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68252eb5 | 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
07972dde PL |
2 | /* |
3 | * Squashfs - a compressed read only filesystem for Linux | |
4 | * | |
5 | * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008 | |
d7f2ff67 | 6 | * Phillip Lougher <phillip@squashfs.org.uk> |
07972dde | 7 | * |
07972dde PL |
8 | * dir.c |
9 | */ | |
10 | ||
11 | /* | |
12 | * This file implements code to read directories from disk. | |
13 | * | |
14 | * See namei.c for a description of directory organisation on disk. | |
15 | */ | |
16 | ||
17 | #include <linux/fs.h> | |
18 | #include <linux/vfs.h> | |
19 | #include <linux/slab.h> | |
07972dde PL |
20 | |
21 | #include "squashfs_fs.h" | |
22 | #include "squashfs_fs_sb.h" | |
23 | #include "squashfs_fs_i.h" | |
24 | #include "squashfs.h" | |
25 | ||
26 | static const unsigned char squashfs_filetype_table[] = { | |
27 | DT_UNKNOWN, DT_DIR, DT_REG, DT_LNK, DT_BLK, DT_CHR, DT_FIFO, DT_SOCK | |
28 | }; | |
29 | ||
30 | /* | |
31 | * Lookup offset (f_pos) in the directory index, returning the | |
32 | * metadata block containing it. | |
33 | * | |
34 | * If we get an error reading the index then return the part of the index | |
35 | * (if any) we have managed to read - the index isn't essential, just | |
36 | * quicker. | |
37 | */ | |
38 | static int get_dir_index_using_offset(struct super_block *sb, | |
39 | u64 *next_block, int *next_offset, u64 index_start, int index_offset, | |
40 | int i_count, u64 f_pos) | |
41 | { | |
42 | struct squashfs_sb_info *msblk = sb->s_fs_info; | |
43 | int err, i, index, length = 0; | |
f960cae5 | 44 | unsigned int size; |
07972dde PL |
45 | struct squashfs_dir_index dir_index; |
46 | ||
47 | TRACE("Entered get_dir_index_using_offset, i_count %d, f_pos %lld\n", | |
48 | i_count, f_pos); | |
49 | ||
50 | /* | |
51 | * Translate from external f_pos to the internal f_pos. This | |
52 | * is offset by 3 because we invent "." and ".." entries which are | |
53 | * not actually stored in the directory. | |
54 | */ | |
2158d3fd | 55 | if (f_pos <= 3) |
07972dde PL |
56 | return f_pos; |
57 | f_pos -= 3; | |
58 | ||
59 | for (i = 0; i < i_count; i++) { | |
60 | err = squashfs_read_metadata(sb, &dir_index, &index_start, | |
61 | &index_offset, sizeof(dir_index)); | |
62 | if (err < 0) | |
63 | break; | |
64 | ||
65 | index = le32_to_cpu(dir_index.index); | |
66 | if (index > f_pos) | |
67 | /* | |
68 | * Found the index we're looking for. | |
69 | */ | |
70 | break; | |
71 | ||
f960cae5 PL |
72 | size = le32_to_cpu(dir_index.size) + 1; |
73 | ||
74 | /* size should never be larger than SQUASHFS_NAME_LEN */ | |
75 | if (size > SQUASHFS_NAME_LEN) | |
76 | break; | |
77 | ||
07972dde | 78 | err = squashfs_read_metadata(sb, NULL, &index_start, |
f960cae5 | 79 | &index_offset, size); |
07972dde PL |
80 | if (err < 0) |
81 | break; | |
82 | ||
83 | length = index; | |
84 | *next_block = le32_to_cpu(dir_index.start_block) + | |
85 | msblk->directory_table; | |
86 | } | |
87 | ||
88 | *next_offset = (length + *next_offset) % SQUASHFS_METADATA_SIZE; | |
89 | ||
90 | /* | |
91 | * Translate back from internal f_pos to external f_pos. | |
92 | */ | |
93 | return length + 3; | |
94 | } | |
95 | ||
96 | ||
5f6039ce | 97 | static int squashfs_readdir(struct file *file, struct dir_context *ctx) |
07972dde | 98 | { |
496ad9aa | 99 | struct inode *inode = file_inode(file); |
07972dde PL |
100 | struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info; |
101 | u64 block = squashfs_i(inode)->start + msblk->directory_table; | |
9e012423 PL |
102 | int offset = squashfs_i(inode)->offset, length, err; |
103 | unsigned int inode_number, dir_count, size, type; | |
07972dde PL |
104 | struct squashfs_dir_header dirh; |
105 | struct squashfs_dir_entry *dire; | |
106 | ||
107 | TRACE("Entered squashfs_readdir [%llx:%x]\n", block, offset); | |
108 | ||
109 | dire = kmalloc(sizeof(*dire) + SQUASHFS_NAME_LEN + 1, GFP_KERNEL); | |
110 | if (dire == NULL) { | |
111 | ERROR("Failed to allocate squashfs_dir_entry\n"); | |
112 | goto finish; | |
113 | } | |
114 | ||
115 | /* | |
116 | * Return "." and ".." entries as the first two filenames in the | |
117 | * directory. To maximise compression these two entries are not | |
118 | * stored in the directory, and so we invent them here. | |
119 | * | |
120 | * It also means that the external f_pos is offset by 3 from the | |
121 | * on-disk directory f_pos. | |
122 | */ | |
5f6039ce | 123 | while (ctx->pos < 3) { |
07972dde PL |
124 | char *name; |
125 | int i_ino; | |
126 | ||
5f6039ce | 127 | if (ctx->pos == 0) { |
07972dde PL |
128 | name = "."; |
129 | size = 1; | |
130 | i_ino = inode->i_ino; | |
131 | } else { | |
132 | name = ".."; | |
133 | size = 2; | |
134 | i_ino = squashfs_i(inode)->parent; | |
135 | } | |
136 | ||
5f6039ce AV |
137 | if (!dir_emit(ctx, name, size, i_ino, |
138 | squashfs_filetype_table[1])) | |
07972dde | 139 | goto finish; |
07972dde | 140 | |
5f6039ce | 141 | ctx->pos += size; |
07972dde PL |
142 | } |
143 | ||
144 | length = get_dir_index_using_offset(inode->i_sb, &block, &offset, | |
145 | squashfs_i(inode)->dir_idx_start, | |
146 | squashfs_i(inode)->dir_idx_offset, | |
147 | squashfs_i(inode)->dir_idx_cnt, | |
5f6039ce | 148 | ctx->pos); |
07972dde PL |
149 | |
150 | while (length < i_size_read(inode)) { | |
151 | /* | |
152 | * Read directory header | |
153 | */ | |
154 | err = squashfs_read_metadata(inode->i_sb, &dirh, &block, | |
155 | &offset, sizeof(dirh)); | |
156 | if (err < 0) | |
157 | goto failed_read; | |
158 | ||
159 | length += sizeof(dirh); | |
160 | ||
161 | dir_count = le32_to_cpu(dirh.count) + 1; | |
44cff8a9 | 162 | |
4826d83d | 163 | if (dir_count > SQUASHFS_DIR_COUNT) |
44cff8a9 PL |
164 | goto failed_read; |
165 | ||
07972dde PL |
166 | while (dir_count--) { |
167 | /* | |
168 | * Read directory entry. | |
169 | */ | |
170 | err = squashfs_read_metadata(inode->i_sb, dire, &block, | |
171 | &offset, sizeof(*dire)); | |
172 | if (err < 0) | |
173 | goto failed_read; | |
174 | ||
175 | size = le16_to_cpu(dire->size) + 1; | |
176 | ||
44cff8a9 PL |
177 | /* size should never be larger than SQUASHFS_NAME_LEN */ |
178 | if (size > SQUASHFS_NAME_LEN) | |
179 | goto failed_read; | |
180 | ||
07972dde PL |
181 | err = squashfs_read_metadata(inode->i_sb, dire->name, |
182 | &block, &offset, size); | |
183 | if (err < 0) | |
184 | goto failed_read; | |
185 | ||
186 | length += sizeof(*dire) + size; | |
187 | ||
5f6039ce | 188 | if (ctx->pos >= length) |
07972dde PL |
189 | continue; |
190 | ||
191 | dire->name[size] = '\0'; | |
192 | inode_number = le32_to_cpu(dirh.inode_number) + | |
193 | ((short) le16_to_cpu(dire->inode_number)); | |
194 | type = le16_to_cpu(dire->type); | |
195 | ||
9e012423 PL |
196 | if (type > SQUASHFS_MAX_DIR_TYPE) |
197 | goto failed_read; | |
198 | ||
5f6039ce | 199 | if (!dir_emit(ctx, dire->name, size, |
07972dde | 200 | inode_number, |
5f6039ce | 201 | squashfs_filetype_table[type])) |
07972dde | 202 | goto finish; |
07972dde | 203 | |
5f6039ce | 204 | ctx->pos = length; |
07972dde PL |
205 | } |
206 | } | |
207 | ||
208 | finish: | |
209 | kfree(dire); | |
210 | return 0; | |
211 | ||
212 | failed_read: | |
213 | ERROR("Unable to read directory block [%llx:%x]\n", block, offset); | |
214 | kfree(dire); | |
215 | return 0; | |
216 | } | |
217 | ||
218 | ||
219 | const struct file_operations squashfs_dir_ops = { | |
220 | .read = generic_read_dir, | |
d375570f AV |
221 | .iterate_shared = squashfs_readdir, |
222 | .llseek = generic_file_llseek, | |
07972dde | 223 | }; |