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