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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 <linux/iversion.h>
 27 #include "ctree.h"
 28 #include "btrfs_inode.h"
 29 #include "transaction.h"
 30 #include "xattr.h"
 31 #include "disk-io.h"
 32 #include "props.h"
 33 #include "locking.h"
 34 
 35 
 36 ssize_t __btrfs_getxattr(struct inode *inode, const char *name,
 37                                 void *buffer, size_t size)
 38 {
 39         struct btrfs_dir_item *di;
 40         struct btrfs_root *root = BTRFS_I(inode)->root;
 41         struct btrfs_path *path;
 42         struct extent_buffer *leaf;
 43         int ret = 0;
 44         unsigned long data_ptr;
 45 
 46         path = btrfs_alloc_path();
 47         if (!path)
 48                 return -ENOMEM;
 49 
 50         /* lookup the xattr by name */
 51         di = btrfs_lookup_xattr(NULL, root, path, btrfs_ino(BTRFS_I(inode)),
 52                         name, strlen(name), 0);
 53         if (!di) {
 54                 ret = -ENODATA;
 55                 goto out;
 56         } else if (IS_ERR(di)) {
 57                 ret = PTR_ERR(di);
 58                 goto out;
 59         }
 60 
 61         leaf = path->nodes[0];
 62         /* if size is 0, that means we want the size of the attr */
 63         if (!size) {
 64                 ret = btrfs_dir_data_len(leaf, di);
 65                 goto out;
 66         }
 67 
 68         /* now get the data out of our dir_item */
 69         if (btrfs_dir_data_len(leaf, di) > size) {
 70                 ret = -ERANGE;
 71                 goto out;
 72         }
 73 
 74         /*
 75          * The way things are packed into the leaf is like this
 76          * |struct btrfs_dir_item|name|data|
 77          * where name is the xattr name, so security.foo, and data is the
 78          * content of the xattr.  data_ptr points to the location in memory
 79          * where the data starts in the in memory leaf
 80          */
 81         data_ptr = (unsigned long)((char *)(di + 1) +
 82                                    btrfs_dir_name_len(leaf, di));
 83         read_extent_buffer(leaf, buffer, data_ptr,
 84                            btrfs_dir_data_len(leaf, di));
 85         ret = btrfs_dir_data_len(leaf, di);
 86 
 87 out:
 88         btrfs_free_path(path);
 89         return ret;
 90 }
 91 
 92 static int do_setxattr(struct btrfs_trans_handle *trans,
 93                        struct inode *inode, const char *name,
 94                        const void *value, size_t size, int flags)
 95 {
 96         struct btrfs_dir_item *di = NULL;
 97         struct btrfs_root *root = BTRFS_I(inode)->root;
 98         struct btrfs_fs_info *fs_info = root->fs_info;
 99         struct btrfs_path *path;
100         size_t name_len = strlen(name);
101         int ret = 0;
102 
103         if (name_len + size > BTRFS_MAX_XATTR_SIZE(root->fs_info))
104                 return -ENOSPC;
105 
106         path = btrfs_alloc_path();
107         if (!path)
108                 return -ENOMEM;
109         path->skip_release_on_error = 1;
110 
111         if (!value) {
112                 di = btrfs_lookup_xattr(trans, root, path,
113                                 btrfs_ino(BTRFS_I(inode)), name, name_len, -1);
114                 if (!di && (flags & XATTR_REPLACE))
115                         ret = -ENODATA;
116                 else if (IS_ERR(di))
117                         ret = PTR_ERR(di);
118                 else if (di)
119                         ret = btrfs_delete_one_dir_name(trans, root, path, di);
120                 goto out;
121         }
122 
123         /*
124          * For a replace we can't just do the insert blindly.
125          * Do a lookup first (read-only btrfs_search_slot), and return if xattr
126          * doesn't exist. If it exists, fall down below to the insert/replace
127          * path - we can't race with a concurrent xattr delete, because the VFS
128          * locks the inode's i_mutex before calling setxattr or removexattr.
129          */
130         if (flags & XATTR_REPLACE) {
131                 ASSERT(inode_is_locked(inode));
132                 di = btrfs_lookup_xattr(NULL, root, path,
133                                 btrfs_ino(BTRFS_I(inode)), name, name_len, 0);
134                 if (!di)
135                         ret = -ENODATA;
136                 else if (IS_ERR(di))
137                         ret = PTR_ERR(di);
138                 if (ret)
139                         goto out;
140                 btrfs_release_path(path);
141                 di = NULL;
142         }
143 
144         ret = btrfs_insert_xattr_item(trans, root, path, btrfs_ino(BTRFS_I(inode)),
145                                       name, name_len, value, size);
146         if (ret == -EOVERFLOW) {
147                 /*
148                  * We have an existing item in a leaf, split_leaf couldn't
149                  * expand it. That item might have or not a dir_item that
150                  * matches our target xattr, so lets check.
151                  */
152                 ret = 0;
153                 btrfs_assert_tree_locked(path->nodes[0]);
154                 di = btrfs_match_dir_item_name(fs_info, path, name, name_len);
155                 if (!di && !(flags & XATTR_REPLACE)) {
156                         ret = -ENOSPC;
157                         goto out;
158                 }
159         } else if (ret == -EEXIST) {
160                 ret = 0;
161                 di = btrfs_match_dir_item_name(fs_info, path, name, name_len);
162                 ASSERT(di); /* logic error */
163         } else if (ret) {
164                 goto out;
165         }
166 
167         if (di && (flags & XATTR_CREATE)) {
168                 ret = -EEXIST;
169                 goto out;
170         }
171 
172         if (di) {
173                 /*
174                  * We're doing a replace, and it must be atomic, that is, at
175                  * any point in time we have either the old or the new xattr
176                  * value in the tree. We don't want readers (getxattr and
177                  * listxattrs) to miss a value, this is specially important
178                  * for ACLs.
179                  */
180                 const int slot = path->slots[0];
181                 struct extent_buffer *leaf = path->nodes[0];
182                 const u16 old_data_len = btrfs_dir_data_len(leaf, di);
183                 const u32 item_size = btrfs_item_size_nr(leaf, slot);
184                 const u32 data_size = sizeof(*di) + name_len + size;
185                 struct btrfs_item *item;
186                 unsigned long data_ptr;
187                 char *ptr;
188 
189                 if (size > old_data_len) {
190                         if (btrfs_leaf_free_space(fs_info, leaf) <
191                             (size - old_data_len)) {
192                                 ret = -ENOSPC;
193                                 goto out;
194                         }
195                 }
196 
197                 if (old_data_len + name_len + sizeof(*di) == item_size) {
198                         /* No other xattrs packed in the same leaf item. */
199                         if (size > old_data_len)
200                                 btrfs_extend_item(fs_info, path,
201                                                   size - old_data_len);
202                         else if (size < old_data_len)
203                                 btrfs_truncate_item(fs_info, path,
204                                                     data_size, 1);
205                 } else {
206                         /* There are other xattrs packed in the same item. */
207                         ret = btrfs_delete_one_dir_name(trans, root, path, di);
208                         if (ret)
209                                 goto out;
210                         btrfs_extend_item(fs_info, path, data_size);
211                 }
212 
213                 item = btrfs_item_nr(slot);
214                 ptr = btrfs_item_ptr(leaf, slot, char);
215                 ptr += btrfs_item_size(leaf, item) - data_size;
216                 di = (struct btrfs_dir_item *)ptr;
217                 btrfs_set_dir_data_len(leaf, di, size);
218                 data_ptr = ((unsigned long)(di + 1)) + name_len;
219                 write_extent_buffer(leaf, value, data_ptr, size);
220                 btrfs_mark_buffer_dirty(leaf);
221         } else {
222                 /*
223                  * Insert, and we had space for the xattr, so path->slots[0] is
224                  * where our xattr dir_item is and btrfs_insert_xattr_item()
225                  * filled it.
226                  */
227         }
228 out:
229         btrfs_free_path(path);
230         return ret;
231 }
232 
233 /*
234  * @value: "" makes the attribute to empty, NULL removes it
235  */
236 int __btrfs_setxattr(struct btrfs_trans_handle *trans,
237                      struct inode *inode, const char *name,
238                      const void *value, size_t size, int flags)
239 {
240         struct btrfs_root *root = BTRFS_I(inode)->root;
241         int ret;
242 
243         if (btrfs_root_readonly(root))
244                 return -EROFS;
245 
246         if (trans)
247                 return do_setxattr(trans, inode, name, value, size, flags);
248 
249         trans = btrfs_start_transaction(root, 2);
250         if (IS_ERR(trans))
251                 return PTR_ERR(trans);
252 
253         ret = do_setxattr(trans, inode, name, value, size, flags);
254         if (ret)
255                 goto out;
256 
257         inode_inc_iversion(inode);
258         inode->i_ctime = current_time(inode);
259         set_bit(BTRFS_INODE_COPY_EVERYTHING, &BTRFS_I(inode)->runtime_flags);
260         ret = btrfs_update_inode(trans, root, inode);
261         BUG_ON(ret);
262 out:
263         btrfs_end_transaction(trans);
264         return ret;
265 }
266 
267 ssize_t btrfs_listxattr(struct dentry *dentry, char *buffer, size_t size)
268 {
269         struct btrfs_key key;
270         struct inode *inode = d_inode(dentry);
271         struct btrfs_root *root = BTRFS_I(inode)->root;
272         struct btrfs_path *path;
273         int ret = 0;
274         size_t total_size = 0, size_left = size;
275 
276         /*
277          * ok we want all objects associated with this id.
278          * NOTE: we set key.offset = 0; because we want to start with the
279          * first xattr that we find and walk forward
280          */
281         key.objectid = btrfs_ino(BTRFS_I(inode));
282         key.type = BTRFS_XATTR_ITEM_KEY;
283         key.offset = 0;
284 
285         path = btrfs_alloc_path();
286         if (!path)
287                 return -ENOMEM;
288         path->reada = READA_FORWARD;
289 
290         /* search for our xattrs */
291         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
292         if (ret < 0)
293                 goto err;
294 
295         while (1) {
296                 struct extent_buffer *leaf;
297                 int slot;
298                 struct btrfs_dir_item *di;
299                 struct btrfs_key found_key;
300                 u32 item_size;
301                 u32 cur;
302 
303                 leaf = path->nodes[0];
304                 slot = path->slots[0];
305 
306                 /* this is where we start walking through the path */
307                 if (slot >= btrfs_header_nritems(leaf)) {
308                         /*
309                          * if we've reached the last slot in this leaf we need
310                          * to go to the next leaf and reset everything
311                          */
312                         ret = btrfs_next_leaf(root, path);
313                         if (ret < 0)
314                                 goto err;
315                         else if (ret > 0)
316                                 break;
317                         continue;
318                 }
319 
320                 btrfs_item_key_to_cpu(leaf, &found_key, slot);
321 
322                 /* check to make sure this item is what we want */
323                 if (found_key.objectid != key.objectid)
324                         break;
325                 if (found_key.type > BTRFS_XATTR_ITEM_KEY)
326                         break;
327                 if (found_key.type < BTRFS_XATTR_ITEM_KEY)
328                         goto next_item;
329 
330                 di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
331                 item_size = btrfs_item_size_nr(leaf, slot);
332                 cur = 0;
333                 while (cur < item_size) {
334                         u16 name_len = btrfs_dir_name_len(leaf, di);
335                         u16 data_len = btrfs_dir_data_len(leaf, di);
336                         u32 this_len = sizeof(*di) + name_len + data_len;
337                         unsigned long name_ptr = (unsigned long)(di + 1);
338 
339                         total_size += name_len + 1;
340                         /*
341                          * We are just looking for how big our buffer needs to
342                          * be.
343                          */
344                         if (!size)
345                                 goto next;
346 
347                         if (!buffer || (name_len + 1) > size_left) {
348                                 ret = -ERANGE;
349                                 goto err;
350                         }
351 
352                         read_extent_buffer(leaf, buffer, name_ptr, name_len);
353                         buffer[name_len] = '\0';
354 
355                         size_left -= name_len + 1;
356                         buffer += name_len + 1;
357 next:
358                         cur += this_len;
359                         di = (struct btrfs_dir_item *)((char *)di + this_len);
360                 }
361 next_item:
362                 path->slots[0]++;
363         }
364         ret = total_size;
365 
366 err:
367         btrfs_free_path(path);
368 
369         return ret;
370 }
371 
372 static int btrfs_xattr_handler_get(const struct xattr_handler *handler,
373                                    struct dentry *unused, struct inode *inode,
374                                    const char *name, void *buffer, size_t size)
375 {
376         name = xattr_full_name(handler, name);
377         return __btrfs_getxattr(inode, name, buffer, size);
378 }
379 
380 static int btrfs_xattr_handler_set(const struct xattr_handler *handler,
381                                    struct dentry *unused, struct inode *inode,
382                                    const char *name, const void *buffer,
383                                    size_t size, int flags)
384 {
385         name = xattr_full_name(handler, name);
386         return __btrfs_setxattr(NULL, inode, name, buffer, size, flags);
387 }
388 
389 static int btrfs_xattr_handler_set_prop(const struct xattr_handler *handler,
390                                         struct dentry *unused, struct inode *inode,
391                                         const char *name, const void *value,
392                                         size_t size, int flags)
393 {
394         name = xattr_full_name(handler, name);
395         return btrfs_set_prop(inode, name, value, size, flags);
396 }
397 
398 static const struct xattr_handler btrfs_security_xattr_handler = {
399         .prefix = XATTR_SECURITY_PREFIX,
400         .get = btrfs_xattr_handler_get,
401         .set = btrfs_xattr_handler_set,
402 };
403 
404 static const struct xattr_handler btrfs_trusted_xattr_handler = {
405         .prefix = XATTR_TRUSTED_PREFIX,
406         .get = btrfs_xattr_handler_get,
407         .set = btrfs_xattr_handler_set,
408 };
409 
410 static const struct xattr_handler btrfs_user_xattr_handler = {
411         .prefix = XATTR_USER_PREFIX,
412         .get = btrfs_xattr_handler_get,
413         .set = btrfs_xattr_handler_set,
414 };
415 
416 static const struct xattr_handler btrfs_btrfs_xattr_handler = {
417         .prefix = XATTR_BTRFS_PREFIX,
418         .get = btrfs_xattr_handler_get,
419         .set = btrfs_xattr_handler_set_prop,
420 };
421 
422 const struct xattr_handler *btrfs_xattr_handlers[] = {
423         &btrfs_security_xattr_handler,
424 #ifdef CONFIG_BTRFS_FS_POSIX_ACL
425         &posix_acl_access_xattr_handler,
426         &posix_acl_default_xattr_handler,
427 #endif
428         &btrfs_trusted_xattr_handler,
429         &btrfs_user_xattr_handler,
430         &btrfs_btrfs_xattr_handler,
431         NULL,
432 };
433 
434 static int btrfs_initxattrs(struct inode *inode,
435                             const struct xattr *xattr_array, void *fs_info)
436 {
437         const struct xattr *xattr;
438         struct btrfs_trans_handle *trans = fs_info;
439         char *name;
440         int err = 0;
441 
442         for (xattr = xattr_array; xattr->name != NULL; xattr++) {
443                 name = kmalloc(XATTR_SECURITY_PREFIX_LEN +
444                                strlen(xattr->name) + 1, GFP_KERNEL);
445                 if (!name) {
446                         err = -ENOMEM;
447                         break;
448                 }
449                 strcpy(name, XATTR_SECURITY_PREFIX);
450                 strcpy(name + XATTR_SECURITY_PREFIX_LEN, xattr->name);
451                 err = __btrfs_setxattr(trans, inode, name,
452                                        xattr->value, xattr->value_len, 0);
453                 kfree(name);
454                 if (err < 0)
455                         break;
456         }
457         return err;
458 }
459 
460 int btrfs_xattr_security_init(struct btrfs_trans_handle *trans,
461                               struct inode *inode, struct inode *dir,
462                               const struct qstr *qstr)
463 {
464         return security_inode_init_security(inode, dir, qstr,
465                                             &btrfs_initxattrs, trans);
466 }
467 

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