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Commit | Line | Data |
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8ed5eec9 AG |
1 | /* |
2 | * Overlayfs NFS export support. | |
3 | * | |
4 | * Amir Goldstein <amir73il@gmail.com> | |
5 | * | |
6 | * Copyright (C) 2017-2018 CTERA Networks. All Rights Reserved. | |
7 | * | |
8 | * This program is free software; you can redistribute it and/or modify it | |
9 | * under the terms of the GNU General Public License version 2 as published by | |
10 | * the Free Software Foundation. | |
11 | */ | |
12 | ||
13 | #include <linux/fs.h> | |
14 | #include <linux/cred.h> | |
15 | #include <linux/mount.h> | |
16 | #include <linux/namei.h> | |
17 | #include <linux/xattr.h> | |
18 | #include <linux/exportfs.h> | |
19 | #include <linux/ratelimit.h> | |
20 | #include "overlayfs.h" | |
21 | ||
22 | static int ovl_d_to_fh(struct dentry *dentry, char *buf, int buflen) | |
23 | { | |
24 | struct dentry *upper = ovl_dentry_upper(dentry); | |
25 | struct dentry *origin = ovl_dentry_lower(dentry); | |
26 | struct ovl_fh *fh = NULL; | |
27 | int err; | |
28 | ||
29 | /* | |
30 | * On overlay with an upper layer, overlay root inode is encoded as | |
31 | * an upper file handle, because upper root dir is not indexed. | |
32 | */ | |
33 | if (dentry == dentry->d_sb->s_root && upper) | |
34 | origin = NULL; | |
35 | ||
36 | err = -EACCES; | |
37 | if (!upper || origin) | |
38 | goto fail; | |
39 | ||
40 | /* TODO: encode non pure-upper by origin */ | |
41 | fh = ovl_encode_fh(upper, true); | |
42 | ||
43 | err = -EOVERFLOW; | |
44 | if (fh->len > buflen) | |
45 | goto fail; | |
46 | ||
47 | memcpy(buf, (char *)fh, fh->len); | |
48 | err = fh->len; | |
49 | ||
50 | out: | |
51 | kfree(fh); | |
52 | return err; | |
53 | ||
54 | fail: | |
55 | pr_warn_ratelimited("overlayfs: failed to encode file handle (%pd2, err=%i, buflen=%d, len=%d, type=%d)\n", | |
56 | dentry, err, buflen, fh ? (int)fh->len : 0, | |
57 | fh ? fh->type : 0); | |
58 | goto out; | |
59 | } | |
60 | ||
61 | static int ovl_dentry_to_fh(struct dentry *dentry, u32 *fid, int *max_len) | |
62 | { | |
63 | int res, len = *max_len << 2; | |
64 | ||
65 | res = ovl_d_to_fh(dentry, (char *)fid, len); | |
66 | if (res <= 0) | |
67 | return FILEID_INVALID; | |
68 | ||
69 | len = res; | |
70 | ||
71 | /* Round up to dwords */ | |
72 | *max_len = (len + 3) >> 2; | |
73 | return OVL_FILEID; | |
74 | } | |
75 | ||
76 | static int ovl_encode_inode_fh(struct inode *inode, u32 *fid, int *max_len, | |
77 | struct inode *parent) | |
78 | { | |
79 | struct dentry *dentry; | |
80 | int type; | |
81 | ||
82 | /* TODO: encode connectable file handles */ | |
83 | if (parent) | |
84 | return FILEID_INVALID; | |
85 | ||
86 | dentry = d_find_any_alias(inode); | |
87 | if (WARN_ON(!dentry)) | |
88 | return FILEID_INVALID; | |
89 | ||
90 | type = ovl_dentry_to_fh(dentry, fid, max_len); | |
91 | ||
92 | dput(dentry); | |
93 | return type; | |
94 | } | |
95 | ||
8556a420 AG |
96 | /* |
97 | * Find or instantiate an overlay dentry from real dentries. | |
98 | */ | |
99 | static struct dentry *ovl_obtain_alias(struct super_block *sb, | |
100 | struct dentry *upper, | |
101 | struct ovl_path *lowerpath) | |
102 | { | |
103 | struct inode *inode; | |
104 | struct dentry *dentry; | |
105 | struct ovl_entry *oe; | |
106 | void *fsdata = &oe; | |
107 | ||
108 | /* TODO: obtain non pure-upper */ | |
109 | if (lowerpath) | |
110 | return ERR_PTR(-EIO); | |
111 | ||
112 | inode = ovl_get_inode(sb, dget(upper), NULL, NULL, 0); | |
113 | if (IS_ERR(inode)) { | |
114 | dput(upper); | |
115 | return ERR_CAST(inode); | |
116 | } | |
117 | ||
118 | dentry = d_find_any_alias(inode); | |
119 | if (!dentry) { | |
120 | dentry = d_alloc_anon(inode->i_sb); | |
121 | if (!dentry) | |
122 | goto nomem; | |
123 | oe = ovl_alloc_entry(0); | |
124 | if (!oe) | |
125 | goto nomem; | |
126 | ||
127 | dentry->d_fsdata = oe; | |
128 | ovl_dentry_set_upper_alias(dentry); | |
129 | } | |
130 | ||
131 | return d_instantiate_anon(dentry, inode); | |
132 | ||
133 | nomem: | |
134 | iput(inode); | |
135 | dput(dentry); | |
136 | return ERR_PTR(-ENOMEM); | |
137 | } | |
138 | ||
139 | static struct dentry *ovl_upper_fh_to_d(struct super_block *sb, | |
140 | struct ovl_fh *fh) | |
141 | { | |
142 | struct ovl_fs *ofs = sb->s_fs_info; | |
143 | struct dentry *dentry; | |
144 | struct dentry *upper; | |
145 | ||
146 | if (!ofs->upper_mnt) | |
147 | return ERR_PTR(-EACCES); | |
148 | ||
149 | upper = ovl_decode_fh(fh, ofs->upper_mnt); | |
150 | if (IS_ERR_OR_NULL(upper)) | |
151 | return upper; | |
152 | ||
153 | dentry = ovl_obtain_alias(sb, upper, NULL); | |
154 | dput(upper); | |
155 | ||
156 | return dentry; | |
157 | } | |
158 | ||
159 | static struct dentry *ovl_fh_to_dentry(struct super_block *sb, struct fid *fid, | |
160 | int fh_len, int fh_type) | |
161 | { | |
162 | struct dentry *dentry = NULL; | |
163 | struct ovl_fh *fh = (struct ovl_fh *) fid; | |
164 | int len = fh_len << 2; | |
165 | unsigned int flags = 0; | |
166 | int err; | |
167 | ||
168 | err = -EINVAL; | |
169 | if (fh_type != OVL_FILEID) | |
170 | goto out_err; | |
171 | ||
172 | err = ovl_check_fh_len(fh, len); | |
173 | if (err) | |
174 | goto out_err; | |
175 | ||
176 | /* TODO: decode non-upper */ | |
177 | flags = fh->flags; | |
178 | if (flags & OVL_FH_FLAG_PATH_UPPER) | |
179 | dentry = ovl_upper_fh_to_d(sb, fh); | |
180 | err = PTR_ERR(dentry); | |
181 | if (IS_ERR(dentry) && err != -ESTALE) | |
182 | goto out_err; | |
183 | ||
184 | return dentry; | |
185 | ||
186 | out_err: | |
187 | pr_warn_ratelimited("overlayfs: failed to decode file handle (len=%d, type=%d, flags=%x, err=%i)\n", | |
188 | len, fh_type, flags, err); | |
189 | return ERR_PTR(err); | |
190 | } | |
191 | ||
8ed5eec9 AG |
192 | const struct export_operations ovl_export_operations = { |
193 | .encode_fh = ovl_encode_inode_fh, | |
8556a420 | 194 | .fh_to_dentry = ovl_fh_to_dentry, |
8ed5eec9 | 195 | }; |