168252eb5SThomas Gleixner // SPDX-License-Identifier: GPL-2.0-or-later
2122edd15SPhillip Lougher /*
3122edd15SPhillip Lougher * Squashfs - a compressed read only filesystem for Linux
4122edd15SPhillip Lougher *
5122edd15SPhillip Lougher * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
6d7f2ff67SPhillip Lougher * Phillip Lougher <phillip@squashfs.org.uk>
7122edd15SPhillip Lougher *
8122edd15SPhillip Lougher * fragment.c
9122edd15SPhillip Lougher */
10122edd15SPhillip Lougher
11122edd15SPhillip Lougher /*
12122edd15SPhillip Lougher * This file implements code to handle compressed fragments (tail-end packed
13122edd15SPhillip Lougher * datablocks).
14122edd15SPhillip Lougher *
15122edd15SPhillip Lougher * Regular files contain a fragment index which is mapped to a fragment
16122edd15SPhillip Lougher * location on disk and compressed size using a fragment lookup table.
17122edd15SPhillip Lougher * Like everything in Squashfs this fragment lookup table is itself stored
18122edd15SPhillip Lougher * compressed into metadata blocks. A second index table is used to locate
19122edd15SPhillip Lougher * these. This second index table for speed of access (and because it
20122edd15SPhillip Lougher * is small) is read at mount time and cached in memory.
21122edd15SPhillip Lougher */
22122edd15SPhillip Lougher
23122edd15SPhillip Lougher #include <linux/fs.h>
24122edd15SPhillip Lougher #include <linux/vfs.h>
25122edd15SPhillip Lougher #include <linux/slab.h>
26122edd15SPhillip Lougher
27122edd15SPhillip Lougher #include "squashfs_fs.h"
28122edd15SPhillip Lougher #include "squashfs_fs_sb.h"
29122edd15SPhillip Lougher #include "squashfs.h"
30122edd15SPhillip Lougher
31122edd15SPhillip Lougher /*
32122edd15SPhillip Lougher * Look-up fragment using the fragment index table. Return the on disk
33122edd15SPhillip Lougher * location of the fragment and its compressed size
34122edd15SPhillip Lougher */
squashfs_frag_lookup(struct super_block * sb,unsigned int fragment,u64 * fragment_block)35122edd15SPhillip Lougher int squashfs_frag_lookup(struct super_block *sb, unsigned int fragment,
36122edd15SPhillip Lougher u64 *fragment_block)
37122edd15SPhillip Lougher {
38122edd15SPhillip Lougher struct squashfs_sb_info *msblk = sb->s_fs_info;
3971755ee5SLinus Torvalds int block, offset, size;
40122edd15SPhillip Lougher struct squashfs_fragment_entry fragment_entry;
4171755ee5SLinus Torvalds u64 start_block;
4271755ee5SLinus Torvalds
4371755ee5SLinus Torvalds if (fragment >= msblk->fragments)
4471755ee5SLinus Torvalds return -EIO;
4571755ee5SLinus Torvalds block = SQUASHFS_FRAGMENT_INDEX(fragment);
4671755ee5SLinus Torvalds offset = SQUASHFS_FRAGMENT_INDEX_OFFSET(fragment);
4771755ee5SLinus Torvalds
4871755ee5SLinus Torvalds start_block = le64_to_cpu(msblk->fragment_index[block]);
49122edd15SPhillip Lougher
50122edd15SPhillip Lougher size = squashfs_read_metadata(sb, &fragment_entry, &start_block,
51122edd15SPhillip Lougher &offset, sizeof(fragment_entry));
52122edd15SPhillip Lougher if (size < 0)
53122edd15SPhillip Lougher return size;
54122edd15SPhillip Lougher
55122edd15SPhillip Lougher *fragment_block = le64_to_cpu(fragment_entry.start_block);
5601cfb793SLinus Torvalds return squashfs_block_size(fragment_entry.size);
57122edd15SPhillip Lougher }
58122edd15SPhillip Lougher
59122edd15SPhillip Lougher
60122edd15SPhillip Lougher /*
61122edd15SPhillip Lougher * Read the uncompressed fragment lookup table indexes off disk into memory
62122edd15SPhillip Lougher */
squashfs_read_fragment_index_table(struct super_block * sb,u64 fragment_table_start,u64 next_table,unsigned int fragments)63122edd15SPhillip Lougher __le64 *squashfs_read_fragment_index_table(struct super_block *sb,
641cac63ccSPhillip Lougher u64 fragment_table_start, u64 next_table, unsigned int fragments)
65122edd15SPhillip Lougher {
66122edd15SPhillip Lougher unsigned int length = SQUASHFS_FRAGMENT_INDEX_BYTES(fragments);
671cac63ccSPhillip Lougher __le64 *table;
68122edd15SPhillip Lougher
691cac63ccSPhillip Lougher /*
701cac63ccSPhillip Lougher * Sanity check, length bytes should not extend into the next table -
711cac63ccSPhillip Lougher * this check also traps instances where fragment_table_start is
721cac63ccSPhillip Lougher * incorrectly larger than the next table start
731cac63ccSPhillip Lougher */
741cac63ccSPhillip Lougher if (fragment_table_start + length > next_table)
751cac63ccSPhillip Lougher return ERR_PTR(-EINVAL);
761cac63ccSPhillip Lougher
771cac63ccSPhillip Lougher table = squashfs_read_table(sb, fragment_table_start, length);
781cac63ccSPhillip Lougher
791cac63ccSPhillip Lougher /*
801cac63ccSPhillip Lougher * table[0] points to the first fragment table metadata block, this
811cac63ccSPhillip Lougher * should be less than fragment_table_start
821cac63ccSPhillip Lougher */
83d5b72ce1SPhillip Lougher if (!IS_ERR(table) && le64_to_cpu(table[0]) >= fragment_table_start) {
841cac63ccSPhillip Lougher kfree(table);
851cac63ccSPhillip Lougher return ERR_PTR(-EINVAL);
861cac63ccSPhillip Lougher }
871cac63ccSPhillip Lougher
881cac63ccSPhillip Lougher return table;
89122edd15SPhillip Lougher }
90