2 * Squashfs - a compressed read only filesystem for Linux
4 * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
5 * Phillip Lougher <phillip@squashfs.org.uk>
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.
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.
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.
25 * This file implements code to handle uids and gids.
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.
35 #include <linux/vfs.h>
36 #include <linux/slab.h>
38 #include "squashfs_fs.h"
39 #include "squashfs_fs_sb.h"
43 * Map uid/gid index into real 32-bit uid/gid using the id look up table
45 int squashfs_get_id(struct super_block
*sb
, unsigned int index
,
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
= le64_to_cpu(msblk
->id_table
[block
]);
55 err
= squashfs_read_metadata(sb
, &disk_id
, &start_block
, &offset
,
60 *id
= le32_to_cpu(disk_id
);
66 * Read uncompressed id lookup table indexes from disk into memory
68 __le64
*squashfs_read_id_index_table(struct super_block
*sb
,
69 u64 id_table_start
, u64 next_table
, unsigned short no_ids
)
71 unsigned int length
= SQUASHFS_ID_BLOCK_BYTES(no_ids
);
74 TRACE("In read_id_index_table, length %d\n", length
);
76 /* Sanity check values */
78 /* there should always be at least one id */
80 return ERR_PTR(-EINVAL
);
83 * length bytes should not extend into the next table - this check
84 * also traps instances where id_table_start is incorrectly larger
85 * than the next table start
87 if (id_table_start
+ length
> next_table
)
88 return ERR_PTR(-EINVAL
);
90 table
= squashfs_read_table(sb
, id_table_start
, length
);
93 * table[0] points to the first id lookup table metadata block, this
94 * should be less than id_table_start
96 if (!IS_ERR(table
) && le64_to_cpu(table
[0]) >= id_table_start
) {
98 return ERR_PTR(-EINVAL
);
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