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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); | |
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 | ||
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 | ||
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 | ||
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 | ||
98 | static struct dentry *squashfs_get_parent(struct dentry *child) | |
99 | { | |
2b0143b5 | 100 | struct inode *inode = d_inode(child); |
12260140 PL |
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 | */ | |
110 | __le64 *squashfs_read_inode_lookup_table(struct super_block *sb, | |
ac51a0a7 | 111 | u64 lookup_table_start, u64 next_table, unsigned int inodes) |
12260140 PL |
112 | { |
113 | unsigned int length = SQUASHFS_LOOKUP_BLOCK_BYTES(inodes); | |
ac51a0a7 | 114 | __le64 *table; |
12260140 PL |
115 | |
116 | TRACE("In read_inode_lookup_table, length %d\n", length); | |
117 | ||
ac51a0a7 PL |
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 | */ | |
d5b72ce1 | 137 | if (!IS_ERR(table) && le64_to_cpu(table[0]) >= lookup_table_start) { |
ac51a0a7 PL |
138 | kfree(table); |
139 | return ERR_PTR(-EINVAL); | |
140 | } | |
141 | ||
142 | return table; | |
12260140 PL |
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 | }; |