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1// SPDX-License-Identifier: GPL-2.0-or-later2/*3 * Squashfs - a compressed read only filesystem for Linux4 *5 * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 20086 * Phillip Lougher <phillip@squashfs.org.uk>7 *8 * fragment.c9 */10 11/*12 * This file implements code to handle compressed fragments (tail-end packed13 * datablocks).14 *15 * Regular files contain a fragment index which is mapped to a fragment16 * location on disk and compressed size using a fragment lookup table.17 * Like everything in Squashfs this fragment lookup table is itself stored18 * compressed into metadata blocks. A second index table is used to locate19 * these. This second index table for speed of access (and because it20 * 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 disk33 * location of the fragment and its compressed size34 */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 memory62 */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 is72 * incorrectly larger than the next table start73 */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, this81 * should be less than fragment_table_start82 */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