1/*
2 * linux/fs/ext4/acl.c
3 *
4 * Copyright (C) 2001-2003 Andreas Gruenbacher, <agruen@suse.de>
5 */
6
7#include <linux/init.h>
8#include <linux/sched.h>
9#include <linux/slab.h>
10#include <linux/capability.h>
11#include <linux/fs.h>
12#include "ext4_jbd2.h"
13#include "ext4.h"
14#include "xattr.h"
15#include "acl.h"
16
17/*
18 * Convert from filesystem to in-memory representation.
19 */
20static struct posix_acl *
21ext4_acl_from_disk(const void *value, size_t size)
22{
23	const char *end = (char *)value + size;
24	int n, count;
25	struct posix_acl *acl;
26
27	if (!value)
28		return NULL;
29	if (size < sizeof(ext4_acl_header))
30		 return ERR_PTR(-EINVAL);
31	if (((ext4_acl_header *)value)->a_version !=
32	    cpu_to_le32(EXT4_ACL_VERSION))
33		return ERR_PTR(-EINVAL);
34	value = (char *)value + sizeof(ext4_acl_header);
35	count = ext4_acl_count(size);
36	if (count < 0)
37		return ERR_PTR(-EINVAL);
38	if (count == 0)
39		return NULL;
40	acl = posix_acl_alloc(count, GFP_NOFS);
41	if (!acl)
42		return ERR_PTR(-ENOMEM);
43	for (n = 0; n < count; n++) {
44		ext4_acl_entry *entry =
45			(ext4_acl_entry *)value;
46		if ((char *)value + sizeof(ext4_acl_entry_short) > end)
47			goto fail;
48		acl->a_entries[n].e_tag  = le16_to_cpu(entry->e_tag);
49		acl->a_entries[n].e_perm = le16_to_cpu(entry->e_perm);
50
51		switch (acl->a_entries[n].e_tag) {
52		case ACL_USER_OBJ:
53		case ACL_GROUP_OBJ:
54		case ACL_MASK:
55		case ACL_OTHER:
56			value = (char *)value +
57				sizeof(ext4_acl_entry_short);
58			acl->a_entries[n].e_id = ACL_UNDEFINED_ID;
59			break;
60
61		case ACL_USER:
62		case ACL_GROUP:
63			value = (char *)value + sizeof(ext4_acl_entry);
64			if ((char *)value > end)
65				goto fail;
66			acl->a_entries[n].e_id =
67				le32_to_cpu(entry->e_id);
68			break;
69
70		default:
71			goto fail;
72		}
73	}
74	if (value != end)
75		goto fail;
76	return acl;
77
78fail:
79	posix_acl_release(acl);
80	return ERR_PTR(-EINVAL);
81}
82
83/*
84 * Convert from in-memory to filesystem representation.
85 */
86static void *
87ext4_acl_to_disk(const struct posix_acl *acl, size_t *size)
88{
89	ext4_acl_header *ext_acl;
90	char *e;
91	size_t n;
92
93	*size = ext4_acl_size(acl->a_count);
94	ext_acl = kmalloc(sizeof(ext4_acl_header) + acl->a_count *
95			sizeof(ext4_acl_entry), GFP_NOFS);
96	if (!ext_acl)
97		return ERR_PTR(-ENOMEM);
98	ext_acl->a_version = cpu_to_le32(EXT4_ACL_VERSION);
99	e = (char *)ext_acl + sizeof(ext4_acl_header);
100	for (n = 0; n < acl->a_count; n++) {
101		ext4_acl_entry *entry = (ext4_acl_entry *)e;
102		entry->e_tag  = cpu_to_le16(acl->a_entries[n].e_tag);
103		entry->e_perm = cpu_to_le16(acl->a_entries[n].e_perm);
104		switch (acl->a_entries[n].e_tag) {
105		case ACL_USER:
106		case ACL_GROUP:
107			entry->e_id = cpu_to_le32(acl->a_entries[n].e_id);
108			e += sizeof(ext4_acl_entry);
109			break;
110
111		case ACL_USER_OBJ:
112		case ACL_GROUP_OBJ:
113		case ACL_MASK:
114		case ACL_OTHER:
115			e += sizeof(ext4_acl_entry_short);
116			break;
117
118		default:
119			goto fail;
120		}
121	}
122	return (char *)ext_acl;
123
124fail:
125	kfree(ext_acl);
126	return ERR_PTR(-EINVAL);
127}
128
129/*
130 * Inode operation get_posix_acl().
131 *
132 * inode->i_mutex: don't care
133 */
134static struct posix_acl *
135ext4_get_acl(struct inode *inode, int type)
136{
137	int name_index;
138	char *value = NULL;
139	struct posix_acl *acl;
140	int retval;
141
142	if (!test_opt(inode->i_sb, POSIX_ACL))
143		return NULL;
144
145	acl = get_cached_acl(inode, type);
146	if (acl != ACL_NOT_CACHED)
147		return acl;
148
149	switch (type) {
150	case ACL_TYPE_ACCESS:
151		name_index = EXT4_XATTR_INDEX_POSIX_ACL_ACCESS;
152		break;
153	case ACL_TYPE_DEFAULT:
154		name_index = EXT4_XATTR_INDEX_POSIX_ACL_DEFAULT;
155		break;
156	default:
157		BUG();
158	}
159	retval = ext4_xattr_get(inode, name_index, "", NULL, 0);
160	if (retval > 0) {
161		value = kmalloc(retval, GFP_NOFS);
162		if (!value)
163			return ERR_PTR(-ENOMEM);
164		retval = ext4_xattr_get(inode, name_index, "", value, retval);
165	}
166	if (retval > 0)
167		acl = ext4_acl_from_disk(value, retval);
168	else if (retval == -ENODATA || retval == -ENOSYS)
169		acl = NULL;
170	else
171		acl = ERR_PTR(retval);
172	kfree(value);
173
174	if (!IS_ERR(acl))
175		set_cached_acl(inode, type, acl);
176
177	return acl;
178}
179
180/*
181 * Set the access or default ACL of an inode.
182 *
183 * inode->i_mutex: down unless called from ext4_new_inode
184 */
185static int
186ext4_set_acl(handle_t *handle, struct inode *inode, int type,
187	     struct posix_acl *acl)
188{
189	int name_index;
190	void *value = NULL;
191	size_t size = 0;
192	int error;
193
194	if (S_ISLNK(inode->i_mode))
195		return -EOPNOTSUPP;
196
197	switch (type) {
198	case ACL_TYPE_ACCESS:
199		name_index = EXT4_XATTR_INDEX_POSIX_ACL_ACCESS;
200		if (acl) {
201			mode_t mode = inode->i_mode;
202			error = posix_acl_equiv_mode(acl, &mode);
203			if (error < 0)
204				return error;
205			else {
206				inode->i_mode = mode;
207				inode->i_ctime = ext4_current_time(inode);
208				ext4_mark_inode_dirty(handle, inode);
209				if (error == 0)
210					acl = NULL;
211			}
212		}
213		break;
214
215	case ACL_TYPE_DEFAULT:
216		name_index = EXT4_XATTR_INDEX_POSIX_ACL_DEFAULT;
217		if (!S_ISDIR(inode->i_mode))
218			return acl ? -EACCES : 0;
219		break;
220
221	default:
222		return -EINVAL;
223	}
224	if (acl) {
225		value = ext4_acl_to_disk(acl, &size);
226		if (IS_ERR(value))
227			return (int)PTR_ERR(value);
228	}
229
230	error = ext4_xattr_set_handle(handle, inode, name_index, "",
231				      value, size, 0);
232
233	kfree(value);
234	if (!error)
235		set_cached_acl(inode, type, acl);
236
237	return error;
238}
239
240int
241ext4_check_acl(struct inode *inode, int mask)
242{
243	struct posix_acl *acl = ext4_get_acl(inode, ACL_TYPE_ACCESS);
244
245	if (IS_ERR(acl))
246		return PTR_ERR(acl);
247	if (acl) {
248		int error = posix_acl_permission(inode, acl, mask);
249		posix_acl_release(acl);
250		return error;
251	}
252
253	return -EAGAIN;
254}
255
256/*
257 * Initialize the ACLs of a new inode. Called from ext4_new_inode.
258 *
259 * dir->i_mutex: down
260 * inode->i_mutex: up (access to inode is still exclusive)
261 */
262int
263ext4_init_acl(handle_t *handle, struct inode *inode, struct inode *dir)
264{
265	struct posix_acl *acl = NULL;
266	int error = 0;
267
268	if (!S_ISLNK(inode->i_mode)) {
269		if (test_opt(dir->i_sb, POSIX_ACL)) {
270			acl = ext4_get_acl(dir, ACL_TYPE_DEFAULT);
271			if (IS_ERR(acl))
272				return PTR_ERR(acl);
273		}
274		if (!acl)
275			inode->i_mode &= ~current_umask();
276	}
277	if (test_opt(inode->i_sb, POSIX_ACL) && acl) {
278		struct posix_acl *clone;
279		mode_t mode;
280
281		if (S_ISDIR(inode->i_mode)) {
282			error = ext4_set_acl(handle, inode,
283					     ACL_TYPE_DEFAULT, acl);
284			if (error)
285				goto cleanup;
286		}
287		clone = posix_acl_clone(acl, GFP_NOFS);
288		error = -ENOMEM;
289		if (!clone)
290			goto cleanup;
291
292		mode = inode->i_mode;
293		error = posix_acl_create_masq(clone, &mode);
294		if (error >= 0) {
295			inode->i_mode = mode;
296			if (error > 0) {
297				/* This is an extended ACL */
298				error = ext4_set_acl(handle, inode,
299						     ACL_TYPE_ACCESS, clone);
300			}
301		}
302		posix_acl_release(clone);
303	}
304cleanup:
305	posix_acl_release(acl);
306	return error;
307}
308
309/*
310 * Does chmod for an inode that may have an Access Control List. The
311 * inode->i_mode field must be updated to the desired value by the caller
312 * before calling this function.
313 * Returns 0 on success, or a negative error number.
314 *
315 * We change the ACL rather than storing some ACL entries in the file
316 * mode permission bits (which would be more efficient), because that
317 * would break once additional permissions (like  ACL_APPEND, ACL_DELETE
318 * for directories) are added. There are no more bits available in the
319 * file mode.
320 *
321 * inode->i_mutex: down
322 */
323int
324ext4_acl_chmod(struct inode *inode)
325{
326	struct posix_acl *acl, *clone;
327	int error;
328
329	if (S_ISLNK(inode->i_mode))
330		return -EOPNOTSUPP;
331	if (!test_opt(inode->i_sb, POSIX_ACL))
332		return 0;
333	acl = ext4_get_acl(inode, ACL_TYPE_ACCESS);
334	if (IS_ERR(acl) || !acl)
335		return PTR_ERR(acl);
336	clone = posix_acl_clone(acl, GFP_KERNEL);
337	posix_acl_release(acl);
338	if (!clone)
339		return -ENOMEM;
340	error = posix_acl_chmod_masq(clone, inode->i_mode);
341	if (!error) {
342		handle_t *handle;
343		int retries = 0;
344
345	retry:
346		handle = ext4_journal_start(inode,
347				EXT4_DATA_TRANS_BLOCKS(inode->i_sb));
348		if (IS_ERR(handle)) {
349			error = PTR_ERR(handle);
350			ext4_std_error(inode->i_sb, error);
351			goto out;
352		}
353		error = ext4_set_acl(handle, inode, ACL_TYPE_ACCESS, clone);
354		ext4_journal_stop(handle);
355		if (error == -ENOSPC &&
356		    ext4_should_retry_alloc(inode->i_sb, &retries))
357			goto retry;
358	}
359out:
360	posix_acl_release(clone);
361	return error;
362}
363
364/*
365 * Extended attribute handlers
366 */
367static size_t
368ext4_xattr_list_acl_access(struct dentry *dentry, char *list, size_t list_len,
369			   const char *name, size_t name_len, int type)
370{
371	const size_t size = sizeof(POSIX_ACL_XATTR_ACCESS);
372
373	if (!test_opt(dentry->d_sb, POSIX_ACL))
374		return 0;
375	if (list && size <= list_len)
376		memcpy(list, POSIX_ACL_XATTR_ACCESS, size);
377	return size;
378}
379
380static size_t
381ext4_xattr_list_acl_default(struct dentry *dentry, char *list, size_t list_len,
382			    const char *name, size_t name_len, int type)
383{
384	const size_t size = sizeof(POSIX_ACL_XATTR_DEFAULT);
385
386	if (!test_opt(dentry->d_sb, POSIX_ACL))
387		return 0;
388	if (list && size <= list_len)
389		memcpy(list, POSIX_ACL_XATTR_DEFAULT, size);
390	return size;
391}
392
393static int
394ext4_xattr_get_acl(struct dentry *dentry, const char *name, void *buffer,
395		   size_t size, int type)
396{
397	struct posix_acl *acl;
398	int error;
399
400	if (strcmp(name, "") != 0)
401		return -EINVAL;
402	if (!test_opt(dentry->d_sb, POSIX_ACL))
403		return -EOPNOTSUPP;
404
405	acl = ext4_get_acl(dentry->d_inode, type);
406	if (IS_ERR(acl))
407		return PTR_ERR(acl);
408	if (acl == NULL)
409		return -ENODATA;
410	error = posix_acl_to_xattr(acl, buffer, size);
411	posix_acl_release(acl);
412
413	return error;
414}
415
416static int
417ext4_xattr_set_acl(struct dentry *dentry, const char *name, const void *value,
418		   size_t size, int flags, int type)
419{
420	struct inode *inode = dentry->d_inode;
421	handle_t *handle;
422	struct posix_acl *acl;
423	int error, retries = 0;
424
425	if (strcmp(name, "") != 0)
426		return -EINVAL;
427	if (!test_opt(inode->i_sb, POSIX_ACL))
428		return -EOPNOTSUPP;
429	if (!is_owner_or_cap(inode))
430		return -EPERM;
431
432	if (value) {
433		acl = posix_acl_from_xattr(value, size);
434		if (IS_ERR(acl))
435			return PTR_ERR(acl);
436		else if (acl) {
437			error = posix_acl_valid(acl);
438			if (error)
439				goto release_and_out;
440		}
441	} else
442		acl = NULL;
443
444retry:
445	handle = ext4_journal_start(inode, EXT4_DATA_TRANS_BLOCKS(inode->i_sb));
446	if (IS_ERR(handle))
447		return PTR_ERR(handle);
448	error = ext4_set_acl(handle, inode, type, acl);
449	ext4_journal_stop(handle);
450	if (error == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
451		goto retry;
452
453release_and_out:
454	posix_acl_release(acl);
455	return error;
456}
457
458const struct xattr_handler ext4_xattr_acl_access_handler = {
459	.prefix	= POSIX_ACL_XATTR_ACCESS,
460	.flags	= ACL_TYPE_ACCESS,
461	.list	= ext4_xattr_list_acl_access,
462	.get	= ext4_xattr_get_acl,
463	.set	= ext4_xattr_set_acl,
464};
465
466const struct xattr_handler ext4_xattr_acl_default_handler = {
467	.prefix	= POSIX_ACL_XATTR_DEFAULT,
468	.flags	= ACL_TYPE_DEFAULT,
469	.list	= ext4_xattr_list_acl_default,
470	.get	= ext4_xattr_get_acl,
471	.set	= ext4_xattr_set_acl,
472};
473