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 | * 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> |
29 | #include <linux/slab.h> |
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); |
44 | u64 start; |
45 | __le64 ino; |
46 | int err; |
47 | |
48 | TRACE("Entered squashfs_inode_lookup, inode_number = %d\n" , ino_num); |
49 | |
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 | |
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(error: -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, ino_num: 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, ino_num: fid->i32.parent_ino); |
100 | } |
101 | |
102 | |
103 | static struct dentry *squashfs_get_parent(struct dentry *child) |
104 | { |
105 | struct inode *inode = d_inode(dentry: child); |
106 | unsigned int parent_ino = squashfs_i(inode)->parent; |
107 | |
108 | return squashfs_export_iget(sb: inode->i_sb, ino_num: 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, |
116 | u64 lookup_table_start, u64 next_table, unsigned int inodes) |
117 | { |
118 | unsigned int length = SQUASHFS_LOOKUP_BLOCK_BYTES(inodes); |
119 | unsigned int indexes = SQUASHFS_LOOKUP_BLOCKS(inodes); |
120 | int n; |
121 | __le64 *table; |
122 | u64 start, end; |
123 | |
124 | TRACE("In read_inode_lookup_table, length %d\n" , length); |
125 | |
126 | /* Sanity check values */ |
127 | |
128 | /* there should always be at least one inode */ |
129 | if (inodes == 0) |
130 | return ERR_PTR(error: -EINVAL); |
131 | |
132 | /* |
133 | * The computed size of the lookup table (length bytes) should exactly |
134 | * match the table start and end points |
135 | */ |
136 | if (length != (next_table - lookup_table_start)) |
137 | return ERR_PTR(error: -EINVAL); |
138 | |
139 | table = squashfs_read_table(sb, lookup_table_start, length); |
140 | if (IS_ERR(ptr: table)) |
141 | return table; |
142 | |
143 | /* |
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 |
150 | */ |
151 | for (n = 0; n < (indexes - 1); n++) { |
152 | start = le64_to_cpu(table[n]); |
153 | end = le64_to_cpu(table[n + 1]); |
154 | |
155 | if (start >= end |
156 | || (end - start) > |
157 | (SQUASHFS_METADATA_SIZE + SQUASHFS_BLOCK_OFFSET)) { |
158 | kfree(objp: table); |
159 | return ERR_PTR(error: -EINVAL); |
160 | } |
161 | } |
162 | |
163 | start = le64_to_cpu(table[indexes - 1]); |
164 | if (start >= lookup_table_start || |
165 | (lookup_table_start - start) > |
166 | (SQUASHFS_METADATA_SIZE + SQUASHFS_BLOCK_OFFSET)) { |
167 | kfree(objp: table); |
168 | return ERR_PTR(error: -EINVAL); |
169 | } |
170 | |
171 | return table; |
172 | } |
173 | |
174 | |
175 | const struct export_operations squashfs_export_ops = { |
176 | .encode_fh = generic_encode_ino32_fh, |
177 | .fh_to_dentry = squashfs_fh_to_dentry, |
178 | .fh_to_parent = squashfs_fh_to_parent, |
179 | .get_parent = squashfs_get_parent |
180 | }; |
181 | |