xref: /linux/fs/nfs/namespace.c (revision b61104e7a6349bd2c2b3e2fb3260d87f15eda8f4) 
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 	unsigned long s_flags = path->dentry->d_sb->s_flags;
153 	int timeout = READ_ONCE(nfs_mountpoint_expiry_timeout);
154 	int ret;
155 
156 	if (IS_ROOT(path->dentry))
157 		return ERR_PTR(-ESTALE);
158 
159 	/* Open a new filesystem context, transferring parameters from the
160 	 * parent superblock, including the network namespace.
161 	 */
162 	fc = fs_context_for_submount(path->mnt->mnt_sb->s_type, path->dentry);
163 	if (IS_ERR(fc))
164 		return ERR_CAST(fc);
165 
166 	ctx = nfs_fc2context(fc);
167 	ctx->clone_data.dentry	= path->dentry;
168 	ctx->clone_data.sb	= path->dentry->d_sb;
169 	ctx->clone_data.fattr	= nfs_alloc_fattr();
170 	if (!ctx->clone_data.fattr)
171 		goto out_fc;
172 
173 	if (fc->cred != server->cred) {
174 		put_cred(fc->cred);
175 		fc->cred = get_cred(server->cred);
176 	}
177 
178 	if (fc->net_ns != client->cl_net) {
179 		put_net(fc->net_ns);
180 		fc->net_ns = get_net(client->cl_net);
181 	}
182 
183 	/* Inherit the flags covered by NFS_SB_MASK */
184 	fc->sb_flags_mask |= NFS_SB_MASK;
185 	fc->sb_flags &= ~NFS_SB_MASK;
186 	fc->sb_flags |= s_flags & NFS_SB_MASK;
187 
188 	/* for submounts we want the same server; referrals will reassign */
189 	memcpy(&ctx->nfs_server._address, &client->cl_addr, client->cl_addrlen);
190 	ctx->nfs_server.addrlen	= client->cl_addrlen;
191 	ctx->nfs_server.port	= server->port;
192 
193 	ctx->version		= client->rpc_ops->version;
194 	ctx->minorversion	= client->cl_minorversion;
195 	ctx->nfs_mod		= client->cl_nfs_mod;
196 	get_nfs_version(ctx->nfs_mod);
197 
198 	/* Inherit block sizes if they were specified as mount parameters */
199 	if (server->automount_inherit & NFS_AUTOMOUNT_INHERIT_BSIZE)
200 		ctx->bsize = server->bsize;
201 
202 	ret = client->rpc_ops->submount(fc, server);
203 	if (ret < 0) {
204 		mnt = ERR_PTR(ret);
205 		goto out_fc;
206 	}
207 
208 	up_write(&fc->root->d_sb->s_umount);
209 	mnt = vfs_create_mount(fc);
210 	if (IS_ERR(mnt))
211 		goto out_fc;
212 
213 	if (timeout <= 0)
214 		goto out_fc;
215 
216 	mnt_set_expiry(mnt, &nfs_automount_list);
217 	schedule_delayed_work(&nfs_automount_task, timeout);
218 
219 out_fc:
220 	put_fs_context(fc);
221 	return mnt;
222 }
223 
224 static int
225 nfs_namespace_getattr(struct mnt_idmap *idmap,
226 		      const struct path *path, struct kstat *stat,
227 		      u32 request_mask, unsigned int query_flags)
228 {
229 	if (NFS_FH(d_inode(path->dentry))->size != 0)
230 		return nfs_getattr(idmap, path, stat, request_mask,
231 				   query_flags);
232 	generic_fillattr(&nop_mnt_idmap, request_mask, d_inode(path->dentry),
233 			 stat);
234 	return 0;
235 }
236 
237 static int
238 nfs_namespace_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
239 		      struct iattr *attr)
240 {
241 	if (NFS_FH(d_inode(dentry))->size != 0)
242 		return nfs_setattr(idmap, dentry, attr);
243 	return -EACCES;
244 }
245 
246 const struct inode_operations nfs_mountpoint_inode_operations = {
247 	.getattr	= nfs_getattr,
248 	.setattr	= nfs_setattr,
249 };
250 
251 const struct inode_operations nfs_referral_inode_operations = {
252 	.getattr	= nfs_namespace_getattr,
253 	.setattr	= nfs_namespace_setattr,
254 };
255 
256 static void nfs_expire_automounts(struct work_struct *work)
257 {
258 	struct list_head *list = &nfs_automount_list;
259 	int timeout = READ_ONCE(nfs_mountpoint_expiry_timeout);
260 
261 	mark_mounts_for_expiry(list);
262 	if (!list_empty(list) && timeout > 0)
263 		schedule_delayed_work(&nfs_automount_task, timeout);
264 }
265 
266 void nfs_release_automount_timer(void)
267 {
268 	if (list_empty(&nfs_automount_list))
269 		cancel_delayed_work(&nfs_automount_task);
270 }
271 
272 /**
273  * nfs_do_submount - set up mountpoint when crossing a filesystem boundary
274  * @fc: pointer to struct nfs_fs_context
275  *
276  */
277 int nfs_do_submount(struct fs_context *fc)
278 {
279 	struct nfs_fs_context *ctx = nfs_fc2context(fc);
280 	struct dentry *dentry = ctx->clone_data.dentry;
281 	struct nfs_server *server;
282 	char *buffer, *p;
283 	int ret;
284 
285 	/* create a new volume representation */
286 	server = ctx->nfs_mod->rpc_ops->clone_server(NFS_SB(ctx->clone_data.sb),
287 						     ctx->mntfh,
288 						     ctx->clone_data.fattr,
289 						     ctx->selected_flavor);
290 
291 	if (IS_ERR(server))
292 		return PTR_ERR(server);
293 
294 	ctx->server = server;
295 
296 	buffer = kmalloc(4096, GFP_USER);
297 	if (!buffer)
298 		return -ENOMEM;
299 
300 	ctx->internal		= true;
301 
302 	p = nfs_devname(dentry, buffer, 4096);
303 	if (IS_ERR(p)) {
304 		nfs_errorf(fc, "NFS: Couldn't determine submount pathname");
305 		ret = PTR_ERR(p);
306 	} else {
307 		ret = vfs_parse_fs_qstr(fc, "source",
308 					&QSTR_LEN(p, buffer + 4096 - p));
309 		if (!ret)
310 			ret = vfs_get_tree(fc);
311 	}
312 	kfree(buffer);
313 	return ret;
314 }
315 EXPORT_SYMBOL_GPL(nfs_do_submount);
316 
317 int nfs_submount(struct fs_context *fc, struct nfs_server *server)
318 {
319 	struct nfs_fs_context *ctx = nfs_fc2context(fc);
320 	struct dentry *dentry = ctx->clone_data.dentry;
321 	struct dentry *parent = dget_parent(dentry);
322 	int err;
323 
324 	/* Look it up again to get its attributes */
325 	err = server->nfs_client->rpc_ops->lookup(d_inode(parent), dentry, &dentry->d_name,
326 						  ctx->mntfh, ctx->clone_data.fattr);
327 	dput(parent);
328 	if (err != 0)
329 		return err;
330 
331 	ctx->selected_flavor = server->client->cl_auth->au_flavor;
332 	return nfs_do_submount(fc);
333 }
334 EXPORT_SYMBOL_GPL(nfs_submount);
335 
336 static int param_set_nfs_timeout(const char *val, const struct kernel_param *kp)
337 {
338 	long num;
339 	int ret;
340 
341 	if (!val)
342 		return -EINVAL;
343 	ret = kstrtol(val, 0, &num);
344 	if (ret)
345 		return -EINVAL;
346 	if (num > 0) {
347 		if (num >= INT_MAX / HZ)
348 			num = INT_MAX;
349 		else
350 			num *= HZ;
351 		*((int *)kp->arg) = num;
352 		if (!list_empty(&nfs_automount_list))
353 			mod_delayed_work(system_percpu_wq, &nfs_automount_task, num);
354 	} else {
355 		*((int *)kp->arg) = -1*HZ;
356 		cancel_delayed_work(&nfs_automount_task);
357 	}
358 	return 0;
359 }
360 
361 static int param_get_nfs_timeout(char *buffer, const struct kernel_param *kp)
362 {
363 	long num = *((int *)kp->arg);
364 
365 	if (num > 0) {
366 		if (num >= INT_MAX - (HZ - 1))
367 			num = INT_MAX / HZ;
368 		else
369 			num = (num + (HZ - 1)) / HZ;
370 	} else
371 		num = -1;
372 	return sysfs_emit(buffer, "%li\n", num);
373 }
374 
375 static const struct kernel_param_ops param_ops_nfs_timeout = {
376 	.set = param_set_nfs_timeout,
377 	.get = param_get_nfs_timeout,
378 };
379 #define param_check_nfs_timeout(name, p) __param_check(name, p, int)
380 
381 module_param(nfs_mountpoint_expiry_timeout, nfs_timeout, 0644);
382 MODULE_PARM_DESC(nfs_mountpoint_expiry_timeout,
383 		"Set the NFS automounted mountpoint timeout value (seconds)."
384 		"Values <= 0 turn expiration off.");
385