squashfs: fix use of uninitialised variable in zlib & xz decompressors
[linux-3.10.git] / fs / squashfs / block.c
1 /*
2  * Squashfs - a compressed read only filesystem for Linux
3  *
4  * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
5  * Phillip Lougher <phillip@lougher.demon.co.uk>
6  *
7  * This program is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU General Public License
9  * as published by the Free Software Foundation; either version 2,
10  * or (at your option) any later version.
11  *
12  * This program is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15  * GNU General Public License for more details.
16  *
17  * You should have received a copy of the GNU General Public License
18  * along with this program; if not, write to the Free Software
19  * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
20  *
21  * block.c
22  */
23
24 /*
25  * This file implements the low-level routines to read and decompress
26  * datablocks and metadata blocks.
27  */
28
29 #include <linux/fs.h>
30 #include <linux/vfs.h>
31 #include <linux/slab.h>
32 #include <linux/string.h>
33 #include <linux/buffer_head.h>
34
35 #include "squashfs_fs.h"
36 #include "squashfs_fs_sb.h"
37 #include "squashfs.h"
38 #include "decompressor.h"
39
40 /*
41  * Read the metadata block length, this is stored in the first two
42  * bytes of the metadata block.
43  */
44 static struct buffer_head *get_block_length(struct super_block *sb,
45                         u64 *cur_index, int *offset, int *length)
46 {
47         struct squashfs_sb_info *msblk = sb->s_fs_info;
48         struct buffer_head *bh;
49
50         bh = sb_bread(sb, *cur_index);
51         if (bh == NULL)
52                 return NULL;
53
54         if (msblk->devblksize - *offset == 1) {
55                 *length = (unsigned char) bh->b_data[*offset];
56                 put_bh(bh);
57                 bh = sb_bread(sb, ++(*cur_index));
58                 if (bh == NULL)
59                         return NULL;
60                 *length |= (unsigned char) bh->b_data[0] << 8;
61                 *offset = 1;
62         } else {
63                 *length = (unsigned char) bh->b_data[*offset] |
64                         (unsigned char) bh->b_data[*offset + 1] << 8;
65                 *offset += 2;
66
67                 if (*offset == msblk->devblksize) {
68                         put_bh(bh);
69                         bh = sb_bread(sb, ++(*cur_index));
70                         if (bh == NULL)
71                                 return NULL;
72                         *offset = 0;
73                 }
74         }
75
76         return bh;
77 }
78
79
80 /*
81  * Read and decompress a metadata block or datablock.  Length is non-zero
82  * if a datablock is being read (the size is stored elsewhere in the
83  * filesystem), otherwise the length is obtained from the first two bytes of
84  * the metadata block.  A bit in the length field indicates if the block
85  * is stored uncompressed in the filesystem (usually because compression
86  * generated a larger block - this does occasionally happen with zlib).
87  */
88 int squashfs_read_data(struct super_block *sb, void **buffer, u64 index,
89                         int length, u64 *next_index, int srclength, int pages)
90 {
91         struct squashfs_sb_info *msblk = sb->s_fs_info;
92         struct buffer_head **bh;
93         int offset = index & ((1 << msblk->devblksize_log2) - 1);
94         u64 cur_index = index >> msblk->devblksize_log2;
95         int bytes, compressed, b = 0, k = 0, page = 0, avail;
96
97         bh = kcalloc(((srclength + msblk->devblksize - 1)
98                 >> msblk->devblksize_log2) + 1, sizeof(*bh), GFP_KERNEL);
99         if (bh == NULL)
100                 return -ENOMEM;
101
102         if (length) {
103                 /*
104                  * Datablock.
105                  */
106                 bytes = -offset;
107                 compressed = SQUASHFS_COMPRESSED_BLOCK(length);
108                 length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length);
109                 if (next_index)
110                         *next_index = index + length;
111
112                 TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n",
113                         index, compressed ? "" : "un", length, srclength);
114
115                 if (length < 0 || length > srclength ||
116                                 (index + length) > msblk->bytes_used)
117                         goto read_failure;
118
119                 for (b = 0; bytes < length; b++, cur_index++) {
120                         bh[b] = sb_getblk(sb, cur_index);
121                         if (bh[b] == NULL)
122                                 goto block_release;
123                         bytes += msblk->devblksize;
124                 }
125                 ll_rw_block(READ, b, bh);
126         } else {
127                 /*
128                  * Metadata block.
129                  */
130                 if ((index + 2) > msblk->bytes_used)
131                         goto read_failure;
132
133                 bh[0] = get_block_length(sb, &cur_index, &offset, &length);
134                 if (bh[0] == NULL)
135                         goto read_failure;
136                 b = 1;
137
138                 bytes = msblk->devblksize - offset;
139                 compressed = SQUASHFS_COMPRESSED(length);
140                 length = SQUASHFS_COMPRESSED_SIZE(length);
141                 if (next_index)
142                         *next_index = index + length + 2;
143
144                 TRACE("Block @ 0x%llx, %scompressed size %d\n", index,
145                                 compressed ? "" : "un", length);
146
147                 if (length < 0 || length > srclength ||
148                                         (index + length) > msblk->bytes_used)
149                         goto block_release;
150
151                 for (; bytes < length; b++) {
152                         bh[b] = sb_getblk(sb, ++cur_index);
153                         if (bh[b] == NULL)
154                                 goto block_release;
155                         bytes += msblk->devblksize;
156                 }
157                 ll_rw_block(READ, b - 1, bh + 1);
158         }
159
160         if (compressed) {
161                 length = squashfs_decompress(msblk, buffer, bh, b, offset,
162                          length, srclength, pages);
163                 if (length < 0)
164                         goto read_failure;
165         } else {
166                 /*
167                  * Block is uncompressed.
168                  */
169                 int i, in, pg_offset = 0;
170
171                 for (i = 0; i < b; i++) {
172                         wait_on_buffer(bh[i]);
173                         if (!buffer_uptodate(bh[i]))
174                                 goto block_release;
175                 }
176
177                 for (bytes = length; k < b; k++) {
178                         in = min(bytes, msblk->devblksize - offset);
179                         bytes -= in;
180                         while (in) {
181                                 if (pg_offset == PAGE_CACHE_SIZE) {
182                                         page++;
183                                         pg_offset = 0;
184                                 }
185                                 avail = min_t(int, in, PAGE_CACHE_SIZE -
186                                                 pg_offset);
187                                 memcpy(buffer[page] + pg_offset,
188                                                 bh[k]->b_data + offset, avail);
189                                 in -= avail;
190                                 pg_offset += avail;
191                                 offset += avail;
192                         }
193                         offset = 0;
194                         put_bh(bh[k]);
195                 }
196         }
197
198         kfree(bh);
199         return length;
200
201 block_release:
202         for (; k < b; k++)
203                 put_bh(bh[k]);
204
205 read_failure:
206         ERROR("squashfs_read_data failed to read block 0x%llx\n",
207                                         (unsigned long long) index);
208         kfree(bh);
209         return -EIO;
210 }