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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 * 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 */
39static 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
66static 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
82static 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
93static 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
103static struct dentry *squashfs_get_parent(struct dentry *child)
104{
105 struct inode *inode = d_inode(child);
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,
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(-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(-EINVAL);
138
139 table = squashfs_read_table(sb, lookup_table_start, length);
140 if (IS_ERR(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(table);
159 return ERR_PTR(-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(table);
168 return ERR_PTR(-EINVAL);
169 }
170
171 return table;
172}
173
174
175const 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};