source: src/linux/universal/linux-4.9/fs/squashfs/id.c @ 31630

Last change on this file since 31630 was 31630, checked in by brainslayer, 7 weeks ago

new fs is compatible with standard squashfs, just smaller

File size: 2.9 KB
Line 
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 */
45int 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 = le64_to_cpu(msblk->id_table[block]);
52        __le32 disk_id;
53        int err;
54
55        err = squashfs_read_metadata(sb, &disk_id, &start_block, &offset,
56                                                        sizeof(disk_id));
57        if (err < 0)
58                return err;
59
60        *id = le32_to_cpu(disk_id);
61        return 0;
62}
63
64
65/*
66 * Read uncompressed id lookup table indexes from disk into memory
67 */
68__le64 *squashfs_read_id_index_table(struct super_block *sb,
69                u64 id_table_start, u64 next_table, unsigned short no_ids)
70{
71        unsigned int length = SQUASHFS_ID_BLOCK_BYTES(no_ids);
72        __le64 *table;
73
74        TRACE("In read_id_index_table, length %d\n", length);
75
76        /* Sanity check values */
77
78        /* there should always be at least one id */
79        if (no_ids == 0)
80                return ERR_PTR(-EINVAL);
81
82        /*
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
86         */
87        if (id_table_start + length > next_table)
88                return ERR_PTR(-EINVAL);
89
90        table = squashfs_read_table(sb, id_table_start, length);
91
92        /*
93         * table[0] points to the first id lookup table metadata block, this
94         * should be less than id_table_start
95         */
96        if (!IS_ERR(table) && le64_to_cpu(table[0]) >= id_table_start) {
97                kfree(table);
98                return ERR_PTR(-EINVAL);
99        }
100
101        return table;
102}
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