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 */
squashfs_inode_lookup(struct super_block * sb,int ino_num)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 = le64_to_cpu(msblk->inode_lookup_table[blk]);
45 __le64 ino;
46 int err;
47
48 TRACE("Entered squashfs_inode_lookup, inode_number = %d\n", ino_num);
49
50 err = squashfs_read_metadata(sb, &ino, &start, &offset, sizeof(ino));
51 if (err < 0)
52 return err;
53
54 TRACE("squashfs_inode_lookup, inode = 0x%llx\n",
55 (u64) le64_to_cpu(ino));
56
57 return le64_to_cpu(ino);
58 }
59
60
squashfs_export_iget(struct super_block * sb,unsigned int ino_num)61 static struct dentry *squashfs_export_iget(struct super_block *sb,
62 unsigned int ino_num)
63 {
64 long long ino;
65 struct dentry *dentry = ERR_PTR(-ENOENT);
66
67 TRACE("Entered squashfs_export_iget\n");
68
69 ino = squashfs_inode_lookup(sb, ino_num);
70 if (ino >= 0)
71 dentry = d_obtain_alias(squashfs_iget(sb, ino, ino_num));
72
73 return dentry;
74 }
75
76
squashfs_fh_to_dentry(struct super_block * sb,struct fid * fid,int fh_len,int fh_type)77 static struct dentry *squashfs_fh_to_dentry(struct super_block *sb,
78 struct fid *fid, int fh_len, int fh_type)
79 {
80 if ((fh_type != FILEID_INO32_GEN && fh_type != FILEID_INO32_GEN_PARENT)
81 || fh_len < 2)
82 return NULL;
83
84 return squashfs_export_iget(sb, fid->i32.ino);
85 }
86
87
squashfs_fh_to_parent(struct super_block * sb,struct fid * fid,int fh_len,int fh_type)88 static struct dentry *squashfs_fh_to_parent(struct super_block *sb,
89 struct fid *fid, int fh_len, int fh_type)
90 {
91 if (fh_type != FILEID_INO32_GEN_PARENT || fh_len < 4)
92 return NULL;
93
94 return squashfs_export_iget(sb, fid->i32.parent_ino);
95 }
96
97
squashfs_get_parent(struct dentry * child)98 static struct dentry *squashfs_get_parent(struct dentry *child)
99 {
100 struct inode *inode = d_inode(child);
101 unsigned int parent_ino = squashfs_i(inode)->parent;
102
103 return squashfs_export_iget(inode->i_sb, parent_ino);
104 }
105
106
107 /*
108 * Read uncompressed inode lookup table indexes off disk into memory
109 */
squashfs_read_inode_lookup_table(struct super_block * sb,u64 lookup_table_start,u64 next_table,unsigned int inodes)110 __le64 *squashfs_read_inode_lookup_table(struct super_block *sb,
111 u64 lookup_table_start, u64 next_table, unsigned int inodes)
112 {
113 unsigned int length = SQUASHFS_LOOKUP_BLOCK_BYTES(inodes);
114 __le64 *table;
115
116 TRACE("In read_inode_lookup_table, length %d\n", length);
117
118 /* Sanity check values */
119
120 /* there should always be at least one inode */
121 if (inodes == 0)
122 return ERR_PTR(-EINVAL);
123
124 /* length bytes should not extend into the next table - this check
125 * also traps instances where lookup_table_start is incorrectly larger
126 * than the next table start
127 */
128 if (lookup_table_start + length > next_table)
129 return ERR_PTR(-EINVAL);
130
131 table = squashfs_read_table(sb, lookup_table_start, length);
132
133 /*
134 * table[0] points to the first inode lookup table metadata block,
135 * this should be less than lookup_table_start
136 */
137 if (!IS_ERR(table) && le64_to_cpu(table[0]) >= lookup_table_start) {
138 kfree(table);
139 return ERR_PTR(-EINVAL);
140 }
141
142 return table;
143 }
144
145
146 const struct export_operations squashfs_export_ops = {
147 .fh_to_dentry = squashfs_fh_to_dentry,
148 .fh_to_parent = squashfs_fh_to_parent,
149 .get_parent = squashfs_get_parent
150 };
151