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 * block.c 9 */ 10 11 /* 12 * This file implements the low-level routines to read and decompress 13 * datablocks and metadata blocks. 14 */ 15 16 #include <linux/fs.h> 17 #include <linux/vfs.h> 18 #include <linux/slab.h> 19 #include <linux/string.h> 20 #include <linux/buffer_head.h> 21 #include <linux/bio.h> 22 23 #include "squashfs_fs.h" 24 #include "squashfs_fs_sb.h" 25 #include "squashfs.h" 26 #include "decompressor.h" 27 #include "page_actor.h" 28 29 /* 30 * Read the metadata block length, this is stored in the first two 31 * bytes of the metadata block. 32 */ 33 static struct buffer_head *get_block_length(struct super_block *sb, 34 u64 *cur_index, int *offset, int *length) 35 { 36 struct squashfs_sb_info *msblk = sb->s_fs_info; 37 struct buffer_head *bh; 38 39 bh = sb_bread(sb, *cur_index); 40 if (bh == NULL) 41 return NULL; 42 43 if (msblk->devblksize - *offset == 1) { 44 *length = (unsigned char) bh->b_data[*offset]; 45 put_bh(bh); 46 bh = sb_bread(sb, ++(*cur_index)); 47 if (bh == NULL) 48 return NULL; 49 *length |= (unsigned char) bh->b_data[0] << 8; 50 *offset = 1; 51 } else { 52 *length = (unsigned char) bh->b_data[*offset] | 53 (unsigned char) bh->b_data[*offset + 1] << 8; 54 *offset += 2; 55 56 if (*offset == msblk->devblksize) { 57 put_bh(bh); 58 bh = sb_bread(sb, ++(*cur_index)); 59 if (bh == NULL) 60 return NULL; 61 *offset = 0; 62 } 63 } 64 65 return bh; 66 } 67 68 69 /* 70 * Read and decompress a metadata block or datablock. Length is non-zero 71 * if a datablock is being read (the size is stored elsewhere in the 72 * filesystem), otherwise the length is obtained from the first two bytes of 73 * the metadata block. A bit in the length field indicates if the block 74 * is stored uncompressed in the filesystem (usually because compression 75 * generated a larger block - this does occasionally happen with compression 76 * algorithms). 77 */ 78 int squashfs_read_data(struct super_block *sb, u64 index, int length, 79 u64 *next_index, struct squashfs_page_actor *output) 80 { 81 struct squashfs_sb_info *msblk = sb->s_fs_info; 82 struct buffer_head **bh; 83 int offset = index & ((1 << msblk->devblksize_log2) - 1); 84 u64 cur_index = index >> msblk->devblksize_log2; 85 int bytes, compressed, b = 0, k = 0, avail, i; 86 87 bh = kcalloc(((output->length + msblk->devblksize - 1) 88 >> msblk->devblksize_log2) + 1, sizeof(*bh), GFP_KERNEL); 89 if (bh == NULL) 90 return -ENOMEM; 91 92 if (length) { 93 /* 94 * Datablock. 95 */ 96 bytes = -offset; 97 compressed = SQUASHFS_COMPRESSED_BLOCK(length); 98 length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length); 99 if (next_index) 100 *next_index = index + length; 101 102 TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n", 103 index, compressed ? "" : "un", length, output->length); 104 105 if (length < 0 || length > output->length || 106 (index + length) > msblk->bytes_used) 107 goto read_failure; 108 109 for (b = 0; bytes < length; b++, cur_index++) { 110 bh[b] = sb_getblk(sb, cur_index); 111 if (bh[b] == NULL) 112 goto block_release; 113 bytes += msblk->devblksize; 114 } 115 ll_rw_block(REQ_OP_READ, 0, b, bh); 116 } else { 117 /* 118 * Metadata block. 119 */ 120 if ((index + 2) > msblk->bytes_used) 121 goto read_failure; 122 123 bh[0] = get_block_length(sb, &cur_index, &offset, &length); 124 if (bh[0] == NULL) 125 goto read_failure; 126 b = 1; 127 128 bytes = msblk->devblksize - offset; 129 compressed = SQUASHFS_COMPRESSED(length); 130 length = SQUASHFS_COMPRESSED_SIZE(length); 131 if (next_index) 132 *next_index = index + length + 2; 133 134 TRACE("Block @ 0x%llx, %scompressed size %d\n", index, 135 compressed ? "" : "un", length); 136 137 if (length < 0 || length > output->length || 138 (index + length) > msblk->bytes_used) 139 goto block_release; 140 141 for (; bytes < length; b++) { 142 bh[b] = sb_getblk(sb, ++cur_index); 143 if (bh[b] == NULL) 144 goto block_release; 145 bytes += msblk->devblksize; 146 } 147 ll_rw_block(REQ_OP_READ, 0, b - 1, bh + 1); 148 } 149 150 for (i = 0; i < b; i++) { 151 wait_on_buffer(bh[i]); 152 if (!buffer_uptodate(bh[i])) 153 goto block_release; 154 } 155 156 if (compressed) { 157 if (!msblk->stream) 158 goto read_failure; 159 length = squashfs_decompress(msblk, bh, b, offset, length, 160 output); 161 if (length < 0) 162 goto read_failure; 163 } else { 164 /* 165 * Block is uncompressed. 166 */ 167 int in, pg_offset = 0; 168 void *data = squashfs_first_page(output); 169 170 for (bytes = length; k < b; k++) { 171 in = min(bytes, msblk->devblksize - offset); 172 bytes -= in; 173 while (in) { 174 if (pg_offset == PAGE_SIZE) { 175 data = squashfs_next_page(output); 176 pg_offset = 0; 177 } 178 avail = min_t(int, in, PAGE_SIZE - 179 pg_offset); 180 memcpy(data + pg_offset, bh[k]->b_data + offset, 181 avail); 182 in -= avail; 183 pg_offset += avail; 184 offset += avail; 185 } 186 offset = 0; 187 put_bh(bh[k]); 188 } 189 squashfs_finish_page(output); 190 } 191 192 kfree(bh); 193 return length; 194 195 block_release: 196 for (; k < b; k++) 197 put_bh(bh[k]); 198 199 read_failure: 200 ERROR("squashfs_read_data failed to read block 0x%llx\n", 201 (unsigned long long) index); 202 kfree(bh); 203 return -EIO; 204 } 205