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 */
35int 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