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68252eb5 | 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
12260140 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> |
12260140 | 7 | * |
12260140 PL |
8 | * export.c |
9 | */ | |
10 | ||
11 | /* | |
12 | * This file implements code to make Squashfs filesystems exportable (NFS etc.) | |
13 | * | |
14 | * The export code uses an inode lookup table to map inode numbers passed in | |
15 | * filehandles to an inode location on disk. This table is stored compressed | |
16 | * into metadata blocks. A second index table is used to locate these. This | |
17 | * second index table for speed of access (and because it is small) is read at | |
18 | * mount time and cached in memory. | |
19 | * | |
20 | * The inode lookup table is used only by the export code, inode disk | |
21 | * locations are directly encoded in directories, enabling direct access | |
22 | * without an intermediate lookup for all operations except the export ops. | |
23 | */ | |
24 | ||
25 | #include <linux/fs.h> | |
26 | #include <linux/vfs.h> | |
27 | #include <linux/dcache.h> | |
28 | #include <linux/exportfs.h> | |
23516dc7 | 29 | #include <linux/slab.h> |
12260140 PL |
30 | |
31 | #include "squashfs_fs.h" | |
32 | #include "squashfs_fs_sb.h" | |
33 | #include "squashfs_fs_i.h" | |
34 | #include "squashfs.h" | |
35 | ||
36 | /* | |
37 | * Look-up inode number (ino) in table, returning the inode location. | |
38 | */ | |
39 | static long long squashfs_inode_lookup(struct super_block *sb, int ino_num) | |
40 | { | |
41 | struct squashfs_sb_info *msblk = sb->s_fs_info; | |
42 | int blk = SQUASHFS_LOOKUP_BLOCK(ino_num - 1); | |
43 | int offset = SQUASHFS_LOOKUP_BLOCK_OFFSET(ino_num - 1); | |
eabac19e | 44 | u64 start; |
12260140 PL |
45 | __le64 ino; |
46 | int err; | |
47 | ||
48 | TRACE("Entered squashfs_inode_lookup, inode_number = %d\n", ino_num); | |
49 | ||
eabac19e PL |
50 | if (ino_num == 0 || (ino_num - 1) >= msblk->inodes) |
51 | return -EINVAL; | |
52 | ||
53 | start = le64_to_cpu(msblk->inode_lookup_table[blk]); | |
54 | ||
12260140 PL |
55 | err = squashfs_read_metadata(sb, &ino, &start, &offset, sizeof(ino)); |
56 | if (err < 0) | |
57 | return err; | |
58 | ||
59 | TRACE("squashfs_inode_lookup, inode = 0x%llx\n", | |
60 | (u64) le64_to_cpu(ino)); | |
61 | ||
62 | return le64_to_cpu(ino); | |
63 | } | |
64 | ||
65 | ||
66 | static struct dentry *squashfs_export_iget(struct super_block *sb, | |
67 | unsigned int ino_num) | |
68 | { | |
69 | long long ino; | |
70 | struct dentry *dentry = ERR_PTR(-ENOENT); | |
71 | ||
72 | TRACE("Entered squashfs_export_iget\n"); | |
73 | ||
74 | ino = squashfs_inode_lookup(sb, ino_num); | |
75 | if (ino >= 0) | |
76 | dentry = d_obtain_alias(squashfs_iget(sb, ino, ino_num)); | |
77 | ||
78 | return dentry; | |
79 | } | |
80 | ||
81 | ||
82 | static struct dentry *squashfs_fh_to_dentry(struct super_block *sb, | |
83 | struct fid *fid, int fh_len, int fh_type) | |
84 | { | |
85 | if ((fh_type != FILEID_INO32_GEN && fh_type != FILEID_INO32_GEN_PARENT) | |
86 | || fh_len < 2) | |
87 | return NULL; | |
88 | ||
89 | return squashfs_export_iget(sb, fid->i32.ino); | |
90 | } | |
91 | ||
92 | ||
93 | static struct dentry *squashfs_fh_to_parent(struct super_block *sb, | |
94 | struct fid *fid, int fh_len, int fh_type) | |
95 | { | |
96 | if (fh_type != FILEID_INO32_GEN_PARENT || fh_len < 4) | |
97 | return NULL; | |
98 | ||
99 | return squashfs_export_iget(sb, fid->i32.parent_ino); | |
100 | } | |
101 | ||
102 | ||
103 | static struct dentry *squashfs_get_parent(struct dentry *child) | |
104 | { | |
2b0143b5 | 105 | struct inode *inode = d_inode(child); |
12260140 PL |
106 | unsigned int parent_ino = squashfs_i(inode)->parent; |
107 | ||
108 | return squashfs_export_iget(inode->i_sb, parent_ino); | |
109 | } | |
110 | ||
111 | ||
112 | /* | |
113 | * Read uncompressed inode lookup table indexes off disk into memory | |
114 | */ | |
115 | __le64 *squashfs_read_inode_lookup_table(struct super_block *sb, | |
ac51a0a7 | 116 | u64 lookup_table_start, u64 next_table, unsigned int inodes) |
12260140 PL |
117 | { |
118 | unsigned int length = SQUASHFS_LOOKUP_BLOCK_BYTES(inodes); | |
eabac19e PL |
119 | unsigned int indexes = SQUASHFS_LOOKUP_BLOCKS(inodes); |
120 | int n; | |
ac51a0a7 | 121 | __le64 *table; |
eabac19e | 122 | u64 start, end; |
12260140 PL |
123 | |
124 | TRACE("In read_inode_lookup_table, length %d\n", length); | |
125 | ||
ac51a0a7 PL |
126 | /* Sanity check values */ |
127 | ||
128 | /* there should always be at least one inode */ | |
129 | if (inodes == 0) | |
130 | return ERR_PTR(-EINVAL); | |
131 | ||
eabac19e PL |
132 | /* |
133 | * The computed size of the lookup table (length bytes) should exactly | |
134 | * match the table start and end points | |
ac51a0a7 | 135 | */ |
eabac19e | 136 | if (length != (next_table - lookup_table_start)) |
ac51a0a7 PL |
137 | return ERR_PTR(-EINVAL); |
138 | ||
139 | table = squashfs_read_table(sb, lookup_table_start, length); | |
eabac19e PL |
140 | if (IS_ERR(table)) |
141 | return table; | |
ac51a0a7 PL |
142 | |
143 | /* | |
eabac19e PL |
144 | * table0], table[1], ... table[indexes - 1] store the locations |
145 | * of the compressed inode lookup blocks. Each entry should be | |
146 | * less than the next (i.e. table[0] < table[1]), and the difference | |
147 | * between them should be SQUASHFS_METADATA_SIZE or less. | |
148 | * table[indexes - 1] should be less than lookup_table_start, and | |
149 | * again the difference should be SQUASHFS_METADATA_SIZE or less | |
ac51a0a7 | 150 | */ |
eabac19e PL |
151 | for (n = 0; n < (indexes - 1); n++) { |
152 | start = le64_to_cpu(table[n]); | |
153 | end = le64_to_cpu(table[n + 1]); | |
154 | ||
c1b20283 SN |
155 | if (start >= end |
156 | || (end - start) > | |
157 | (SQUASHFS_METADATA_SIZE + SQUASHFS_BLOCK_OFFSET)) { | |
eabac19e PL |
158 | kfree(table); |
159 | return ERR_PTR(-EINVAL); | |
160 | } | |
161 | } | |
162 | ||
163 | start = le64_to_cpu(table[indexes - 1]); | |
c1b20283 SN |
164 | if (start >= lookup_table_start || |
165 | (lookup_table_start - start) > | |
166 | (SQUASHFS_METADATA_SIZE + SQUASHFS_BLOCK_OFFSET)) { | |
ac51a0a7 PL |
167 | kfree(table); |
168 | return ERR_PTR(-EINVAL); | |
169 | } | |
170 | ||
171 | return table; | |
12260140 PL |
172 | } |
173 | ||
174 | ||
175 | const struct export_operations squashfs_export_ops = { | |
176 | .fh_to_dentry = squashfs_fh_to_dentry, | |
177 | .fh_to_parent = squashfs_fh_to_parent, | |
178 | .get_parent = squashfs_get_parent | |
179 | }; |