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 * 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>
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;
44 unsigned int size;
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 */
55 if (f_pos <= 3)
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
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
78 err = squashfs_read_metadata(sb, NULL, &index_start,
79 &index_offset, size);
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
97 static int squashfs_readdir(struct file *file, struct dir_context *ctx)
98 {
99 struct inode *inode = file_inode(file);
100 struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
101 u64 block = squashfs_i(inode)->start + msblk->directory_table;
102 int offset = squashfs_i(inode)->offset, length, err;
103 unsigned int inode_number, dir_count, size, type;
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 */
123 while (ctx->pos < 3) {
124 char *name;
125 int i_ino;
126
127 if (ctx->pos == 0) {
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
137 if (!dir_emit(ctx, name, size, i_ino,
138 squashfs_filetype_table[1]))
139 goto finish;
140
141 ctx->pos += size;
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,
148 ctx->pos);
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;
162
163 if (dir_count > SQUASHFS_DIR_COUNT)
164 goto failed_read;
165
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
177 /* size should never be larger than SQUASHFS_NAME_LEN */
178 if (size > SQUASHFS_NAME_LEN)
179 goto failed_read;
180
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
188 if (ctx->pos >= length)
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
196 if (type > SQUASHFS_MAX_DIR_TYPE)
197 goto failed_read;
198
199 if (!dir_emit(ctx, dire->name, size,
200 inode_number,
201 squashfs_filetype_table[type]))
202 goto finish;
203
204 ctx->pos = length;
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,
221 .iterate_shared = squashfs_readdir,
222 .llseek = generic_file_llseek,
223 };
224
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