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 #include "nfs.h"
23
24 #define NFSDBG_FACILITY NFSDBG_VFS
25
26 static void nfs_expire_automounts(struct work_struct *work);
27
28 static LIST_HEAD(nfs_automount_list);
29 static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts);
30 int nfs_mountpoint_expiry_timeout = 500 * HZ;
31
32 /*
33 * nfs_path - reconstruct the path given an arbitrary dentry
34 * @base - used to return pointer to the end of devname part of path
35 * @dentry_in - pointer to dentry
36 * @buffer - result buffer
37 * @buflen_in - length of buffer
38 * @flags - options (see below)
39 *
40 * Helper function for constructing the server pathname
41 * by arbitrary hashed dentry.
42 *
43 * This is mainly for use in figuring out the path on the
44 * server side when automounting on top of an existing partition
45 * and in generating /proc/mounts and friends.
46 *
47 * Supported flags:
48 * NFS_PATH_CANONICAL: ensure there is exactly one slash after
49 * the original device (export) name
50 * (if unset, the original name is returned verbatim)
51 */
52 char *nfs_path(char **p, struct dentry *dentry_in, char *buffer,
53 ssize_t buflen_in, unsigned flags)
54 {
55 char *end;
56 int namelen;
57 unsigned seq;
58 const char *base;
59 struct dentry *dentry;
60 ssize_t buflen;
61
62 rename_retry:
63 buflen = buflen_in;
64 dentry = dentry_in;
65 end = buffer+buflen;
66 *--end = '\0';
67 buflen--;
68
69 seq = read_seqbegin(&rename_lock);
70 rcu_read_lock();
71 while (1) {
72 spin_lock(&dentry->d_lock);
73 if (IS_ROOT(dentry))
74 break;
75 namelen = dentry->d_name.len;
76 buflen -= namelen + 1;
77 if (buflen < 0)
78 goto Elong_unlock;
79 end -= namelen;
80 memcpy(end, dentry->d_name.name, namelen);
81 *--end = '/';
82 spin_unlock(&dentry->d_lock);
83 dentry = dentry->d_parent;
84 }
85 if (read_seqretry(&rename_lock, seq)) {
86 spin_unlock(&dentry->d_lock);
87 rcu_read_unlock();
88 goto rename_retry;
89 }
90 if ((flags & NFS_PATH_CANONICAL) && *end != '/') {
91 if (--buflen < 0) {
92 spin_unlock(&dentry->d_lock);
93 rcu_read_unlock();
94 goto Elong;
95 }
96 *--end = '/';
97 }
98 *p = end;
99 base = dentry->d_fsdata;
100 if (!base) {
101 spin_unlock(&dentry->d_lock);
102 rcu_read_unlock();
103 WARN_ON(1);
104 return end;
105 }
106 namelen = strlen(base);
107 if (*end == '/') {
108 /* Strip off excess slashes in base string */
109 while (namelen > 0 && base[namelen - 1] == '/')
110 namelen--;
111 }
112 buflen -= namelen;
113 if (buflen < 0) {
114 spin_unlock(&dentry->d_lock);
115 rcu_read_unlock();
116 goto Elong;
117 }
118 end -= namelen;
119 memcpy(end, base, namelen);
120 spin_unlock(&dentry->d_lock);
121 rcu_read_unlock();
122 return end;
123 Elong_unlock:
124 spin_unlock(&dentry->d_lock);
125 rcu_read_unlock();
126 if (read_seqretry(&rename_lock, seq))
127 goto rename_retry;
128 Elong:
129 return ERR_PTR(-ENAMETOOLONG);
130 }
131 EXPORT_SYMBOL_GPL(nfs_path);
132
133 /*
134 * nfs_d_automount - Handle crossing a mountpoint on the server
135 * @path - The mountpoint
136 *
137 * When we encounter a mountpoint on the server, we want to set up
138 * a mountpoint on the client too, to prevent inode numbers from
139 * colliding, and to allow "df" to work properly.
140 * On NFSv4, we also want to allow for the fact that different
141 * filesystems may be migrated to different servers in a failover
142 * situation, and that different filesystems may want to use
143 * different security flavours.
144 */
145 struct vfsmount *nfs_d_automount(struct path *path)
146 {
147 struct nfs_fs_context *ctx;
148 struct fs_context *fc;
149 struct vfsmount *mnt = ERR_PTR(-ENOMEM);
150 struct nfs_server *server = NFS_SB(path->dentry->d_sb);
151 struct nfs_client *client = server->nfs_client;
152 int timeout = READ_ONCE(nfs_mountpoint_expiry_timeout);
153 int ret;
154
155 if (IS_ROOT(path->dentry))
156 return ERR_PTR(-ESTALE);
157
158 /* Open a new filesystem context, transferring parameters from the
159 * parent superblock, including the network namespace.
160 */
161 fc = fs_context_for_submount(path->mnt->mnt_sb->s_type, path->dentry);
162 if (IS_ERR(fc))
163 return ERR_CAST(fc);
164
165 ctx = nfs_fc2context(fc);
166 ctx->clone_data.dentry = path->dentry;
167 ctx->clone_data.sb = path->dentry->d_sb;
168 ctx->clone_data.fattr = nfs_alloc_fattr();
169 if (!ctx->clone_data.fattr)
170 goto out_fc;
171
172 if (fc->net_ns != client->cl_net) {
173 put_net(fc->net_ns);
174 fc->net_ns = get_net(client->cl_net);
175 }
176
177 /* for submounts we want the same server; referrals will reassign */
178 memcpy(&ctx->nfs_server._address, &client->cl_addr, client->cl_addrlen);
179 ctx->nfs_server.addrlen = client->cl_addrlen;
180 ctx->nfs_server.port = server->port;
181
182 ctx->version = client->rpc_ops->version;
183 ctx->minorversion = client->cl_minorversion;
184 ctx->nfs_mod = client->cl_nfs_mod;
185 __module_get(ctx->nfs_mod->owner);
186
187 ret = client->rpc_ops->submount(fc, server);
188 if (ret < 0) {
189 mnt = ERR_PTR(ret);
190 goto out_fc;
191 }
192
193 up_write(&fc->root->d_sb->s_umount);
194 mnt = vfs_create_mount(fc);
195 if (IS_ERR(mnt))
196 goto out_fc;
197
198 mntget(mnt); /* prevent immediate expiration */
199 if (timeout <= 0)
200 goto out_fc;
201
202 mnt_set_expiry(mnt, &nfs_automount_list);
203 schedule_delayed_work(&nfs_automount_task, timeout);
204
205 out_fc:
206 put_fs_context(fc);
207 return mnt;
208 }
209
210 static int
211 nfs_namespace_getattr(struct mnt_idmap *idmap,
212 const struct path *path, struct kstat *stat,
213 u32 request_mask, unsigned int query_flags)
214 {
215 if (NFS_FH(d_inode(path->dentry))->size != 0)
216 return nfs_getattr(idmap, path, stat, request_mask,
217 query_flags);
218 generic_fillattr(&nop_mnt_idmap, request_mask, d_inode(path->dentry),
219 stat);
220 return 0;
221 }
222
223 static int
224 nfs_namespace_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
225 struct iattr *attr)
226 {
227 if (NFS_FH(d_inode(dentry))->size != 0)
228 return nfs_setattr(idmap, dentry, attr);
229 return -EACCES;
230 }
231
232 const struct inode_operations nfs_mountpoint_inode_operations = {
233 .getattr = nfs_getattr,
234 .setattr = nfs_setattr,
235 };
236
237 const struct inode_operations nfs_referral_inode_operations = {
238 .getattr = nfs_namespace_getattr,
239 .setattr = nfs_namespace_setattr,
240 };
241
242 static void nfs_expire_automounts(struct work_struct *work)
243 {
244 struct list_head *list = &nfs_automount_list;
245 int timeout = READ_ONCE(nfs_mountpoint_expiry_timeout);
246
247 mark_mounts_for_expiry(list);
248 if (!list_empty(list) && timeout > 0)
249 schedule_delayed_work(&nfs_automount_task, timeout);
250 }
251
252 void nfs_release_automount_timer(void)
253 {
254 if (list_empty(&nfs_automount_list))
255 cancel_delayed_work(&nfs_automount_task);
256 }
257
258 /**
259 * nfs_do_submount - set up mountpoint when crossing a filesystem boundary
260 * @fc: pointer to struct nfs_fs_context
261 *
262 */
263 int nfs_do_submount(struct fs_context *fc)
264 {
265 struct nfs_fs_context *ctx = nfs_fc2context(fc);
266 struct dentry *dentry = ctx->clone_data.dentry;
267 struct nfs_server *server;
268 char *buffer, *p;
269 int ret;
270
271 /* create a new volume representation */
272 server = ctx->nfs_mod->rpc_ops->clone_server(NFS_SB(ctx->clone_data.sb),
273 ctx->mntfh,
274 ctx->clone_data.fattr,
275 ctx->selected_flavor);
276
277 if (IS_ERR(server))
278 return PTR_ERR(server);
279
280 ctx->server = server;
281
282 buffer = kmalloc(4096, GFP_USER);
283 if (!buffer)
284 return -ENOMEM;
285
286 ctx->internal = true;
287 ctx->clone_data.inherited_bsize = ctx->clone_data.sb->s_blocksize_bits;
288
289 p = nfs_devname(dentry, buffer, 4096);
290 if (IS_ERR(p)) {
291 nfs_errorf(fc, "NFS: Couldn't determine submount pathname");
292 ret = PTR_ERR(p);
293 } else {
294 ret = vfs_parse_fs_string(fc, "source", p, buffer + 4096 - p);
295 if (!ret)
296 ret = vfs_get_tree(fc);
297 }
298 kfree(buffer);
299 return ret;
300 }
301 EXPORT_SYMBOL_GPL(nfs_do_submount);
302
303 int nfs_submount(struct fs_context *fc, struct nfs_server *server)
304 {
305 struct nfs_fs_context *ctx = nfs_fc2context(fc);
306 struct dentry *dentry = ctx->clone_data.dentry;
307 struct dentry *parent = dget_parent(dentry);
308 int err;
309
310 /* Look it up again to get its attributes */
311 err = server->nfs_client->rpc_ops->lookup(d_inode(parent), dentry,
312 ctx->mntfh, ctx->clone_data.fattr);
313 dput(parent);
314 if (err != 0)
315 return err;
316
317 ctx->selected_flavor = server->client->cl_auth->au_flavor;
318 return nfs_do_submount(fc);
319 }
320 EXPORT_SYMBOL_GPL(nfs_submount);
321
322 static int param_set_nfs_timeout(const char *val, const struct kernel_param *kp)
323 {
324 long num;
325 int ret;
326
327 if (!val)
328 return -EINVAL;
329 ret = kstrtol(val, 0, &num);
330 if (ret)
331 return -EINVAL;
332 if (num > 0) {
333 if (num >= INT_MAX / HZ)
334 num = INT_MAX;
335 else
336 num *= HZ;
337 *((int *)kp->arg) = num;
338 if (!list_empty(&nfs_automount_list))
339 mod_delayed_work(system_wq, &nfs_automount_task, num);
340 } else {
341 *((int *)kp->arg) = -1*HZ;
342 cancel_delayed_work(&nfs_automount_task);
343 }
344 return 0;
345 }
346
347 static int param_get_nfs_timeout(char *buffer, const struct kernel_param *kp)
348 {
349 long num = *((int *)kp->arg);
350
351 if (num > 0) {
352 if (num >= INT_MAX - (HZ - 1))
353 num = INT_MAX / HZ;
354 else
355 num = (num + (HZ - 1)) / HZ;
356 } else
357 num = -1;
358 return sysfs_emit(buffer, "%li\n", num);
359 }
360
361 static const struct kernel_param_ops param_ops_nfs_timeout = {
362 .set = param_set_nfs_timeout,
363 .get = param_get_nfs_timeout,
364 };
365 #define param_check_nfs_timeout(name, p) __param_check(name, p, int)
366
367 module_param(nfs_mountpoint_expiry_timeout, nfs_timeout, 0644);
368 MODULE_PARM_DESC(nfs_mountpoint_expiry_timeout,
369 "Set the NFS automounted mountpoint timeout value (seconds)."
370 "Values <= 0 turn expiration off.");
371
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