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Linux/fs/btrfs/xattr.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  * Copyright (C) 2007 Red Hat.  All rights reserved.
  4  */
  5 
  6 #include <linux/init.h>
  7 #include <linux/fs.h>
  8 #include <linux/slab.h>
  9 #include <linux/rwsem.h>
 10 #include <linux/xattr.h>
 11 #include <linux/security.h>
 12 #include <linux/posix_acl_xattr.h>
 13 #include <linux/iversion.h>
 14 #include "ctree.h"
 15 #include "btrfs_inode.h"
 16 #include "transaction.h"
 17 #include "xattr.h"
 18 #include "disk-io.h"
 19 #include "props.h"
 20 #include "locking.h"
 21 
 22 int btrfs_getxattr(struct inode *inode, const char *name,
 23                                 void *buffer, size_t size)
 24 {
 25         struct btrfs_dir_item *di;
 26         struct btrfs_root *root = BTRFS_I(inode)->root;
 27         struct btrfs_path *path;
 28         struct extent_buffer *leaf;
 29         int ret = 0;
 30         unsigned long data_ptr;
 31 
 32         path = btrfs_alloc_path();
 33         if (!path)
 34                 return -ENOMEM;
 35 
 36         /* lookup the xattr by name */
 37         di = btrfs_lookup_xattr(NULL, root, path, btrfs_ino(BTRFS_I(inode)),
 38                         name, strlen(name), 0);
 39         if (!di) {
 40                 ret = -ENODATA;
 41                 goto out;
 42         } else if (IS_ERR(di)) {
 43                 ret = PTR_ERR(di);
 44                 goto out;
 45         }
 46 
 47         leaf = path->nodes[0];
 48         /* if size is 0, that means we want the size of the attr */
 49         if (!size) {
 50                 ret = btrfs_dir_data_len(leaf, di);
 51                 goto out;
 52         }
 53 
 54         /* now get the data out of our dir_item */
 55         if (btrfs_dir_data_len(leaf, di) > size) {
 56                 ret = -ERANGE;
 57                 goto out;
 58         }
 59 
 60         /*
 61          * The way things are packed into the leaf is like this
 62          * |struct btrfs_dir_item|name|data|
 63          * where name is the xattr name, so security.foo, and data is the
 64          * content of the xattr.  data_ptr points to the location in memory
 65          * where the data starts in the in memory leaf
 66          */
 67         data_ptr = (unsigned long)((char *)(di + 1) +
 68                                    btrfs_dir_name_len(leaf, di));
 69         read_extent_buffer(leaf, buffer, data_ptr,
 70                            btrfs_dir_data_len(leaf, di));
 71         ret = btrfs_dir_data_len(leaf, di);
 72 
 73 out:
 74         btrfs_free_path(path);
 75         return ret;
 76 }
 77 
 78 static int do_setxattr(struct btrfs_trans_handle *trans,
 79                        struct inode *inode, const char *name,
 80                        const void *value, size_t size, int flags)
 81 {
 82         struct btrfs_dir_item *di = NULL;
 83         struct btrfs_root *root = BTRFS_I(inode)->root;
 84         struct btrfs_fs_info *fs_info = root->fs_info;
 85         struct btrfs_path *path;
 86         size_t name_len = strlen(name);
 87         int ret = 0;
 88 
 89         if (name_len + size > BTRFS_MAX_XATTR_SIZE(root->fs_info))
 90                 return -ENOSPC;
 91 
 92         path = btrfs_alloc_path();
 93         if (!path)
 94                 return -ENOMEM;
 95         path->skip_release_on_error = 1;
 96 
 97         if (!value) {
 98                 di = btrfs_lookup_xattr(trans, root, path,
 99                                 btrfs_ino(BTRFS_I(inode)), name, name_len, -1);
100                 if (!di && (flags & XATTR_REPLACE))
101                         ret = -ENODATA;
102                 else if (IS_ERR(di))
103                         ret = PTR_ERR(di);
104                 else if (di)
105                         ret = btrfs_delete_one_dir_name(trans, root, path, di);
106                 goto out;
107         }
108 
109         /*
110          * For a replace we can't just do the insert blindly.
111          * Do a lookup first (read-only btrfs_search_slot), and return if xattr
112          * doesn't exist. If it exists, fall down below to the insert/replace
113          * path - we can't race with a concurrent xattr delete, because the VFS
114          * locks the inode's i_mutex before calling setxattr or removexattr.
115          */
116         if (flags & XATTR_REPLACE) {
117                 ASSERT(inode_is_locked(inode));
118                 di = btrfs_lookup_xattr(NULL, root, path,
119                                 btrfs_ino(BTRFS_I(inode)), name, name_len, 0);
120                 if (!di)
121                         ret = -ENODATA;
122                 else if (IS_ERR(di))
123                         ret = PTR_ERR(di);
124                 if (ret)
125                         goto out;
126                 btrfs_release_path(path);
127                 di = NULL;
128         }
129 
130         ret = btrfs_insert_xattr_item(trans, root, path, btrfs_ino(BTRFS_I(inode)),
131                                       name, name_len, value, size);
132         if (ret == -EOVERFLOW) {
133                 /*
134                  * We have an existing item in a leaf, split_leaf couldn't
135                  * expand it. That item might have or not a dir_item that
136                  * matches our target xattr, so lets check.
137                  */
138                 ret = 0;
139                 btrfs_assert_tree_locked(path->nodes[0]);
140                 di = btrfs_match_dir_item_name(fs_info, path, name, name_len);
141                 if (!di && !(flags & XATTR_REPLACE)) {
142                         ret = -ENOSPC;
143                         goto out;
144                 }
145         } else if (ret == -EEXIST) {
146                 ret = 0;
147                 di = btrfs_match_dir_item_name(fs_info, path, name, name_len);
148                 ASSERT(di); /* logic error */
149         } else if (ret) {
150                 goto out;
151         }
152 
153         if (di && (flags & XATTR_CREATE)) {
154                 ret = -EEXIST;
155                 goto out;
156         }
157 
158         if (di) {
159                 /*
160                  * We're doing a replace, and it must be atomic, that is, at
161                  * any point in time we have either the old or the new xattr
162                  * value in the tree. We don't want readers (getxattr and
163                  * listxattrs) to miss a value, this is specially important
164                  * for ACLs.
165                  */
166                 const int slot = path->slots[0];
167                 struct extent_buffer *leaf = path->nodes[0];
168                 const u16 old_data_len = btrfs_dir_data_len(leaf, di);
169                 const u32 item_size = btrfs_item_size_nr(leaf, slot);
170                 const u32 data_size = sizeof(*di) + name_len + size;
171                 struct btrfs_item *item;
172                 unsigned long data_ptr;
173                 char *ptr;
174 
175                 if (size > old_data_len) {
176                         if (btrfs_leaf_free_space(fs_info, leaf) <
177                             (size - old_data_len)) {
178                                 ret = -ENOSPC;
179                                 goto out;
180                         }
181                 }
182 
183                 if (old_data_len + name_len + sizeof(*di) == item_size) {
184                         /* No other xattrs packed in the same leaf item. */
185                         if (size > old_data_len)
186                                 btrfs_extend_item(fs_info, path,
187                                                   size - old_data_len);
188                         else if (size < old_data_len)
189                                 btrfs_truncate_item(fs_info, path,
190                                                     data_size, 1);
191                 } else {
192                         /* There are other xattrs packed in the same item. */
193                         ret = btrfs_delete_one_dir_name(trans, root, path, di);
194                         if (ret)
195                                 goto out;
196                         btrfs_extend_item(fs_info, path, data_size);
197                 }
198 
199                 item = btrfs_item_nr(slot);
200                 ptr = btrfs_item_ptr(leaf, slot, char);
201                 ptr += btrfs_item_size(leaf, item) - data_size;
202                 di = (struct btrfs_dir_item *)ptr;
203                 btrfs_set_dir_data_len(leaf, di, size);
204                 data_ptr = ((unsigned long)(di + 1)) + name_len;
205                 write_extent_buffer(leaf, value, data_ptr, size);
206                 btrfs_mark_buffer_dirty(leaf);
207         } else {
208                 /*
209                  * Insert, and we had space for the xattr, so path->slots[0] is
210                  * where our xattr dir_item is and btrfs_insert_xattr_item()
211                  * filled it.
212                  */
213         }
214 out:
215         btrfs_free_path(path);
216         return ret;
217 }
218 
219 /*
220  * @value: "" makes the attribute to empty, NULL removes it
221  */
222 int btrfs_setxattr(struct btrfs_trans_handle *trans,
223                      struct inode *inode, const char *name,
224                      const void *value, size_t size, int flags)
225 {
226         struct btrfs_root *root = BTRFS_I(inode)->root;
227         int ret;
228 
229         if (btrfs_root_readonly(root))
230                 return -EROFS;
231 
232         if (trans)
233                 return do_setxattr(trans, inode, name, value, size, flags);
234 
235         trans = btrfs_start_transaction(root, 2);
236         if (IS_ERR(trans))
237                 return PTR_ERR(trans);
238 
239         ret = do_setxattr(trans, inode, name, value, size, flags);
240         if (ret)
241                 goto out;
242 
243         inode_inc_iversion(inode);
244         inode->i_ctime = current_time(inode);
245         set_bit(BTRFS_INODE_COPY_EVERYTHING, &BTRFS_I(inode)->runtime_flags);
246         ret = btrfs_update_inode(trans, root, inode);
247         BUG_ON(ret);
248 out:
249         btrfs_end_transaction(trans);
250         return ret;
251 }
252 
253 ssize_t btrfs_listxattr(struct dentry *dentry, char *buffer, size_t size)
254 {
255         struct btrfs_key key;
256         struct inode *inode = d_inode(dentry);
257         struct btrfs_root *root = BTRFS_I(inode)->root;
258         struct btrfs_path *path;
259         int ret = 0;
260         size_t total_size = 0, size_left = size;
261 
262         /*
263          * ok we want all objects associated with this id.
264          * NOTE: we set key.offset = 0; because we want to start with the
265          * first xattr that we find and walk forward
266          */
267         key.objectid = btrfs_ino(BTRFS_I(inode));
268         key.type = BTRFS_XATTR_ITEM_KEY;
269         key.offset = 0;
270 
271         path = btrfs_alloc_path();
272         if (!path)
273                 return -ENOMEM;
274         path->reada = READA_FORWARD;
275 
276         /* search for our xattrs */
277         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
278         if (ret < 0)
279                 goto err;
280 
281         while (1) {
282                 struct extent_buffer *leaf;
283                 int slot;
284                 struct btrfs_dir_item *di;
285                 struct btrfs_key found_key;
286                 u32 item_size;
287                 u32 cur;
288 
289                 leaf = path->nodes[0];
290                 slot = path->slots[0];
291 
292                 /* this is where we start walking through the path */
293                 if (slot >= btrfs_header_nritems(leaf)) {
294                         /*
295                          * if we've reached the last slot in this leaf we need
296                          * to go to the next leaf and reset everything
297                          */
298                         ret = btrfs_next_leaf(root, path);
299                         if (ret < 0)
300                                 goto err;
301                         else if (ret > 0)
302                                 break;
303                         continue;
304                 }
305 
306                 btrfs_item_key_to_cpu(leaf, &found_key, slot);
307 
308                 /* check to make sure this item is what we want */
309                 if (found_key.objectid != key.objectid)
310                         break;
311                 if (found_key.type > BTRFS_XATTR_ITEM_KEY)
312                         break;
313                 if (found_key.type < BTRFS_XATTR_ITEM_KEY)
314                         goto next_item;
315 
316                 di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
317                 item_size = btrfs_item_size_nr(leaf, slot);
318                 cur = 0;
319                 while (cur < item_size) {
320                         u16 name_len = btrfs_dir_name_len(leaf, di);
321                         u16 data_len = btrfs_dir_data_len(leaf, di);
322                         u32 this_len = sizeof(*di) + name_len + data_len;
323                         unsigned long name_ptr = (unsigned long)(di + 1);
324 
325                         total_size += name_len + 1;
326                         /*
327                          * We are just looking for how big our buffer needs to
328                          * be.
329                          */
330                         if (!size)
331                                 goto next;
332 
333                         if (!buffer || (name_len + 1) > size_left) {
334                                 ret = -ERANGE;
335                                 goto err;
336                         }
337 
338                         read_extent_buffer(leaf, buffer, name_ptr, name_len);
339                         buffer[name_len] = '\0';
340 
341                         size_left -= name_len + 1;
342                         buffer += name_len + 1;
343 next:
344                         cur += this_len;
345                         di = (struct btrfs_dir_item *)((char *)di + this_len);
346                 }
347 next_item:
348                 path->slots[0]++;
349         }
350         ret = total_size;
351 
352 err:
353         btrfs_free_path(path);
354 
355         return ret;
356 }
357 
358 static int btrfs_xattr_handler_get(const struct xattr_handler *handler,
359                                    struct dentry *unused, struct inode *inode,
360                                    const char *name, void *buffer, size_t size)
361 {
362         name = xattr_full_name(handler, name);
363         return btrfs_getxattr(inode, name, buffer, size);
364 }
365 
366 static int btrfs_xattr_handler_set(const struct xattr_handler *handler,
367                                    struct dentry *unused, struct inode *inode,
368                                    const char *name, const void *buffer,
369                                    size_t size, int flags)
370 {
371         name = xattr_full_name(handler, name);
372         return btrfs_setxattr(NULL, inode, name, buffer, size, flags);
373 }
374 
375 static int btrfs_xattr_handler_set_prop(const struct xattr_handler *handler,
376                                         struct dentry *unused, struct inode *inode,
377                                         const char *name, const void *value,
378                                         size_t size, int flags)
379 {
380         name = xattr_full_name(handler, name);
381         return btrfs_set_prop(inode, name, value, size, flags);
382 }
383 
384 static const struct xattr_handler btrfs_security_xattr_handler = {
385         .prefix = XATTR_SECURITY_PREFIX,
386         .get = btrfs_xattr_handler_get,
387         .set = btrfs_xattr_handler_set,
388 };
389 
390 static const struct xattr_handler btrfs_trusted_xattr_handler = {
391         .prefix = XATTR_TRUSTED_PREFIX,
392         .get = btrfs_xattr_handler_get,
393         .set = btrfs_xattr_handler_set,
394 };
395 
396 static const struct xattr_handler btrfs_user_xattr_handler = {
397         .prefix = XATTR_USER_PREFIX,
398         .get = btrfs_xattr_handler_get,
399         .set = btrfs_xattr_handler_set,
400 };
401 
402 static const struct xattr_handler btrfs_btrfs_xattr_handler = {
403         .prefix = XATTR_BTRFS_PREFIX,
404         .get = btrfs_xattr_handler_get,
405         .set = btrfs_xattr_handler_set_prop,
406 };
407 
408 const struct xattr_handler *btrfs_xattr_handlers[] = {
409         &btrfs_security_xattr_handler,
410 #ifdef CONFIG_BTRFS_FS_POSIX_ACL
411         &posix_acl_access_xattr_handler,
412         &posix_acl_default_xattr_handler,
413 #endif
414         &btrfs_trusted_xattr_handler,
415         &btrfs_user_xattr_handler,
416         &btrfs_btrfs_xattr_handler,
417         NULL,
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_KERNEL);
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, xattr->value,
438                                 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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