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 */
nfs_path(char ** p,struct dentry * dentry_in,char * buffer,ssize_t buflen_in,unsigned flags)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 */
nfs_d_automount(struct path * path)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
nfs_namespace_getattr(struct mnt_idmap * idmap,const struct path * path,struct kstat * stat,u32 request_mask,unsigned int query_flags)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
nfs_namespace_setattr(struct mnt_idmap * idmap,struct dentry * dentry,struct iattr * attr)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
nfs_expire_automounts(struct work_struct * work)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
nfs_release_automount_timer(void)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 */
nfs_do_submount(struct fs_context * fc)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
nfs_submount(struct fs_context * fc,struct nfs_server * server)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
param_set_nfs_timeout(const char * val,const struct kernel_param * kp)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
param_get_nfs_timeout(char * buffer,const struct kernel_param * kp)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