1/*
2 * This file is part of UBIFS.
3 *
4 * Copyright (C) 2006-2008 Nokia Corporation.
5 *
6 * This program is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 as published by
8 * the Free Software Foundation.
9 *
10 * This program is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
13 * more details.
14 *
15 * You should have received a copy of the GNU General Public License along with
16 * this program; if not, write to the Free Software Foundation, Inc., 51
17 * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
18 *
19 * Authors: Artem Bityutskiy (Битюцкий Артём)
20 *          Adrian Hunter
21 */
22
23/*
24 * This file implements UBIFS extended attributes support.
25 *
26 * Extended attributes are implemented as regular inodes with attached data,
27 * which limits extended attribute size to UBIFS block size (4KiB). Names of
28 * extended attributes are described by extended attribute entries (xentries),
29 * which are almost identical to directory entries, but have different key type.
30 *
31 * In other words, the situation with extended attributes is very similar to
32 * directories. Indeed, any inode (but of course not xattr inodes) may have a
33 * number of associated xentries, just like directory inodes have associated
34 * directory entries. Extended attribute entries store the name of the extended
35 * attribute, the host inode number, and the extended attribute inode number.
36 * Similarly, direntries store the name, the parent and the target inode
37 * numbers. Thus, most of the common UBIFS mechanisms may be re-used for
38 * extended attributes.
39 *
40 * The number of extended attributes is not limited, but there is Linux
41 * limitation on the maximum possible size of the list of all extended
42 * attributes associated with an inode (%XATTR_LIST_MAX), so UBIFS makes sure
43 * the sum of all extended attribute names of the inode does not exceed that
44 * limit.
45 *
46 * Extended attributes are synchronous, which means they are written to the
47 * flash media synchronously and there is no write-back for extended attribute
48 * inodes. The extended attribute values are not stored in compressed form on
49 * the media.
50 *
51 * Since extended attributes are represented by regular inodes, they are cached
52 * in the VFS inode cache. The xentries are cached in the LNC cache (see
53 * tnc.c).
54 *
55 * ACL support is not implemented.
56 */
57
58#include "ubifs.h"
59#include <linux/fs.h>
60#include <linux/slab.h>
61#include <linux/xattr.h>
62#include <linux/posix_acl_xattr.h>
63
64/*
65 * Limit the number of extended attributes per inode so that the total size
66 * (@xattr_size) is guaranteeded to fit in an 'unsigned int'.
67 */
68#define MAX_XATTRS_PER_INODE 65535
69
70/*
71 * Extended attribute type constants.
72 *
73 * USER_XATTR: user extended attribute ("user.*")
74 * TRUSTED_XATTR: trusted extended attribute ("trusted.*)
75 * SECURITY_XATTR: security extended attribute ("security.*")
76 */
77enum {
78	USER_XATTR,
79	TRUSTED_XATTR,
80	SECURITY_XATTR,
81};
82
83static const struct inode_operations empty_iops;
84static const struct file_operations empty_fops;
85
86/**
87 * create_xattr - create an extended attribute.
88 * @c: UBIFS file-system description object
89 * @host: host inode
90 * @nm: extended attribute name
91 * @value: extended attribute value
92 * @size: size of extended attribute value
93 *
94 * This is a helper function which creates an extended attribute of name @nm
95 * and value @value for inode @host. The host inode is also updated on flash
96 * because the ctime and extended attribute accounting data changes. This
97 * function returns zero in case of success and a negative error code in case
98 * of failure.
99 */
100static int create_xattr(struct ubifs_info *c, struct inode *host,
101			const struct qstr *nm, const void *value, int size)
102{
103	int err, names_len;
104	struct inode *inode;
105	struct ubifs_inode *ui, *host_ui = ubifs_inode(host);
106	struct ubifs_budget_req req = { .new_ino = 1, .new_dent = 1,
107				.new_ino_d = ALIGN(size, 8), .dirtied_ino = 1,
108				.dirtied_ino_d = ALIGN(host_ui->data_len, 8) };
109
110	if (host_ui->xattr_cnt >= MAX_XATTRS_PER_INODE) {
111		ubifs_err(c, "inode %lu already has too many xattrs (%d), cannot create more",
112			  host->i_ino, host_ui->xattr_cnt);
113		return -ENOSPC;
114	}
115	/*
116	 * Linux limits the maximum size of the extended attribute names list
117	 * to %XATTR_LIST_MAX. This means we should not allow creating more
118	 * extended attributes if the name list becomes larger. This limitation
119	 * is artificial for UBIFS, though.
120	 */
121	names_len = host_ui->xattr_names + host_ui->xattr_cnt + nm->len + 1;
122	if (names_len > XATTR_LIST_MAX) {
123		ubifs_err(c, "cannot add one more xattr name to inode %lu, total names length would become %d, max. is %d",
124			  host->i_ino, names_len, XATTR_LIST_MAX);
125		return -ENOSPC;
126	}
127
128	err = ubifs_budget_space(c, &req);
129	if (err)
130		return err;
131
132	inode = ubifs_new_inode(c, host, S_IFREG | S_IRWXUGO);
133	if (IS_ERR(inode)) {
134		err = PTR_ERR(inode);
135		goto out_budg;
136	}
137
138	/* Re-define all operations to be "nothing" */
139	inode->i_mapping->a_ops = &empty_aops;
140	inode->i_op = &empty_iops;
141	inode->i_fop = &empty_fops;
142
143	inode->i_flags |= S_SYNC | S_NOATIME | S_NOCMTIME | S_NOQUOTA;
144	ui = ubifs_inode(inode);
145	ui->xattr = 1;
146	ui->flags |= UBIFS_XATTR_FL;
147	ui->data = kmemdup(value, size, GFP_NOFS);
148	if (!ui->data) {
149		err = -ENOMEM;
150		goto out_free;
151	}
152	inode->i_size = ui->ui_size = size;
153	ui->data_len = size;
154
155	mutex_lock(&host_ui->ui_mutex);
156	host->i_ctime = ubifs_current_time(host);
157	host_ui->xattr_cnt += 1;
158	host_ui->xattr_size += CALC_DENT_SIZE(nm->len);
159	host_ui->xattr_size += CALC_XATTR_BYTES(size);
160	host_ui->xattr_names += nm->len;
161
162	err = ubifs_jnl_update(c, host, nm, inode, 0, 1);
163	if (err)
164		goto out_cancel;
165	mutex_unlock(&host_ui->ui_mutex);
166
167	ubifs_release_budget(c, &req);
168	insert_inode_hash(inode);
169	iput(inode);
170	return 0;
171
172out_cancel:
173	host_ui->xattr_cnt -= 1;
174	host_ui->xattr_size -= CALC_DENT_SIZE(nm->len);
175	host_ui->xattr_size -= CALC_XATTR_BYTES(size);
176	mutex_unlock(&host_ui->ui_mutex);
177out_free:
178	make_bad_inode(inode);
179	iput(inode);
180out_budg:
181	ubifs_release_budget(c, &req);
182	return err;
183}
184
185/**
186 * change_xattr - change an extended attribute.
187 * @c: UBIFS file-system description object
188 * @host: host inode
189 * @inode: extended attribute inode
190 * @value: extended attribute value
191 * @size: size of extended attribute value
192 *
193 * This helper function changes the value of extended attribute @inode with new
194 * data from @value. Returns zero in case of success and a negative error code
195 * in case of failure.
196 */
197static int change_xattr(struct ubifs_info *c, struct inode *host,
198			struct inode *inode, const void *value, int size)
199{
200	int err;
201	struct ubifs_inode *host_ui = ubifs_inode(host);
202	struct ubifs_inode *ui = ubifs_inode(inode);
203	struct ubifs_budget_req req = { .dirtied_ino = 2,
204		.dirtied_ino_d = ALIGN(size, 8) + ALIGN(host_ui->data_len, 8) };
205
206	ubifs_assert(ui->data_len == inode->i_size);
207	err = ubifs_budget_space(c, &req);
208	if (err)
209		return err;
210
211	kfree(ui->data);
212	ui->data = kmemdup(value, size, GFP_NOFS);
213	if (!ui->data) {
214		err = -ENOMEM;
215		goto out_free;
216	}
217	inode->i_size = ui->ui_size = size;
218	ui->data_len = size;
219
220	mutex_lock(&host_ui->ui_mutex);
221	host->i_ctime = ubifs_current_time(host);
222	host_ui->xattr_size -= CALC_XATTR_BYTES(ui->data_len);
223	host_ui->xattr_size += CALC_XATTR_BYTES(size);
224
225	/*
226	 * It is important to write the host inode after the xattr inode
227	 * because if the host inode gets synchronized (via 'fsync()'), then
228	 * the extended attribute inode gets synchronized, because it goes
229	 * before the host inode in the write-buffer.
230	 */
231	err = ubifs_jnl_change_xattr(c, inode, host);
232	if (err)
233		goto out_cancel;
234	mutex_unlock(&host_ui->ui_mutex);
235
236	ubifs_release_budget(c, &req);
237	return 0;
238
239out_cancel:
240	host_ui->xattr_size -= CALC_XATTR_BYTES(size);
241	host_ui->xattr_size += CALC_XATTR_BYTES(ui->data_len);
242	mutex_unlock(&host_ui->ui_mutex);
243	make_bad_inode(inode);
244out_free:
245	ubifs_release_budget(c, &req);
246	return err;
247}
248
249/**
250 * check_namespace - check extended attribute name-space.
251 * @nm: extended attribute name
252 *
253 * This function makes sure the extended attribute name belongs to one of the
254 * supported extended attribute name-spaces. Returns name-space index in case
255 * of success and a negative error code in case of failure.
256 */
257static int check_namespace(const struct qstr *nm)
258{
259	int type;
260
261	if (nm->len > UBIFS_MAX_NLEN)
262		return -ENAMETOOLONG;
263
264	if (!strncmp(nm->name, XATTR_TRUSTED_PREFIX,
265		     XATTR_TRUSTED_PREFIX_LEN)) {
266		if (nm->name[sizeof(XATTR_TRUSTED_PREFIX) - 1] == '\0')
267			return -EINVAL;
268		type = TRUSTED_XATTR;
269	} else if (!strncmp(nm->name, XATTR_USER_PREFIX,
270				      XATTR_USER_PREFIX_LEN)) {
271		if (nm->name[XATTR_USER_PREFIX_LEN] == '\0')
272			return -EINVAL;
273		type = USER_XATTR;
274	} else if (!strncmp(nm->name, XATTR_SECURITY_PREFIX,
275				     XATTR_SECURITY_PREFIX_LEN)) {
276		if (nm->name[sizeof(XATTR_SECURITY_PREFIX) - 1] == '\0')
277			return -EINVAL;
278		type = SECURITY_XATTR;
279	} else
280		return -EOPNOTSUPP;
281
282	return type;
283}
284
285static struct inode *iget_xattr(struct ubifs_info *c, ino_t inum)
286{
287	struct inode *inode;
288
289	inode = ubifs_iget(c->vfs_sb, inum);
290	if (IS_ERR(inode)) {
291		ubifs_err(c, "dead extended attribute entry, error %d",
292			  (int)PTR_ERR(inode));
293		return inode;
294	}
295	if (ubifs_inode(inode)->xattr)
296		return inode;
297	ubifs_err(c, "corrupt extended attribute entry");
298	iput(inode);
299	return ERR_PTR(-EINVAL);
300}
301
302static int setxattr(struct inode *host, const char *name, const void *value,
303		    size_t size, int flags)
304{
305	struct inode *inode;
306	struct ubifs_info *c = host->i_sb->s_fs_info;
307	struct qstr nm = QSTR_INIT(name, strlen(name));
308	struct ubifs_dent_node *xent;
309	union ubifs_key key;
310	int err, type;
311
312	ubifs_assert(mutex_is_locked(&host->i_mutex));
313
314	if (size > UBIFS_MAX_INO_DATA)
315		return -ERANGE;
316
317	type = check_namespace(&nm);
318	if (type < 0)
319		return type;
320
321	xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS);
322	if (!xent)
323		return -ENOMEM;
324
325	/*
326	 * The extended attribute entries are stored in LNC, so multiple
327	 * look-ups do not involve reading the flash.
328	 */
329	xent_key_init(c, &key, host->i_ino, &nm);
330	err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
331	if (err) {
332		if (err != -ENOENT)
333			goto out_free;
334
335		if (flags & XATTR_REPLACE)
336			/* We are asked not to create the xattr */
337			err = -ENODATA;
338		else
339			err = create_xattr(c, host, &nm, value, size);
340		goto out_free;
341	}
342
343	if (flags & XATTR_CREATE) {
344		/* We are asked not to replace the xattr */
345		err = -EEXIST;
346		goto out_free;
347	}
348
349	inode = iget_xattr(c, le64_to_cpu(xent->inum));
350	if (IS_ERR(inode)) {
351		err = PTR_ERR(inode);
352		goto out_free;
353	}
354
355	err = change_xattr(c, host, inode, value, size);
356	iput(inode);
357
358out_free:
359	kfree(xent);
360	return err;
361}
362
363int ubifs_setxattr(struct dentry *dentry, const char *name,
364		   const void *value, size_t size, int flags)
365{
366	dbg_gen("xattr '%s', host ino %lu ('%pd'), size %zd",
367		name, d_inode(dentry)->i_ino, dentry, size);
368
369	return setxattr(d_inode(dentry), name, value, size, flags);
370}
371
372ssize_t ubifs_getxattr(struct dentry *dentry, const char *name, void *buf,
373		       size_t size)
374{
375	struct inode *inode, *host = d_inode(dentry);
376	struct ubifs_info *c = host->i_sb->s_fs_info;
377	struct qstr nm = QSTR_INIT(name, strlen(name));
378	struct ubifs_inode *ui;
379	struct ubifs_dent_node *xent;
380	union ubifs_key key;
381	int err;
382
383	dbg_gen("xattr '%s', ino %lu ('%pd'), buf size %zd", name,
384		host->i_ino, dentry, size);
385
386	err = check_namespace(&nm);
387	if (err < 0)
388		return err;
389
390	xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS);
391	if (!xent)
392		return -ENOMEM;
393
394	xent_key_init(c, &key, host->i_ino, &nm);
395	err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
396	if (err) {
397		if (err == -ENOENT)
398			err = -ENODATA;
399		goto out_unlock;
400	}
401
402	inode = iget_xattr(c, le64_to_cpu(xent->inum));
403	if (IS_ERR(inode)) {
404		err = PTR_ERR(inode);
405		goto out_unlock;
406	}
407
408	ui = ubifs_inode(inode);
409	ubifs_assert(inode->i_size == ui->data_len);
410	ubifs_assert(ubifs_inode(host)->xattr_size > ui->data_len);
411
412	if (buf) {
413		/* If @buf is %NULL we are supposed to return the length */
414		if (ui->data_len > size) {
415			ubifs_err(c, "buffer size %zd, xattr len %d",
416				  size, ui->data_len);
417			err = -ERANGE;
418			goto out_iput;
419		}
420
421		memcpy(buf, ui->data, ui->data_len);
422	}
423	err = ui->data_len;
424
425out_iput:
426	iput(inode);
427out_unlock:
428	kfree(xent);
429	return err;
430}
431
432ssize_t ubifs_listxattr(struct dentry *dentry, char *buffer, size_t size)
433{
434	union ubifs_key key;
435	struct inode *host = d_inode(dentry);
436	struct ubifs_info *c = host->i_sb->s_fs_info;
437	struct ubifs_inode *host_ui = ubifs_inode(host);
438	struct ubifs_dent_node *xent, *pxent = NULL;
439	int err, len, written = 0;
440	struct qstr nm = { .name = NULL };
441
442	dbg_gen("ino %lu ('%pd'), buffer size %zd", host->i_ino,
443		dentry, size);
444
445	len = host_ui->xattr_names + host_ui->xattr_cnt;
446	if (!buffer)
447		/*
448		 * We should return the minimum buffer size which will fit a
449		 * null-terminated list of all the extended attribute names.
450		 */
451		return len;
452
453	if (len > size)
454		return -ERANGE;
455
456	lowest_xent_key(c, &key, host->i_ino);
457	while (1) {
458		int type;
459
460		xent = ubifs_tnc_next_ent(c, &key, &nm);
461		if (IS_ERR(xent)) {
462			err = PTR_ERR(xent);
463			break;
464		}
465
466		nm.name = xent->name;
467		nm.len = le16_to_cpu(xent->nlen);
468
469		type = check_namespace(&nm);
470		if (unlikely(type < 0)) {
471			err = type;
472			break;
473		}
474
475		/* Show trusted namespace only for "power" users */
476		if (type != TRUSTED_XATTR || capable(CAP_SYS_ADMIN)) {
477			memcpy(buffer + written, nm.name, nm.len + 1);
478			written += nm.len + 1;
479		}
480
481		kfree(pxent);
482		pxent = xent;
483		key_read(c, &xent->key, &key);
484	}
485
486	kfree(pxent);
487	if (err != -ENOENT) {
488		ubifs_err(c, "cannot find next direntry, error %d", err);
489		return err;
490	}
491
492	ubifs_assert(written <= size);
493	return written;
494}
495
496static int remove_xattr(struct ubifs_info *c, struct inode *host,
497			struct inode *inode, const struct qstr *nm)
498{
499	int err;
500	struct ubifs_inode *host_ui = ubifs_inode(host);
501	struct ubifs_inode *ui = ubifs_inode(inode);
502	struct ubifs_budget_req req = { .dirtied_ino = 2, .mod_dent = 1,
503				.dirtied_ino_d = ALIGN(host_ui->data_len, 8) };
504
505	ubifs_assert(ui->data_len == inode->i_size);
506
507	err = ubifs_budget_space(c, &req);
508	if (err)
509		return err;
510
511	mutex_lock(&host_ui->ui_mutex);
512	host->i_ctime = ubifs_current_time(host);
513	host_ui->xattr_cnt -= 1;
514	host_ui->xattr_size -= CALC_DENT_SIZE(nm->len);
515	host_ui->xattr_size -= CALC_XATTR_BYTES(ui->data_len);
516	host_ui->xattr_names -= nm->len;
517
518	err = ubifs_jnl_delete_xattr(c, host, inode, nm);
519	if (err)
520		goto out_cancel;
521	mutex_unlock(&host_ui->ui_mutex);
522
523	ubifs_release_budget(c, &req);
524	return 0;
525
526out_cancel:
527	host_ui->xattr_cnt += 1;
528	host_ui->xattr_size += CALC_DENT_SIZE(nm->len);
529	host_ui->xattr_size += CALC_XATTR_BYTES(ui->data_len);
530	mutex_unlock(&host_ui->ui_mutex);
531	ubifs_release_budget(c, &req);
532	make_bad_inode(inode);
533	return err;
534}
535
536int ubifs_removexattr(struct dentry *dentry, const char *name)
537{
538	struct inode *inode, *host = d_inode(dentry);
539	struct ubifs_info *c = host->i_sb->s_fs_info;
540	struct qstr nm = QSTR_INIT(name, strlen(name));
541	struct ubifs_dent_node *xent;
542	union ubifs_key key;
543	int err;
544
545	dbg_gen("xattr '%s', ino %lu ('%pd')", name,
546		host->i_ino, dentry);
547	ubifs_assert(mutex_is_locked(&host->i_mutex));
548
549	err = check_namespace(&nm);
550	if (err < 0)
551		return err;
552
553	xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS);
554	if (!xent)
555		return -ENOMEM;
556
557	xent_key_init(c, &key, host->i_ino, &nm);
558	err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
559	if (err) {
560		if (err == -ENOENT)
561			err = -ENODATA;
562		goto out_free;
563	}
564
565	inode = iget_xattr(c, le64_to_cpu(xent->inum));
566	if (IS_ERR(inode)) {
567		err = PTR_ERR(inode);
568		goto out_free;
569	}
570
571	ubifs_assert(inode->i_nlink == 1);
572	clear_nlink(inode);
573	err = remove_xattr(c, host, inode, &nm);
574	if (err)
575		set_nlink(inode, 1);
576
577	/* If @i_nlink is 0, 'iput()' will delete the inode */
578	iput(inode);
579
580out_free:
581	kfree(xent);
582	return err;
583}
584
585static size_t security_listxattr(struct dentry *d, char *list, size_t list_size,
586				 const char *name, size_t name_len, int flags)
587{
588	const int prefix_len = XATTR_SECURITY_PREFIX_LEN;
589	const size_t total_len = prefix_len + name_len + 1;
590
591	if (list && total_len <= list_size) {
592		memcpy(list, XATTR_SECURITY_PREFIX, prefix_len);
593		memcpy(list + prefix_len, name, name_len);
594		list[prefix_len + name_len] = '\0';
595	}
596
597	return total_len;
598}
599
600static int security_getxattr(struct dentry *d, const char *name, void *buffer,
601		      size_t size, int flags)
602{
603	return ubifs_getxattr(d, name, buffer, size);
604}
605
606static int security_setxattr(struct dentry *d, const char *name,
607			     const void *value, size_t size, int flags,
608			     int handler_flags)
609{
610	return ubifs_setxattr(d, name, value, size, flags);
611}
612
613static const struct xattr_handler ubifs_xattr_security_handler = {
614	.prefix = XATTR_SECURITY_PREFIX,
615	.list   = security_listxattr,
616	.get    = security_getxattr,
617	.set    = security_setxattr,
618};
619
620const struct xattr_handler *ubifs_xattr_handlers[] = {
621	&ubifs_xattr_security_handler,
622	NULL,
623};
624
625static int init_xattrs(struct inode *inode, const struct xattr *xattr_array,
626		      void *fs_info)
627{
628	const struct xattr *xattr;
629	char *name;
630	int err = 0;
631
632	for (xattr = xattr_array; xattr->name != NULL; xattr++) {
633		name = kmalloc(XATTR_SECURITY_PREFIX_LEN +
634			       strlen(xattr->name) + 1, GFP_NOFS);
635		if (!name) {
636			err = -ENOMEM;
637			break;
638		}
639		strcpy(name, XATTR_SECURITY_PREFIX);
640		strcpy(name + XATTR_SECURITY_PREFIX_LEN, xattr->name);
641		err = setxattr(inode, name, xattr->value, xattr->value_len, 0);
642		kfree(name);
643		if (err < 0)
644			break;
645	}
646
647	return err;
648}
649
650int ubifs_init_security(struct inode *dentry, struct inode *inode,
651			const struct qstr *qstr)
652{
653	int err;
654
655	err = security_inode_init_security(inode, dentry, qstr,
656					   &init_xattrs, 0);
657	if (err) {
658		struct ubifs_info *c = dentry->i_sb->s_fs_info;
659		ubifs_err(c, "cannot initialize security for inode %lu, error %d",
660			  inode->i_ino, err);
661	}
662	return err;
663}
664