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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 <[email protected]>
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/filelock.h>
19#include <linux/vfs.h>
20#include <linux/slab.h>
21
22#include "squashfs_fs.h"
23#include "squashfs_fs_sb.h"
24#include "squashfs_fs_i.h"
25#include "squashfs.h"
26
27static const unsigned char squashfs_filetype_table[] = {
28 DT_UNKNOWN, DT_DIR, DT_REG, DT_LNK, DT_BLK, DT_CHR, DT_FIFO, DT_SOCK
29};
30
31/*
32 * Lookup offset (f_pos) in the directory index, returning the
33 * metadata block containing it.
34 *
35 * If we get an error reading the index then return the part of the index
36 * (if any) we have managed to read - the index isn't essential, just
37 * quicker.
38 */
39static int get_dir_index_using_offset(struct super_block *sb,
40 u64 *next_block, int *next_offset, u64 index_start, int index_offset,
41 int i_count, u64 f_pos)
42{
43 struct squashfs_sb_info *msblk = sb->s_fs_info;
44 int err, i, index, length = 0;
45 unsigned int size;
46 struct squashfs_dir_index dir_index;
47
48 TRACE("Entered get_dir_index_using_offset, i_count %d, f_pos %lld\n",
49 i_count, f_pos);
50
51 /*
52 * Translate from external f_pos to the internal f_pos. This
53 * is offset by 3 because we invent "." and ".." entries which are
54 * not actually stored in the directory.
55 */
56 if (f_pos <= 3)
57 return f_pos;
58 f_pos -= 3;
59
60 for (i = 0; i < i_count; i++) {
61 err = squashfs_read_metadata(sb, &dir_index, &index_start,
62 &index_offset, sizeof(dir_index));
63 if (err < 0)
64 break;
65
66 index = le32_to_cpu(dir_index.index);
67 if (index > f_pos)
68 /*
69 * Found the index we're looking for.
70 */
71 break;
72
73 size = le32_to_cpu(dir_index.size) + 1;
74
75 /* size should never be larger than SQUASHFS_NAME_LEN */
76 if (size > SQUASHFS_NAME_LEN)
77 break;
78
79 err = squashfs_read_metadata(sb, NULL, &index_start,
80 &index_offset, size);
81 if (err < 0)
82 break;
83
84 length = index;
85 *next_block = le32_to_cpu(dir_index.start_block) +
86 msblk->directory_table;
87 }
88
89 *next_offset = (length + *next_offset) % SQUASHFS_METADATA_SIZE;
90
91 /*
92 * Translate back from internal f_pos to external f_pos.
93 */
94 return length + 3;
95}
96
97
98static int squashfs_readdir(struct file *file, struct dir_context *ctx)
99{
100 struct inode *inode = file_inode(file);
101 struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
102 u64 block = squashfs_i(inode)->start + msblk->directory_table;
103 int offset = squashfs_i(inode)->offset, length, err;
104 unsigned int inode_number, dir_count, size, type;
105 struct squashfs_dir_header dirh;
106 struct squashfs_dir_entry *dire;
107
108 TRACE("Entered squashfs_readdir [%llx:%x]\n", block, offset);
109
110 dire = kmalloc(sizeof(*dire) + SQUASHFS_NAME_LEN + 1, GFP_KERNEL);
111 if (dire == NULL) {
112 ERROR("Failed to allocate squashfs_dir_entry\n");
113 goto finish;
114 }
115
116 /*
117 * Return "." and ".." entries as the first two filenames in the
118 * directory. To maximise compression these two entries are not
119 * stored in the directory, and so we invent them here.
120 *
121 * It also means that the external f_pos is offset by 3 from the
122 * on-disk directory f_pos.
123 */
124 while (ctx->pos < 3) {
125 char *name;
126 int i_ino;
127
128 if (ctx->pos == 0) {
129 name = ".";
130 size = 1;
131 i_ino = inode->i_ino;
132 } else {
133 name = "..";
134 size = 2;
135 i_ino = squashfs_i(inode)->parent;
136 }
137
138 if (!dir_emit(ctx, name, size, i_ino,
139 squashfs_filetype_table[1]))
140 goto finish;
141
142 ctx->pos += size;
143 }
144
145 length = get_dir_index_using_offset(inode->i_sb, &block, &offset,
146 squashfs_i(inode)->dir_idx_start,
147 squashfs_i(inode)->dir_idx_offset,
148 squashfs_i(inode)->dir_idx_cnt,
149 ctx->pos);
150
151 while (length < i_size_read(inode)) {
152 /*
153 * Read directory header
154 */
155 err = squashfs_read_metadata(inode->i_sb, &dirh, &block,
156 &offset, sizeof(dirh));
157 if (err < 0)
158 goto failed_read;
159
160 length += sizeof(dirh);
161
162 dir_count = le32_to_cpu(dirh.count) + 1;
163
164 if (dir_count > SQUASHFS_DIR_COUNT)
165 goto failed_read;
166
167 while (dir_count--) {
168 /*
169 * Read directory entry.
170 */
171 err = squashfs_read_metadata(inode->i_sb, dire, &block,
172 &offset, sizeof(*dire));
173 if (err < 0)
174 goto failed_read;
175
176 size = le16_to_cpu(dire->size) + 1;
177
178 /* size should never be larger than SQUASHFS_NAME_LEN */
179 if (size > SQUASHFS_NAME_LEN)
180 goto failed_read;
181
182 err = squashfs_read_metadata(inode->i_sb, dire->name,
183 &block, &offset, size);
184 if (err < 0)
185 goto failed_read;
186
187 length += sizeof(*dire) + size;
188
189 if (ctx->pos >= length)
190 continue;
191
192 dire->name[size] = '\0';
193 inode_number = le32_to_cpu(dirh.inode_number) +
194 ((short) le16_to_cpu(dire->inode_number));
195 type = le16_to_cpu(dire->type);
196
197 if (type > SQUASHFS_MAX_DIR_TYPE)
198 goto failed_read;
199
200 if (!dir_emit(ctx, dire->name, size,
201 inode_number,
202 squashfs_filetype_table[type]))
203 goto finish;
204
205 ctx->pos = length;
206 }
207 }
208
209finish:
210 kfree(dire);
211 return 0;
212
213failed_read:
214 ERROR("Unable to read directory block [%llx:%x]\n", block, offset);
215 kfree(dire);
216 return 0;
217}
218
219
220const struct file_operations squashfs_dir_ops = {
221 .read = generic_read_dir,
222 .iterate_shared = squashfs_readdir,
223 .llseek = generic_file_llseek,
224 .setlease = generic_setlease,
225};