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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;
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 	squashfs_actor_nobuff(actor);
44 	actor_addr = squashfs_first_page(actor);
45 
46 	if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all)))
47 		return 0;
48 
49 	while (copied_bytes < req_length) {
50 		int bytes_to_copy = min_t(int, bvec->bv_len - offset,
51 					  PAGE_SIZE - actor_offset);
52 
53 		bytes_to_copy = min_t(int, bytes_to_copy,
54 				      req_length - copied_bytes);
55 		if (!IS_ERR(actor_addr))
56 			memcpy(actor_addr + actor_offset, bvec_virt(bvec) +
57 					offset, bytes_to_copy);
58 
59 		actor_offset += bytes_to_copy;
60 		copied_bytes += bytes_to_copy;
61 		offset += bytes_to_copy;
62 
63 		if (actor_offset >= PAGE_SIZE) {
64 			actor_addr = squashfs_next_page(actor);
65 			if (!actor_addr)
66 				break;
67 			actor_offset = 0;
68 		}
69 		if (offset >= bvec->bv_len) {
70 			if (!bio_next_segment(bio, &iter_all))
71 				break;
72 			offset = 0;
73 		}
74 	}
75 	squashfs_finish_page(actor);
76 	return copied_bytes;
77 }
78 
squashfs_bio_read(struct super_block * sb,u64 index,int length,struct bio ** biop,int * block_offset)79 static int squashfs_bio_read(struct super_block *sb, u64 index, int length,
80 			     struct bio **biop, int *block_offset)
81 {
82 	struct squashfs_sb_info *msblk = sb->s_fs_info;
83 	const u64 read_start = round_down(index, msblk->devblksize);
84 	const sector_t block = read_start >> msblk->devblksize_log2;
85 	const u64 read_end = round_up(index + length, msblk->devblksize);
86 	const sector_t block_end = read_end >> msblk->devblksize_log2;
87 	int offset = read_start - round_down(index, PAGE_SIZE);
88 	int total_len = (block_end - block) << msblk->devblksize_log2;
89 	const int page_count = DIV_ROUND_UP(total_len + offset, PAGE_SIZE);
90 	int error, i;
91 	struct bio *bio;
92 
93 	bio = bio_kmalloc(page_count, GFP_NOIO);
94 	if (!bio)
95 		return -ENOMEM;
96 	bio_init(bio, sb->s_bdev, bio->bi_inline_vecs, page_count, REQ_OP_READ);
97 	bio->bi_iter.bi_sector = block * (msblk->devblksize >> SECTOR_SHIFT);
98 
99 	for (i = 0; i < page_count; ++i) {
100 		unsigned int len =
101 			min_t(unsigned int, PAGE_SIZE - offset, total_len);
102 		struct page *page = alloc_page(GFP_NOIO);
103 
104 		if (!page) {
105 			error = -ENOMEM;
106 			goto out_free_bio;
107 		}
108 		if (!bio_add_page(bio, page, len, offset)) {
109 			error = -EIO;
110 			goto out_free_bio;
111 		}
112 		offset = 0;
113 		total_len -= len;
114 	}
115 
116 	error = submit_bio_wait(bio);
117 	if (error)
118 		goto out_free_bio;
119 
120 	*biop = bio;
121 	*block_offset = index & ((1 << msblk->devblksize_log2) - 1);
122 	return 0;
123 
124 out_free_bio:
125 	bio_free_pages(bio);
126 	bio_uninit(bio);
127 	kfree(bio);
128 	return error;
129 }
130 
131 /*
132  * Read and decompress a metadata block or datablock.  Length is non-zero
133  * if a datablock is being read (the size is stored elsewhere in the
134  * filesystem), otherwise the length is obtained from the first two bytes of
135  * the metadata block.  A bit in the length field indicates if the block
136  * is stored uncompressed in the filesystem (usually because compression
137  * generated a larger block - this does occasionally happen with compression
138  * algorithms).
139  */
squashfs_read_data(struct super_block * sb,u64 index,int length,u64 * next_index,struct squashfs_page_actor * output)140 int squashfs_read_data(struct super_block *sb, u64 index, int length,
141 		       u64 *next_index, struct squashfs_page_actor *output)
142 {
143 	struct squashfs_sb_info *msblk = sb->s_fs_info;
144 	struct bio *bio = NULL;
145 	int compressed;
146 	int res;
147 	int offset;
148 
149 	if (length) {
150 		/*
151 		 * Datablock.
152 		 */
153 		compressed = SQUASHFS_COMPRESSED_BLOCK(length);
154 		length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length);
155 		TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n",
156 			index, compressed ? "" : "un", length, output->length);
157 	} else {
158 		/*
159 		 * Metadata block.
160 		 */
161 		const u8 *data;
162 		struct bvec_iter_all iter_all = {};
163 		struct bio_vec *bvec = bvec_init_iter_all(&iter_all);
164 
165 		if (index + 2 > msblk->bytes_used) {
166 			res = -EIO;
167 			goto out;
168 		}
169 		res = squashfs_bio_read(sb, index, 2, &bio, &offset);
170 		if (res)
171 			goto out;
172 
173 		if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) {
174 			res = -EIO;
175 			goto out_free_bio;
176 		}
177 		/* Extract the length of the metadata block */
178 		data = bvec_virt(bvec);
179 		length = data[offset];
180 		if (offset < bvec->bv_len - 1) {
181 			length |= data[offset + 1] << 8;
182 		} else {
183 			if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) {
184 				res = -EIO;
185 				goto out_free_bio;
186 			}
187 			data = bvec_virt(bvec);
188 			length |= data[0] << 8;
189 		}
190 		bio_free_pages(bio);
191 		bio_uninit(bio);
192 		kfree(bio);
193 
194 		compressed = SQUASHFS_COMPRESSED(length);
195 		length = SQUASHFS_COMPRESSED_SIZE(length);
196 		index += 2;
197 
198 		TRACE("Block @ 0x%llx, %scompressed size %d\n", index - 2,
199 		      compressed ? "" : "un", length);
200 	}
201 	if (length < 0 || length > output->length ||
202 			(index + length) > msblk->bytes_used) {
203 		res = -EIO;
204 		goto out;
205 	}
206 
207 	if (next_index)
208 		*next_index = index + length;
209 
210 	res = squashfs_bio_read(sb, index, length, &bio, &offset);
211 	if (res)
212 		goto out;
213 
214 	if (compressed) {
215 		if (!msblk->stream) {
216 			res = -EIO;
217 			goto out_free_bio;
218 		}
219 		res = squashfs_decompress(msblk, bio, offset, length, output);
220 	} else {
221 		res = copy_bio_to_actor(bio, output, offset, length);
222 	}
223 
224 out_free_bio:
225 	bio_free_pages(bio);
226 	bio_uninit(bio);
227 	kfree(bio);
228 out:
229 	if (res < 0) {
230 		ERROR("Failed to read block 0x%llx: %d\n", index, res);
231 		if (msblk->panic_on_errors)
232 			panic("squashfs read failed");
233 	}
234 
235 	return res;
236 }
237