir_item|name|data|
 75          * where name is the xattr name, so security.foo, and data is the
 76          * content of the xattr.  data_ptr points to the location in memory
 77          * where the data starts in the in memory leaf
 78          */
 79         data_ptr = (unsigned long)((char *)(di + 1) +
 80                                    btrfs_dir_name_len(leaf, di));
 81         read_extent_buffer(leaf, buffer, data_ptr,
 82                            btrfs_dir_data_len(leaf, di));
 83         ret = btrfs_dir_data_len(leaf, di);
 84 
 85 out:
 86         btrfs_free_path(path);
 87         return ret;
 88 }
 89 
 90 static int do_setxattr(struct btrfs_trans_handle *trans,
 91                        struct inode *inode, const char *name,
 92                        const void *value, size_t size, int flags)
 93 {
 94         struct btrfs_dir_item *di;
 95         struct btrfs_root *root = BTRFS_I(inode)->root;
 96         struct btrfs_path *path;
 97         size_t name_len = strlen(name);
 98         int ret = 0;
 99 
100         if (name_len + size > BTRFS_MAX_XATTR_SIZE(root))
101                 return -ENOSPC;
102 
103         path = btrfs_alloc_path();
104         if (!path)
105                 return -ENOMEM;
106 
107         if (flags & XATTR_REPLACE) {
108                 di = btrfs_lookup_xattr(trans, root, path, btrfs_ino(inode), name,
109                                         name_len, -1);
110                 if (IS_ERR(di)) {
111                         ret = PTR_ERR(di);
112                         goto out;
113                 } else if (!di) {
114                         ret = -ENODATA;
115                         goto out;
116                 }
117                 ret = btrfs_delete_one_dir_name(trans, root, path, di);
118                 if (ret)
119                         goto out;
120                 btrfs_release_path(path);
121 
122                 /*
123                  * remove the attribute
124                  */
125                 if (!value)
126                         goto out;
127         } else {
128                 di = btrfs_lookup_xattr(NULL, root, path, btrfs_ino(inode),
129                                         name, name_len, 0);
130                 if (IS_ERR(di)) {
131                         ret = PTR_ERR(di);
132                         goto out;
133                 }
134                 if (!di && !value)
135                         goto out;
136                 btrfs_release_path(path);
137         }
138 
139 again:
140         ret = btrfs_insert_xattr_item(trans, root, path, btrfs_ino(inode),
141                                       name, name_len, value, size);
142         /*
143          * If we're setting an xattr to a new value but the new value is say
144          * exactly BTRFS_MAX_XATTR_SIZE, we could end up with EOVERFLOW getting
145          * back from split_leaf.  This is because it thinks we'll be extending
146          * the existing item size, but we're asking for enough space to add the
147          * item itself.  So if we get EOVERFLOW just set ret to EEXIST and let
148          * the rest of the function figure it out.
149          */
150         if (ret == -EOVERFLOW)
151                 ret = -EEXIST;
152 
153         if (ret == -EEXIST) {
154                 if (flags & XATTR_CREATE)
155                         goto out;
156                 /*
157                  * We can't use the path we already have since we won't have the
158                  * proper locking for a delete, so release the path and
159                  * re-lookup to delete the thing.
160                  */
161                 btrfs_release_path(path);
162                 di = btrfs_lookup_xattr(trans, root, path, btrfs_ino(inode),
163                                         name, name_len, -1);
164                 if (IS_ERR(di)) {
165                         ret = PTR_ERR(di);
166                         goto out;
167                 } else if (!di) {
168                         /* Shouldn't happen but just in case... */
169                         btrfs_release_path(path);
170                         goto again;
171                 }
172 
173                 ret = btrfs_delete_one_dir_name(trans, root, path, di);
174                 if (ret)
175                         goto out;
176 
177                 /*
178                  * We have a value to set, so go back and try to insert it now.
179                  */
180                 if (value) {
181                         btrfs_release_path(path);
182                         goto again;
183                 }
184         }
185 out:
186         btrfs_free_path(path);
187         return ret;
188 }
189 
190 /*
191  * @value: "" makes the attribute to empty, NULL removes it
192  */
193 int __btrfs_setxattr(struct btrfs_trans_handle *trans,
194                      struct inode *inode, const char *name,
195                      const void *value, size_t size, int flags)
196 {
197         struct btrfs_root *root = BTRFS_I(inode)->root;
198         int ret;
199 
200         if (trans)
201                 return do_setxattr(trans, inode, name, value, size, flags);
202 
203         trans = btrfs_start_transaction(root, 2);
204         if (IS_ERR(trans))
205                 return PTR_ERR(trans);
206 
207         ret = do_setxattr(trans, inode, name, value, size, flags);
208         if (ret)
209                 goto out;
210 
211         inode_inc_iversion(inode);
212         inode->i_ctime = CURRENT_TIME;
213         set_bit(BTRFS_INODE_COPY_EVERYTHING, &BTRFS_I(inode)->runtime_flags);
214         ret = btrfs_update_inode(trans, root, inode);
215         BUG_ON(ret);
216 out:
217         btrfs_end_transaction(trans, root);
218         return ret;
219 }
220 
221 ssize_t btrfs_listxattr(struct dentry *dentry, char *buffer, size_t size)
222 {
223         struct btrfs_key key, found_key;
224         struct inode *inode = dentry->d_inode;
225         struct btrfs_root *root = BTRFS_I(inode)->root;
226         struct btrfs_path *path;
227         struct extent_buffer *leaf;
228         struct btrfs_dir_item *di;
229         int ret = 0, slot;
230         size_t total_size = 0, size_left = size;
231         unsigned long name_ptr;
232         size_t name_len;
233 
234         /*
235          * ok we want all objects associated with this id.
236          * NOTE: we set key.offset = 0; because we want to start with the
237          * first xattr that we find and walk forward
238          */
239         key.objectid = btrfs_ino(inode);
240         btrfs_set_key_type(&key, BTRFS_XATTR_ITEM_KEY);
241         key.offset = 0;
242 
243         path = btrfs_alloc_path();
244         if (!path)
245                 return -ENOMEM;
246         path->reada = 2;
247 
248         /* search for our xattrs */
249         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
250         if (ret < 0)
251                 goto err;
252 
253         while (1) {
254                 leaf = path->nodes[0];
255                 slot = path->slots[0];
256 
257                 /* this is where we start walking through the path */
258                 if (slot >= btrfs_header_nritems(leaf)) {
259                         /*
260                          * if we've reached the last slot in this leaf we need
261                          * to go to the next leaf and reset everything
262                          */
263                         ret = btrfs_next_leaf(root, path);
264                         if (ret < 0)
265                                 goto err;
266                         else if (ret > 0)
267                                 break;
268                         continue;
269                 }
270 
271                 btrfs_item_key_to_cpu(leaf, &found_key, slot);
272 
273                 /* check to make sure this item is what we want */
274                 if (found_key.objectid != key.objectid)
275                         break;
276                 if (btrfs_key_type(&found_key) != BTRFS_XATTR_ITEM_KEY)
277                         break;
278 
279                 di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
280                 if (verify_dir_item(root, leaf, di))
281                         goto next;
282 
283                 name_len = btrfs_dir_name_len(leaf, di);
284                 total_size += name_len + 1;
285 
286                 /* we are just looking for how big our buffer needs to be */
287                 if (!size)
288                         goto next;
289 
290                 if (!buffer || (name_len + 1) > size_left) {
291                         ret = -ERANGE;
292                         goto err;
293                 }
294 
295                 name_ptr = (unsigned long)(di + 1);
296                 read_extent_buffer(leaf, buffer, name_ptr, name_len);
297                 buffer[name_len] = '\0';
298 
299                 size_left -= name_len + 1;
300                 buffer += name_len + 1;
301 next:
302                 path->slots[0]++;
303         }
304         ret = total_size;
305 
306 err:
307         btrfs_free_path(path);
308 
309         return ret;
310 }
311 
312 /*
313  * List of handlers for synthetic system.* attributes.  All real ondisk
314  * attributes are handled directly.
315  */
316 const struct xattr_handler *btrfs_xattr_handlers[] = {
317 #ifdef CONFIG_BTRFS_FS_POSIX_ACL
318         &posix_acl_access_xattr_handler,
319         &posix_acl_default_xattr_handler,
320 #endif
321         NULL,
322 };
323 
324 /*
325  * Check if the attribute is in a supported namespace.
326  *
327  * This applied after the check for the synthetic attributes in the system
328  * namespace.
329  */
330 static bool btrfs_is_valid_xattr(const char *name)
331 {
332         return !strncmp(name, XATTR_SECURITY_PREFIX,
333                         XATTR_SECURITY_PREFIX_LEN) ||
334                !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN) ||
335                !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) ||
336                !strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN) ||
337                 !strncmp(name, XATTR_BTRFS_PREFIX, XATTR_BTRFS_PREFIX_LEN);
338 }
339 
340 ssize_t btrfs_getxattr(struct dentry *dentry, const char *name,
341                        void *buffer, size_t size)
342 {
343         /*
344          * If this is a request for a synthetic attribute in the system.*
345          * namespace use the generic infrastructure to resolve a handler
346          * for it via sb->s_xattr.
347          */
348         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
349                 return generic_getxattr(dentry, name, buffer, size);
350 
351         if (!btrfs_is_valid_xattr(name))
352                 return -EOPNOTSUPP;
353         return __btrfs_getxattr(dentry->d_inode, name, buffer, size);
354 }
355 
356 int btrfs_setxattr(struct dentry *dentry, const char *name, const void *value,
357                    size_t size, int flags)
358 {
359         struct btrfs_root *root = BTRFS_I(dentry->d_inode)->root;
360 
361         /*
362          * The permission on security.* and system.* is not checked
363          * in permission().
364          */
365         if (btrfs_root_readonly(root))
366                 return -EROFS;
367 
368         /*
369          * If this is a request for a synthetic attribute in the system.*
370          * namespace use the generic infrastructure to resolve a handler
371          * for it via sb->s_xattr.
372          */
373         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
374                 return generic_setxattr(dentry, name, value, size, flags);
375 
376         if (!btrfs_is_valid_xattr(name))
377                 return -EOPNOTSUPP;
378 
379         if (!strncmp(name, XATTR_BTRFS_PREFIX, XATTR_BTRFS_PREFIX_LEN))
380                 return btrfs_set_prop(dentry->d_inode, name,
381                                       value, size, flags);
382 
383         if (size == 0)
384                 value = "";  /* empty EA, do not remove */
385 
386         return __btrfs_setxattr(NULL, dentry->d_inode, name, value, size,
387                                 flags);
388 }
389 
390 int btrfs_removexattr(struct dentry *dentry, const char *name)
391 {
392         struct btrfs_root *root = BTRFS_I(dentry->d_inode)->root;
393 
394         /*
395          * The permission on security.* and system.* is not checked
396          * in permission().
397          */
398         if (btrfs_root_readonly(root))
399                 return -EROFS;
400 
401         /*
402          * If this is a request for a synthetic attribute in the system.*
403          * namespace use the generic infrastructure to resolve a handler
404          * for it via sb->s_xattr.
405          */
406         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
407                 return generic_removexattr(dentry, name);
408 
409         if (!btrfs_is_valid_xattr(name))
410                 return -EOPNOTSUPP;
411 
412         if (!strncmp(name, XATTR_BTRFS_PREFIX, XATTR_BTRFS_PREFIX_LEN))
413                 return btrfs_set_prop(dentry->d_inode, name,
414                                       NULL, 0, XATTR_REPLACE);
415 
416         return __btrfs_setxattr(NULL, dentry->d_inode, name, NULL, 0,
417                                 XATTR_REPLACE);
418 }
419 
420 static int btrfs_initxattrs(struct inode *inode,
421                             const struct xattr *xattr_array, void *fs_info)
422 {
423         const struct xattr *xattr;
424         struct btrfs_trans_handle *trans = fs_info;
425         char *name;
426         int err = 0;
427 
428         for (xattr = xattr_array; xattr->name != NULL; xattr++) {
429                 name = kmalloc(XATTR_SECURITY_PREFIX_LEN +
430                                strlen(xattr->name) + 1, GFP_NOFS);
431                 if (!name) {
432                         err = -ENOMEM;
433                         break;
434                 }
435                 strcpy(name, XATTR_SECURITY_PREFIX);
436                 strcpy(name + XATTR_SECURITY_PREFIX_LEN, xattr->name);
437                 err = __btrfs_setxattr(trans, inode, name,
438                                        xattr->value, xattr->value_len, 0);
439                 kfree(name);
440                 if (err < 0)
441                         break;
442         }
443         return err;
444 }
445 
446 int btrfs_xattr_security_init(struct btrfs_trans_handle *trans,
447                               struct inode *inode, struct inode *dir,
448                               const struct qstr *qstr)
449 {
450         return security_inode_init_security(inode, dir, qstr,
451                                             &btrfs_initxattrs, trans);
452 }
453 

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