1 /* getroot.c: get the root dentry for an NFS mount
2 *
3 * Copyright (C) 2006 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
10 */
11
12 #include <linux/module.h>
13 #include <linux/init.h>
14
15 #include <linux/time.h>
16 #include <linux/kernel.h>
17 #include <linux/mm.h>
18 #include <linux/string.h>
19 #include <linux/stat.h>
20 #include <linux/errno.h>
21 #include <linux/unistd.h>
22 #include <linux/sunrpc/clnt.h>
23 #include <linux/sunrpc/stats.h>
24 #include <linux/nfs_fs.h>
25 #include <linux/nfs_mount.h>
26 #include <linux/nfs4_mount.h>
27 #include <linux/lockd/bind.h>
28 #include <linux/seq_file.h>
29 #include <linux/mount.h>
30 #include <linux/nfs_idmap.h>
31 #include <linux/vfs.h>
32 #include <linux/namei.h>
33 #include <linux/mnt_namespace.h>
34 #include <linux/security.h>
35
36 #include <asm/system.h>
37 #include <asm/uaccess.h>
38
39 #include "nfs4_fs.h"
40 #include "delegation.h"
41 #include "internal.h"
42
43 #define NFSDBG_FACILITY NFSDBG_CLIENT
44
45 /*
46 * Set the superblock root dentry.
47 * Note that this function frees the inode in case of error.
48 */
49 static int nfs_superblock_set_dummy_root(struct super_block *sb, struct inode *inode)
50 {
51 /* The mntroot acts as the dummy root dentry for this superblock */
52 if (sb->s_root == NULL) {
53 sb->s_root = d_alloc_root(inode);
54 if (sb->s_root == NULL) {
55 iput(inode);
56 return -ENOMEM;
57 }
58 /* Circumvent igrab(): we know the inode is not being freed */
59 atomic_inc(&inode->i_count);
60 /*
61 * Ensure that this dentry is invisible to d_find_alias().
62 * Otherwise, it may be spliced into the tree by
63 * d_materialise_unique if a parent directory from the same
64 * filesystem gets mounted at a later time.
65 * This again causes shrink_dcache_for_umount_subtree() to
66 * Oops, since the test for IS_ROOT() will fail.
67 */
68 spin_lock(&dcache_lock);
69 list_del_init(&sb->s_root->d_alias);
70 spin_unlock(&dcache_lock);
71 }
72 return 0;
73 }
74
75 /*
76 * get an NFS2/NFS3 root dentry from the root filehandle
77 */
78 struct dentry *nfs_get_root(struct super_block *sb, struct nfs_fh *mntfh)
79 {
80 struct nfs_server *server = NFS_SB(sb);
81 struct nfs_fsinfo fsinfo;
82 struct nfs_fattr fattr;
83 struct dentry *mntroot;
84 struct inode *inode;
85 int error;
86
87 /* get the actual root for this mount */
88 fsinfo.fattr = &fattr;
89
90 error = server->nfs_client->rpc_ops->getroot(server, mntfh, &fsinfo);
91 if (error < 0) {
92 dprintk("nfs_get_root: getattr error = %d\n", -error);
93 return ERR_PTR(error);
94 }
95
96 inode = nfs_fhget(sb, mntfh, fsinfo.fattr);
97 if (IS_ERR(inode)) {
98 dprintk("nfs_get_root: get root inode failed\n");
99 return ERR_CAST(inode);
100 }
101
102 error = nfs_superblock_set_dummy_root(sb, inode);
103 if (error != 0)
104 return ERR_PTR(error);
105
106 /* root dentries normally start off anonymous and get spliced in later
107 * if the dentry tree reaches them; however if the dentry already
108 * exists, we'll pick it up at this point and use it as the root
109 */
110 mntroot = d_alloc_anon(inode);
111 if (!mntroot) {
112 iput(inode);
113 dprintk("nfs_get_root: get root dentry failed\n");
114 return ERR_PTR(-ENOMEM);
115 }
116
117 security_d_instantiate(mntroot, inode);
118
119 if (!mntroot->d_op)
120 mntroot->d_op = server->nfs_client->rpc_ops->dentry_ops;
121
122 return mntroot;
123 }
124
125 #ifdef CONFIG_NFS_V4
126
127 /*
128 * Do a simple pathwalk from the root FH of the server to the nominated target
129 * of the mountpoint
130 * - give error on symlinks
131 * - give error on ".." occurring in the path
132 * - follow traversals
133 */
134 int nfs4_path_walk(struct nfs_server *server,
135 struct nfs_fh *mntfh,
136 const char *path)
137 {
138 struct nfs_fsinfo fsinfo;
139 struct nfs_fattr fattr;
140 struct nfs_fh lastfh;
141 struct qstr name;
142 int ret;
143
144 dprintk("--> nfs4_path_walk(,,%s)\n", path);
145
146 fsinfo.fattr = &fattr;
147 nfs_fattr_init(&fattr);
148
149 /* Eat leading slashes */
150 while (*path == '/')
151 path++;
152
153 /* Start by getting the root filehandle from the server */
154 ret = server->nfs_client->rpc_ops->getroot(server, mntfh, &fsinfo);
155 if (ret < 0) {
156 dprintk("nfs4_get_root: getroot error = %d\n", -ret);
157 return ret;
158 }
159
160 if (fattr.type != NFDIR) {
161 printk(KERN_ERR "nfs4_get_root:"
162 " getroot encountered non-directory\n");
163 return -ENOTDIR;
164 }
165
166 /* FIXME: It is quite valid for the server to return a referral here */
167 if (fattr.valid & NFS_ATTR_FATTR_V4_REFERRAL) {
168 printk(KERN_ERR "nfs4_get_root:"
169 " getroot obtained referral\n");
170 return -EREMOTE;
171 }
172
173 next_component:
174 dprintk("Next: %s\n", path);
175
176 /* extract the next bit of the path */
177 if (!*path)
178 goto path_walk_complete;
179
180 name.name = path;
181 while (*path && *path != '/')
182 path++;
183 name.len = path - (const char *) name.name;
184
185 if (name.len > NFS4_MAXNAMLEN)
186 return -ENAMETOOLONG;
187
188 eat_dot_dir:
189 while (*path == '/')
190 path++;
191
192 if (path[0] == '.' && (path[1] == '/' || !path[1])) {
193 path += 2;
194 goto eat_dot_dir;
195 }
196
197 /* FIXME: Why shouldn't the user be able to use ".." in the path? */
198 if (path[0] == '.' && path[1] == '.' && (path[2] == '/' || !path[2])
199 ) {
200 printk(KERN_ERR "nfs4_get_root:"
201 " Mount path contains reference to \"..\"\n");
202 return -EINVAL;
203 }
204
205 /* lookup the next FH in the sequence */
206 memcpy(&lastfh, mntfh, sizeof(lastfh));
207
208 dprintk("LookupFH: %*.*s [%s]\n", name.len, name.len, name.name, path);
209
210 ret = server->nfs_client->rpc_ops->lookupfh(server, &lastfh, &name,
211 mntfh, &fattr);
212 if (ret < 0) {
213 dprintk("nfs4_get_root: getroot error = %d\n", -ret);
214 return ret;
215 }
216
217 if (fattr.type != NFDIR) {
218 printk(KERN_ERR "nfs4_get_root:"
219 " lookupfh encountered non-directory\n");
220 return -ENOTDIR;
221 }
222
223 /* FIXME: Referrals are quite valid here too */
224 if (fattr.valid & NFS_ATTR_FATTR_V4_REFERRAL) {
225 printk(KERN_ERR "nfs4_get_root:"
226 " lookupfh obtained referral\n");
227 return -EREMOTE;
228 }
229
230 goto next_component;
231
232 path_walk_complete:
233 memcpy(&server->fsid, &fattr.fsid, sizeof(server->fsid));
234 dprintk("<-- nfs4_path_walk() = 0\n");
235 return 0;
236 }
237
238 /*
239 * get an NFS4 root dentry from the root filehandle
240 */
241 struct dentry *nfs4_get_root(struct super_block *sb, struct nfs_fh *mntfh)
242 {
243 struct nfs_server *server = NFS_SB(sb);
244 struct nfs_fattr fattr;
245 struct dentry *mntroot;
246 struct inode *inode;
247 int error;
248
249 dprintk("--> nfs4_get_root()\n");
250
251 /* get the info about the server and filesystem */
252 error = nfs4_server_capabilities(server, mntfh);
253 if (error < 0) {
254 dprintk("nfs_get_root: getcaps error = %d\n",
255 -error);
256 return ERR_PTR(error);
257 }
258
259 /* get the actual root for this mount */
260 error = server->nfs_client->rpc_ops->getattr(server, mntfh, &fattr);
261 if (error < 0) {
262 dprintk("nfs_get_root: getattr error = %d\n", -error);
263 return ERR_PTR(error);
264 }
265
266 inode = nfs_fhget(sb, mntfh, &fattr);
267 if (IS_ERR(inode)) {
268 dprintk("nfs_get_root: get root inode failed\n");
269 return ERR_CAST(inode);
270 }
271
272 error = nfs_superblock_set_dummy_root(sb, inode);
273 if (error != 0)
274 return ERR_PTR(error);
275
276 /* root dentries normally start off anonymous and get spliced in later
277 * if the dentry tree reaches them; however if the dentry already
278 * exists, we'll pick it up at this point and use it as the root
279 */
280 mntroot = d_alloc_anon(inode);
281 if (!mntroot) {
282 iput(inode);
283 dprintk("nfs_get_root: get root dentry failed\n");
284 return ERR_PTR(-ENOMEM);
285 }
286
287 security_d_instantiate(mntroot, inode);
288
289 if (!mntroot->d_op)
290 mntroot->d_op = server->nfs_client->rpc_ops->dentry_ops;
291
292 dprintk("<-- nfs4_get_root()\n");
293 return mntroot;
294 }
295
296 #endif /* CONFIG_NFS_V4 */
297
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