xattr.c

  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 <linux/sched/mm.h>
 15#include "ctree.h"
 16#include "fs.h"
 17#include "messages.h"
 18#include "btrfs_inode.h"
 19#include "transaction.h"
 20#include "xattr.h"
 21#include "disk-io.h"
 22#include "props.h"
 23#include "locking.h"
 24#include "accessors.h"
 25#include "dir-item.h"
 26
 27int btrfs_getxattr(const struct inode *inode, const char *name,
 28				void *buffer, size_t size)
 29{
 30	struct btrfs_dir_item *di;
 31	struct btrfs_root *root = BTRFS_I(inode)->root;
 32	BTRFS_PATH_AUTO_FREE(path);
 33	struct extent_buffer *leaf;
 34	unsigned long data_ptr;
 35
 36	path = btrfs_alloc_path();
 37	if (!path)
 38		return -ENOMEM;
 39
 40	/* lookup the xattr by name */
 41	di = btrfs_lookup_xattr(NULL, root, path, btrfs_ino(BTRFS_I(inode)),
 42			name, strlen(name), 0);
 43	if (!di)
 44		return -ENODATA;
 45	if (IS_ERR(di))
 46		return PTR_ERR(di);
 47
 48	leaf = path->nodes[0];
 49	/* if size is 0, that means we want the size of the attr */
 50	if (!size)
 51		return btrfs_dir_data_len(leaf, di);
 52
 53	/* now get the data out of our dir_item */
 54	if (btrfs_dir_data_len(leaf, di) > size)
 55		return -ERANGE;
 56
 57	/*
 58	 * The way things are packed into the leaf is like this
 59	 * |struct btrfs_dir_item|name|data|
 60	 * where name is the xattr name, so security.foo, and data is the
 61	 * content of the xattr.  data_ptr points to the location in memory
 62	 * where the data starts in the in memory leaf
 63	 */
 64	data_ptr = (unsigned long)((char *)(di + 1) +
 65				   btrfs_dir_name_len(leaf, di));
 66	read_extent_buffer(leaf, buffer, data_ptr,
 67			   btrfs_dir_data_len(leaf, di));
 68	return btrfs_dir_data_len(leaf, di);
 69}
 70
 71int btrfs_setxattr(struct btrfs_trans_handle *trans, struct inode *inode,
 72		   const char *name, const void *value, size_t size, int flags)
 73{
 74	struct btrfs_dir_item *di = NULL;
 75	struct btrfs_root *root = BTRFS_I(inode)->root;
 76	BTRFS_PATH_AUTO_FREE(path);
 77	size_t name_len = strlen(name);
 78	int ret = 0;
 79
 80	ASSERT(trans);
 81
 82	if (name_len + size > BTRFS_MAX_XATTR_SIZE(root->fs_info))
 83		return -ENOSPC;
 84
 85	path = btrfs_alloc_path();
 86	if (!path)
 87		return -ENOMEM;
 88	path->skip_release_on_error = true;
 89
 90	if (!value) {
 91		di = btrfs_lookup_xattr(trans, root, path,
 92				btrfs_ino(BTRFS_I(inode)), name, name_len, -1);
 93		if (!di && (flags & XATTR_REPLACE))
 94			ret = -ENODATA;
 95		else if (IS_ERR(di))
 96			ret = PTR_ERR(di);
 97		else if (di)
 98			ret = btrfs_delete_one_dir_name(trans, root, path, di);
 99		goto out;
100	}
101
102	/*
103	 * For a replace we can't just do the insert blindly.
104	 * Do a lookup first (read-only btrfs_search_slot), and return if xattr
105	 * doesn't exist. If it exists, fall down below to the insert/replace
106	 * path - we can't race with a concurrent xattr delete, because the VFS
107	 * locks the inode's i_mutex before calling setxattr or removexattr.
108	 */
109	if (flags & XATTR_REPLACE) {
110		btrfs_assert_inode_locked(BTRFS_I(inode));
111		di = btrfs_lookup_xattr(NULL, root, path,
112				btrfs_ino(BTRFS_I(inode)), name, name_len, 0);
113		if (!di)
114			ret = -ENODATA;
115		else if (IS_ERR(di))
116			ret = PTR_ERR(di);
117		if (ret)
118			goto out;
119		btrfs_release_path(path);
120		di = NULL;
121	}
122
123	ret = btrfs_insert_xattr_item(trans, root, path, btrfs_ino(BTRFS_I(inode)),
124				      name, name_len, value, size);
125	if (ret == -EOVERFLOW) {
126		/*
127		 * We have an existing item in a leaf, split_leaf couldn't
128		 * expand it. That item might have or not a dir_item that
129		 * matches our target xattr, so lets check.
130		 */
131		ret = 0;
132		btrfs_assert_tree_write_locked(path->nodes[0]);
133		di = btrfs_match_dir_item_name(path, name, name_len);
134		if (!di && !(flags & XATTR_REPLACE)) {
135			ret = -ENOSPC;
136			goto out;
137		}
138	} else if (ret == -EEXIST) {
139		ret = 0;
140		di = btrfs_match_dir_item_name(path, name, name_len);
141		ASSERT(di); /* logic error */
142	} else if (ret) {
143		goto out;
144	}
145
146	if (di && (flags & XATTR_CREATE)) {
147		ret = -EEXIST;
148		goto out;
149	}
150
151	if (di) {
152		/*
153		 * We're doing a replace, and it must be atomic, that is, at
154		 * any point in time we have either the old or the new xattr
155		 * value in the tree. We don't want readers (getxattr and
156		 * listxattrs) to miss a value, this is specially important
157		 * for ACLs.
158		 */
159		const int slot = path->slots[0];
160		struct extent_buffer *leaf = path->nodes[0];
161		const u16 old_data_len = btrfs_dir_data_len(leaf, di);
162		const u32 item_size = btrfs_item_size(leaf, slot);
163		const u32 data_size = sizeof(*di) + name_len + size;
164		unsigned long data_ptr;
165		char *ptr;
166
167		if (size > old_data_len) {
168			if (btrfs_leaf_free_space(leaf) <
169			    (size - old_data_len)) {
170				ret = -ENOSPC;
171				goto out;
172			}
173		}
174
175		if (old_data_len + name_len + sizeof(*di) == item_size) {
176			/* No other xattrs packed in the same leaf item. */
177			if (size > old_data_len)
178				btrfs_extend_item(trans, path, size - old_data_len);
179			else if (size < old_data_len)
180				btrfs_truncate_item(trans, path, data_size, 1);
181		} else {
182			/* There are other xattrs packed in the same item. */
183			ret = btrfs_delete_one_dir_name(trans, root, path, di);
184			if (ret)
185				goto out;
186			btrfs_extend_item(trans, path, data_size);
187		}
188
189		ptr = btrfs_item_ptr(leaf, slot, char);
190		ptr += btrfs_item_size(leaf, slot) - data_size;
191		di = (struct btrfs_dir_item *)ptr;
192		btrfs_set_dir_data_len(leaf, di, size);
193		data_ptr = ((unsigned long)(di + 1)) + name_len;
194		write_extent_buffer(leaf, value, data_ptr, size);
195	} else {
196		/*
197		 * Insert, and we had space for the xattr, so path->slots[0] is
198		 * where our xattr dir_item is and btrfs_insert_xattr_item()
199		 * filled it.
200		 */
201	}
202out:
203	if (!ret) {
204		set_bit(BTRFS_INODE_COPY_EVERYTHING,
205			&BTRFS_I(inode)->runtime_flags);
206		clear_bit(BTRFS_INODE_NO_XATTRS, &BTRFS_I(inode)->runtime_flags);
207	}
208	return ret;
209}
210
211/*
212 * @value: "" makes the attribute to empty, NULL removes it
213 */
214int btrfs_setxattr_trans(struct inode *inode, const char *name,
215			 const void *value, size_t size, int flags)
216{
217	struct btrfs_root *root = BTRFS_I(inode)->root;
218	struct btrfs_trans_handle *trans;
219	const bool start_trans = (current->journal_info == NULL);
220	int ret;
221
222	if (start_trans) {
223		/*
224		 * 1 unit for inserting/updating/deleting the xattr
225		 * 1 unit for the inode item update
226		 */
227		trans = btrfs_start_transaction(root, 2);
228		if (IS_ERR(trans))
229			return PTR_ERR(trans);
230	} else {
231		/*
232		 * This can happen when smack is enabled and a directory is being
233		 * created. It happens through d_instantiate_new(), which calls
234		 * smack_d_instantiate(), which in turn calls __vfs_setxattr() to
235		 * set the transmute xattr (XATTR_NAME_SMACKTRANSMUTE) on the
236		 * inode. We have already reserved space for the xattr and inode
237		 * update at btrfs_mkdir(), so just use the transaction handle.
238		 * We don't join or start a transaction, as that will reset the
239		 * block_rsv of the handle and trigger a warning for the start
240		 * case.
241		 */
242		ASSERT(strncmp(name, XATTR_SECURITY_PREFIX,
243			       XATTR_SECURITY_PREFIX_LEN) == 0);
244		trans = current->journal_info;
245	}
246
247	ret = btrfs_setxattr(trans, inode, name, value, size, flags);
248	if (ret)
249		goto out;
250
251	inode_inc_iversion(inode);
252	inode_set_ctime_current(inode);
253	ret = btrfs_update_inode(trans, BTRFS_I(inode));
254	if (ret)
255		btrfs_abort_transaction(trans, ret);
256out:
257	if (start_trans)
258		btrfs_end_transaction(trans);
259	return ret;
260}
261
262ssize_t btrfs_listxattr(struct dentry *dentry, char *buffer, size_t size)
263{
264	struct btrfs_key found_key;
265	struct btrfs_key key;
266	struct inode *inode = d_inode(dentry);
267	struct btrfs_root *root = BTRFS_I(inode)->root;
268	BTRFS_PATH_AUTO_FREE(path);
269	int iter_ret = 0;
270	int ret = 0;
271	size_t total_size = 0, size_left = size;
272
273	/*
274	 * ok we want all objects associated with this id.
275	 * NOTE: we set key.offset = 0; because we want to start with the
276	 * first xattr that we find and walk forward
277	 */
278	key.objectid = btrfs_ino(BTRFS_I(inode));
279	key.type = BTRFS_XATTR_ITEM_KEY;
280	key.offset = 0;
281
282	path = btrfs_alloc_path();
283	if (!path)
284		return -ENOMEM;
285	path->reada = READA_FORWARD;
286
287	/* search for our xattrs */
288	btrfs_for_each_slot(root, &key, &found_key, path, iter_ret) {
289		struct extent_buffer *leaf;
290		int slot;
291		struct btrfs_dir_item *di;
292		u32 item_size;
293		u32 cur;
294
295		leaf = path->nodes[0];
296		slot = path->slots[0];
297
298		/* check to make sure this item is what we want */
299		if (found_key.objectid != key.objectid)
300			break;
301		if (found_key.type > BTRFS_XATTR_ITEM_KEY)
302			break;
303		if (found_key.type < BTRFS_XATTR_ITEM_KEY)
304			continue;
305
306		di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
307		item_size = btrfs_item_size(leaf, slot);
308		cur = 0;
309		while (cur < item_size) {
310			u16 name_len = btrfs_dir_name_len(leaf, di);
311			u16 data_len = btrfs_dir_data_len(leaf, di);
312			u32 this_len = sizeof(*di) + name_len + data_len;
313			unsigned long name_ptr = (unsigned long)(di + 1);
314
315			total_size += name_len + 1;
316			/*
317			 * We are just looking for how big our buffer needs to
318			 * be.
319			 */
320			if (!size)
321				goto next;
322
323			if (!buffer || (name_len + 1) > size_left) {
324			        iter_ret = -ERANGE;
325				break;
326			}
327
328			read_extent_buffer(leaf, buffer, name_ptr, name_len);
329			buffer[name_len] = '\0';
330
331			size_left -= name_len + 1;
332			buffer += name_len + 1;
333next:
334			cur += this_len;
335			di = (struct btrfs_dir_item *)((char *)di + this_len);
336		}
337	}
338
339	if (iter_ret < 0)
340		ret = iter_ret;
341	else
342		ret = total_size;
343
344	return ret;
345}
346
347static int btrfs_xattr_handler_get(const struct xattr_handler *handler,
348				   struct dentry *unused, struct inode *inode,
349				   const char *name, void *buffer, size_t size)
350{
351	name = xattr_full_name(handler, name);
352	return btrfs_getxattr(inode, name, buffer, size);
353}
354
355static int btrfs_xattr_handler_set(const struct xattr_handler *handler,
356				   struct mnt_idmap *idmap,
357				   struct dentry *unused, struct inode *inode,
358				   const char *name, const void *buffer,
359				   size_t size, int flags)
360{
361	if (btrfs_root_readonly(BTRFS_I(inode)->root))
362		return -EROFS;
363
364	name = xattr_full_name(handler, name);
365	return btrfs_setxattr_trans(inode, name, buffer, size, flags);
366}
367
368static int btrfs_xattr_handler_get_security(const struct xattr_handler *handler,
369					    struct dentry *unused,
370					    struct inode *inode,
371					    const char *name, void *buffer,
372					    size_t size)
373{
374	int ret;
375	bool is_cap = false;
376
377	name = xattr_full_name(handler, name);
378
379	/*
380	 * security.capability doesn't cache the results, so calls into us
381	 * constantly to see if there's a capability xattr.  Cache the result
382	 * here in order to avoid wasting time doing lookups for xattrs we know
383	 * don't exist.
384	 */
385	if (strcmp(name, XATTR_NAME_CAPS) == 0) {
386		is_cap = true;
387		if (test_bit(BTRFS_INODE_NO_CAP_XATTR, &BTRFS_I(inode)->runtime_flags))
388			return -ENODATA;
389	}
390
391	ret = btrfs_getxattr(inode, name, buffer, size);
392	if (ret == -ENODATA && is_cap)
393		set_bit(BTRFS_INODE_NO_CAP_XATTR, &BTRFS_I(inode)->runtime_flags);
394	return ret;
395}
396
397static int btrfs_xattr_handler_set_security(const struct xattr_handler *handler,
398					    struct mnt_idmap *idmap,
399					    struct dentry *unused,
400					    struct inode *inode,
401					    const char *name,
402					    const void *buffer,
403					    size_t size, int flags)
404{
405	if (btrfs_root_readonly(BTRFS_I(inode)->root))
406		return -EROFS;
407
408	name = xattr_full_name(handler, name);
409	if (strcmp(name, XATTR_NAME_CAPS) == 0)
410		clear_bit(BTRFS_INODE_NO_CAP_XATTR, &BTRFS_I(inode)->runtime_flags);
411
412	return btrfs_setxattr_trans(inode, name, buffer, size, flags);
413}
414
415static int btrfs_xattr_handler_set_prop(const struct xattr_handler *handler,
416					struct mnt_idmap *idmap,
417					struct dentry *unused, struct inode *inode,
418					const char *name, const void *value,
419					size_t size, int flags)
420{
421	int ret;
422	struct btrfs_trans_handle *trans;
423	struct btrfs_root *root = BTRFS_I(inode)->root;
424
425	name = xattr_full_name(handler, name);
426	ret = btrfs_validate_prop(BTRFS_I(inode), name, value, size);
427	if (ret)
428		return ret;
429
430	if (btrfs_ignore_prop(BTRFS_I(inode), name))
431		return 0;
432
433	trans = btrfs_start_transaction(root, 2);
434	if (IS_ERR(trans))
435		return PTR_ERR(trans);
436
437	ret = btrfs_set_prop(trans, BTRFS_I(inode), name, value, size, flags);
438	if (!ret) {
439		inode_inc_iversion(inode);
440		inode_set_ctime_current(inode);
441		ret = btrfs_update_inode(trans, BTRFS_I(inode));
442		if (ret)
443			btrfs_abort_transaction(trans, ret);
444	}
445
446	btrfs_end_transaction(trans);
447
448	return ret;
449}
450
451static const struct xattr_handler btrfs_security_xattr_handler = {
452	.prefix = XATTR_SECURITY_PREFIX,
453	.get = btrfs_xattr_handler_get_security,
454	.set = btrfs_xattr_handler_set_security,
455};
456
457static const struct xattr_handler btrfs_trusted_xattr_handler = {
458	.prefix = XATTR_TRUSTED_PREFIX,
459	.get = btrfs_xattr_handler_get,
460	.set = btrfs_xattr_handler_set,
461};
462
463static const struct xattr_handler btrfs_user_xattr_handler = {
464	.prefix = XATTR_USER_PREFIX,
465	.get = btrfs_xattr_handler_get,
466	.set = btrfs_xattr_handler_set,
467};
468
469static const struct xattr_handler btrfs_btrfs_xattr_handler = {
470	.prefix = XATTR_BTRFS_PREFIX,
471	.get = btrfs_xattr_handler_get,
472	.set = btrfs_xattr_handler_set_prop,
473};
474
475const struct xattr_handler * const btrfs_xattr_handlers[] = {
476	&btrfs_security_xattr_handler,
477	&btrfs_trusted_xattr_handler,
478	&btrfs_user_xattr_handler,
479	&btrfs_btrfs_xattr_handler,
480	NULL,
481};
482
483static int btrfs_initxattrs(struct inode *inode,
484			    const struct xattr *xattr_array, void *fs_private)
485{
486	struct btrfs_trans_handle *trans = fs_private;
487	const struct xattr *xattr;
488	unsigned int nofs_flag;
489	char *name;
490	int ret = 0;
491
492	/*
493	 * We're holding a transaction handle, so use a NOFS memory allocation
494	 * context to avoid deadlock if reclaim happens.
495	 */
496	nofs_flag = memalloc_nofs_save();
497	for (xattr = xattr_array; xattr->name != NULL; xattr++) {
498		const size_t name_len = XATTR_SECURITY_PREFIX_LEN +
499					strlen(xattr->name) + 1;
500
501		name = kmalloc(name_len, GFP_KERNEL);
502		if (!name) {
503			ret = -ENOMEM;
504			break;
505		}
506		scnprintf(name, name_len, "%s%s", XATTR_SECURITY_PREFIX, xattr->name);
507
508		if (strcmp(name, XATTR_NAME_CAPS) == 0)
509			clear_bit(BTRFS_INODE_NO_CAP_XATTR, &BTRFS_I(inode)->runtime_flags);
510
511		ret = btrfs_setxattr(trans, inode, name, xattr->value,
512				     xattr->value_len, 0);
513		kfree(name);
514		if (ret < 0)
515			break;
516	}
517	memalloc_nofs_restore(nofs_flag);
518	return ret;
519}
520
521int btrfs_xattr_security_init(struct btrfs_trans_handle *trans,
522			      struct inode *inode, struct inode *dir,
523			      const struct qstr *qstr)
524{
525	return security_inode_init_security(inode, dir, qstr,
526					    &btrfs_initxattrs, trans);
527}