Root/fs/ext4/acl.c

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                ext4_mark_inode_dirty(handle, inode);
208                if (error == 0)
209                    acl = NULL;
210            }
211        }
212        break;
213
214    case ACL_TYPE_DEFAULT:
215        name_index = EXT4_XATTR_INDEX_POSIX_ACL_DEFAULT;
216        if (!S_ISDIR(inode->i_mode))
217            return acl ? -EACCES : 0;
218        break;
219
220    default:
221        return -EINVAL;
222    }
223    if (acl) {
224        value = ext4_acl_to_disk(acl, &size);
225        if (IS_ERR(value))
226            return (int)PTR_ERR(value);
227    }
228
229    error = ext4_xattr_set_handle(handle, inode, name_index, "",
230                      value, size, 0);
231
232    kfree(value);
233    if (!error)
234        set_cached_acl(inode, type, acl);
235
236    return error;
237}
238
239static int
240ext4_check_acl(struct inode *inode, int mask)
241{
242    struct posix_acl *acl = ext4_get_acl(inode, ACL_TYPE_ACCESS);
243
244    if (IS_ERR(acl))
245        return PTR_ERR(acl);
246    if (acl) {
247        int error = posix_acl_permission(inode, acl, mask);
248        posix_acl_release(acl);
249        return error;
250    }
251
252    return -EAGAIN;
253}
254
255int
256ext4_permission(struct inode *inode, int mask)
257{
258    return generic_permission(inode, mask, ext4_check_acl);
259}
260
261/*
262 * Initialize the ACLs of a new inode. Called from ext4_new_inode.
263 *
264 * dir->i_mutex: down
265 * inode->i_mutex: up (access to inode is still exclusive)
266 */
267int
268ext4_init_acl(handle_t *handle, struct inode *inode, struct inode *dir)
269{
270    struct posix_acl *acl = NULL;
271    int error = 0;
272
273    if (!S_ISLNK(inode->i_mode)) {
274        if (test_opt(dir->i_sb, POSIX_ACL)) {
275            acl = ext4_get_acl(dir, ACL_TYPE_DEFAULT);
276            if (IS_ERR(acl))
277                return PTR_ERR(acl);
278        }
279        if (!acl)
280            inode->i_mode &= ~current_umask();
281    }
282    if (test_opt(inode->i_sb, POSIX_ACL) && acl) {
283        struct posix_acl *clone;
284        mode_t mode;
285
286        if (S_ISDIR(inode->i_mode)) {
287            error = ext4_set_acl(handle, inode,
288                         ACL_TYPE_DEFAULT, acl);
289            if (error)
290                goto cleanup;
291        }
292        clone = posix_acl_clone(acl, GFP_NOFS);
293        error = -ENOMEM;
294        if (!clone)
295            goto cleanup;
296
297        mode = inode->i_mode;
298        error = posix_acl_create_masq(clone, &mode);
299        if (error >= 0) {
300            inode->i_mode = mode;
301            if (error > 0) {
302                /* This is an extended ACL */
303                error = ext4_set_acl(handle, inode,
304                             ACL_TYPE_ACCESS, clone);
305            }
306        }
307        posix_acl_release(clone);
308    }
309cleanup:
310    posix_acl_release(acl);
311    return error;
312}
313
314/*
315 * Does chmod for an inode that may have an Access Control List. The
316 * inode->i_mode field must be updated to the desired value by the caller
317 * before calling this function.
318 * Returns 0 on success, or a negative error number.
319 *
320 * We change the ACL rather than storing some ACL entries in the file
321 * mode permission bits (which would be more efficient), because that
322 * would break once additional permissions (like ACL_APPEND, ACL_DELETE
323 * for directories) are added. There are no more bits available in the
324 * file mode.
325 *
326 * inode->i_mutex: down
327 */
328int
329ext4_acl_chmod(struct inode *inode)
330{
331    struct posix_acl *acl, *clone;
332    int error;
333
334    if (S_ISLNK(inode->i_mode))
335        return -EOPNOTSUPP;
336    if (!test_opt(inode->i_sb, POSIX_ACL))
337        return 0;
338    acl = ext4_get_acl(inode, ACL_TYPE_ACCESS);
339    if (IS_ERR(acl) || !acl)
340        return PTR_ERR(acl);
341    clone = posix_acl_clone(acl, GFP_KERNEL);
342    posix_acl_release(acl);
343    if (!clone)
344        return -ENOMEM;
345    error = posix_acl_chmod_masq(clone, inode->i_mode);
346    if (!error) {
347        handle_t *handle;
348        int retries = 0;
349
350    retry:
351        handle = ext4_journal_start(inode,
352                EXT4_DATA_TRANS_BLOCKS(inode->i_sb));
353        if (IS_ERR(handle)) {
354            error = PTR_ERR(handle);
355            ext4_std_error(inode->i_sb, error);
356            goto out;
357        }
358        error = ext4_set_acl(handle, inode, ACL_TYPE_ACCESS, clone);
359        ext4_journal_stop(handle);
360        if (error == -ENOSPC &&
361            ext4_should_retry_alloc(inode->i_sb, &retries))
362            goto retry;
363    }
364out:
365    posix_acl_release(clone);
366    return error;
367}
368
369/*
370 * Extended attribute handlers
371 */
372static size_t
373ext4_xattr_list_acl_access(struct inode *inode, char *list, size_t list_len,
374               const char *name, size_t name_len)
375{
376    const size_t size = sizeof(POSIX_ACL_XATTR_ACCESS);
377
378    if (!test_opt(inode->i_sb, POSIX_ACL))
379        return 0;
380    if (list && size <= list_len)
381        memcpy(list, POSIX_ACL_XATTR_ACCESS, size);
382    return size;
383}
384
385static size_t
386ext4_xattr_list_acl_default(struct inode *inode, char *list, size_t list_len,
387                const char *name, size_t name_len)
388{
389    const size_t size = sizeof(POSIX_ACL_XATTR_DEFAULT);
390
391    if (!test_opt(inode->i_sb, POSIX_ACL))
392        return 0;
393    if (list && size <= list_len)
394        memcpy(list, POSIX_ACL_XATTR_DEFAULT, size);
395    return size;
396}
397
398static int
399ext4_xattr_get_acl(struct inode *inode, int type, void *buffer, size_t size)
400{
401    struct posix_acl *acl;
402    int error;
403
404    if (!test_opt(inode->i_sb, POSIX_ACL))
405        return -EOPNOTSUPP;
406
407    acl = ext4_get_acl(inode, type);
408    if (IS_ERR(acl))
409        return PTR_ERR(acl);
410    if (acl == NULL)
411        return -ENODATA;
412    error = posix_acl_to_xattr(acl, buffer, size);
413    posix_acl_release(acl);
414
415    return error;
416}
417
418static int
419ext4_xattr_get_acl_access(struct inode *inode, const char *name,
420              void *buffer, size_t size)
421{
422    if (strcmp(name, "") != 0)
423        return -EINVAL;
424    return ext4_xattr_get_acl(inode, ACL_TYPE_ACCESS, buffer, size);
425}
426
427static int
428ext4_xattr_get_acl_default(struct inode *inode, const char *name,
429               void *buffer, size_t size)
430{
431    if (strcmp(name, "") != 0)
432        return -EINVAL;
433    return ext4_xattr_get_acl(inode, ACL_TYPE_DEFAULT, buffer, size);
434}
435
436static int
437ext4_xattr_set_acl(struct inode *inode, int type, const void *value,
438           size_t size)
439{
440    handle_t *handle;
441    struct posix_acl *acl;
442    int error, retries = 0;
443
444    if (!test_opt(inode->i_sb, POSIX_ACL))
445        return -EOPNOTSUPP;
446    if (!is_owner_or_cap(inode))
447        return -EPERM;
448
449    if (value) {
450        acl = posix_acl_from_xattr(value, size);
451        if (IS_ERR(acl))
452            return PTR_ERR(acl);
453        else if (acl) {
454            error = posix_acl_valid(acl);
455            if (error)
456                goto release_and_out;
457        }
458    } else
459        acl = NULL;
460
461retry:
462    handle = ext4_journal_start(inode, EXT4_DATA_TRANS_BLOCKS(inode->i_sb));
463    if (IS_ERR(handle))
464        return PTR_ERR(handle);
465    error = ext4_set_acl(handle, inode, type, acl);
466    ext4_journal_stop(handle);
467    if (error == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
468        goto retry;
469
470release_and_out:
471    posix_acl_release(acl);
472    return error;
473}
474
475static int
476ext4_xattr_set_acl_access(struct inode *inode, const char *name,
477              const void *value, size_t size, int flags)
478{
479    if (strcmp(name, "") != 0)
480        return -EINVAL;
481    return ext4_xattr_set_acl(inode, ACL_TYPE_ACCESS, value, size);
482}
483
484static int
485ext4_xattr_set_acl_default(struct inode *inode, const char *name,
486               const void *value, size_t size, int flags)
487{
488    if (strcmp(name, "") != 0)
489        return -EINVAL;
490    return ext4_xattr_set_acl(inode, ACL_TYPE_DEFAULT, value, size);
491}
492
493struct xattr_handler ext4_xattr_acl_access_handler = {
494    .prefix = POSIX_ACL_XATTR_ACCESS,
495    .list = ext4_xattr_list_acl_access,
496    .get = ext4_xattr_get_acl_access,
497    .set = ext4_xattr_set_acl_access,
498};
499
500struct xattr_handler ext4_xattr_acl_default_handler = {
501    .prefix = POSIX_ACL_XATTR_DEFAULT,
502    .list = ext4_xattr_list_acl_default,
503    .get = ext4_xattr_get_acl_default,
504    .set = ext4_xattr_set_acl_default,
505};
506

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