Commit | Line | Data |
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68252eb5 | 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
c88da2c9 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> |
c88da2c9 | 7 | * |
c88da2c9 PL |
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> | |
67f66cc6 | 47 | #include <linux/xattr.h> |
c88da2c9 PL |
48 | |
49 | #include "squashfs_fs.h" | |
50 | #include "squashfs_fs_sb.h" | |
51 | #include "squashfs_fs_i.h" | |
52 | #include "squashfs.h" | |
01e5b4e4 | 53 | #include "xattr.h" |
c88da2c9 PL |
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 | */ | |
63 | static 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; | |
28d7b568 DC |
69 | int i, length = 0, err; |
70 | unsigned int size; | |
c88da2c9 PL |
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; | |
9dbc41d5 | 94 | if (size > SQUASHFS_NAME_LEN) |
28d7b568 | 95 | break; |
c88da2c9 PL |
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 | ||
115 | out: | |
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 | ||
126 | static struct dentry *squashfs_lookup(struct inode *dir, struct dentry *dentry, | |
00cd8dd3 | 127 | unsigned int flags) |
c88da2c9 PL |
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; | |
52e9ce1c PL |
137 | int err, length; |
138 | unsigned int dir_count, size; | |
c88da2c9 PL |
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; | |
44cff8a9 | 170 | |
4826d83d | 171 | if (dir_count > SQUASHFS_DIR_COUNT) |
44cff8a9 PL |
172 | goto data_error; |
173 | ||
c88da2c9 PL |
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 | ||
44cff8a9 PL |
185 | /* size should never be larger than SQUASHFS_NAME_LEN */ |
186 | if (size > SQUASHFS_NAME_LEN) | |
187 | goto data_error; | |
188 | ||
c88da2c9 PL |
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); | |
c88da2c9 PL |
213 | goto exit_lookup; |
214 | } | |
215 | } | |
216 | } | |
217 | ||
218 | exit_lookup: | |
219 | kfree(dire); | |
0c1aa9a9 | 220 | return d_splice_alias(inode, dentry); |
c88da2c9 | 221 | |
44cff8a9 PL |
222 | data_error: |
223 | err = -EIO; | |
224 | ||
c88da2c9 PL |
225 | read_failure: |
226 | ERROR("Unable to read directory block [%llx:%x]\n", | |
227 | squashfs_i(dir)->start + msblk->directory_table, | |
228 | squashfs_i(dir)->offset); | |
229 | failed: | |
230 | kfree(dire); | |
231 | return ERR_PTR(err); | |
232 | } | |
233 | ||
234 | ||
235 | const struct inode_operations squashfs_dir_inode_ops = { | |
67f66cc6 | 236 | .lookup = squashfs_lookup, |
67f66cc6 | 237 | .listxattr = squashfs_listxattr |
c88da2c9 | 238 | }; |