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