1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Squashfs - a compressed read only filesystem for Linux
4 *
5 * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
6 * Phillip Lougher <phillip@squashfs.org.uk>
7 *
8 * id.c
9 */
10
11/*
12 * This file implements code to handle uids and gids.
13 *
14 * For space efficiency regular files store uid and gid indexes, which are
15 * converted to 32-bit uids/gids using an id look up table. This table is
16 * stored compressed into metadata blocks. A second index table is used to
17 * locate these. This second index table for speed of access (and because it
18 * is small) is read at mount time and cached in memory.
19 */
20
21#include <linux/fs.h>
22#include <linux/vfs.h>
23#include <linux/slab.h>
24
25#include "squashfs_fs.h"
26#include "squashfs_fs_sb.h"
27#include "squashfs.h"
28
29/*
30 * Map uid/gid index into real 32-bit uid/gid using the id look up table
31 */
32int squashfs_get_id(struct super_block *sb, unsigned int index,
33 unsigned int *id)
34{
35 struct squashfs_sb_info *msblk = sb->s_fs_info;
36 int block = SQUASHFS_ID_BLOCK(index);
37 int offset = SQUASHFS_ID_BLOCK_OFFSET(index);
38 u64 start_block;
39 __le32 disk_id;
40 int err;
41
42 if (index >= msblk->ids)
43 return -EINVAL;
44
45 start_block = le64_to_cpu(msblk->id_table[block]);
46
47 err = squashfs_read_metadata(sb, &disk_id, &start_block, &offset,
48 sizeof(disk_id));
49 if (err < 0)
50 return err;
51
52 *id = le32_to_cpu(disk_id);
53 return 0;
54}
55
56
57/*
58 * Read uncompressed id lookup table indexes from disk into memory
59 */
60__le64 *squashfs_read_id_index_table(struct super_block *sb,
61 u64 id_table_start, u64 next_table, unsigned short no_ids)
62{
63 unsigned int length = SQUASHFS_ID_BLOCK_BYTES(no_ids);
64 unsigned int indexes = SQUASHFS_ID_BLOCKS(no_ids);
65 int n;
66 __le64 *table;
67 u64 start, end;
68
69 TRACE("In read_id_index_table, length %d\n", length);
70
71 /* Sanity check values */
72
73 /* there should always be at least one id */
74 if (no_ids == 0)
75 return ERR_PTR(error: -EINVAL);
76
77 /*
78 * The computed size of the index table (length bytes) should exactly
79 * match the table start and end points
80 */
81 if (length != (next_table - id_table_start))
82 return ERR_PTR(error: -EINVAL);
83
84 table = squashfs_read_table(sb, id_table_start, length);
85 if (IS_ERR(ptr: table))
86 return table;
87
88 /*
89 * table[0], table[1], ... table[indexes - 1] store the locations
90 * of the compressed id blocks. Each entry should be less than
91 * the next (i.e. table[0] < table[1]), and the difference between them
92 * should be SQUASHFS_METADATA_SIZE or less. table[indexes - 1]
93 * should be less than id_table_start, and again the difference
94 * should be SQUASHFS_METADATA_SIZE or less
95 */
96 for (n = 0; n < (indexes - 1); n++) {
97 start = le64_to_cpu(table[n]);
98 end = le64_to_cpu(table[n + 1]);
99
100 if (start >= end || (end - start) >
101 (SQUASHFS_METADATA_SIZE + SQUASHFS_BLOCK_OFFSET)) {
102 kfree(objp: table);
103 return ERR_PTR(error: -EINVAL);
104 }
105 }
106
107 start = le64_to_cpu(table[indexes - 1]);
108 if (start >= id_table_start || (id_table_start - start) >
109 (SQUASHFS_METADATA_SIZE + SQUASHFS_BLOCK_OFFSET)) {
110 kfree(objp: table);
111 return ERR_PTR(error: -EINVAL);
112 }
113
114 return table;
115}
116

source code of linux/fs/squashfs/id.c