1 | // SPDX-License-Identifier: GPL-2.0 |
2 | /* |
3 | * fs/isofs/export.c |
4 | * |
5 | * (C) 2004 Paul Serice - The new inode scheme requires switching |
6 | * from iget() to iget5_locked() which means |
7 | * the NFS export operations have to be hand |
8 | * coded because the default routines rely on |
9 | * iget(). |
10 | * |
11 | * The following files are helpful: |
12 | * |
13 | * Documentation/filesystems/nfs/exporting.rst |
14 | * fs/exportfs/expfs.c. |
15 | */ |
16 | |
17 | #include "isofs.h" |
18 | |
19 | static struct dentry * |
20 | isofs_export_iget(struct super_block *sb, |
21 | unsigned long block, |
22 | unsigned long offset, |
23 | __u32 generation) |
24 | { |
25 | struct inode *inode; |
26 | |
27 | if (block == 0) |
28 | return ERR_PTR(error: -ESTALE); |
29 | inode = isofs_iget(sb, block, offset); |
30 | if (IS_ERR(ptr: inode)) |
31 | return ERR_CAST(ptr: inode); |
32 | if (generation && inode->i_generation != generation) { |
33 | iput(inode); |
34 | return ERR_PTR(error: -ESTALE); |
35 | } |
36 | return d_obtain_alias(inode); |
37 | } |
38 | |
39 | /* This function is surprisingly simple. The trick is understanding |
40 | * that "child" is always a directory. So, to find its parent, you |
41 | * simply need to find its ".." entry, normalize its block and offset, |
42 | * and return the underlying inode. See the comments for |
43 | * isofs_normalize_block_and_offset(). */ |
44 | static struct dentry *isofs_export_get_parent(struct dentry *child) |
45 | { |
46 | unsigned long parent_block = 0; |
47 | unsigned long parent_offset = 0; |
48 | struct inode *child_inode = d_inode(dentry: child); |
49 | struct iso_inode_info *e_child_inode = ISOFS_I(inode: child_inode); |
50 | struct iso_directory_record *de = NULL; |
51 | struct buffer_head * bh = NULL; |
52 | struct dentry *rv = NULL; |
53 | |
54 | /* "child" must always be a directory. */ |
55 | if (!S_ISDIR(child_inode->i_mode)) { |
56 | printk(KERN_ERR "isofs: isofs_export_get_parent(): " |
57 | "child is not a directory!\n" ); |
58 | rv = ERR_PTR(error: -EACCES); |
59 | goto out; |
60 | } |
61 | |
62 | /* It is an invariant that the directory offset is zero. If |
63 | * it is not zero, it means the directory failed to be |
64 | * normalized for some reason. */ |
65 | if (e_child_inode->i_iget5_offset != 0) { |
66 | printk(KERN_ERR "isofs: isofs_export_get_parent(): " |
67 | "child directory not normalized!\n" ); |
68 | rv = ERR_PTR(error: -EACCES); |
69 | goto out; |
70 | } |
71 | |
72 | /* The child inode has been normalized such that its |
73 | * i_iget5_block value points to the "." entry. Fortunately, |
74 | * the ".." entry is located in the same block. */ |
75 | parent_block = e_child_inode->i_iget5_block; |
76 | |
77 | /* Get the block in question. */ |
78 | bh = sb_bread(sb: child_inode->i_sb, block: parent_block); |
79 | if (bh == NULL) { |
80 | rv = ERR_PTR(error: -EACCES); |
81 | goto out; |
82 | } |
83 | |
84 | /* This is the "." entry. */ |
85 | de = (struct iso_directory_record*)bh->b_data; |
86 | |
87 | /* The ".." entry is always the second entry. */ |
88 | parent_offset = (unsigned long)isonum_711(p: de->length); |
89 | de = (struct iso_directory_record*)(bh->b_data + parent_offset); |
90 | |
91 | /* Verify it is in fact the ".." entry. */ |
92 | if ((isonum_711(p: de->name_len) != 1) || (de->name[0] != 1)) { |
93 | printk(KERN_ERR "isofs: Unable to find the \"..\" " |
94 | "directory for NFS.\n" ); |
95 | rv = ERR_PTR(error: -EACCES); |
96 | goto out; |
97 | } |
98 | |
99 | /* Normalize */ |
100 | isofs_normalize_block_and_offset(de, block: &parent_block, offset: &parent_offset); |
101 | |
102 | rv = d_obtain_alias(isofs_iget(sb: child_inode->i_sb, block: parent_block, |
103 | offset: parent_offset)); |
104 | out: |
105 | if (bh) |
106 | brelse(bh); |
107 | return rv; |
108 | } |
109 | |
110 | static int |
111 | isofs_export_encode_fh(struct inode *inode, |
112 | __u32 *fh32, |
113 | int *max_len, |
114 | struct inode *parent) |
115 | { |
116 | struct iso_inode_info * ei = ISOFS_I(inode); |
117 | int len = *max_len; |
118 | int type = 1; |
119 | __u16 *fh16 = (__u16*)fh32; |
120 | |
121 | /* |
122 | * WARNING: max_len is 5 for NFSv2. Because of this |
123 | * limitation, we use the lower 16 bits of fh32[1] to hold the |
124 | * offset of the inode and the upper 16 bits of fh32[1] to |
125 | * hold the offset of the parent. |
126 | */ |
127 | if (parent && (len < 5)) { |
128 | *max_len = 5; |
129 | return FILEID_INVALID; |
130 | } else if (len < 3) { |
131 | *max_len = 3; |
132 | return FILEID_INVALID; |
133 | } |
134 | |
135 | len = 3; |
136 | fh32[0] = ei->i_iget5_block; |
137 | fh16[2] = (__u16)ei->i_iget5_offset; /* fh16 [sic] */ |
138 | fh16[3] = 0; /* avoid leaking uninitialized data */ |
139 | fh32[2] = inode->i_generation; |
140 | if (parent) { |
141 | struct iso_inode_info *eparent; |
142 | eparent = ISOFS_I(inode: parent); |
143 | fh32[3] = eparent->i_iget5_block; |
144 | fh16[3] = (__u16)eparent->i_iget5_offset; /* fh16 [sic] */ |
145 | fh32[4] = parent->i_generation; |
146 | len = 5; |
147 | type = 2; |
148 | } |
149 | *max_len = len; |
150 | return type; |
151 | } |
152 | |
153 | struct isofs_fid { |
154 | u32 block; |
155 | u16 offset; |
156 | u16 parent_offset; |
157 | u32 generation; |
158 | u32 parent_block; |
159 | u32 parent_generation; |
160 | }; |
161 | |
162 | static struct dentry *isofs_fh_to_dentry(struct super_block *sb, |
163 | struct fid *fid, int fh_len, int fh_type) |
164 | { |
165 | struct isofs_fid *ifid = (struct isofs_fid *)fid; |
166 | |
167 | if (fh_len < 3 || fh_type > 2) |
168 | return NULL; |
169 | |
170 | return isofs_export_iget(sb, block: ifid->block, offset: ifid->offset, |
171 | generation: ifid->generation); |
172 | } |
173 | |
174 | static struct dentry *isofs_fh_to_parent(struct super_block *sb, |
175 | struct fid *fid, int fh_len, int fh_type) |
176 | { |
177 | struct isofs_fid *ifid = (struct isofs_fid *)fid; |
178 | |
179 | if (fh_len < 2 || fh_type != 2) |
180 | return NULL; |
181 | |
182 | return isofs_export_iget(sb, |
183 | block: fh_len > 2 ? ifid->parent_block : 0, |
184 | offset: ifid->parent_offset, |
185 | generation: fh_len > 4 ? ifid->parent_generation : 0); |
186 | } |
187 | |
188 | const struct export_operations isofs_export_ops = { |
189 | .encode_fh = isofs_export_encode_fh, |
190 | .fh_to_dentry = isofs_fh_to_dentry, |
191 | .fh_to_parent = isofs_fh_to_parent, |
192 | .get_parent = isofs_export_get_parent, |
193 | }; |
194 | |