LXR linux/fs/squashfs/fragment.c

   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