1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * linux/fs/nfs/namespace.c
4 *
5 * Copyright (C) 2005 Trond Myklebust <Trond.Myklebust@netapp.com>
6 * - Modified by David Howells <dhowells@redhat.com>
7 *
8 * NFS namespace
9 */
10
11 #include <linux/module.h>
12 #include <linux/dcache.h>
13 #include <linux/gfp.h>
14 #include <linux/mount.h>
15 #include <linux/namei.h>
16 #include <linux/nfs_fs.h>
17 #include <linux/string.h>
18 #include <linux/sunrpc/clnt.h>
19 #include <linux/vfs.h>
20 #include <linux/sunrpc/gss_api.h>
21 #include "internal.h"
22
23 #define NFSDBG_FACILITY NFSDBG_VFS
24
25 static void nfs_expire_automounts(struct work_struct *work);
26
27 static LIST_HEAD(nfs_automount_list);
28 static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts);
29 int nfs_mountpoint_expiry_timeout = 500 * HZ;
30
31 /*
32 * nfs_path - reconstruct the path given an arbitrary dentry
33 * @base - used to return pointer to the end of devname part of path
34 * @dentry - pointer to dentry
35 * @buffer - result buffer
36 * @buflen - length of buffer
37 * @flags - options (see below)
38 *
39 * Helper function for constructing the server pathname
40 * by arbitrary hashed dentry.
41 *
42 * This is mainly for use in figuring out the path on the
43 * server side when automounting on top of an existing partition
44 * and in generating /proc/mounts and friends.
45 *
46 * Supported flags:
47 * NFS_PATH_CANONICAL: ensure there is exactly one slash after
48 * the original device (export) name
49 * (if unset, the original name is returned verbatim)
50 */
nfs_path(char ** p,struct dentry * dentry,char * buffer,ssize_t buflen,unsigned flags)51 char *nfs_path(char **p, struct dentry *dentry, char *buffer, ssize_t buflen,
52 unsigned flags)
53 {
54 char *end;
55 int namelen;
56 unsigned seq;
57 const char *base;
58
59 rename_retry:
60 end = buffer+buflen;
61 *--end = '\0';
62 buflen--;
63
64 seq = read_seqbegin(&rename_lock);
65 rcu_read_lock();
66 while (1) {
67 spin_lock(&dentry->d_lock);
68 if (IS_ROOT(dentry))
69 break;
70 namelen = dentry->d_name.len;
71 buflen -= namelen + 1;
72 if (buflen < 0)
73 goto Elong_unlock;
74 end -= namelen;
75 memcpy(end, dentry->d_name.name, namelen);
76 *--end = '/';
77 spin_unlock(&dentry->d_lock);
78 dentry = dentry->d_parent;
79 }
80 if (read_seqretry(&rename_lock, seq)) {
81 spin_unlock(&dentry->d_lock);
82 rcu_read_unlock();
83 goto rename_retry;
84 }
85 if ((flags & NFS_PATH_CANONICAL) && *end != '/') {
86 if (--buflen < 0) {
87 spin_unlock(&dentry->d_lock);
88 rcu_read_unlock();
89 goto Elong;
90 }
91 *--end = '/';
92 }
93 *p = end;
94 base = dentry->d_fsdata;
95 if (!base) {
96 spin_unlock(&dentry->d_lock);
97 rcu_read_unlock();
98 WARN_ON(1);
99 return end;
100 }
101 namelen = strlen(base);
102 if (*end == '/') {
103 /* Strip off excess slashes in base string */
104 while (namelen > 0 && base[namelen - 1] == '/')
105 namelen--;
106 }
107 buflen -= namelen;
108 if (buflen < 0) {
109 spin_unlock(&dentry->d_lock);
110 rcu_read_unlock();
111 goto Elong;
112 }
113 end -= namelen;
114 memcpy(end, base, namelen);
115 spin_unlock(&dentry->d_lock);
116 rcu_read_unlock();
117 return end;
118 Elong_unlock:
119 spin_unlock(&dentry->d_lock);
120 rcu_read_unlock();
121 if (read_seqretry(&rename_lock, seq))
122 goto rename_retry;
123 Elong:
124 return ERR_PTR(-ENAMETOOLONG);
125 }
126 EXPORT_SYMBOL_GPL(nfs_path);
127
128 /*
129 * nfs_d_automount - Handle crossing a mountpoint on the server
130 * @path - The mountpoint
131 *
132 * When we encounter a mountpoint on the server, we want to set up
133 * a mountpoint on the client too, to prevent inode numbers from
134 * colliding, and to allow "df" to work properly.
135 * On NFSv4, we also want to allow for the fact that different
136 * filesystems may be migrated to different servers in a failover
137 * situation, and that different filesystems may want to use
138 * different security flavours.
139 */
nfs_d_automount(struct path * path)140 struct vfsmount *nfs_d_automount(struct path *path)
141 {
142 struct vfsmount *mnt;
143 struct nfs_server *server = NFS_SERVER(d_inode(path->dentry));
144 struct nfs_fh *fh = NULL;
145 struct nfs_fattr *fattr = NULL;
146
147 if (IS_ROOT(path->dentry))
148 return ERR_PTR(-ESTALE);
149
150 mnt = ERR_PTR(-ENOMEM);
151 fh = nfs_alloc_fhandle();
152 fattr = nfs_alloc_fattr();
153 if (fh == NULL || fattr == NULL)
154 goto out;
155
156 mnt = server->nfs_client->rpc_ops->submount(server, path->dentry, fh, fattr);
157 if (IS_ERR(mnt))
158 goto out;
159
160 mntget(mnt); /* prevent immediate expiration */
161 mnt_set_expiry(mnt, &nfs_automount_list);
162 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
163
164 out:
165 nfs_free_fattr(fattr);
166 nfs_free_fhandle(fh);
167 return mnt;
168 }
169
170 static int
nfs_namespace_getattr(const struct path * path,struct kstat * stat,u32 request_mask,unsigned int query_flags)171 nfs_namespace_getattr(const struct path *path, struct kstat *stat,
172 u32 request_mask, unsigned int query_flags)
173 {
174 if (NFS_FH(d_inode(path->dentry))->size != 0)
175 return nfs_getattr(path, stat, request_mask, query_flags);
176 generic_fillattr(d_inode(path->dentry), stat);
177 return 0;
178 }
179
180 static int
nfs_namespace_setattr(struct dentry * dentry,struct iattr * attr)181 nfs_namespace_setattr(struct dentry *dentry, struct iattr *attr)
182 {
183 if (NFS_FH(d_inode(dentry))->size != 0)
184 return nfs_setattr(dentry, attr);
185 return -EACCES;
186 }
187
188 const struct inode_operations nfs_mountpoint_inode_operations = {
189 .getattr = nfs_getattr,
190 .setattr = nfs_setattr,
191 };
192
193 const struct inode_operations nfs_referral_inode_operations = {
194 .getattr = nfs_namespace_getattr,
195 .setattr = nfs_namespace_setattr,
196 };
197
nfs_expire_automounts(struct work_struct * work)198 static void nfs_expire_automounts(struct work_struct *work)
199 {
200 struct list_head *list = &nfs_automount_list;
201
202 mark_mounts_for_expiry(list);
203 if (!list_empty(list))
204 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
205 }
206
nfs_release_automount_timer(void)207 void nfs_release_automount_timer(void)
208 {
209 if (list_empty(&nfs_automount_list))
210 cancel_delayed_work(&nfs_automount_task);
211 }
212
213 /*
214 * Clone a mountpoint of the appropriate type
215 */
nfs_do_clone_mount(struct nfs_server * server,const char * devname,struct nfs_clone_mount * mountdata)216 static struct vfsmount *nfs_do_clone_mount(struct nfs_server *server,
217 const char *devname,
218 struct nfs_clone_mount *mountdata)
219 {
220 return vfs_submount(mountdata->dentry, &nfs_xdev_fs_type, devname, mountdata);
221 }
222
223 /**
224 * nfs_do_submount - set up mountpoint when crossing a filesystem boundary
225 * @dentry: parent directory
226 * @fh: filehandle for new root dentry
227 * @fattr: attributes for new root inode
228 * @authflavor: security flavor to use when performing the mount
229 *
230 */
nfs_do_submount(struct dentry * dentry,struct nfs_fh * fh,struct nfs_fattr * fattr,rpc_authflavor_t authflavor)231 struct vfsmount *nfs_do_submount(struct dentry *dentry, struct nfs_fh *fh,
232 struct nfs_fattr *fattr, rpc_authflavor_t authflavor)
233 {
234 struct nfs_clone_mount mountdata = {
235 .sb = dentry->d_sb,
236 .dentry = dentry,
237 .fh = fh,
238 .fattr = fattr,
239 .authflavor = authflavor,
240 };
241 struct vfsmount *mnt;
242 char *page = (char *) __get_free_page(GFP_USER);
243 char *devname;
244
245 if (page == NULL)
246 return ERR_PTR(-ENOMEM);
247
248 devname = nfs_devname(dentry, page, PAGE_SIZE);
249 if (IS_ERR(devname))
250 mnt = ERR_CAST(devname);
251 else
252 mnt = nfs_do_clone_mount(NFS_SB(dentry->d_sb), devname, &mountdata);
253
254 free_page((unsigned long)page);
255 return mnt;
256 }
257 EXPORT_SYMBOL_GPL(nfs_do_submount);
258
nfs_submount(struct nfs_server * server,struct dentry * dentry,struct nfs_fh * fh,struct nfs_fattr * fattr)259 struct vfsmount *nfs_submount(struct nfs_server *server, struct dentry *dentry,
260 struct nfs_fh *fh, struct nfs_fattr *fattr)
261 {
262 int err;
263 struct dentry *parent = dget_parent(dentry);
264
265 /* Look it up again to get its attributes */
266 err = server->nfs_client->rpc_ops->lookup(d_inode(parent), &dentry->d_name, fh, fattr, NULL);
267 dput(parent);
268 if (err != 0)
269 return ERR_PTR(err);
270
271 return nfs_do_submount(dentry, fh, fattr, server->client->cl_auth->au_flavor);
272 }
273 EXPORT_SYMBOL_GPL(nfs_submount);
274