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/blkdev.h>
17 #include <linux/fs.h>
18 #include <linux/vfs.h>
19 #include <linux/slab.h>
20 #include <linux/string.h>
21 #include <linux/buffer_head.h>
22 #include <linux/bio.h>
23
24 #include "squashfs_fs.h"
25 #include "squashfs_fs_sb.h"
26 #include "squashfs.h"
27 #include "decompressor.h"
28 #include "page_actor.h"
29
30 /*
31 * Returns the amount of bytes copied to the page actor.
32 */
copy_bio_to_actor(struct bio * bio,struct squashfs_page_actor * actor,int offset,int req_length)33 static int copy_bio_to_actor(struct bio *bio,
34 struct squashfs_page_actor *actor,
35 int offset, int req_length)
36 {
37 void *actor_addr = squashfs_first_page(actor);
38 struct bvec_iter_all iter_all = {};
39 struct bio_vec *bvec = bvec_init_iter_all(&iter_all);
40 int copied_bytes = 0;
41 int actor_offset = 0;
42
43 if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all)))
44 return 0;
45
46 while (copied_bytes < req_length) {
47 int bytes_to_copy = min_t(int, bvec->bv_len - offset,
48 PAGE_SIZE - actor_offset);
49
50 bytes_to_copy = min_t(int, bytes_to_copy,
51 req_length - copied_bytes);
52 memcpy(actor_addr + actor_offset, bvec_virt(bvec) + offset,
53 bytes_to_copy);
54
55 actor_offset += bytes_to_copy;
56 copied_bytes += bytes_to_copy;
57 offset += bytes_to_copy;
58
59 if (actor_offset >= PAGE_SIZE) {
60 actor_addr = squashfs_next_page(actor);
61 if (!actor_addr)
62 break;
63 actor_offset = 0;
64 }
65 if (offset >= bvec->bv_len) {
66 if (!bio_next_segment(bio, &iter_all))
67 break;
68 offset = 0;
69 }
70 }
71 squashfs_finish_page(actor);
72 return copied_bytes;
73 }
74
squashfs_bio_read(struct super_block * sb,u64 index,int length,struct bio ** biop,int * block_offset)75 static int squashfs_bio_read(struct super_block *sb, u64 index, int length,
76 struct bio **biop, int *block_offset)
77 {
78 struct squashfs_sb_info *msblk = sb->s_fs_info;
79 const u64 read_start = round_down(index, msblk->devblksize);
80 const sector_t block = read_start >> msblk->devblksize_log2;
81 const u64 read_end = round_up(index + length, msblk->devblksize);
82 const sector_t block_end = read_end >> msblk->devblksize_log2;
83 int offset = read_start - round_down(index, PAGE_SIZE);
84 int total_len = (block_end - block) << msblk->devblksize_log2;
85 const int page_count = DIV_ROUND_UP(total_len + offset, PAGE_SIZE);
86 int error, i;
87 struct bio *bio;
88
89 bio = bio_kmalloc(page_count, GFP_NOIO);
90 if (!bio)
91 return -ENOMEM;
92 bio_init(bio, sb->s_bdev, bio->bi_inline_vecs, page_count, REQ_OP_READ);
93 bio->bi_iter.bi_sector = block * (msblk->devblksize >> SECTOR_SHIFT);
94
95 for (i = 0; i < page_count; ++i) {
96 unsigned int len =
97 min_t(unsigned int, PAGE_SIZE - offset, total_len);
98 struct page *page = alloc_page(GFP_NOIO);
99
100 if (!page) {
101 error = -ENOMEM;
102 goto out_free_bio;
103 }
104 if (!bio_add_page(bio, page, len, offset)) {
105 error = -EIO;
106 goto out_free_bio;
107 }
108 offset = 0;
109 total_len -= len;
110 }
111
112 error = submit_bio_wait(bio);
113 if (error)
114 goto out_free_bio;
115
116 *biop = bio;
117 *block_offset = index & ((1 << msblk->devblksize_log2) - 1);
118 return 0;
119
120 out_free_bio:
121 bio_free_pages(bio);
122 bio_uninit(bio);
123 kfree(bio);
124 return error;
125 }
126
127 /*
128 * Read and decompress a metadata block or datablock. Length is non-zero
129 * if a datablock is being read (the size is stored elsewhere in the
130 * filesystem), otherwise the length is obtained from the first two bytes of
131 * the metadata block. A bit in the length field indicates if the block
132 * is stored uncompressed in the filesystem (usually because compression
133 * generated a larger block - this does occasionally happen with compression
134 * algorithms).
135 */
squashfs_read_data(struct super_block * sb,u64 index,int length,u64 * next_index,struct squashfs_page_actor * output)136 int squashfs_read_data(struct super_block *sb, u64 index, int length,
137 u64 *next_index, struct squashfs_page_actor *output)
138 {
139 struct squashfs_sb_info *msblk = sb->s_fs_info;
140 struct bio *bio = NULL;
141 int compressed;
142 int res;
143 int offset;
144
145 if (length) {
146 /*
147 * Datablock.
148 */
149 compressed = SQUASHFS_COMPRESSED_BLOCK(length);
150 length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length);
151 TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n",
152 index, compressed ? "" : "un", length, output->length);
153 } else {
154 /*
155 * Metadata block.
156 */
157 const u8 *data;
158 struct bvec_iter_all iter_all = {};
159 struct bio_vec *bvec = bvec_init_iter_all(&iter_all);
160
161 if (index + 2 > msblk->bytes_used) {
162 res = -EIO;
163 goto out;
164 }
165 res = squashfs_bio_read(sb, index, 2, &bio, &offset);
166 if (res)
167 goto out;
168
169 if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) {
170 res = -EIO;
171 goto out_free_bio;
172 }
173 /* Extract the length of the metadata block */
174 data = bvec_virt(bvec);
175 length = data[offset];
176 if (offset < bvec->bv_len - 1) {
177 length |= data[offset + 1] << 8;
178 } else {
179 if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) {
180 res = -EIO;
181 goto out_free_bio;
182 }
183 data = bvec_virt(bvec);
184 length |= data[0] << 8;
185 }
186 bio_free_pages(bio);
187 bio_uninit(bio);
188 kfree(bio);
189
190 compressed = SQUASHFS_COMPRESSED(length);
191 length = SQUASHFS_COMPRESSED_SIZE(length);
192 index += 2;
193
194 TRACE("Block @ 0x%llx, %scompressed size %d\n", index - 2,
195 compressed ? "" : "un", length);
196 }
197 if (length < 0 || length > output->length ||
198 (index + length) > msblk->bytes_used) {
199 res = -EIO;
200 goto out;
201 }
202
203 if (next_index)
204 *next_index = index + length;
205
206 res = squashfs_bio_read(sb, index, length, &bio, &offset);
207 if (res)
208 goto out;
209
210 if (compressed) {
211 if (!msblk->stream) {
212 res = -EIO;
213 goto out_free_bio;
214 }
215 res = squashfs_decompress(msblk, bio, offset, length, output);
216 } else {
217 res = copy_bio_to_actor(bio, output, offset, length);
218 }
219
220 out_free_bio:
221 bio_free_pages(bio);
222 bio_uninit(bio);
223 kfree(bio);
224 out:
225 if (res < 0) {
226 ERROR("Failed to read block 0x%llx: %d\n", index, res);
227 if (msblk->panic_on_errors)
228 panic("squashfs read failed");
229 }
230
231 return res;
232 }
233