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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (C) Neil Brown 2002
4 * Copyright (C) Christoph Hellwig 2007
5 *
6 * This file contains the code mapping from inodes to NFS file handles,
7 * and for mapping back from file handles to dentries.
8 *
9 * For details on why we do all the strange and hairy things in here
10 * take a look at Documentation/filesystems/nfs/exporting.rst.
11 */
12#include <linux/exportfs.h>
13#include <linux/fs.h>
14#include <linux/file.h>
15#include <linux/module.h>
16#include <linux/mount.h>
17#include <linux/namei.h>
18#include <linux/sched.h>
19#include <linux/cred.h>
20
21#define dprintk(fmt, args...) pr_debug(fmt, ##args)
22
23
24static int get_name(const struct path *path, char *name, struct dentry *child);
25
26
27static int exportfs_get_name(struct vfsmount *mnt, struct dentry *dir,
28 char *name, struct dentry *child)
29{
30 const struct export_operations *nop = dir->d_sb->s_export_op;
31 struct path path = {.mnt = mnt, .dentry = dir};
32
33 if (nop->get_name)
34 return nop->get_name(dir, name, child);
35 else
36 return get_name(&path, name, child);
37}
38
39/*
40 * Check if the dentry or any of it's aliases is acceptable.
41 */
42static struct dentry *
43find_acceptable_alias(struct dentry *result,
44 int (*acceptable)(void *context, struct dentry *dentry),
45 void *context)
46{
47 struct dentry *dentry, *toput = NULL;
48 struct inode *inode;
49
50 if (acceptable(context, result))
51 return result;
52
53 inode = result->d_inode;
54 spin_lock(&inode->i_lock);
55 hlist_for_each_entry(dentry, &inode->i_dentry, d_u.d_alias) {
56 dget(dentry);
57 spin_unlock(&inode->i_lock);
58 if (toput)
59 dput(toput);
60 if (dentry != result && acceptable(context, dentry)) {
61 dput(result);
62 return dentry;
63 }
64 spin_lock(&inode->i_lock);
65 toput = dentry;
66 }
67 spin_unlock(&inode->i_lock);
68
69 if (toput)
70 dput(toput);
71 return NULL;
72}
73
74static bool dentry_connected(struct dentry *dentry)
75{
76 dget(dentry);
77 while (dentry->d_flags & DCACHE_DISCONNECTED) {
78 struct dentry *parent = dget_parent(dentry);
79
80 dput(dentry);
81 if (dentry == parent) {
82 dput(parent);
83 return false;
84 }
85 dentry = parent;
86 }
87 dput(dentry);
88 return true;
89}
90
91static void clear_disconnected(struct dentry *dentry)
92{
93 dget(dentry);
94 while (dentry->d_flags & DCACHE_DISCONNECTED) {
95 struct dentry *parent = dget_parent(dentry);
96
97 WARN_ON_ONCE(IS_ROOT(dentry));
98
99 spin_lock(&dentry->d_lock);
100 dentry->d_flags &= ~DCACHE_DISCONNECTED;
101 spin_unlock(&dentry->d_lock);
102
103 dput(dentry);
104 dentry = parent;
105 }
106 dput(dentry);
107}
108
109/*
110 * Reconnect a directory dentry with its parent.
111 *
112 * This can return a dentry, or NULL, or an error.
113 *
114 * In the first case the returned dentry is the parent of the given
115 * dentry, and may itself need to be reconnected to its parent.
116 *
117 * In the NULL case, a concurrent VFS operation has either renamed or
118 * removed this directory. The concurrent operation has reconnected our
119 * dentry, so we no longer need to.
120 */
121static struct dentry *reconnect_one(struct vfsmount *mnt,
122 struct dentry *dentry, char *nbuf)
123{
124 struct dentry *parent;
125 struct dentry *tmp;
126 int err;
127
128 parent = ERR_PTR(-EACCES);
129 inode_lock(dentry->d_inode);
130 if (mnt->mnt_sb->s_export_op->get_parent)
131 parent = mnt->mnt_sb->s_export_op->get_parent(dentry);
132 inode_unlock(dentry->d_inode);
133
134 if (IS_ERR(parent)) {
135 dprintk("get_parent of %lu failed, err %ld\n",
136 dentry->d_inode->i_ino, PTR_ERR(parent));
137 return parent;
138 }
139
140 dprintk("%s: find name of %lu in %lu\n", __func__,
141 dentry->d_inode->i_ino, parent->d_inode->i_ino);
142 err = exportfs_get_name(mnt, parent, nbuf, dentry);
143 if (err == -ENOENT)
144 goto out_reconnected;
145 if (err)
146 goto out_err;
147 dprintk("%s: found name: %s\n", __func__, nbuf);
148 tmp = lookup_one_unlocked(mnt_idmap(mnt), nbuf, parent, strlen(nbuf));
149 if (IS_ERR(tmp)) {
150 dprintk("lookup failed: %ld\n", PTR_ERR(tmp));
151 err = PTR_ERR(tmp);
152 goto out_err;
153 }
154 if (tmp != dentry) {
155 /*
156 * Somebody has renamed it since exportfs_get_name();
157 * great, since it could've only been renamed if it
158 * got looked up and thus connected, and it would
159 * remain connected afterwards. We are done.
160 */
161 dput(tmp);
162 goto out_reconnected;
163 }
164 dput(tmp);
165 if (IS_ROOT(dentry)) {
166 err = -ESTALE;
167 goto out_err;
168 }
169 return parent;
170
171out_err:
172 dput(parent);
173 return ERR_PTR(err);
174out_reconnected:
175 dput(parent);
176 /*
177 * Someone must have renamed our entry into another parent, in
178 * which case it has been reconnected by the rename.
179 *
180 * Or someone removed it entirely, in which case filehandle
181 * lookup will succeed but the directory is now IS_DEAD and
182 * subsequent operations on it will fail.
183 *
184 * Alternatively, maybe there was no race at all, and the
185 * filesystem is just corrupt and gave us a parent that doesn't
186 * actually contain any entry pointing to this inode. So,
187 * double check that this worked and return -ESTALE if not:
188 */
189 if (!dentry_connected(dentry))
190 return ERR_PTR(-ESTALE);
191 return NULL;
192}
193
194/*
195 * Make sure target_dir is fully connected to the dentry tree.
196 *
197 * On successful return, DCACHE_DISCONNECTED will be cleared on
198 * target_dir, and target_dir->d_parent->...->d_parent will reach the
199 * root of the filesystem.
200 *
201 * Whenever DCACHE_DISCONNECTED is unset, target_dir is fully connected.
202 * But the converse is not true: target_dir may have DCACHE_DISCONNECTED
203 * set but already be connected. In that case we'll verify the
204 * connection to root and then clear the flag.
205 *
206 * Note that target_dir could be removed by a concurrent operation. In
207 * that case reconnect_path may still succeed with target_dir fully
208 * connected, but further operations using the filehandle will fail when
209 * necessary (due to S_DEAD being set on the directory).
210 */
211static int
212reconnect_path(struct vfsmount *mnt, struct dentry *target_dir, char *nbuf)
213{
214 struct dentry *dentry, *parent;
215
216 dentry = dget(target_dir);
217
218 while (dentry->d_flags & DCACHE_DISCONNECTED) {
219 BUG_ON(dentry == mnt->mnt_sb->s_root);
220
221 if (IS_ROOT(dentry))
222 parent = reconnect_one(mnt, dentry, nbuf);
223 else
224 parent = dget_parent(dentry);
225
226 if (!parent)
227 break;
228 dput(dentry);
229 if (IS_ERR(parent))
230 return PTR_ERR(parent);
231 dentry = parent;
232 }
233 dput(dentry);
234 clear_disconnected(target_dir);
235 return 0;
236}
237
238struct getdents_callback {
239 struct dir_context ctx;
240 char *name; /* name that was found. It already points to a
241 buffer NAME_MAX+1 is size */
242 u64 ino; /* the inum we are looking for */
243 int found; /* inode matched? */
244 int sequence; /* sequence counter */
245};
246
247/*
248 * A rather strange filldir function to capture
249 * the name matching the specified inode number.
250 */
251static bool filldir_one(struct dir_context *ctx, const char *name, int len,
252 loff_t pos, u64 ino, unsigned int d_type)
253{
254 struct getdents_callback *buf =
255 container_of(ctx, struct getdents_callback, ctx);
256
257 buf->sequence++;
258 if (buf->ino == ino && len <= NAME_MAX && !is_dot_dotdot(name, len)) {
259 memcpy(buf->name, name, len);
260 buf->name[len] = '\0';
261 buf->found = 1;
262 return false; // no more
263 }
264 return true;
265}
266
267/**
268 * get_name - default export_operations->get_name function
269 * @path: the directory in which to find a name
270 * @name: a pointer to a %NAME_MAX+1 char buffer to store the name
271 * @child: the dentry for the child directory.
272 *
273 * calls readdir on the parent until it finds an entry with
274 * the same inode number as the child, and returns that.
275 */
276static int get_name(const struct path *path, char *name, struct dentry *child)
277{
278 const struct cred *cred = current_cred();
279 struct inode *dir = path->dentry->d_inode;
280 int error;
281 struct file *file;
282 struct kstat stat;
283 struct path child_path = {
284 .mnt = path->mnt,
285 .dentry = child,
286 };
287 struct getdents_callback buffer = {
288 .ctx.actor = filldir_one,
289 .name = name,
290 };
291
292 error = -ENOTDIR;
293 if (!dir || !S_ISDIR(dir->i_mode))
294 goto out;
295 error = -EINVAL;
296 if (!dir->i_fop)
297 goto out;
298 /*
299 * inode->i_ino is unsigned long, kstat->ino is u64, so the
300 * former would be insufficient on 32-bit hosts when the
301 * filesystem supports 64-bit inode numbers. So we need to
302 * actually call ->getattr, not just read i_ino:
303 */
304 error = vfs_getattr_nosec(&child_path, &stat,
305 STATX_INO, AT_STATX_SYNC_AS_STAT);
306 if (error)
307 return error;
308 buffer.ino = stat.ino;
309 /*
310 * Open the directory ...
311 */
312 file = dentry_open(path, O_RDONLY, cred);
313 error = PTR_ERR(file);
314 if (IS_ERR(file))
315 goto out;
316
317 error = -EINVAL;
318 if (!file->f_op->iterate_shared)
319 goto out_close;
320
321 buffer.sequence = 0;
322 while (1) {
323 int old_seq = buffer.sequence;
324
325 error = iterate_dir(file, &buffer.ctx);
326 if (buffer.found) {
327 error = 0;
328 break;
329 }
330
331 if (error < 0)
332 break;
333
334 error = -ENOENT;
335 if (old_seq == buffer.sequence)
336 break;
337 }
338
339out_close:
340 fput(file);
341out:
342 return error;
343}
344
345#define FILEID_INO64_GEN_LEN 3
346
347/**
348 * exportfs_encode_ino64_fid - encode non-decodeable 64bit ino file id
349 * @inode: the object to encode
350 * @fid: where to store the file handle fragment
351 * @max_len: maximum length to store there (in 4 byte units)
352 *
353 * This generic function is used to encode a non-decodeable file id for
354 * fanotify for filesystems that do not support NFS export.
355 */
356static int exportfs_encode_ino64_fid(struct inode *inode, struct fid *fid,
357 int *max_len)
358{
359 if (*max_len < FILEID_INO64_GEN_LEN) {
360 *max_len = FILEID_INO64_GEN_LEN;
361 return FILEID_INVALID;
362 }
363
364 fid->i64.ino = inode->i_ino;
365 fid->i64.gen = inode->i_generation;
366 *max_len = FILEID_INO64_GEN_LEN;
367
368 return FILEID_INO64_GEN;
369}
370
371/**
372 * exportfs_encode_inode_fh - encode a file handle from inode
373 * @inode: the object to encode
374 * @fid: where to store the file handle fragment
375 * @max_len: maximum length to store there
376 * @parent: parent directory inode, if wanted
377 * @flags: properties of the requested file handle
378 *
379 * Returns an enum fid_type or a negative errno.
380 */
381int exportfs_encode_inode_fh(struct inode *inode, struct fid *fid,
382 int *max_len, struct inode *parent, int flags)
383{
384 const struct export_operations *nop = inode->i_sb->s_export_op;
385 enum fid_type type;
386
387 if (!exportfs_can_encode_fh(nop, flags))
388 return -EOPNOTSUPP;
389
390 if (!nop && (flags & EXPORT_FH_FID))
391 type = exportfs_encode_ino64_fid(inode, fid, max_len);
392 else
393 type = nop->encode_fh(inode, fid->raw, max_len, parent);
394
395 if (type > 0 && FILEID_USER_FLAGS(type)) {
396 pr_warn_once("%s: unexpected fh type value 0x%x from fstype %s.\n",
397 __func__, type, inode->i_sb->s_type->name);
398 return -EINVAL;
399 }
400
401 return type;
402
403}
404EXPORT_SYMBOL_GPL(exportfs_encode_inode_fh);
405
406/**
407 * exportfs_encode_fh - encode a file handle from dentry
408 * @dentry: the object to encode
409 * @fid: where to store the file handle fragment
410 * @max_len: maximum length to store there
411 * @flags: properties of the requested file handle
412 *
413 * Returns an enum fid_type or a negative errno.
414 */
415int exportfs_encode_fh(struct dentry *dentry, struct fid *fid, int *max_len,
416 int flags)
417{
418 int error;
419 struct dentry *p = NULL;
420 struct inode *inode = dentry->d_inode, *parent = NULL;
421
422 if ((flags & EXPORT_FH_CONNECTABLE) && !S_ISDIR(inode->i_mode)) {
423 p = dget_parent(dentry);
424 /*
425 * note that while p might've ceased to be our parent already,
426 * it's still pinned by and still positive.
427 */
428 parent = p->d_inode;
429 }
430
431 error = exportfs_encode_inode_fh(inode, fid, max_len, parent, flags);
432 dput(p);
433
434 return error;
435}
436EXPORT_SYMBOL_GPL(exportfs_encode_fh);
437
438struct dentry *
439exportfs_decode_fh_raw(struct vfsmount *mnt, struct fid *fid, int fh_len,
440 int fileid_type, unsigned int flags,
441 int (*acceptable)(void *, struct dentry *),
442 void *context)
443{
444 const struct export_operations *nop = mnt->mnt_sb->s_export_op;
445 struct dentry *result, *alias;
446 char nbuf[NAME_MAX+1];
447 int err;
448
449 if (fileid_type < 0 || FILEID_USER_FLAGS(fileid_type))
450 return ERR_PTR(-EINVAL);
451
452 /*
453 * Try to get any dentry for the given file handle from the filesystem.
454 */
455 if (!exportfs_can_decode_fh(nop))
456 return ERR_PTR(-ESTALE);
457 result = nop->fh_to_dentry(mnt->mnt_sb, fid, fh_len, fileid_type);
458 if (IS_ERR_OR_NULL(result))
459 return result;
460
461 if ((flags & EXPORT_FH_DIR_ONLY) && !d_is_dir(result)) {
462 err = -ENOTDIR;
463 goto err_result;
464 }
465
466 /*
467 * If no acceptance criteria was specified by caller, a disconnected
468 * dentry is also accepatable. Callers may use this mode to query if
469 * file handle is stale or to get a reference to an inode without
470 * risking the high overhead caused by directory reconnect.
471 */
472 if (!acceptable)
473 return result;
474
475 if (d_is_dir(result)) {
476 /*
477 * This request is for a directory.
478 *
479 * On the positive side there is only one dentry for each
480 * directory inode. On the negative side this implies that we
481 * to ensure our dentry is connected all the way up to the
482 * filesystem root.
483 */
484 if (result->d_flags & DCACHE_DISCONNECTED) {
485 err = reconnect_path(mnt, result, nbuf);
486 if (err)
487 goto err_result;
488 }
489
490 if (!acceptable(context, result)) {
491 err = -EACCES;
492 goto err_result;
493 }
494
495 return result;
496 } else {
497 /*
498 * It's not a directory. Life is a little more complicated.
499 */
500 struct dentry *target_dir, *nresult;
501
502 /*
503 * See if either the dentry we just got from the filesystem
504 * or any alias for it is acceptable. This is always true
505 * if this filesystem is exported without the subtreecheck
506 * option. If the filesystem is exported with the subtree
507 * check option there's a fair chance we need to look at
508 * the parent directory in the file handle and make sure
509 * it's connected to the filesystem root.
510 */
511 alias = find_acceptable_alias(result, acceptable, context);
512 if (alias)
513 return alias;
514
515 /*
516 * Try to extract a dentry for the parent directory from the
517 * file handle. If this fails we'll have to give up.
518 */
519 err = -ESTALE;
520 if (!nop->fh_to_parent)
521 goto err_result;
522
523 target_dir = nop->fh_to_parent(mnt->mnt_sb, fid,
524 fh_len, fileid_type);
525 if (!target_dir)
526 goto err_result;
527 err = PTR_ERR(target_dir);
528 if (IS_ERR(target_dir))
529 goto err_result;
530
531 /*
532 * And as usual we need to make sure the parent directory is
533 * connected to the filesystem root. The VFS really doesn't
534 * like disconnected directories..
535 */
536 err = reconnect_path(mnt, target_dir, nbuf);
537 if (err) {
538 dput(target_dir);
539 goto err_result;
540 }
541
542 /*
543 * Now that we've got both a well-connected parent and a
544 * dentry for the inode we're after, make sure that our
545 * inode is actually connected to the parent.
546 */
547 err = exportfs_get_name(mnt, target_dir, nbuf, result);
548 if (err) {
549 dput(target_dir);
550 goto err_result;
551 }
552
553 inode_lock(target_dir->d_inode);
554 nresult = lookup_one(mnt_idmap(mnt), nbuf,
555 target_dir, strlen(nbuf));
556 if (!IS_ERR(nresult)) {
557 if (unlikely(nresult->d_inode != result->d_inode)) {
558 dput(nresult);
559 nresult = ERR_PTR(-ESTALE);
560 }
561 }
562 inode_unlock(target_dir->d_inode);
563 /*
564 * At this point we are done with the parent, but it's pinned
565 * by the child dentry anyway.
566 */
567 dput(target_dir);
568
569 if (IS_ERR(nresult)) {
570 err = PTR_ERR(nresult);
571 goto err_result;
572 }
573 dput(result);
574 result = nresult;
575
576 /*
577 * And finally make sure the dentry is actually acceptable
578 * to NFSD.
579 */
580 alias = find_acceptable_alias(result, acceptable, context);
581 if (!alias) {
582 err = -EACCES;
583 goto err_result;
584 }
585
586 return alias;
587 }
588
589 err_result:
590 dput(result);
591 return ERR_PTR(err);
592}
593EXPORT_SYMBOL_GPL(exportfs_decode_fh_raw);
594
595struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
596 int fh_len, int fileid_type,
597 int (*acceptable)(void *, struct dentry *),
598 void *context)
599{
600 struct dentry *ret;
601
602 ret = exportfs_decode_fh_raw(mnt, fid, fh_len, fileid_type, 0,
603 acceptable, context);
604 if (IS_ERR_OR_NULL(ret)) {
605 if (ret == ERR_PTR(-ENOMEM))
606 return ret;
607 return ERR_PTR(-ESTALE);
608 }
609 return ret;
610}
611EXPORT_SYMBOL_GPL(exportfs_decode_fh);
612
613MODULE_LICENSE("GPL");
1/*
2 * Copyright (C) Neil Brown 2002
3 * Copyright (C) Christoph Hellwig 2007
4 *
5 * This file contains the code mapping from inodes to NFS file handles,
6 * and for mapping back from file handles to dentries.
7 *
8 * For details on why we do all the strange and hairy things in here
9 * take a look at Documentation/filesystems/nfs/Exporting.
10 */
11#include <linux/exportfs.h>
12#include <linux/fs.h>
13#include <linux/file.h>
14#include <linux/module.h>
15#include <linux/mount.h>
16#include <linux/namei.h>
17#include <linux/sched.h>
18
19#define dprintk(fmt, args...) do{}while(0)
20
21
22static int get_name(struct vfsmount *mnt, struct dentry *dentry, char *name,
23 struct dentry *child);
24
25
26static int exportfs_get_name(struct vfsmount *mnt, struct dentry *dir,
27 char *name, struct dentry *child)
28{
29 const struct export_operations *nop = dir->d_sb->s_export_op;
30
31 if (nop->get_name)
32 return nop->get_name(dir, name, child);
33 else
34 return get_name(mnt, dir, name, child);
35}
36
37/*
38 * Check if the dentry or any of it's aliases is acceptable.
39 */
40static struct dentry *
41find_acceptable_alias(struct dentry *result,
42 int (*acceptable)(void *context, struct dentry *dentry),
43 void *context)
44{
45 struct dentry *dentry, *toput = NULL;
46 struct inode *inode;
47
48 if (acceptable(context, result))
49 return result;
50
51 inode = result->d_inode;
52 spin_lock(&inode->i_lock);
53 list_for_each_entry(dentry, &inode->i_dentry, d_alias) {
54 dget(dentry);
55 spin_unlock(&inode->i_lock);
56 if (toput)
57 dput(toput);
58 if (dentry != result && acceptable(context, dentry)) {
59 dput(result);
60 return dentry;
61 }
62 spin_lock(&inode->i_lock);
63 toput = dentry;
64 }
65 spin_unlock(&inode->i_lock);
66
67 if (toput)
68 dput(toput);
69 return NULL;
70}
71
72/*
73 * Find root of a disconnected subtree and return a reference to it.
74 */
75static struct dentry *
76find_disconnected_root(struct dentry *dentry)
77{
78 dget(dentry);
79 while (!IS_ROOT(dentry)) {
80 struct dentry *parent = dget_parent(dentry);
81
82 if (!(parent->d_flags & DCACHE_DISCONNECTED)) {
83 dput(parent);
84 break;
85 }
86
87 dput(dentry);
88 dentry = parent;
89 }
90 return dentry;
91}
92
93/*
94 * Make sure target_dir is fully connected to the dentry tree.
95 *
96 * It may already be, as the flag isn't always updated when connection happens.
97 */
98static int
99reconnect_path(struct vfsmount *mnt, struct dentry *target_dir, char *nbuf)
100{
101 int noprogress = 0;
102 int err = -ESTALE;
103
104 /*
105 * It is possible that a confused file system might not let us complete
106 * the path to the root. For example, if get_parent returns a directory
107 * in which we cannot find a name for the child. While this implies a
108 * very sick filesystem we don't want it to cause knfsd to spin. Hence
109 * the noprogress counter. If we go through the loop 10 times (2 is
110 * probably enough) without getting anywhere, we just give up
111 */
112 while (target_dir->d_flags & DCACHE_DISCONNECTED && noprogress++ < 10) {
113 struct dentry *pd = find_disconnected_root(target_dir);
114
115 if (!IS_ROOT(pd)) {
116 /* must have found a connected parent - great */
117 spin_lock(&pd->d_lock);
118 pd->d_flags &= ~DCACHE_DISCONNECTED;
119 spin_unlock(&pd->d_lock);
120 noprogress = 0;
121 } else if (pd == mnt->mnt_sb->s_root) {
122 printk(KERN_ERR "export: Eeek filesystem root is not connected, impossible\n");
123 spin_lock(&pd->d_lock);
124 pd->d_flags &= ~DCACHE_DISCONNECTED;
125 spin_unlock(&pd->d_lock);
126 noprogress = 0;
127 } else {
128 /*
129 * We have hit the top of a disconnected path, try to
130 * find parent and connect.
131 *
132 * Racing with some other process renaming a directory
133 * isn't much of a problem here. If someone renames
134 * the directory, it will end up properly connected,
135 * which is what we want
136 *
137 * Getting the parent can't be supported generically,
138 * the locking is too icky.
139 *
140 * Instead we just return EACCES. If server reboots
141 * or inodes get flushed, you lose
142 */
143 struct dentry *ppd = ERR_PTR(-EACCES);
144 struct dentry *npd;
145
146 mutex_lock(&pd->d_inode->i_mutex);
147 if (mnt->mnt_sb->s_export_op->get_parent)
148 ppd = mnt->mnt_sb->s_export_op->get_parent(pd);
149 mutex_unlock(&pd->d_inode->i_mutex);
150
151 if (IS_ERR(ppd)) {
152 err = PTR_ERR(ppd);
153 dprintk("%s: get_parent of %ld failed, err %d\n",
154 __func__, pd->d_inode->i_ino, err);
155 dput(pd);
156 break;
157 }
158
159 dprintk("%s: find name of %lu in %lu\n", __func__,
160 pd->d_inode->i_ino, ppd->d_inode->i_ino);
161 err = exportfs_get_name(mnt, ppd, nbuf, pd);
162 if (err) {
163 dput(ppd);
164 dput(pd);
165 if (err == -ENOENT)
166 /* some race between get_parent and
167 * get_name? just try again
168 */
169 continue;
170 break;
171 }
172 dprintk("%s: found name: %s\n", __func__, nbuf);
173 mutex_lock(&ppd->d_inode->i_mutex);
174 npd = lookup_one_len(nbuf, ppd, strlen(nbuf));
175 mutex_unlock(&ppd->d_inode->i_mutex);
176 if (IS_ERR(npd)) {
177 err = PTR_ERR(npd);
178 dprintk("%s: lookup failed: %d\n",
179 __func__, err);
180 dput(ppd);
181 dput(pd);
182 break;
183 }
184 /* we didn't really want npd, we really wanted
185 * a side-effect of the lookup.
186 * hopefully, npd == pd, though it isn't really
187 * a problem if it isn't
188 */
189 if (npd == pd)
190 noprogress = 0;
191 else
192 printk("%s: npd != pd\n", __func__);
193 dput(npd);
194 dput(ppd);
195 if (IS_ROOT(pd)) {
196 /* something went wrong, we have to give up */
197 dput(pd);
198 break;
199 }
200 }
201 dput(pd);
202 }
203
204 if (target_dir->d_flags & DCACHE_DISCONNECTED) {
205 /* something went wrong - oh-well */
206 if (!err)
207 err = -ESTALE;
208 return err;
209 }
210
211 return 0;
212}
213
214struct getdents_callback {
215 char *name; /* name that was found. It already points to a
216 buffer NAME_MAX+1 is size */
217 unsigned long ino; /* the inum we are looking for */
218 int found; /* inode matched? */
219 int sequence; /* sequence counter */
220};
221
222/*
223 * A rather strange filldir function to capture
224 * the name matching the specified inode number.
225 */
226static int filldir_one(void * __buf, const char * name, int len,
227 loff_t pos, u64 ino, unsigned int d_type)
228{
229 struct getdents_callback *buf = __buf;
230 int result = 0;
231
232 buf->sequence++;
233 if (buf->ino == ino) {
234 memcpy(buf->name, name, len);
235 buf->name[len] = '\0';
236 buf->found = 1;
237 result = -1;
238 }
239 return result;
240}
241
242/**
243 * get_name - default export_operations->get_name function
244 * @dentry: the directory in which to find a name
245 * @name: a pointer to a %NAME_MAX+1 char buffer to store the name
246 * @child: the dentry for the child directory.
247 *
248 * calls readdir on the parent until it finds an entry with
249 * the same inode number as the child, and returns that.
250 */
251static int get_name(struct vfsmount *mnt, struct dentry *dentry,
252 char *name, struct dentry *child)
253{
254 const struct cred *cred = current_cred();
255 struct inode *dir = dentry->d_inode;
256 int error;
257 struct file *file;
258 struct getdents_callback buffer;
259
260 error = -ENOTDIR;
261 if (!dir || !S_ISDIR(dir->i_mode))
262 goto out;
263 error = -EINVAL;
264 if (!dir->i_fop)
265 goto out;
266 /*
267 * Open the directory ...
268 */
269 file = dentry_open(dget(dentry), mntget(mnt), O_RDONLY, cred);
270 error = PTR_ERR(file);
271 if (IS_ERR(file))
272 goto out;
273
274 error = -EINVAL;
275 if (!file->f_op->readdir)
276 goto out_close;
277
278 buffer.name = name;
279 buffer.ino = child->d_inode->i_ino;
280 buffer.found = 0;
281 buffer.sequence = 0;
282 while (1) {
283 int old_seq = buffer.sequence;
284
285 error = vfs_readdir(file, filldir_one, &buffer);
286 if (buffer.found) {
287 error = 0;
288 break;
289 }
290
291 if (error < 0)
292 break;
293
294 error = -ENOENT;
295 if (old_seq == buffer.sequence)
296 break;
297 }
298
299out_close:
300 fput(file);
301out:
302 return error;
303}
304
305/**
306 * export_encode_fh - default export_operations->encode_fh function
307 * @inode: the object to encode
308 * @fh: where to store the file handle fragment
309 * @max_len: maximum length to store there
310 * @parent: parent directory inode, if wanted
311 *
312 * This default encode_fh function assumes that the 32 inode number
313 * is suitable for locating an inode, and that the generation number
314 * can be used to check that it is still valid. It places them in the
315 * filehandle fragment where export_decode_fh expects to find them.
316 */
317static int export_encode_fh(struct inode *inode, struct fid *fid,
318 int *max_len, struct inode *parent)
319{
320 int len = *max_len;
321 int type = FILEID_INO32_GEN;
322
323 if (parent && (len < 4)) {
324 *max_len = 4;
325 return 255;
326 } else if (len < 2) {
327 *max_len = 2;
328 return 255;
329 }
330
331 len = 2;
332 fid->i32.ino = inode->i_ino;
333 fid->i32.gen = inode->i_generation;
334 if (parent) {
335 fid->i32.parent_ino = parent->i_ino;
336 fid->i32.parent_gen = parent->i_generation;
337 len = 4;
338 type = FILEID_INO32_GEN_PARENT;
339 }
340 *max_len = len;
341 return type;
342}
343
344int exportfs_encode_fh(struct dentry *dentry, struct fid *fid, int *max_len,
345 int connectable)
346{
347 const struct export_operations *nop = dentry->d_sb->s_export_op;
348 int error;
349 struct dentry *p = NULL;
350 struct inode *inode = dentry->d_inode, *parent = NULL;
351
352 if (connectable && !S_ISDIR(inode->i_mode)) {
353 p = dget_parent(dentry);
354 /*
355 * note that while p might've ceased to be our parent already,
356 * it's still pinned by and still positive.
357 */
358 parent = p->d_inode;
359 }
360 if (nop->encode_fh)
361 error = nop->encode_fh(inode, fid->raw, max_len, parent);
362 else
363 error = export_encode_fh(inode, fid, max_len, parent);
364 dput(p);
365
366 return error;
367}
368EXPORT_SYMBOL_GPL(exportfs_encode_fh);
369
370struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
371 int fh_len, int fileid_type,
372 int (*acceptable)(void *, struct dentry *), void *context)
373{
374 const struct export_operations *nop = mnt->mnt_sb->s_export_op;
375 struct dentry *result, *alias;
376 char nbuf[NAME_MAX+1];
377 int err;
378
379 /*
380 * Try to get any dentry for the given file handle from the filesystem.
381 */
382 if (!nop || !nop->fh_to_dentry)
383 return ERR_PTR(-ESTALE);
384 result = nop->fh_to_dentry(mnt->mnt_sb, fid, fh_len, fileid_type);
385 if (!result)
386 result = ERR_PTR(-ESTALE);
387 if (IS_ERR(result))
388 return result;
389
390 if (S_ISDIR(result->d_inode->i_mode)) {
391 /*
392 * This request is for a directory.
393 *
394 * On the positive side there is only one dentry for each
395 * directory inode. On the negative side this implies that we
396 * to ensure our dentry is connected all the way up to the
397 * filesystem root.
398 */
399 if (result->d_flags & DCACHE_DISCONNECTED) {
400 err = reconnect_path(mnt, result, nbuf);
401 if (err)
402 goto err_result;
403 }
404
405 if (!acceptable(context, result)) {
406 err = -EACCES;
407 goto err_result;
408 }
409
410 return result;
411 } else {
412 /*
413 * It's not a directory. Life is a little more complicated.
414 */
415 struct dentry *target_dir, *nresult;
416
417 /*
418 * See if either the dentry we just got from the filesystem
419 * or any alias for it is acceptable. This is always true
420 * if this filesystem is exported without the subtreecheck
421 * option. If the filesystem is exported with the subtree
422 * check option there's a fair chance we need to look at
423 * the parent directory in the file handle and make sure
424 * it's connected to the filesystem root.
425 */
426 alias = find_acceptable_alias(result, acceptable, context);
427 if (alias)
428 return alias;
429
430 /*
431 * Try to extract a dentry for the parent directory from the
432 * file handle. If this fails we'll have to give up.
433 */
434 err = -ESTALE;
435 if (!nop->fh_to_parent)
436 goto err_result;
437
438 target_dir = nop->fh_to_parent(mnt->mnt_sb, fid,
439 fh_len, fileid_type);
440 if (!target_dir)
441 goto err_result;
442 err = PTR_ERR(target_dir);
443 if (IS_ERR(target_dir))
444 goto err_result;
445
446 /*
447 * And as usual we need to make sure the parent directory is
448 * connected to the filesystem root. The VFS really doesn't
449 * like disconnected directories..
450 */
451 err = reconnect_path(mnt, target_dir, nbuf);
452 if (err) {
453 dput(target_dir);
454 goto err_result;
455 }
456
457 /*
458 * Now that we've got both a well-connected parent and a
459 * dentry for the inode we're after, make sure that our
460 * inode is actually connected to the parent.
461 */
462 err = exportfs_get_name(mnt, target_dir, nbuf, result);
463 if (!err) {
464 mutex_lock(&target_dir->d_inode->i_mutex);
465 nresult = lookup_one_len(nbuf, target_dir,
466 strlen(nbuf));
467 mutex_unlock(&target_dir->d_inode->i_mutex);
468 if (!IS_ERR(nresult)) {
469 if (nresult->d_inode) {
470 dput(result);
471 result = nresult;
472 } else
473 dput(nresult);
474 }
475 }
476
477 /*
478 * At this point we are done with the parent, but it's pinned
479 * by the child dentry anyway.
480 */
481 dput(target_dir);
482
483 /*
484 * And finally make sure the dentry is actually acceptable
485 * to NFSD.
486 */
487 alias = find_acceptable_alias(result, acceptable, context);
488 if (!alias) {
489 err = -EACCES;
490 goto err_result;
491 }
492
493 return alias;
494 }
495
496 err_result:
497 dput(result);
498 return ERR_PTR(err);
499}
500EXPORT_SYMBOL_GPL(exportfs_decode_fh);
501
502MODULE_LICENSE("GPL");