xref: /linux/fs/nfsd/nfsfh.c (revision 1f20a5769446a1acae67ac9e63d07a594829a789)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * NFS server file handle treatment.
4  *
5  * Copyright (C) 1995, 1996 Olaf Kirch <okir@monad.swb.de>
6  * Portions Copyright (C) 1999 G. Allen Morris III <gam3@acm.org>
7  * Extensive rewrite by Neil Brown <neilb@cse.unsw.edu.au> Southern-Spring 1999
8  * ... and again Southern-Winter 2001 to support export_operations
9  */
10 
11 #include <linux/exportfs.h>
12 
13 #include <linux/sunrpc/svcauth_gss.h>
14 #include "nfsd.h"
15 #include "vfs.h"
16 #include "auth.h"
17 #include "trace.h"
18 
19 #define NFSDDBG_FACILITY		NFSDDBG_FH
20 
21 
22 /*
23  * our acceptability function.
24  * if NOSUBTREECHECK, accept anything
25  * if not, require that we can walk up to exp->ex_dentry
26  * doing some checks on the 'x' bits
27  */
28 static int nfsd_acceptable(void *expv, struct dentry *dentry)
29 {
30 	struct svc_export *exp = expv;
31 	int rv;
32 	struct dentry *tdentry;
33 	struct dentry *parent;
34 
35 	if (exp->ex_flags & NFSEXP_NOSUBTREECHECK)
36 		return 1;
37 
38 	tdentry = dget(dentry);
39 	while (tdentry != exp->ex_path.dentry && !IS_ROOT(tdentry)) {
40 		/* make sure parents give x permission to user */
41 		int err;
42 		parent = dget_parent(tdentry);
43 		err = inode_permission(&nop_mnt_idmap,
44 				       d_inode(parent), MAY_EXEC);
45 		if (err < 0) {
46 			dput(parent);
47 			break;
48 		}
49 		dput(tdentry);
50 		tdentry = parent;
51 	}
52 	if (tdentry != exp->ex_path.dentry)
53 		dprintk("nfsd_acceptable failed at %p %pd\n", tdentry, tdentry);
54 	rv = (tdentry == exp->ex_path.dentry);
55 	dput(tdentry);
56 	return rv;
57 }
58 
59 /* Type check. The correct error return for type mismatches does not seem to be
60  * generally agreed upon. SunOS seems to use EISDIR if file isn't S_IFREG; a
61  * comment in the NFSv3 spec says this is incorrect (implementation notes for
62  * the write call).
63  */
64 static inline __be32
65 nfsd_mode_check(struct svc_rqst *rqstp, struct dentry *dentry,
66 		umode_t requested)
67 {
68 	umode_t mode = d_inode(dentry)->i_mode & S_IFMT;
69 
70 	if (requested == 0) /* the caller doesn't care */
71 		return nfs_ok;
72 	if (mode == requested) {
73 		if (mode == S_IFDIR && !d_can_lookup(dentry)) {
74 			WARN_ON_ONCE(1);
75 			return nfserr_notdir;
76 		}
77 		return nfs_ok;
78 	}
79 	/*
80 	 * v4 has an error more specific than err_notdir which we should
81 	 * return in preference to err_notdir:
82 	 */
83 	if (rqstp->rq_vers == 4 && mode == S_IFLNK)
84 		return nfserr_symlink;
85 	if (requested == S_IFDIR)
86 		return nfserr_notdir;
87 	if (mode == S_IFDIR)
88 		return nfserr_isdir;
89 	return nfserr_inval;
90 }
91 
92 static bool nfsd_originating_port_ok(struct svc_rqst *rqstp, int flags)
93 {
94 	if (flags & NFSEXP_INSECURE_PORT)
95 		return true;
96 	/* We don't require gss requests to use low ports: */
97 	if (rqstp->rq_cred.cr_flavor >= RPC_AUTH_GSS)
98 		return true;
99 	return test_bit(RQ_SECURE, &rqstp->rq_flags);
100 }
101 
102 static __be32 nfsd_setuser_and_check_port(struct svc_rqst *rqstp,
103 					  struct svc_export *exp)
104 {
105 	int flags = nfsexp_flags(rqstp, exp);
106 
107 	/* Check if the request originated from a secure port. */
108 	if (!nfsd_originating_port_ok(rqstp, flags)) {
109 		RPC_IFDEBUG(char buf[RPC_MAX_ADDRBUFLEN]);
110 		dprintk("nfsd: request from insecure port %s!\n",
111 		        svc_print_addr(rqstp, buf, sizeof(buf)));
112 		return nfserr_perm;
113 	}
114 
115 	/* Set user creds for this exportpoint */
116 	return nfserrno(nfsd_setuser(rqstp, exp));
117 }
118 
119 static inline __be32 check_pseudo_root(struct svc_rqst *rqstp,
120 	struct dentry *dentry, struct svc_export *exp)
121 {
122 	if (!(exp->ex_flags & NFSEXP_V4ROOT))
123 		return nfs_ok;
124 	/*
125 	 * v2/v3 clients have no need for the V4ROOT export--they use
126 	 * the mount protocl instead; also, further V4ROOT checks may be
127 	 * in v4-specific code, in which case v2/v3 clients could bypass
128 	 * them.
129 	 */
130 	if (!nfsd_v4client(rqstp))
131 		return nfserr_stale;
132 	/*
133 	 * We're exposing only the directories and symlinks that have to be
134 	 * traversed on the way to real exports:
135 	 */
136 	if (unlikely(!d_is_dir(dentry) &&
137 		     !d_is_symlink(dentry)))
138 		return nfserr_stale;
139 	/*
140 	 * A pseudoroot export gives permission to access only one
141 	 * single directory; the kernel has to make another upcall
142 	 * before granting access to anything else under it:
143 	 */
144 	if (unlikely(dentry != exp->ex_path.dentry))
145 		return nfserr_stale;
146 	return nfs_ok;
147 }
148 
149 /*
150  * Use the given filehandle to look up the corresponding export and
151  * dentry.  On success, the results are used to set fh_export and
152  * fh_dentry.
153  */
154 static __be32 nfsd_set_fh_dentry(struct svc_rqst *rqstp, struct svc_fh *fhp)
155 {
156 	struct knfsd_fh	*fh = &fhp->fh_handle;
157 	struct fid *fid = NULL;
158 	struct svc_export *exp;
159 	struct dentry *dentry;
160 	int fileid_type;
161 	int data_left = fh->fh_size/4;
162 	int len;
163 	__be32 error;
164 
165 	error = nfserr_stale;
166 	if (rqstp->rq_vers > 2)
167 		error = nfserr_badhandle;
168 	if (rqstp->rq_vers == 4 && fh->fh_size == 0)
169 		return nfserr_nofilehandle;
170 
171 	if (fh->fh_version != 1)
172 		return error;
173 
174 	if (--data_left < 0)
175 		return error;
176 	if (fh->fh_auth_type != 0)
177 		return error;
178 	len = key_len(fh->fh_fsid_type) / 4;
179 	if (len == 0)
180 		return error;
181 	if (fh->fh_fsid_type == FSID_MAJOR_MINOR) {
182 		/* deprecated, convert to type 3 */
183 		len = key_len(FSID_ENCODE_DEV)/4;
184 		fh->fh_fsid_type = FSID_ENCODE_DEV;
185 		/*
186 		 * struct knfsd_fh uses host-endian fields, which are
187 		 * sometimes used to hold net-endian values. This
188 		 * confuses sparse, so we must use __force here to
189 		 * keep it from complaining.
190 		 */
191 		fh->fh_fsid[0] = new_encode_dev(MKDEV(ntohl((__force __be32)fh->fh_fsid[0]),
192 						      ntohl((__force __be32)fh->fh_fsid[1])));
193 		fh->fh_fsid[1] = fh->fh_fsid[2];
194 	}
195 	data_left -= len;
196 	if (data_left < 0)
197 		return error;
198 	exp = rqst_exp_find(rqstp, fh->fh_fsid_type, fh->fh_fsid);
199 	fid = (struct fid *)(fh->fh_fsid + len);
200 
201 	error = nfserr_stale;
202 	if (IS_ERR(exp)) {
203 		trace_nfsd_set_fh_dentry_badexport(rqstp, fhp, PTR_ERR(exp));
204 
205 		if (PTR_ERR(exp) == -ENOENT)
206 			return error;
207 
208 		return nfserrno(PTR_ERR(exp));
209 	}
210 
211 	if (exp->ex_flags & NFSEXP_NOSUBTREECHECK) {
212 		/* Elevate privileges so that the lack of 'r' or 'x'
213 		 * permission on some parent directory will
214 		 * not stop exportfs_decode_fh from being able
215 		 * to reconnect a directory into the dentry cache.
216 		 * The same problem can affect "SUBTREECHECK" exports,
217 		 * but as nfsd_acceptable depends on correct
218 		 * access control settings being in effect, we cannot
219 		 * fix that case easily.
220 		 */
221 		struct cred *new = prepare_creds();
222 		if (!new) {
223 			error =  nfserrno(-ENOMEM);
224 			goto out;
225 		}
226 		new->cap_effective =
227 			cap_raise_nfsd_set(new->cap_effective,
228 					   new->cap_permitted);
229 		put_cred(override_creds(new));
230 		put_cred(new);
231 	} else {
232 		error = nfsd_setuser_and_check_port(rqstp, exp);
233 		if (error)
234 			goto out;
235 	}
236 
237 	/*
238 	 * Look up the dentry using the NFS file handle.
239 	 */
240 	error = nfserr_stale;
241 	if (rqstp->rq_vers > 2)
242 		error = nfserr_badhandle;
243 
244 	fileid_type = fh->fh_fileid_type;
245 
246 	if (fileid_type == FILEID_ROOT)
247 		dentry = dget(exp->ex_path.dentry);
248 	else {
249 		dentry = exportfs_decode_fh_raw(exp->ex_path.mnt, fid,
250 						data_left, fileid_type,
251 						nfsd_acceptable, exp);
252 		if (IS_ERR_OR_NULL(dentry)) {
253 			trace_nfsd_set_fh_dentry_badhandle(rqstp, fhp,
254 					dentry ?  PTR_ERR(dentry) : -ESTALE);
255 			switch (PTR_ERR(dentry)) {
256 			case -ENOMEM:
257 			case -ETIMEDOUT:
258 				break;
259 			default:
260 				dentry = ERR_PTR(-ESTALE);
261 			}
262 		}
263 	}
264 	if (dentry == NULL)
265 		goto out;
266 	if (IS_ERR(dentry)) {
267 		if (PTR_ERR(dentry) != -EINVAL)
268 			error = nfserrno(PTR_ERR(dentry));
269 		goto out;
270 	}
271 
272 	if (d_is_dir(dentry) &&
273 			(dentry->d_flags & DCACHE_DISCONNECTED)) {
274 		printk("nfsd: find_fh_dentry returned a DISCONNECTED directory: %pd2\n",
275 				dentry);
276 	}
277 
278 	fhp->fh_dentry = dentry;
279 	fhp->fh_export = exp;
280 
281 	switch (rqstp->rq_vers) {
282 	case 4:
283 		if (dentry->d_sb->s_export_op->flags & EXPORT_OP_NOATOMIC_ATTR)
284 			fhp->fh_no_atomic_attr = true;
285 		break;
286 	case 3:
287 		if (dentry->d_sb->s_export_op->flags & EXPORT_OP_NOWCC)
288 			fhp->fh_no_wcc = true;
289 		break;
290 	case 2:
291 		fhp->fh_no_wcc = true;
292 	}
293 
294 	return 0;
295 out:
296 	exp_put(exp);
297 	return error;
298 }
299 
300 /**
301  * fh_verify - filehandle lookup and access checking
302  * @rqstp: pointer to current rpc request
303  * @fhp: filehandle to be verified
304  * @type: expected type of object pointed to by filehandle
305  * @access: type of access needed to object
306  *
307  * Look up a dentry from the on-the-wire filehandle, check the client's
308  * access to the export, and set the current task's credentials.
309  *
310  * Regardless of success or failure of fh_verify(), fh_put() should be
311  * called on @fhp when the caller is finished with the filehandle.
312  *
313  * fh_verify() may be called multiple times on a given filehandle, for
314  * example, when processing an NFSv4 compound.  The first call will look
315  * up a dentry using the on-the-wire filehandle.  Subsequent calls will
316  * skip the lookup and just perform the other checks and possibly change
317  * the current task's credentials.
318  *
319  * @type specifies the type of object expected using one of the S_IF*
320  * constants defined in include/linux/stat.h.  The caller may use zero
321  * to indicate that it doesn't care, or a negative integer to indicate
322  * that it expects something not of the given type.
323  *
324  * @access is formed from the NFSD_MAY_* constants defined in
325  * fs/nfsd/vfs.h.
326  */
327 __be32
328 fh_verify(struct svc_rqst *rqstp, struct svc_fh *fhp, umode_t type, int access)
329 {
330 	struct nfsd_net *nn = net_generic(SVC_NET(rqstp), nfsd_net_id);
331 	struct svc_export *exp = NULL;
332 	struct dentry	*dentry;
333 	__be32		error;
334 
335 	if (!fhp->fh_dentry) {
336 		error = nfsd_set_fh_dentry(rqstp, fhp);
337 		if (error)
338 			goto out;
339 	}
340 	dentry = fhp->fh_dentry;
341 	exp = fhp->fh_export;
342 
343 	trace_nfsd_fh_verify(rqstp, fhp, type, access);
344 
345 	/*
346 	 * We still have to do all these permission checks, even when
347 	 * fh_dentry is already set:
348 	 * 	- fh_verify may be called multiple times with different
349 	 * 	  "access" arguments (e.g. nfsd_proc_create calls
350 	 * 	  fh_verify(...,NFSD_MAY_EXEC) first, then later (in
351 	 * 	  nfsd_create) calls fh_verify(...,NFSD_MAY_CREATE).
352 	 *	- in the NFSv4 case, the filehandle may have been filled
353 	 *	  in by fh_compose, and given a dentry, but further
354 	 *	  compound operations performed with that filehandle
355 	 *	  still need permissions checks.  In the worst case, a
356 	 *	  mountpoint crossing may have changed the export
357 	 *	  options, and we may now need to use a different uid
358 	 *	  (for example, if different id-squashing options are in
359 	 *	  effect on the new filesystem).
360 	 */
361 	error = check_pseudo_root(rqstp, dentry, exp);
362 	if (error)
363 		goto out;
364 
365 	error = nfsd_setuser_and_check_port(rqstp, exp);
366 	if (error)
367 		goto out;
368 
369 	error = nfsd_mode_check(rqstp, dentry, type);
370 	if (error)
371 		goto out;
372 
373 	/*
374 	 * pseudoflavor restrictions are not enforced on NLM,
375 	 * which clients virtually always use auth_sys for,
376 	 * even while using RPCSEC_GSS for NFS.
377 	 */
378 	if (access & NFSD_MAY_LOCK || access & NFSD_MAY_BYPASS_GSS)
379 		goto skip_pseudoflavor_check;
380 	/*
381 	 * Clients may expect to be able to use auth_sys during mount,
382 	 * even if they use gss for everything else; see section 2.3.2
383 	 * of rfc 2623.
384 	 */
385 	if (access & NFSD_MAY_BYPASS_GSS_ON_ROOT
386 			&& exp->ex_path.dentry == dentry)
387 		goto skip_pseudoflavor_check;
388 
389 	error = check_nfsd_access(exp, rqstp);
390 	if (error)
391 		goto out;
392 
393 skip_pseudoflavor_check:
394 	/* Finally, check access permissions. */
395 	error = nfsd_permission(rqstp, exp, dentry, access);
396 out:
397 	trace_nfsd_fh_verify_err(rqstp, fhp, type, access, error);
398 	if (error == nfserr_stale)
399 		nfsd_stats_fh_stale_inc(nn, exp);
400 	return error;
401 }
402 
403 
404 /*
405  * Compose a file handle for an NFS reply.
406  *
407  * Note that when first composed, the dentry may not yet have
408  * an inode.  In this case a call to fh_update should be made
409  * before the fh goes out on the wire ...
410  */
411 static void _fh_update(struct svc_fh *fhp, struct svc_export *exp,
412 		struct dentry *dentry)
413 {
414 	if (dentry != exp->ex_path.dentry) {
415 		struct fid *fid = (struct fid *)
416 			(fhp->fh_handle.fh_fsid + fhp->fh_handle.fh_size/4 - 1);
417 		int maxsize = (fhp->fh_maxsize - fhp->fh_handle.fh_size)/4;
418 		int fh_flags = (exp->ex_flags & NFSEXP_NOSUBTREECHECK) ? 0 :
419 				EXPORT_FH_CONNECTABLE;
420 		int fileid_type =
421 			exportfs_encode_fh(dentry, fid, &maxsize, fh_flags);
422 
423 		fhp->fh_handle.fh_fileid_type =
424 			fileid_type > 0 ? fileid_type : FILEID_INVALID;
425 		fhp->fh_handle.fh_size += maxsize * 4;
426 	} else {
427 		fhp->fh_handle.fh_fileid_type = FILEID_ROOT;
428 	}
429 }
430 
431 static bool is_root_export(struct svc_export *exp)
432 {
433 	return exp->ex_path.dentry == exp->ex_path.dentry->d_sb->s_root;
434 }
435 
436 static struct super_block *exp_sb(struct svc_export *exp)
437 {
438 	return exp->ex_path.dentry->d_sb;
439 }
440 
441 static bool fsid_type_ok_for_exp(u8 fsid_type, struct svc_export *exp)
442 {
443 	switch (fsid_type) {
444 	case FSID_DEV:
445 		if (!old_valid_dev(exp_sb(exp)->s_dev))
446 			return false;
447 		fallthrough;
448 	case FSID_MAJOR_MINOR:
449 	case FSID_ENCODE_DEV:
450 		return exp_sb(exp)->s_type->fs_flags & FS_REQUIRES_DEV;
451 	case FSID_NUM:
452 		return exp->ex_flags & NFSEXP_FSID;
453 	case FSID_UUID8:
454 	case FSID_UUID16:
455 		if (!is_root_export(exp))
456 			return false;
457 		fallthrough;
458 	case FSID_UUID4_INUM:
459 	case FSID_UUID16_INUM:
460 		return exp->ex_uuid != NULL;
461 	}
462 	return true;
463 }
464 
465 
466 static void set_version_and_fsid_type(struct svc_fh *fhp, struct svc_export *exp, struct svc_fh *ref_fh)
467 {
468 	u8 version;
469 	u8 fsid_type;
470 retry:
471 	version = 1;
472 	if (ref_fh && ref_fh->fh_export == exp) {
473 		version = ref_fh->fh_handle.fh_version;
474 		fsid_type = ref_fh->fh_handle.fh_fsid_type;
475 
476 		ref_fh = NULL;
477 
478 		switch (version) {
479 		case 0xca:
480 			fsid_type = FSID_DEV;
481 			break;
482 		case 1:
483 			break;
484 		default:
485 			goto retry;
486 		}
487 
488 		/*
489 		 * As the fsid -> filesystem mapping was guided by
490 		 * user-space, there is no guarantee that the filesystem
491 		 * actually supports that fsid type. If it doesn't we
492 		 * loop around again without ref_fh set.
493 		 */
494 		if (!fsid_type_ok_for_exp(fsid_type, exp))
495 			goto retry;
496 	} else if (exp->ex_flags & NFSEXP_FSID) {
497 		fsid_type = FSID_NUM;
498 	} else if (exp->ex_uuid) {
499 		if (fhp->fh_maxsize >= 64) {
500 			if (is_root_export(exp))
501 				fsid_type = FSID_UUID16;
502 			else
503 				fsid_type = FSID_UUID16_INUM;
504 		} else {
505 			if (is_root_export(exp))
506 				fsid_type = FSID_UUID8;
507 			else
508 				fsid_type = FSID_UUID4_INUM;
509 		}
510 	} else if (!old_valid_dev(exp_sb(exp)->s_dev))
511 		/* for newer device numbers, we must use a newer fsid format */
512 		fsid_type = FSID_ENCODE_DEV;
513 	else
514 		fsid_type = FSID_DEV;
515 	fhp->fh_handle.fh_version = version;
516 	if (version)
517 		fhp->fh_handle.fh_fsid_type = fsid_type;
518 }
519 
520 __be32
521 fh_compose(struct svc_fh *fhp, struct svc_export *exp, struct dentry *dentry,
522 	   struct svc_fh *ref_fh)
523 {
524 	/* ref_fh is a reference file handle.
525 	 * if it is non-null and for the same filesystem, then we should compose
526 	 * a filehandle which is of the same version, where possible.
527 	 */
528 
529 	struct inode * inode = d_inode(dentry);
530 	dev_t ex_dev = exp_sb(exp)->s_dev;
531 
532 	dprintk("nfsd: fh_compose(exp %02x:%02x/%ld %pd2, ino=%ld)\n",
533 		MAJOR(ex_dev), MINOR(ex_dev),
534 		(long) d_inode(exp->ex_path.dentry)->i_ino,
535 		dentry,
536 		(inode ? inode->i_ino : 0));
537 
538 	/* Choose filehandle version and fsid type based on
539 	 * the reference filehandle (if it is in the same export)
540 	 * or the export options.
541 	 */
542 	set_version_and_fsid_type(fhp, exp, ref_fh);
543 
544 	/* If we have a ref_fh, then copy the fh_no_wcc setting from it. */
545 	fhp->fh_no_wcc = ref_fh ? ref_fh->fh_no_wcc : false;
546 
547 	if (ref_fh == fhp)
548 		fh_put(ref_fh);
549 
550 	if (fhp->fh_dentry) {
551 		printk(KERN_ERR "fh_compose: fh %pd2 not initialized!\n",
552 		       dentry);
553 	}
554 	if (fhp->fh_maxsize < NFS_FHSIZE)
555 		printk(KERN_ERR "fh_compose: called with maxsize %d! %pd2\n",
556 		       fhp->fh_maxsize,
557 		       dentry);
558 
559 	fhp->fh_dentry = dget(dentry); /* our internal copy */
560 	fhp->fh_export = exp_get(exp);
561 
562 	fhp->fh_handle.fh_size =
563 		key_len(fhp->fh_handle.fh_fsid_type) + 4;
564 	fhp->fh_handle.fh_auth_type = 0;
565 
566 	mk_fsid(fhp->fh_handle.fh_fsid_type,
567 		fhp->fh_handle.fh_fsid,
568 		ex_dev,
569 		d_inode(exp->ex_path.dentry)->i_ino,
570 		exp->ex_fsid, exp->ex_uuid);
571 
572 	if (inode)
573 		_fh_update(fhp, exp, dentry);
574 	if (fhp->fh_handle.fh_fileid_type == FILEID_INVALID) {
575 		fh_put(fhp);
576 		return nfserr_opnotsupp;
577 	}
578 
579 	return 0;
580 }
581 
582 /*
583  * Update file handle information after changing a dentry.
584  * This is only called by nfsd_create, nfsd_create_v3 and nfsd_proc_create
585  */
586 __be32
587 fh_update(struct svc_fh *fhp)
588 {
589 	struct dentry *dentry;
590 
591 	if (!fhp->fh_dentry)
592 		goto out_bad;
593 
594 	dentry = fhp->fh_dentry;
595 	if (d_really_is_negative(dentry))
596 		goto out_negative;
597 	if (fhp->fh_handle.fh_fileid_type != FILEID_ROOT)
598 		return 0;
599 
600 	_fh_update(fhp, fhp->fh_export, dentry);
601 	if (fhp->fh_handle.fh_fileid_type == FILEID_INVALID)
602 		return nfserr_opnotsupp;
603 	return 0;
604 out_bad:
605 	printk(KERN_ERR "fh_update: fh not verified!\n");
606 	return nfserr_serverfault;
607 out_negative:
608 	printk(KERN_ERR "fh_update: %pd2 still negative!\n",
609 		dentry);
610 	return nfserr_serverfault;
611 }
612 
613 /**
614  * fh_fill_pre_attrs - Fill in pre-op attributes
615  * @fhp: file handle to be updated
616  *
617  */
618 __be32 __must_check fh_fill_pre_attrs(struct svc_fh *fhp)
619 {
620 	bool v4 = (fhp->fh_maxsize == NFS4_FHSIZE);
621 	struct inode *inode;
622 	struct kstat stat;
623 	__be32 err;
624 
625 	if (fhp->fh_no_wcc || fhp->fh_pre_saved)
626 		return nfs_ok;
627 
628 	inode = d_inode(fhp->fh_dentry);
629 	err = fh_getattr(fhp, &stat);
630 	if (err)
631 		return err;
632 
633 	if (v4)
634 		fhp->fh_pre_change = nfsd4_change_attribute(&stat, inode);
635 
636 	fhp->fh_pre_mtime = stat.mtime;
637 	fhp->fh_pre_ctime = stat.ctime;
638 	fhp->fh_pre_size  = stat.size;
639 	fhp->fh_pre_saved = true;
640 	return nfs_ok;
641 }
642 
643 /**
644  * fh_fill_post_attrs - Fill in post-op attributes
645  * @fhp: file handle to be updated
646  *
647  */
648 __be32 fh_fill_post_attrs(struct svc_fh *fhp)
649 {
650 	bool v4 = (fhp->fh_maxsize == NFS4_FHSIZE);
651 	struct inode *inode = d_inode(fhp->fh_dentry);
652 	__be32 err;
653 
654 	if (fhp->fh_no_wcc)
655 		return nfs_ok;
656 
657 	if (fhp->fh_post_saved)
658 		printk("nfsd: inode locked twice during operation.\n");
659 
660 	err = fh_getattr(fhp, &fhp->fh_post_attr);
661 	if (err)
662 		return err;
663 
664 	fhp->fh_post_saved = true;
665 	if (v4)
666 		fhp->fh_post_change =
667 			nfsd4_change_attribute(&fhp->fh_post_attr, inode);
668 	return nfs_ok;
669 }
670 
671 /**
672  * fh_fill_both_attrs - Fill pre-op and post-op attributes
673  * @fhp: file handle to be updated
674  *
675  * This is used when the directory wasn't changed, but wcc attributes
676  * are needed anyway.
677  */
678 __be32 __must_check fh_fill_both_attrs(struct svc_fh *fhp)
679 {
680 	__be32 err;
681 
682 	err = fh_fill_post_attrs(fhp);
683 	if (err)
684 		return err;
685 
686 	fhp->fh_pre_change = fhp->fh_post_change;
687 	fhp->fh_pre_mtime = fhp->fh_post_attr.mtime;
688 	fhp->fh_pre_ctime = fhp->fh_post_attr.ctime;
689 	fhp->fh_pre_size = fhp->fh_post_attr.size;
690 	fhp->fh_pre_saved = true;
691 	return nfs_ok;
692 }
693 
694 /*
695  * Release a file handle.
696  */
697 void
698 fh_put(struct svc_fh *fhp)
699 {
700 	struct dentry * dentry = fhp->fh_dentry;
701 	struct svc_export * exp = fhp->fh_export;
702 	if (dentry) {
703 		fhp->fh_dentry = NULL;
704 		dput(dentry);
705 		fh_clear_pre_post_attrs(fhp);
706 	}
707 	fh_drop_write(fhp);
708 	if (exp) {
709 		exp_put(exp);
710 		fhp->fh_export = NULL;
711 	}
712 	fhp->fh_no_wcc = false;
713 	return;
714 }
715 
716 /*
717  * Shorthand for dprintk()'s
718  */
719 char * SVCFH_fmt(struct svc_fh *fhp)
720 {
721 	struct knfsd_fh *fh = &fhp->fh_handle;
722 	static char buf[2+1+1+64*3+1];
723 
724 	if (fh->fh_size < 0 || fh->fh_size> 64)
725 		return "bad-fh";
726 	sprintf(buf, "%d: %*ph", fh->fh_size, fh->fh_size, fh->fh_raw);
727 	return buf;
728 }
729 
730 enum fsid_source fsid_source(const struct svc_fh *fhp)
731 {
732 	if (fhp->fh_handle.fh_version != 1)
733 		return FSIDSOURCE_DEV;
734 	switch(fhp->fh_handle.fh_fsid_type) {
735 	case FSID_DEV:
736 	case FSID_ENCODE_DEV:
737 	case FSID_MAJOR_MINOR:
738 		if (exp_sb(fhp->fh_export)->s_type->fs_flags & FS_REQUIRES_DEV)
739 			return FSIDSOURCE_DEV;
740 		break;
741 	case FSID_NUM:
742 		if (fhp->fh_export->ex_flags & NFSEXP_FSID)
743 			return FSIDSOURCE_FSID;
744 		break;
745 	default:
746 		break;
747 	}
748 	/* either a UUID type filehandle, or the filehandle doesn't
749 	 * match the export.
750 	 */
751 	if (fhp->fh_export->ex_flags & NFSEXP_FSID)
752 		return FSIDSOURCE_FSID;
753 	if (fhp->fh_export->ex_uuid)
754 		return FSIDSOURCE_UUID;
755 	return FSIDSOURCE_DEV;
756 }
757 
758 /*
759  * We could use i_version alone as the change attribute.  However, i_version
760  * can go backwards on a regular file after an unclean shutdown.  On its own
761  * that doesn't necessarily cause a problem, but if i_version goes backwards
762  * and then is incremented again it could reuse a value that was previously
763  * used before boot, and a client who queried the two values might incorrectly
764  * assume nothing changed.
765  *
766  * By using both ctime and the i_version counter we guarantee that as long as
767  * time doesn't go backwards we never reuse an old value. If the filesystem
768  * advertises STATX_ATTR_CHANGE_MONOTONIC, then this mitigation is not
769  * needed.
770  *
771  * We only need to do this for regular files as well. For directories, we
772  * assume that the new change attr is always logged to stable storage in some
773  * fashion before the results can be seen.
774  */
775 u64 nfsd4_change_attribute(const struct kstat *stat, const struct inode *inode)
776 {
777 	u64 chattr;
778 
779 	if (stat->result_mask & STATX_CHANGE_COOKIE) {
780 		chattr = stat->change_cookie;
781 		if (S_ISREG(inode->i_mode) &&
782 		    !(stat->attributes & STATX_ATTR_CHANGE_MONOTONIC)) {
783 			chattr += (u64)stat->ctime.tv_sec << 30;
784 			chattr += stat->ctime.tv_nsec;
785 		}
786 	} else {
787 		chattr = time_to_chattr(&stat->ctime);
788 	}
789 	return chattr;
790 }
791