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  */
squashfs_frag_lookup(struct super_block * sb,unsigned int fragment,u64 * fragment_block)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  */
squashfs_read_fragment_index_table(struct super_block * sb,u64 fragment_table_start,u64 next_table,unsigned int fragments)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