Root/fs/btrfs/xattr.c

1/*
2 * Copyright (C) 2007 Red Hat. All rights reserved.
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public
6 * License v2 as published by the Free Software Foundation.
7 *
8 * This program is distributed in the hope that it will be useful,
9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
11 * General Public License for more details.
12 *
13 * You should have received a copy of the GNU General Public
14 * License along with this program; if not, write to the
15 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
16 * Boston, MA 021110-1307, USA.
17 */
18
19#include <linux/init.h>
20#include <linux/fs.h>
21#include <linux/slab.h>
22#include <linux/rwsem.h>
23#include <linux/xattr.h>
24#include <linux/security.h>
25#include "ctree.h"
26#include "btrfs_inode.h"
27#include "transaction.h"
28#include "xattr.h"
29#include "disk-io.h"
30
31
32ssize_t __btrfs_getxattr(struct inode *inode, const char *name,
33                void *buffer, size_t size)
34{
35    struct btrfs_dir_item *di;
36    struct btrfs_root *root = BTRFS_I(inode)->root;
37    struct btrfs_path *path;
38    struct extent_buffer *leaf;
39    int ret = 0;
40    unsigned long data_ptr;
41
42    path = btrfs_alloc_path();
43    if (!path)
44        return -ENOMEM;
45
46    /* lookup the xattr by name */
47    di = btrfs_lookup_xattr(NULL, root, path, inode->i_ino, name,
48                strlen(name), 0);
49    if (!di) {
50        ret = -ENODATA;
51        goto out;
52    } else if (IS_ERR(di)) {
53        ret = PTR_ERR(di);
54        goto out;
55    }
56
57    leaf = path->nodes[0];
58    /* if size is 0, that means we want the size of the attr */
59    if (!size) {
60        ret = btrfs_dir_data_len(leaf, di);
61        goto out;
62    }
63
64    /* now get the data out of our dir_item */
65    if (btrfs_dir_data_len(leaf, di) > size) {
66        ret = -ERANGE;
67        goto out;
68    }
69
70    /*
71     * The way things are packed into the leaf is like this
72     * |struct btrfs_dir_item|name|data|
73     * where name is the xattr name, so security.foo, and data is the
74     * content of the xattr. data_ptr points to the location in memory
75     * where the data starts in the in memory leaf
76     */
77    data_ptr = (unsigned long)((char *)(di + 1) +
78                   btrfs_dir_name_len(leaf, di));
79    read_extent_buffer(leaf, buffer, data_ptr,
80               btrfs_dir_data_len(leaf, di));
81    ret = btrfs_dir_data_len(leaf, di);
82
83out:
84    btrfs_free_path(path);
85    return ret;
86}
87
88static int do_setxattr(struct btrfs_trans_handle *trans,
89               struct inode *inode, const char *name,
90               const void *value, size_t size, int flags)
91{
92    struct btrfs_dir_item *di;
93    struct btrfs_root *root = BTRFS_I(inode)->root;
94    struct btrfs_path *path;
95    size_t name_len = strlen(name);
96    int ret = 0;
97
98    if (name_len + size > BTRFS_MAX_XATTR_SIZE(root))
99        return -ENOSPC;
100
101    path = btrfs_alloc_path();
102    if (!path)
103        return -ENOMEM;
104
105    /* first lets see if we already have this xattr */
106    di = btrfs_lookup_xattr(trans, root, path, inode->i_ino, name,
107                strlen(name), -1);
108    if (IS_ERR(di)) {
109        ret = PTR_ERR(di);
110        goto out;
111    }
112
113    /* ok we already have this xattr, lets remove it */
114    if (di) {
115        /* if we want create only exit */
116        if (flags & XATTR_CREATE) {
117            ret = -EEXIST;
118            goto out;
119        }
120
121        ret = btrfs_delete_one_dir_name(trans, root, path, di);
122        BUG_ON(ret);
123        btrfs_release_path(root, path);
124
125        /* if we don't have a value then we are removing the xattr */
126        if (!value)
127            goto out;
128    } else {
129        btrfs_release_path(root, path);
130
131        if (flags & XATTR_REPLACE) {
132            /* we couldn't find the attr to replace */
133            ret = -ENODATA;
134            goto out;
135        }
136    }
137
138    /* ok we have to create a completely new xattr */
139    ret = btrfs_insert_xattr_item(trans, root, path, inode->i_ino,
140                      name, name_len, value, size);
141    BUG_ON(ret);
142out:
143    btrfs_free_path(path);
144    return ret;
145}
146
147int __btrfs_setxattr(struct btrfs_trans_handle *trans,
148             struct inode *inode, const char *name,
149             const void *value, size_t size, int flags)
150{
151    struct btrfs_root *root = BTRFS_I(inode)->root;
152    int ret;
153
154    if (trans)
155        return do_setxattr(trans, inode, name, value, size, flags);
156
157    ret = btrfs_reserve_metadata_space(root, 2);
158    if (ret)
159        return ret;
160
161    trans = btrfs_start_transaction(root, 1);
162    if (!trans) {
163        ret = -ENOMEM;
164        goto out;
165    }
166    btrfs_set_trans_block_group(trans, inode);
167
168    ret = do_setxattr(trans, inode, name, value, size, flags);
169    if (ret)
170        goto out;
171
172    inode->i_ctime = CURRENT_TIME;
173    ret = btrfs_update_inode(trans, root, inode);
174    BUG_ON(ret);
175out:
176    btrfs_end_transaction_throttle(trans, root);
177    btrfs_unreserve_metadata_space(root, 2);
178    return ret;
179}
180
181ssize_t btrfs_listxattr(struct dentry *dentry, char *buffer, size_t size)
182{
183    struct btrfs_key key, found_key;
184    struct inode *inode = dentry->d_inode;
185    struct btrfs_root *root = BTRFS_I(inode)->root;
186    struct btrfs_path *path;
187    struct btrfs_item *item;
188    struct extent_buffer *leaf;
189    struct btrfs_dir_item *di;
190    int ret = 0, slot, advance;
191    size_t total_size = 0, size_left = size;
192    unsigned long name_ptr;
193    size_t name_len;
194    u32 nritems;
195
196    /*
197     * ok we want all objects associated with this id.
198     * NOTE: we set key.offset = 0; because we want to start with the
199     * first xattr that we find and walk forward
200     */
201    key.objectid = inode->i_ino;
202    btrfs_set_key_type(&key, BTRFS_XATTR_ITEM_KEY);
203    key.offset = 0;
204
205    path = btrfs_alloc_path();
206    if (!path)
207        return -ENOMEM;
208    path->reada = 2;
209
210    /* search for our xattrs */
211    ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
212    if (ret < 0)
213        goto err;
214    advance = 0;
215    while (1) {
216        leaf = path->nodes[0];
217        nritems = btrfs_header_nritems(leaf);
218        slot = path->slots[0];
219
220        /* this is where we start walking through the path */
221        if (advance || slot >= nritems) {
222            /*
223             * if we've reached the last slot in this leaf we need
224             * to go to the next leaf and reset everything
225             */
226            if (slot >= nritems-1) {
227                ret = btrfs_next_leaf(root, path);
228                if (ret)
229                    break;
230                leaf = path->nodes[0];
231                nritems = btrfs_header_nritems(leaf);
232                slot = path->slots[0];
233            } else {
234                /*
235                 * just walking through the slots on this leaf
236                 */
237                slot++;
238                path->slots[0]++;
239            }
240        }
241        advance = 1;
242
243        item = btrfs_item_nr(leaf, slot);
244        btrfs_item_key_to_cpu(leaf, &found_key, slot);
245
246        /* check to make sure this item is what we want */
247        if (found_key.objectid != key.objectid)
248            break;
249        if (btrfs_key_type(&found_key) != BTRFS_XATTR_ITEM_KEY)
250            break;
251
252        di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
253
254        name_len = btrfs_dir_name_len(leaf, di);
255        total_size += name_len + 1;
256
257        /* we are just looking for how big our buffer needs to be */
258        if (!size)
259            continue;
260
261        if (!buffer || (name_len + 1) > size_left) {
262            ret = -ERANGE;
263            goto err;
264        }
265
266        name_ptr = (unsigned long)(di + 1);
267        read_extent_buffer(leaf, buffer, name_ptr, name_len);
268        buffer[name_len] = '\0';
269
270        size_left -= name_len + 1;
271        buffer += name_len + 1;
272    }
273    ret = total_size;
274
275err:
276    btrfs_free_path(path);
277
278    return ret;
279}
280
281/*
282 * List of handlers for synthetic system.* attributes. All real ondisk
283 * attributes are handled directly.
284 */
285struct xattr_handler *btrfs_xattr_handlers[] = {
286#ifdef CONFIG_BTRFS_FS_POSIX_ACL
287    &btrfs_xattr_acl_access_handler,
288    &btrfs_xattr_acl_default_handler,
289#endif
290    NULL,
291};
292
293/*
294 * Check if the attribute is in a supported namespace.
295 *
296 * This applied after the check for the synthetic attributes in the system
297 * namespace.
298 */
299static bool btrfs_is_valid_xattr(const char *name)
300{
301    return !strncmp(name, XATTR_SECURITY_PREFIX,
302            XATTR_SECURITY_PREFIX_LEN) ||
303           !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN) ||
304           !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) ||
305           !strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN);
306}
307
308ssize_t btrfs_getxattr(struct dentry *dentry, const char *name,
309               void *buffer, size_t size)
310{
311    /*
312     * If this is a request for a synthetic attribute in the system.*
313     * namespace use the generic infrastructure to resolve a handler
314     * for it via sb->s_xattr.
315     */
316    if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
317        return generic_getxattr(dentry, name, buffer, size);
318
319    if (!btrfs_is_valid_xattr(name))
320        return -EOPNOTSUPP;
321    return __btrfs_getxattr(dentry->d_inode, name, buffer, size);
322}
323
324int btrfs_setxattr(struct dentry *dentry, const char *name, const void *value,
325           size_t size, int flags)
326{
327    /*
328     * If this is a request for a synthetic attribute in the system.*
329     * namespace use the generic infrastructure to resolve a handler
330     * for it via sb->s_xattr.
331     */
332    if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
333        return generic_setxattr(dentry, name, value, size, flags);
334
335    if (!btrfs_is_valid_xattr(name))
336        return -EOPNOTSUPP;
337
338    if (size == 0)
339        value = ""; /* empty EA, do not remove */
340
341    return __btrfs_setxattr(NULL, dentry->d_inode, name, value, size,
342                flags);
343}
344
345int btrfs_removexattr(struct dentry *dentry, const char *name)
346{
347    /*
348     * If this is a request for a synthetic attribute in the system.*
349     * namespace use the generic infrastructure to resolve a handler
350     * for it via sb->s_xattr.
351     */
352    if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
353        return generic_removexattr(dentry, name);
354
355    if (!btrfs_is_valid_xattr(name))
356        return -EOPNOTSUPP;
357
358    return __btrfs_setxattr(NULL, dentry->d_inode, name, NULL, 0,
359                XATTR_REPLACE);
360}
361
362int btrfs_xattr_security_init(struct btrfs_trans_handle *trans,
363                  struct inode *inode, struct inode *dir)
364{
365    int err;
366    size_t len;
367    void *value;
368    char *suffix;
369    char *name;
370
371    err = security_inode_init_security(inode, dir, &suffix, &value, &len);
372    if (err) {
373        if (err == -EOPNOTSUPP)
374            return 0;
375        return err;
376    }
377
378    name = kmalloc(XATTR_SECURITY_PREFIX_LEN + strlen(suffix) + 1,
379               GFP_NOFS);
380    if (!name) {
381        err = -ENOMEM;
382    } else {
383        strcpy(name, XATTR_SECURITY_PREFIX);
384        strcpy(name + XATTR_SECURITY_PREFIX_LEN, suffix);
385        err = __btrfs_setxattr(trans, inode, name, value, len, 0);
386        kfree(name);
387    }
388
389    kfree(suffix);
390    kfree(value);
391    return err;
392}
393

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