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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@squashfs.org.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 * namei.c
22 */
23
24/*
25 * This file implements code to do filename lookup in directories.
26 *
27 * Like inodes, directories are packed into compressed metadata blocks, stored
28 * in a directory table. Directories are accessed using the start address of
29 * the metablock containing the directory and the offset into the
30 * decompressed block (<block, offset>).
31 *
32 * Directories are organised in a slightly complex way, and are not simply
33 * a list of file names. The organisation takes advantage of the
34 * fact that (in most cases) the inodes of the files will be in the same
35 * compressed metadata block, and therefore, can share the start block.
36 * Directories are therefore organised in a two level list, a directory
37 * header containing the shared start block value, and a sequence of directory
38 * entries, each of which share the shared start block. A new directory header
39 * is written once/if the inode start block changes. The directory
40 * header/directory entry list is repeated as many times as necessary.
41 *
42 * Directories are sorted, and can contain a directory index to speed up
43 * file lookup. Directory indexes store one entry per metablock, each entry
44 * storing the index/filename mapping to the first directory header
45 * in each metadata block. Directories are sorted in alphabetical order,
46 * and at lookup the index is scanned linearly looking for the first filename
47 * alphabetically larger than the filename being looked up. At this point the
48 * location of the metadata block the filename is in has been found.
49 * The general idea of the index is ensure only one metadata block needs to be
50 * decompressed to do a lookup irrespective of the length of the directory.
51 * This scheme has the advantage that it doesn't require extra memory overhead
52 * and doesn't require much extra storage on disk.
53 */
54
55#include <linux/fs.h>
56#include <linux/vfs.h>
57#include <linux/slab.h>
58#include <linux/string.h>
59#include <linux/dcache.h>
60#include <linux/xattr.h>
61
62#include "squashfs_fs.h"
63#include "squashfs_fs_sb.h"
64#include "squashfs_fs_i.h"
65#include "squashfs.h"
66#include "xattr.h"
67
68/*
69 * Lookup name in the directory index, returning the location of the metadata
70 * block containing it, and the directory index this represents.
71 *
72 * If we get an error reading the index then return the part of the index
73 * (if any) we have managed to read - the index isn't essential, just
74 * quicker.
75 */
76static int get_dir_index_using_name(struct super_block *sb,
77 u64 *next_block, int *next_offset, u64 index_start,
78 int index_offset, int i_count, const char *name,
79 int len)
80{
81 struct squashfs_sb_info *msblk = sb->s_fs_info;
82 int i, size, length = 0, err;
83 struct squashfs_dir_index *index;
84 char *str;
85
86 TRACE("Entered get_dir_index_using_name, i_count %d\n", i_count);
87
88 index = kmalloc(sizeof(*index) + SQUASHFS_NAME_LEN * 2 + 2, GFP_KERNEL);
89 if (index == NULL) {
90 ERROR("Failed to allocate squashfs_dir_index\n");
91 goto out;
92 }
93
94 str = &index->name[SQUASHFS_NAME_LEN + 1];
95 strncpy(str, name, len);
96 str[len] = '\0';
97
98 for (i = 0; i < i_count; i++) {
99 err = squashfs_read_metadata(sb, index, &index_start,
100 &index_offset, sizeof(*index));
101 if (err < 0)
102 break;
103
104
105 size = le32_to_cpu(index->size) + 1;
106
107 err = squashfs_read_metadata(sb, index->name, &index_start,
108 &index_offset, size);
109 if (err < 0)
110 break;
111
112 index->name[size] = '\0';
113
114 if (strcmp(index->name, str) > 0)
115 break;
116
117 length = le32_to_cpu(index->index);
118 *next_block = le32_to_cpu(index->start_block) +
119 msblk->directory_table;
120 }
121
122 *next_offset = (length + *next_offset) % SQUASHFS_METADATA_SIZE;
123 kfree(index);
124
125out:
126 /*
127 * Return index (f_pos) of the looked up metadata block. Translate
128 * from internal f_pos to external f_pos which is offset by 3 because
129 * we invent "." and ".." entries which are not actually stored in the
130 * directory.
131 */
132 return length + 3;
133}
134
135
136static struct dentry *squashfs_lookup(struct inode *dir, struct dentry *dentry,
137 struct nameidata *nd)
138{
139 const unsigned char *name = dentry->d_name.name;
140 int len = dentry->d_name.len;
141 struct inode *inode = NULL;
142 struct squashfs_sb_info *msblk = dir->i_sb->s_fs_info;
143 struct squashfs_dir_header dirh;
144 struct squashfs_dir_entry *dire;
145 u64 block = squashfs_i(dir)->start + msblk->directory_table;
146 int offset = squashfs_i(dir)->offset;
147 int err, length = 0, dir_count, size;
148
149 TRACE("Entered squashfs_lookup [%llx:%x]\n", block, offset);
150
151 dire = kmalloc(sizeof(*dire) + SQUASHFS_NAME_LEN + 1, GFP_KERNEL);
152 if (dire == NULL) {
153 ERROR("Failed to allocate squashfs_dir_entry\n");
154 return ERR_PTR(-ENOMEM);
155 }
156
157 if (len > SQUASHFS_NAME_LEN) {
158 err = -ENAMETOOLONG;
159 goto failed;
160 }
161
162 length = get_dir_index_using_name(dir->i_sb, &block, &offset,
163 squashfs_i(dir)->dir_idx_start,
164 squashfs_i(dir)->dir_idx_offset,
165 squashfs_i(dir)->dir_idx_cnt, name, len);
166
167 while (length < i_size_read(dir)) {
168 /*
169 * Read directory header.
170 */
171 err = squashfs_read_metadata(dir->i_sb, &dirh, &block,
172 &offset, sizeof(dirh));
173 if (err < 0)
174 goto read_failure;
175
176 length += sizeof(dirh);
177
178 dir_count = le32_to_cpu(dirh.count) + 1;
179
180 /* dir_count should never be larger than 256 */
181 if (dir_count > 256)
182 goto data_error;
183
184 while (dir_count--) {
185 /*
186 * Read directory entry.
187 */
188 err = squashfs_read_metadata(dir->i_sb, dire, &block,
189 &offset, sizeof(*dire));
190 if (err < 0)
191 goto read_failure;
192
193 size = le16_to_cpu(dire->size) + 1;
194
195 /* size should never be larger than SQUASHFS_NAME_LEN */
196 if (size > SQUASHFS_NAME_LEN)
197 goto data_error;
198
199 err = squashfs_read_metadata(dir->i_sb, dire->name,
200 &block, &offset, size);
201 if (err < 0)
202 goto read_failure;
203
204 length += sizeof(*dire) + size;
205
206 if (name[0] < dire->name[0])
207 goto exit_lookup;
208
209 if (len == size && !strncmp(name, dire->name, len)) {
210 unsigned int blk, off, ino_num;
211 long long ino;
212 blk = le32_to_cpu(dirh.start_block);
213 off = le16_to_cpu(dire->offset);
214 ino_num = le32_to_cpu(dirh.inode_number) +
215 (short) le16_to_cpu(dire->inode_number);
216 ino = SQUASHFS_MKINODE(blk, off);
217
218 TRACE("calling squashfs_iget for directory "
219 "entry %s, inode %x:%x, %d\n", name,
220 blk, off, ino_num);
221
222 inode = squashfs_iget(dir->i_sb, ino, ino_num);
223 goto exit_lookup;
224 }
225 }
226 }
227
228exit_lookup:
229 kfree(dire);
230 return d_splice_alias(inode, dentry);
231
232data_error:
233 err = -EIO;
234
235read_failure:
236 ERROR("Unable to read directory block [%llx:%x]\n",
237 squashfs_i(dir)->start + msblk->directory_table,
238 squashfs_i(dir)->offset);
239failed:
240 kfree(dire);
241 return ERR_PTR(err);
242}
243
244
245const struct inode_operations squashfs_dir_inode_ops = {
246 .lookup = squashfs_lookup,
247 .getxattr = generic_getxattr,
248 .listxattr = squashfs_listxattr
249};
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 * namei.c
9 */
10
11/*
12 * This file implements code to do filename lookup in directories.
13 *
14 * Like inodes, directories are packed into compressed metadata blocks, stored
15 * in a directory table. Directories are accessed using the start address of
16 * the metablock containing the directory and the offset into the
17 * decompressed block (<block, offset>).
18 *
19 * Directories are organised in a slightly complex way, and are not simply
20 * a list of file names. The organisation takes advantage of the
21 * fact that (in most cases) the inodes of the files will be in the same
22 * compressed metadata block, and therefore, can share the start block.
23 * Directories are therefore organised in a two level list, a directory
24 * header containing the shared start block value, and a sequence of directory
25 * entries, each of which share the shared start block. A new directory header
26 * is written once/if the inode start block changes. The directory
27 * header/directory entry list is repeated as many times as necessary.
28 *
29 * Directories are sorted, and can contain a directory index to speed up
30 * file lookup. Directory indexes store one entry per metablock, each entry
31 * storing the index/filename mapping to the first directory header
32 * in each metadata block. Directories are sorted in alphabetical order,
33 * and at lookup the index is scanned linearly looking for the first filename
34 * alphabetically larger than the filename being looked up. At this point the
35 * location of the metadata block the filename is in has been found.
36 * The general idea of the index is ensure only one metadata block needs to be
37 * decompressed to do a lookup irrespective of the length of the directory.
38 * This scheme has the advantage that it doesn't require extra memory overhead
39 * and doesn't require much extra storage on disk.
40 */
41
42#include <linux/fs.h>
43#include <linux/vfs.h>
44#include <linux/slab.h>
45#include <linux/string.h>
46#include <linux/dcache.h>
47#include <linux/xattr.h>
48
49#include "squashfs_fs.h"
50#include "squashfs_fs_sb.h"
51#include "squashfs_fs_i.h"
52#include "squashfs.h"
53#include "xattr.h"
54
55/*
56 * Lookup name in the directory index, returning the location of the metadata
57 * block containing it, and the directory index this represents.
58 *
59 * If we get an error reading the index then return the part of the index
60 * (if any) we have managed to read - the index isn't essential, just
61 * quicker.
62 */
63static int get_dir_index_using_name(struct super_block *sb,
64 u64 *next_block, int *next_offset, u64 index_start,
65 int index_offset, int i_count, const char *name,
66 int len)
67{
68 struct squashfs_sb_info *msblk = sb->s_fs_info;
69 int i, length = 0, err;
70 unsigned int size;
71 struct squashfs_dir_index *index;
72 char *str;
73
74 TRACE("Entered get_dir_index_using_name, i_count %d\n", i_count);
75
76 index = kmalloc(sizeof(*index) + SQUASHFS_NAME_LEN * 2 + 2, GFP_KERNEL);
77 if (index == NULL) {
78 ERROR("Failed to allocate squashfs_dir_index\n");
79 goto out;
80 }
81
82 str = &index->name[SQUASHFS_NAME_LEN + 1];
83 strncpy(str, name, len);
84 str[len] = '\0';
85
86 for (i = 0; i < i_count; i++) {
87 err = squashfs_read_metadata(sb, index, &index_start,
88 &index_offset, sizeof(*index));
89 if (err < 0)
90 break;
91
92
93 size = le32_to_cpu(index->size) + 1;
94 if (size > SQUASHFS_NAME_LEN)
95 break;
96
97 err = squashfs_read_metadata(sb, index->name, &index_start,
98 &index_offset, size);
99 if (err < 0)
100 break;
101
102 index->name[size] = '\0';
103
104 if (strcmp(index->name, str) > 0)
105 break;
106
107 length = le32_to_cpu(index->index);
108 *next_block = le32_to_cpu(index->start_block) +
109 msblk->directory_table;
110 }
111
112 *next_offset = (length + *next_offset) % SQUASHFS_METADATA_SIZE;
113 kfree(index);
114
115out:
116 /*
117 * Return index (f_pos) of the looked up metadata block. Translate
118 * from internal f_pos to external f_pos which is offset by 3 because
119 * we invent "." and ".." entries which are not actually stored in the
120 * directory.
121 */
122 return length + 3;
123}
124
125
126static struct dentry *squashfs_lookup(struct inode *dir, struct dentry *dentry,
127 unsigned int flags)
128{
129 const unsigned char *name = dentry->d_name.name;
130 int len = dentry->d_name.len;
131 struct inode *inode = NULL;
132 struct squashfs_sb_info *msblk = dir->i_sb->s_fs_info;
133 struct squashfs_dir_header dirh;
134 struct squashfs_dir_entry *dire;
135 u64 block = squashfs_i(dir)->start + msblk->directory_table;
136 int offset = squashfs_i(dir)->offset;
137 int err, length;
138 unsigned int dir_count, size;
139
140 TRACE("Entered squashfs_lookup [%llx:%x]\n", block, offset);
141
142 dire = kmalloc(sizeof(*dire) + SQUASHFS_NAME_LEN + 1, GFP_KERNEL);
143 if (dire == NULL) {
144 ERROR("Failed to allocate squashfs_dir_entry\n");
145 return ERR_PTR(-ENOMEM);
146 }
147
148 if (len > SQUASHFS_NAME_LEN) {
149 err = -ENAMETOOLONG;
150 goto failed;
151 }
152
153 length = get_dir_index_using_name(dir->i_sb, &block, &offset,
154 squashfs_i(dir)->dir_idx_start,
155 squashfs_i(dir)->dir_idx_offset,
156 squashfs_i(dir)->dir_idx_cnt, name, len);
157
158 while (length < i_size_read(dir)) {
159 /*
160 * Read directory header.
161 */
162 err = squashfs_read_metadata(dir->i_sb, &dirh, &block,
163 &offset, sizeof(dirh));
164 if (err < 0)
165 goto read_failure;
166
167 length += sizeof(dirh);
168
169 dir_count = le32_to_cpu(dirh.count) + 1;
170
171 if (dir_count > SQUASHFS_DIR_COUNT)
172 goto data_error;
173
174 while (dir_count--) {
175 /*
176 * Read directory entry.
177 */
178 err = squashfs_read_metadata(dir->i_sb, dire, &block,
179 &offset, sizeof(*dire));
180 if (err < 0)
181 goto read_failure;
182
183 size = le16_to_cpu(dire->size) + 1;
184
185 /* size should never be larger than SQUASHFS_NAME_LEN */
186 if (size > SQUASHFS_NAME_LEN)
187 goto data_error;
188
189 err = squashfs_read_metadata(dir->i_sb, dire->name,
190 &block, &offset, size);
191 if (err < 0)
192 goto read_failure;
193
194 length += sizeof(*dire) + size;
195
196 if (name[0] < dire->name[0])
197 goto exit_lookup;
198
199 if (len == size && !strncmp(name, dire->name, len)) {
200 unsigned int blk, off, ino_num;
201 long long ino;
202 blk = le32_to_cpu(dirh.start_block);
203 off = le16_to_cpu(dire->offset);
204 ino_num = le32_to_cpu(dirh.inode_number) +
205 (short) le16_to_cpu(dire->inode_number);
206 ino = SQUASHFS_MKINODE(blk, off);
207
208 TRACE("calling squashfs_iget for directory "
209 "entry %s, inode %x:%x, %d\n", name,
210 blk, off, ino_num);
211
212 inode = squashfs_iget(dir->i_sb, ino, ino_num);
213 goto exit_lookup;
214 }
215 }
216 }
217
218exit_lookup:
219 kfree(dire);
220 return d_splice_alias(inode, dentry);
221
222data_error:
223 err = -EIO;
224
225read_failure:
226 ERROR("Unable to read directory block [%llx:%x]\n",
227 squashfs_i(dir)->start + msblk->directory_table,
228 squashfs_i(dir)->offset);
229failed:
230 kfree(dire);
231 return ERR_PTR(err);
232}
233
234
235const struct inode_operations squashfs_dir_inode_ops = {
236 .lookup = squashfs_lookup,
237 .listxattr = squashfs_listxattr
238};