1 /*
2 * Squashfs - a compressed read only filesystem for Linux
3 *
4 * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
5 * Phillip Lougher <phillip@squashfs.org.uk>
6 *
7 * This program is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU General Public License
9 * as published by the Free Software Foundation; either version 2,
10 * or (at your option) any later version.
11 *
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License
18 * along with this program; if not, write to the Free Software
19 * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
20 *
21 * id.c
22 */
23
24 /*
25 * This file implements code to handle uids and gids.
26 *
27 * For space efficiency regular files store uid and gid indexes, which are
28 * converted to 32-bit uids/gids using an id look up table. This table is
29 * stored compressed into metadata blocks. A second index table is used to
30 * locate these. This second index table for speed of access (and because it
31 * is small) is read at mount time and cached in memory.
32 */
33
34 #include <linux/fs.h>
35 #include <linux/vfs.h>
36 #include <linux/slab.h>
37
38 #include "squashfs_fs.h"
39 #include "squashfs_fs_sb.h"
40 #include "squashfs.h"
41
42 /*
43 * Map uid/gid index into real 32-bit uid/gid using the id look up table
44 */
squashfs_get_id(struct super_block * sb,unsigned int index,unsigned int * id)45 int squashfs_get_id(struct super_block *sb, unsigned int index,
46 unsigned int *id)
47 {
48 struct squashfs_sb_info *msblk = sb->s_fs_info;
49 int block = SQUASHFS_ID_BLOCK(index);
50 int offset = SQUASHFS_ID_BLOCK_OFFSET(index);
51 u64 start_block;
52 __le32 disk_id;
53 int err;
54
55 if (index >= msblk->ids)
56 return -EINVAL;
57
58 start_block = le64_to_cpu(msblk->id_table[block]);
59
60 err = squashfs_read_metadata(sb, &disk_id, &start_block, &offset,
61 sizeof(disk_id));
62 if (err < 0)
63 return err;
64
65 *id = le32_to_cpu(disk_id);
66 return 0;
67 }
68
69
70 /*
71 * Read uncompressed id lookup table indexes from disk into memory
72 */
squashfs_read_id_index_table(struct super_block * sb,u64 id_table_start,u64 next_table,unsigned short no_ids)73 __le64 *squashfs_read_id_index_table(struct super_block *sb,
74 u64 id_table_start, u64 next_table, unsigned short no_ids)
75 {
76 unsigned int length = SQUASHFS_ID_BLOCK_BYTES(no_ids);
77 unsigned int indexes = SQUASHFS_ID_BLOCKS(no_ids);
78 int n;
79 __le64 *table;
80 u64 start, end;
81
82 TRACE("In read_id_index_table, length %d\n", length);
83
84 /* Sanity check values */
85
86 /* there should always be at least one id */
87 if (no_ids == 0)
88 return ERR_PTR(-EINVAL);
89
90 /*
91 * The computed size of the index table (length bytes) should exactly
92 * match the table start and end points
93 */
94 if (length != (next_table - id_table_start))
95 return ERR_PTR(-EINVAL);
96
97 table = squashfs_read_table(sb, id_table_start, length);
98 if (IS_ERR(table))
99 return table;
100
101 /*
102 * table[0], table[1], ... table[indexes - 1] store the locations
103 * of the compressed id blocks. Each entry should be less than
104 * the next (i.e. table[0] < table[1]), and the difference between them
105 * should be SQUASHFS_METADATA_SIZE or less. table[indexes - 1]
106 * should be less than id_table_start, and again the difference
107 * should be SQUASHFS_METADATA_SIZE or less
108 */
109 for (n = 0; n < (indexes - 1); n++) {
110 start = le64_to_cpu(table[n]);
111 end = le64_to_cpu(table[n + 1]);
112
113 if (start >= end || (end - start) >
114 (SQUASHFS_METADATA_SIZE + SQUASHFS_BLOCK_OFFSET)) {
115 kfree(table);
116 return ERR_PTR(-EINVAL);
117 }
118 }
119
120 start = le64_to_cpu(table[indexes - 1]);
121 if (start >= id_table_start || (id_table_start - start) >
122 (SQUASHFS_METADATA_SIZE + SQUASHFS_BLOCK_OFFSET)) {
123 kfree(table);
124 return ERR_PTR(-EINVAL);
125 }
126
127 return table;
128 }
129