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 * fragment.c
9 */
10
11 /*
12 * This file implements code to handle compressed fragments (tail-end packed
13 * datablocks).
14 *
15 * Regular files contain a fragment index which is mapped to a fragment
16 * location on disk and compressed size using a fragment lookup table.
17 * Like everything in Squashfs this fragment lookup table is itself stored
18 * compressed into metadata blocks. A second index table is used to locate
19 * these. This second index table for speed of access (and because it
20 * is small) is read at mount time and cached in memory.
21 */
22
23 #include <linux/fs.h>
24 #include <linux/vfs.h>
25 #include <linux/slab.h>
26
27 #include "squashfs_fs.h"
28 #include "squashfs_fs_sb.h"
29 #include "squashfs.h"
30
31 /*
32 * Look-up fragment using the fragment index table. Return the on disk
33 * location of the fragment and its compressed size
34 */
35 int squashfs_frag_lookup(struct super_block *sb, unsigned int fragment,
36 u64 *fragment_block)
37 {
38 struct squashfs_sb_info *msblk = sb->s_fs_info;
39 int block, offset, size;
40 struct squashfs_fragment_entry fragment_entry;
41 u64 start_block;
42
43 if (fragment >= msblk->fragments)
44 return -EIO;
45 block = SQUASHFS_FRAGMENT_INDEX(fragment);
46 offset = SQUASHFS_FRAGMENT_INDEX_OFFSET(fragment);
47
48 start_block = le64_to_cpu(msblk->fragment_index[block]);
49
50 size = squashfs_read_metadata(sb, &fragment_entry, &start_block,
51 &offset, sizeof(fragment_entry));
52 if (size < 0)
53 return size;
54
55 *fragment_block = le64_to_cpu(fragment_entry.start_block);
56 return squashfs_block_size(fragment_entry.size);
57 }
58
59
60 /*
61 * Read the uncompressed fragment lookup table indexes off disk into memory
62 */
63 __le64 *squashfs_read_fragment_index_table(struct super_block *sb,
64 u64 fragment_table_start, u64 next_table, unsigned int fragments)
65 {
66 unsigned int length = SQUASHFS_FRAGMENT_INDEX_BYTES(fragments);
67 __le64 *table;
68
69 /*
70 * Sanity check, length bytes should not extend into the next table -
71 * this check also traps instances where fragment_table_start is
72 * incorrectly larger than the next table start
73 */
74 if (fragment_table_start + length > next_table)
75 return ERR_PTR(-EINVAL);
76
77 table = squashfs_read_table(sb, fragment_table_start, length);
78
79 /*
80 * table[0] points to the first fragment table metadata block, this
81 * should be less than fragment_table_start
82 */
83 if (!IS_ERR(table) && le64_to_cpu(table[0]) >= fragment_table_start) {
84 kfree(table);
85 return ERR_PTR(-EINVAL);
86 }
87
88 return table;
89 }
90
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