namespace.c

  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
 26static void nfs_expire_automounts(struct work_struct *work);
 27
 28static LIST_HEAD(nfs_automount_list);
 29static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts);
 30int 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 */
 52char *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
 62rename_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;
123Elong_unlock:
124	spin_unlock(&dentry->d_lock);
125	rcu_read_unlock();
126	if (read_seqretry(&rename_lock, seq))
127		goto rename_retry;
128Elong:
129	return ERR_PTR(-ENAMETOOLONG);
130}
131EXPORT_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 */
145struct 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
219out_fc:
220	put_fs_context(fc);
221	return mnt;
222}
223
224static int
225nfs_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
237static int
238nfs_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
246const struct inode_operations nfs_mountpoint_inode_operations = {
247	.getattr	= nfs_getattr,
248	.setattr	= nfs_setattr,
249};
250
251const struct inode_operations nfs_referral_inode_operations = {
252	.getattr	= nfs_namespace_getattr,
253	.setattr	= nfs_namespace_setattr,
254};
255
256static 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
266void 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 */
277int 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}
315EXPORT_SYMBOL_GPL(nfs_do_submount);
316
317int 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}
334EXPORT_SYMBOL_GPL(nfs_submount);
335
336static 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
361static 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
375static 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
381module_param(nfs_mountpoint_expiry_timeout, nfs_timeout, 0644);
382MODULE_PARM_DESC(nfs_mountpoint_expiry_timeout,
383		"Set the NFS automounted mountpoint timeout value (seconds)."
384		"Values <= 0 turn expiration off.");