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 */
get_block_length(struct super_block * sb,u64 * cur_index,int * offset,int * length)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 */
squashfs_read_data(struct super_block * sb,u64 index,int length,u64 * next_index,struct squashfs_page_actor * output)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