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