1 /*
2 * Copyright (c) 2004 The DragonFly Project. All rights reserved.
3 *
4 * This code is derived from software contributed to The DragonFly Project
5 * by Matthew Dillon <dillon@backplane.com>
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 *
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in
15 * the documentation and/or other materials provided with the
16 * distribution.
17 * 3. Neither the name of The DragonFly Project nor the names of its
18 * contributors may be used to endorse or promote products derived
19 * from this software without specific, prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
22 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
23 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
24 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
25 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
26 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
27 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
28 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
29 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
30 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
31 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34 /*
35 * nlookup() is the 'new' namei interface. Rather then return directory and
36 * leaf vnodes (in various lock states) the new interface instead deals in
37 * namecache records. Namecache records may represent both a positive or
38 * a negative hit. The namespace is locked via the namecache record instead
39 * of via the vnode, and only the leaf namecache record (representing the
40 * filename) needs to be locked.
41 *
42 * This greatly improves filesystem parallelism and is a huge simplification
43 * of the API verses the old vnode locking / namei scheme.
44 *
45 * Filesystems must actively control the caching aspects of the namecache,
46 * and since namecache pointers are used as handles they are non-optional
47 * even for filesystems which do not generally wish to cache things. It is
48 * intended that a separate cache coherency API will be constructed to handle
49 * these issues.
50 */
51
52 #include "opt_ktrace.h"
53
54 #include <sys/param.h>
55 #include <sys/systm.h>
56 #include <sys/kernel.h>
57 #include <sys/vnode.h>
58 #include <sys/mount.h>
59 #include <sys/filedesc.h>
60 #include <sys/proc.h>
61 #include <sys/namei.h>
62 #include <sys/nlookup.h>
63 #include <sys/malloc.h>
64 #include <sys/stat.h>
65 #include <sys/objcache.h>
66 #include <sys/file.h>
67
68 #ifdef KTRACE
69 #include <sys/ktrace.h>
70 #endif
71
72 static int naccess(struct nchandle *nch, int vmode, struct ucred *cred,
73 int *stickyp);
74
75 /*
76 * Initialize a nlookup() structure, early error return for copyin faults
77 * or a degenerate empty string (which is not allowed).
78 *
79 * The first process proc0's credentials are used if the calling thread
80 * is not associated with a process context.
81 *
82 * MPSAFE
83 */
84 int
85 nlookup_init(struct nlookupdata *nd,
86 const char *path, enum uio_seg seg, int flags)
87 {
88 size_t pathlen;
89 struct proc *p;
90 thread_t td;
91 int error;
92
93 td = curthread;
94 p = td->td_proc;
95
96 /*
97 * note: the pathlen set by copy*str() includes the terminating \0.
98 */
99 bzero(nd, sizeof(struct nlookupdata));
100 nd->nl_path = objcache_get(namei_oc, M_WAITOK);
101 nd->nl_flags |= NLC_HASBUF;
102 if (seg == UIO_SYSSPACE)
103 error = copystr(path, nd->nl_path, MAXPATHLEN, &pathlen);
104 else
105 error = copyinstr(path, nd->nl_path, MAXPATHLEN, &pathlen);
106
107 /*
108 * Don't allow empty pathnames.
109 * POSIX.1 requirement: "" is not a vaild file name.
110 */
111 if (error == 0 && pathlen <= 1)
112 error = ENOENT;
113
114 if (error == 0) {
115 if (p && p->p_fd) {
116 cache_copy(&p->p_fd->fd_ncdir, &nd->nl_nch);
117 cache_copy(&p->p_fd->fd_nrdir, &nd->nl_rootnch);
118 if (p->p_fd->fd_njdir.ncp)
119 cache_copy(&p->p_fd->fd_njdir, &nd->nl_jailnch);
120 nd->nl_cred = crhold(p->p_ucred);
121 } else {
122 cache_copy(&rootnch, &nd->nl_nch);
123 cache_copy(&nd->nl_nch, &nd->nl_rootnch);
124 cache_copy(&nd->nl_nch, &nd->nl_jailnch);
125 nd->nl_cred = crhold(proc0.p_ucred);
126 }
127 nd->nl_td = td;
128 nd->nl_flags |= flags;
129 } else {
130 nlookup_done(nd);
131 }
132 return(error);
133 }
134
135
136 /*
137 * nlookup_init() for "at" family of syscalls.
138 *
139 * Works similarly to nlookup_init() but if path is relative and fd is not
140 * AT_FDCWD, path is interpreted relative to the directory pointed to by fd.
141 * In this case, the file entry pointed to by fd is ref'ed and returned in
142 * *fpp.
143 *
144 * If the call succeeds, nlookup_done_at() must be called to clean-up the nd
145 * and release the ref to the file entry.
146 */
147 int
148 nlookup_init_at(struct nlookupdata *nd, struct file **fpp, int fd,
149 const char *path, enum uio_seg seg, int flags)
150 {
151 struct thread *td = curthread;
152 struct proc *p = td->td_proc;
153 struct file* fp;
154 struct vnode *vp;
155 int error;
156
157 *fpp = NULL;
158
159 if ((error = nlookup_init(nd, path, seg, flags)) != 0) {
160 return (error);
161 }
162
163 if (nd->nl_path[0] != '/' && fd != AT_FDCWD) {
164 if ((error = holdvnode(p->p_fd, fd, &fp)) != 0)
165 goto done;
166 vp = (struct vnode*)fp->f_data;
167 if (vp->v_type != VDIR || fp->f_nchandle.ncp == NULL) {
168 fdrop(fp);
169 fp = NULL;
170 error = ENOTDIR;
171 goto done;
172 }
173 cache_drop(&nd->nl_nch);
174 cache_copy(&fp->f_nchandle, &nd->nl_nch);
175 *fpp = fp;
176 }
177
178
179 done:
180 if (error)
181 nlookup_done(nd);
182 return (error);
183
184 }
185
186 /*
187 * This works similarly to nlookup_init() but does not assume a process
188 * context. rootnch is always chosen for the root directory and the cred
189 * and starting directory are supplied in arguments.
190 */
191 int
192 nlookup_init_raw(struct nlookupdata *nd,
193 const char *path, enum uio_seg seg, int flags,
194 struct ucred *cred, struct nchandle *ncstart)
195 {
196 size_t pathlen;
197 thread_t td;
198 int error;
199
200 td = curthread;
201
202 bzero(nd, sizeof(struct nlookupdata));
203 nd->nl_path = objcache_get(namei_oc, M_WAITOK);
204 nd->nl_flags |= NLC_HASBUF;
205 if (seg == UIO_SYSSPACE)
206 error = copystr(path, nd->nl_path, MAXPATHLEN, &pathlen);
207 else
208 error = copyinstr(path, nd->nl_path, MAXPATHLEN, &pathlen);
209
210 /*
211 * Don't allow empty pathnames.
212 * POSIX.1 requirement: "" is not a vaild file name.
213 */
214 if (error == 0 && pathlen <= 1)
215 error = ENOENT;
216
217 if (error == 0) {
218 cache_copy(ncstart, &nd->nl_nch);
219 cache_copy(&rootnch, &nd->nl_rootnch);
220 cache_copy(&rootnch, &nd->nl_jailnch);
221 nd->nl_cred = crhold(cred);
222 nd->nl_td = td;
223 nd->nl_flags |= flags;
224 } else {
225 nlookup_done(nd);
226 }
227 return(error);
228 }
229
230 /*
231 * This works similarly to nlookup_init_raw() but does not rely
232 * on rootnch being initialized yet.
233 */
234 int
235 nlookup_init_root(struct nlookupdata *nd,
236 const char *path, enum uio_seg seg, int flags,
237 struct ucred *cred, struct nchandle *ncstart,
238 struct nchandle *ncroot)
239 {
240 size_t pathlen;
241 thread_t td;
242 int error;
243
244 td = curthread;
245
246 bzero(nd, sizeof(struct nlookupdata));
247 nd->nl_path = objcache_get(namei_oc, M_WAITOK);
248 nd->nl_flags |= NLC_HASBUF;
249 if (seg == UIO_SYSSPACE)
250 error = copystr(path, nd->nl_path, MAXPATHLEN, &pathlen);
251 else
252 error = copyinstr(path, nd->nl_path, MAXPATHLEN, &pathlen);
253
254 /*
255 * Don't allow empty pathnames.
256 * POSIX.1 requirement: "" is not a vaild file name.
257 */
258 if (error == 0 && pathlen <= 1)
259 error = ENOENT;
260
261 if (error == 0) {
262 cache_copy(ncstart, &nd->nl_nch);
263 cache_copy(ncroot, &nd->nl_rootnch);
264 cache_copy(ncroot, &nd->nl_jailnch);
265 nd->nl_cred = crhold(cred);
266 nd->nl_td = td;
267 nd->nl_flags |= flags;
268 } else {
269 nlookup_done(nd);
270 }
271 return(error);
272 }
273
274 /*
275 * Set a different credential; this credential will be used by future
276 * operations performed on nd.nl_open_vp and nlookupdata structure.
277 */
278 void
279 nlookup_set_cred(struct nlookupdata *nd, struct ucred *cred)
280 {
281 KKASSERT(nd->nl_cred != NULL);
282
283 if (nd->nl_cred != cred) {
284 cred = crhold(cred);
285 crfree(nd->nl_cred);
286 nd->nl_cred = cred;
287 }
288 }
289
290 /*
291 * Cleanup a nlookupdata structure after we are through with it. This may
292 * be called on any nlookupdata structure initialized with nlookup_init().
293 * Calling nlookup_done() is mandatory in all cases except where nlookup_init()
294 * returns an error, even if as a consumer you believe you have taken all
295 * dynamic elements out of the nlookupdata structure.
296 */
297 void
298 nlookup_done(struct nlookupdata *nd)
299 {
300 if (nd->nl_nch.ncp) {
301 if (nd->nl_flags & NLC_NCPISLOCKED) {
302 nd->nl_flags &= ~NLC_NCPISLOCKED;
303 cache_unlock(&nd->nl_nch);
304 }
305 cache_drop(&nd->nl_nch); /* NULL's out the nch */
306 }
307 if (nd->nl_rootnch.ncp)
308 cache_drop(&nd->nl_rootnch);
309 if (nd->nl_jailnch.ncp)
310 cache_drop(&nd->nl_jailnch);
311 if ((nd->nl_flags & NLC_HASBUF) && nd->nl_path) {
312 objcache_put(namei_oc, nd->nl_path);
313 nd->nl_path = NULL;
314 }
315 if (nd->nl_cred) {
316 crfree(nd->nl_cred);
317 nd->nl_cred = NULL;
318 }
319 if (nd->nl_open_vp) {
320 if (nd->nl_flags & NLC_LOCKVP) {
321 vn_unlock(nd->nl_open_vp);
322 nd->nl_flags &= ~NLC_LOCKVP;
323 }
324 vn_close(nd->nl_open_vp, nd->nl_vp_fmode);
325 nd->nl_open_vp = NULL;
326 }
327 if (nd->nl_dvp) {
328 vrele(nd->nl_dvp);
329 nd->nl_dvp = NULL;
330 }
331 nd->nl_flags = 0; /* clear remaining flags (just clear everything) */
332 }
333
334 /*
335 * Works similarly to nlookup_done() when nd initialized with
336 * nlookup_init_at().
337 */
338 void
339 nlookup_done_at(struct nlookupdata *nd, struct file *fp)
340 {
341 nlookup_done(nd);
342 if (fp != NULL)
343 fdrop(fp);
344 }
345
346 void
347 nlookup_zero(struct nlookupdata *nd)
348 {
349 bzero(nd, sizeof(struct nlookupdata));
350 }
351
352 /*
353 * Simple all-in-one nlookup. Returns a locked namecache structure or NULL
354 * if an error occured.
355 *
356 * Note that the returned ncp is not checked for permissions, though VEXEC
357 * is checked on the directory path leading up to the result. The caller
358 * must call naccess() to check the permissions of the returned leaf.
359 */
360 struct nchandle
361 nlookup_simple(const char *str, enum uio_seg seg,
362 int niflags, int *error)
363 {
364 struct nlookupdata nd;
365 struct nchandle nch;
366
367 *error = nlookup_init(&nd, str, seg, niflags);
368 if (*error == 0) {
369 if ((*error = nlookup(&nd)) == 0) {
370 nch = nd.nl_nch; /* keep hold ref from structure */
371 cache_zero(&nd.nl_nch); /* and NULL out */
372 } else {
373 cache_zero(&nch);
374 }
375 nlookup_done(&nd);
376 } else {
377 cache_zero(&nch);
378 }
379 return(nch);
380 }
381
382 /*
383 * Returns non-zero if the path element is the last element
384 */
385 static
386 int
387 islastelement(const char *ptr)
388 {
389 while (*ptr == '/')
390 ++ptr;
391 return (*ptr == 0);
392 }
393
394 /*
395 * Returns non-zero if we need to lock the namecache element
396 * exclusively. Unless otherwise requested by NLC_SHAREDLOCK,
397 * the last element of the namecache lookup will be locked
398 * exclusively.
399 *
400 * NOTE: Even if we return on-zero, an unresolved namecache record
401 * will always be locked exclusively.
402 */
403 static __inline
404 int
405 wantsexcllock(struct nlookupdata *nd, const char *ptr)
406 {
407 if ((nd->nl_flags & NLC_SHAREDLOCK) == 0)
408 return(islastelement(ptr));
409 return(0);
410 }
411
412
413 /*
414 * Do a generic nlookup. Note that the passed nd is not nlookup_done()'d
415 * on return, even if an error occurs. If no error occurs or NLC_CREATE
416 * is flagged and ENOENT is returned, then the returned nl_nch is always
417 * referenced and locked exclusively.
418 *
419 * WARNING: For any general error other than ENOENT w/NLC_CREATE, the
420 * the resulting nl_nch may or may not be locked and if locked
421 * might be locked either shared or exclusive.
422 *
423 * Intermediate directory elements, including the current directory, require
424 * execute (search) permission. nlookup does not examine the access
425 * permissions on the returned element.
426 *
427 * If NLC_CREATE is set the last directory must allow node creation,
428 * and an error code of 0 will be returned for a non-existant
429 * target (not ENOENT).
430 *
431 * If NLC_RENAME_DST is set the last directory mut allow node deletion,
432 * plus the sticky check is made, and an error code of 0 will be returned
433 * for a non-existant target (not ENOENT).
434 *
435 * If NLC_DELETE is set the last directory mut allow node deletion,
436 * plus the sticky check is made.
437 *
438 * If NLC_REFDVP is set nd->nl_dvp will be set to the directory vnode
439 * of the returned entry. The vnode will be referenced, but not locked,
440 * and will be released by nlookup_done() along with everything else.
441 *
442 * NOTE: As an optimization we attempt to obtain a shared namecache lock
443 * on any intermediate elements. On success, the returned element
444 * is ALWAYS locked exclusively.
445 */
446 int
447 nlookup(struct nlookupdata *nd)
448 {
449 globaldata_t gd = mycpu;
450 struct nlcomponent nlc;
451 struct nchandle nch;
452 struct nchandle par;
453 struct nchandle nctmp;
454 struct mount *mp;
455 struct vnode *hvp; /* hold to prevent recyclement */
456 int wasdotordotdot;
457 char *ptr;
458 int error;
459 int len;
460 int dflags;
461 int hit = 1;
462
463 #ifdef KTRACE
464 if (KTRPOINT(nd->nl_td, KTR_NAMEI))
465 ktrnamei(nd->nl_td->td_lwp, nd->nl_path);
466 #endif
467 bzero(&nlc, sizeof(nlc));
468
469 /*
470 * Setup for the loop. The current working namecache element is
471 * always at least referenced. We lock it as required, but always
472 * return a locked, resolved namecache entry.
473 */
474 nd->nl_loopcnt = 0;
475 if (nd->nl_dvp) {
476 vrele(nd->nl_dvp);
477 nd->nl_dvp = NULL;
478 }
479 ptr = nd->nl_path;
480
481 /*
482 * Loop on the path components. At the top of the loop nd->nl_nch
483 * is ref'd and unlocked and represents our current position.
484 */
485 for (;;) {
486 /*
487 * Make sure nl_nch is locked so we can access the vnode, resolution
488 * state, etc.
489 */
490 if ((nd->nl_flags & NLC_NCPISLOCKED) == 0) {
491 nd->nl_flags |= NLC_NCPISLOCKED;
492 cache_lock_maybe_shared(&nd->nl_nch, wantsexcllock(nd, ptr));
493 }
494
495 /*
496 * Check if the root directory should replace the current
497 * directory. This is done at the start of a translation
498 * or after a symbolic link has been found. In other cases
499 * ptr will never be pointing at a '/'.
500 */
501 if (*ptr == '/') {
502 do {
503 ++ptr;
504 } while (*ptr == '/');
505 cache_unlock(&nd->nl_nch);
506 cache_get_maybe_shared(&nd->nl_rootnch, &nch,
507 wantsexcllock(nd, ptr));
508 cache_drop(&nd->nl_nch);
509 nd->nl_nch = nch; /* remains locked */
510
511 /*
512 * Fast-track termination. There is no parent directory of
513 * the root in the same mount from the point of view of
514 * the caller so return EACCES if NLC_REFDVP is specified,
515 * and EEXIST if NLC_CREATE is also specified.
516 * e.g. 'rmdir /' or 'mkdir /' are not allowed.
517 */
518 if (*ptr == 0) {
519 if (nd->nl_flags & NLC_REFDVP)
520 error = (nd->nl_flags & NLC_CREATE) ? EEXIST : EACCES;
521 else
522 error = 0;
523 break;
524 }
525 continue;
526 }
527
528 /*
529 * Check directory search permissions (nd->nl_nch is locked & refd)
530 */
531 dflags = 0;
532 error = naccess(&nd->nl_nch, NLC_EXEC, nd->nl_cred, &dflags);
533 if (error)
534 break;
535
536 /*
537 * Extract the path component. Path components are limited to
538 * 255 characters.
539 */
540 nlc.nlc_nameptr = ptr;
541 while (*ptr && *ptr != '/')
542 ++ptr;
543 nlc.nlc_namelen = ptr - nlc.nlc_nameptr;
544 if (nlc.nlc_namelen >= 256) {
545 error = ENAMETOOLONG;
546 break;
547 }
548
549 /*
550 * Lookup the path component in the cache, creating an unresolved
551 * entry if necessary. We have to handle "." and ".." as special
552 * cases.
553 *
554 * When handling ".." we have to detect a traversal back through a
555 * mount point. If we are at the root, ".." just returns the root.
556 *
557 * When handling "." or ".." we also have to recalculate dflags
558 * since our dflags will be for some sub-directory instead of the
559 * parent dir.
560 *
561 * This subsection returns a locked, refd 'nch' unless it errors out,
562 * and an unlocked but still ref'd nd->nl_nch.
563 *
564 * The namecache topology is not allowed to be disconnected, so
565 * encountering a NULL parent will generate EINVAL. This typically
566 * occurs when a directory is removed out from under a process.
567 *
568 * WARNING! The unlocking of nd->nl_nch is sensitive code.
569 */
570 KKASSERT(nd->nl_flags & NLC_NCPISLOCKED);
571
572 if (nlc.nlc_namelen == 1 && nlc.nlc_nameptr[0] == '.') {
573 cache_unlock(&nd->nl_nch);
574 nd->nl_flags &= ~NLC_NCPISLOCKED;
575 cache_get_maybe_shared(&nd->nl_nch, &nch, wantsexcllock(nd, ptr));
576 wasdotordotdot = 1;
577 } else if (nlc.nlc_namelen == 2 &&
578 nlc.nlc_nameptr[0] == '.' && nlc.nlc_nameptr[1] == '.') {
579 if (nd->nl_nch.mount == nd->nl_rootnch.mount &&
580 nd->nl_nch.ncp == nd->nl_rootnch.ncp
581 ) {
582 /*
583 * ".." at the root returns the root
584 */
585 cache_unlock(&nd->nl_nch);
586 nd->nl_flags &= ~NLC_NCPISLOCKED;
587 cache_get_maybe_shared(&nd->nl_nch, &nch,
588 wantsexcllock(nd, ptr));
589 } else {
590 /*
591 * Locate the parent ncp. If we are at the root of a
592 * filesystem mount we have to skip to the mounted-on
593 * point in the underlying filesystem.
594 *
595 * Expect the parent to always be good since the
596 * mountpoint doesn't go away. XXX hack. cache_get()
597 * requires the ncp to already have a ref as a safety.
598 */
599 nctmp = nd->nl_nch;
600 while (nctmp.ncp == nctmp.mount->mnt_ncmountpt.ncp)
601 nctmp = nctmp.mount->mnt_ncmounton;
602 nctmp.ncp = nctmp.ncp->nc_parent;
603 KKASSERT(nctmp.ncp != NULL);
604 cache_hold(&nctmp);
605 cache_unlock(&nd->nl_nch);
606 nd->nl_flags &= ~NLC_NCPISLOCKED;
607 cache_get_maybe_shared(&nctmp, &nch, wantsexcllock(nd, ptr));
608 cache_drop(&nctmp); /* NOTE: zero's nctmp */
609 }
610 wasdotordotdot = 2;
611 } else {
612 /*
613 * Must unlock nl_nch when traversing down the path. However,
614 * the child ncp has not yet been found/created and the parent's
615 * child list might be empty. Thus releasing the lock can
616 * allow a race whereby the parent ncp's vnode is recycled.
617 * This case can occur especially when maxvnodes is set very low.
618 *
619 * We need the parent's ncp to remain resolved for all normal
620 * filesystem activities, so we vhold() the vp during the lookup
621 * to prevent recyclement due to vnlru / maxvnodes.
622 *
623 * If we race an unlink or rename the ncp might be marked
624 * DESTROYED after resolution, requiring a retry.
625 */
626 if ((hvp = nd->nl_nch.ncp->nc_vp) != NULL)
627 vhold(hvp);
628 cache_unlock(&nd->nl_nch);
629 nd->nl_flags &= ~NLC_NCPISLOCKED;
630 error = cache_nlookup_maybe_shared(&nd->nl_nch, &nlc,
631 wantsexcllock(nd, ptr), &nch);
632 if (error == EWOULDBLOCK) {
633 nch = cache_nlookup(&nd->nl_nch, &nlc);
634 if (nch.ncp->nc_flag & NCF_UNRESOLVED)
635 hit = 0;
636 for (;;) {
637 error = cache_resolve(&nch, nd->nl_cred);
638 if (error != EAGAIN &&
639 (nch.ncp->nc_flag & NCF_DESTROYED) == 0) {
640 break;
641 }
642 kprintf("[diagnostic] nlookup: relookup %*.*s\n",
643 nch.ncp->nc_nlen, nch.ncp->nc_nlen,
644 nch.ncp->nc_name);
645 cache_put(&nch);
646 nch = cache_nlookup(&nd->nl_nch, &nlc);
647 }
648 }
649 if (hvp)
650 vdrop(hvp);
651 wasdotordotdot = 0;
652 }
653
654 /*
655 * If the last component was "." or ".." our dflags no longer
656 * represents the parent directory and we have to explicitly
657 * look it up.
658 *
659 * Expect the parent to be good since nch is locked.
660 */
661 if (wasdotordotdot && error == 0) {
662 dflags = 0;
663 if ((par.ncp = nch.ncp->nc_parent) != NULL) {
664 par.mount = nch.mount;
665 cache_hold(&par);
666 cache_lock_maybe_shared(&par, wantsexcllock(nd, ptr));
667 error = naccess(&par, 0, nd->nl_cred, &dflags);
668 cache_put(&par);
669 }
670 }
671
672 /*
673 * [end of subsection]
674 *
675 * nch is locked and referenced.
676 * nd->nl_nch is unlocked and referenced.
677 *
678 * nl_nch must be unlocked or we could chain lock to the root
679 * if a resolve gets stuck (e.g. in NFS).
680 */
681 KKASSERT((nd->nl_flags & NLC_NCPISLOCKED) == 0);
682
683 /*
684 * Resolve the namespace if necessary. The ncp returned by
685 * cache_nlookup() is referenced and locked.
686 *
687 * XXX neither '.' nor '..' should return EAGAIN since they were
688 * previously resolved and thus cannot be newly created ncp's.
689 */
690 if (nch.ncp->nc_flag & NCF_UNRESOLVED) {
691 hit = 0;
692 error = cache_resolve(&nch, nd->nl_cred);
693 KKASSERT(error != EAGAIN);
694 } else {
695 error = nch.ncp->nc_error;
696 }
697
698 /*
699 * Early completion. ENOENT is not an error if this is the last
700 * component and NLC_CREATE or NLC_RENAME (rename target) was
701 * requested. Note that ncp->nc_error is left as ENOENT in that
702 * case, which we check later on.
703 *
704 * Also handle invalid '.' or '..' components terminating a path
705 * for a create/rename/delete. The standard requires this and pax
706 * pretty stupidly depends on it.
707 */
708 if (islastelement(ptr)) {
709 if (error == ENOENT &&
710 (nd->nl_flags & (NLC_CREATE | NLC_RENAME_DST))
711 ) {
712 if (nd->nl_flags & NLC_NFS_RDONLY) {
713 error = EROFS;
714 } else {
715 error = naccess(&nch, nd->nl_flags | dflags,
716 nd->nl_cred, NULL);
717 }
718 }
719 if (error == 0 && wasdotordotdot &&
720 (nd->nl_flags & (NLC_CREATE | NLC_DELETE |
721 NLC_RENAME_SRC | NLC_RENAME_DST))) {
722 /*
723 * POSIX junk
724 */
725 if (nd->nl_flags & NLC_CREATE)
726 error = EEXIST;
727 else if (nd->nl_flags & NLC_DELETE)
728 error = (wasdotordotdot == 1) ? EINVAL : ENOTEMPTY;
729 else
730 error = EINVAL;
731 }
732 }
733
734 /*
735 * Early completion on error.
736 */
737 if (error) {
738 cache_put(&nch);
739 break;
740 }
741
742 /*
743 * If the element is a symlink and it is either not the last
744 * element or it is the last element and we are allowed to
745 * follow symlinks, resolve the symlink.
746 */
747 if ((nch.ncp->nc_flag & NCF_ISSYMLINK) &&
748 (*ptr || (nd->nl_flags & NLC_FOLLOW))
749 ) {
750 if (nd->nl_loopcnt++ >= MAXSYMLINKS) {
751 error = ELOOP;
752 cache_put(&nch);
753 break;
754 }
755 error = nreadsymlink(nd, &nch, &nlc);
756 cache_put(&nch);
757 if (error)
758 break;
759
760 /*
761 * Concatenate trailing path elements onto the returned symlink.
762 * Note that if the path component (ptr) is not exhausted, it
763 * will being with a '/', so we do not have to add another one.
764 *
765 * The symlink may not be empty.
766 */
767 len = strlen(ptr);
768 if (nlc.nlc_namelen == 0 || nlc.nlc_namelen + len >= MAXPATHLEN) {
769 error = nlc.nlc_namelen ? ENAMETOOLONG : ENOENT;
770 objcache_put(namei_oc, nlc.nlc_nameptr);
771 break;
772 }
773 bcopy(ptr, nlc.nlc_nameptr + nlc.nlc_namelen, len + 1);
774 if (nd->nl_flags & NLC_HASBUF)
775 objcache_put(namei_oc, nd->nl_path);
776 nd->nl_path = nlc.nlc_nameptr;
777 nd->nl_flags |= NLC_HASBUF;
778 ptr = nd->nl_path;
779
780 /*
781 * Go back up to the top to resolve any initial '/'s in the
782 * symlink.
783 */
784 continue;
785 }
786
787 /*
788 * If the element is a directory and we are crossing a mount point,
789 * Locate the mount.
790 */
791 while ((nch.ncp->nc_flag & NCF_ISMOUNTPT) &&
792 (nd->nl_flags & NLC_NOCROSSMOUNT) == 0 &&
793 (mp = cache_findmount(&nch)) != NULL
794 ) {
795 struct vnode *tdp;
796 int vfs_do_busy = 0;
797
798 /*
799 * VFS must be busied before the namecache entry is locked,
800 * but we don't want to waste time calling vfs_busy() if the
801 * mount point is already resolved.
802 */
803 again:
804 cache_put(&nch);
805 if (vfs_do_busy) {
806 while (vfs_busy(mp, 0)) {
807 if (mp->mnt_kern_flag & MNTK_UNMOUNT) {
808 kprintf("nlookup: warning umount race avoided\n");
809 cache_dropmount(mp);
810 error = EBUSY;
811 vfs_do_busy = 0;
812 goto double_break;
813 }
814 }
815 }
816 cache_get_maybe_shared(&mp->mnt_ncmountpt, &nch,
817 wantsexcllock(nd, ptr));
818
819 if (nch.ncp->nc_flag & NCF_UNRESOLVED) {
820 if (vfs_do_busy == 0) {
821 vfs_do_busy = 1;
822 goto again;
823 }
824 error = VFS_ROOT(mp, &tdp);
825 vfs_unbusy(mp);
826 vfs_do_busy = 0;
827 if (error) {
828 cache_dropmount(mp);
829 break;
830 }
831 cache_setvp(&nch, tdp);
832 vput(tdp);
833 }
834 if (vfs_do_busy)
835 vfs_unbusy(mp);
836 cache_dropmount(mp);
837 }
838
839 if (error) {
840 cache_put(&nch);
841 double_break:
842 break;
843 }
844
845 /*
846 * Skip any slashes to get to the next element. If there
847 * are any slashes at all the current element must be a
848 * directory or, in the create case, intended to become a directory.
849 * If it isn't we break without incrementing ptr and fall through
850 * to the failure case below.
851 */
852 while (*ptr == '/') {
853 if ((nch.ncp->nc_flag & NCF_ISDIR) == 0 &&
854 !(nd->nl_flags & NLC_WILLBEDIR)
855 ) {
856 break;
857 }
858 ++ptr;
859 }
860
861 /*
862 * Continuation case: additional elements and the current
863 * element is a directory.
864 */
865 if (*ptr && (nch.ncp->nc_flag & NCF_ISDIR)) {
866 cache_drop(&nd->nl_nch);
867 cache_unlock(&nch);
868 KKASSERT((nd->nl_flags & NLC_NCPISLOCKED) == 0);
869 nd->nl_nch = nch;
870 continue;
871 }
872
873 /*
874 * Failure case: additional elements and the current element
875 * is not a directory
876 */
877 if (*ptr) {
878 cache_put(&nch);
879 error = ENOTDIR;
880 break;
881 }
882
883 /*
884 * Successful lookup of last element.
885 *
886 * Check permissions if the target exists. If the target does not
887 * exist directory permissions were already tested in the early
888 * completion code above.
889 *
890 * nd->nl_flags will be adjusted on return with NLC_APPENDONLY
891 * if the file is marked append-only, and NLC_STICKY if the directory
892 * containing the file is sticky.
893 */
894 if (nch.ncp->nc_vp && (nd->nl_flags & NLC_ALLCHKS)) {
895 error = naccess(&nch, nd->nl_flags | dflags,
896 nd->nl_cred, NULL);
897 if (error) {
898 cache_put(&nch);
899 break;
900 }
901 }
902
903 /*
904 * Termination: no more elements.
905 *
906 * If NLC_REFDVP is set acquire a referenced parent dvp.
907 */
908 if (nd->nl_flags & NLC_REFDVP) {
909 cache_lock(&nd->nl_nch);
910 error = cache_vref(&nd->nl_nch, nd->nl_cred, &nd->nl_dvp);
911 cache_unlock(&nd->nl_nch);
912 if (error) {
913 kprintf("NLC_REFDVP: Cannot ref dvp of %p\n", nch.ncp);
914 cache_put(&nch);
915 break;
916 }
917 }
918 cache_drop(&nd->nl_nch);
919 nd->nl_nch = nch;
920 nd->nl_flags |= NLC_NCPISLOCKED;
921 error = 0;
922 break;
923 }
924
925 if (hit)
926 ++gd->gd_nchstats->ncs_longhits;
927 else
928 ++gd->gd_nchstats->ncs_longmiss;
929
930 if (nd->nl_flags & NLC_NCPISLOCKED)
931 KKASSERT(cache_lockstatus(&nd->nl_nch) > 0);
932
933 /*
934 * NOTE: If NLC_CREATE was set the ncp may represent a negative hit
935 * (ncp->nc_error will be ENOENT), but we will still return an error
936 * code of 0.
937 */
938 return(error);
939 }
940
941 /*
942 * Resolve a mount point's glue ncp. This ncp connects creates the illusion
943 * of continuity in the namecache tree by connecting the ncp related to the
944 * vnode under the mount to the ncp related to the mount's root vnode.
945 *
946 * If no error occured a locked, ref'd ncp is stored in *ncpp.
947 */
948 int
949 nlookup_mp(struct mount *mp, struct nchandle *nch)
950 {
951 struct vnode *vp;
952 int error;
953
954 error = 0;
955 cache_get(&mp->mnt_ncmountpt, nch);
956 if (nch->ncp->nc_flag & NCF_UNRESOLVED) {
957 while (vfs_busy(mp, 0))
958 ;
959 error = VFS_ROOT(mp, &vp);
960 vfs_unbusy(mp);
961 if (error) {
962 cache_put(nch);
963 } else {
964 cache_setvp(nch, vp);
965 vput(vp);
966 }
967 }
968 return(error);
969 }
970
971 /*
972 * Read the contents of a symlink, allocate a path buffer out of the
973 * namei_oc and initialize the supplied nlcomponent with the result.
974 *
975 * If an error occurs no buffer will be allocated or returned in the nlc.
976 */
977 int
978 nreadsymlink(struct nlookupdata *nd, struct nchandle *nch,
979 struct nlcomponent *nlc)
980 {
981 struct vnode *vp;
982 struct iovec aiov;
983 struct uio auio;
984 int linklen;
985 int error;
986 char *cp;
987
988 nlc->nlc_nameptr = NULL;
989 nlc->nlc_namelen = 0;
990 if (nch->ncp->nc_vp == NULL)
991 return(ENOENT);
992 if ((error = cache_vget(nch, nd->nl_cred, LK_SHARED, &vp)) != 0)
993 return(error);
994 cp = objcache_get(namei_oc, M_WAITOK);
995 aiov.iov_base = cp;
996 aiov.iov_len = MAXPATHLEN;
997 auio.uio_iov = &aiov;
998 auio.uio_iovcnt = 1;
999 auio.uio_offset = 0;
1000 auio.uio_rw = UIO_READ;
1001 auio.uio_segflg = UIO_SYSSPACE;
1002 auio.uio_td = nd->nl_td;
1003 auio.uio_resid = MAXPATHLEN - 1;
1004 error = VOP_READLINK(vp, &auio, nd->nl_cred);
1005 if (error)
1006 goto fail;
1007 linklen = MAXPATHLEN - 1 - auio.uio_resid;
1008 if (varsym_enable) {
1009 linklen = varsymreplace(cp, linklen, MAXPATHLEN - 1);
1010 if (linklen < 0) {
1011 error = ENAMETOOLONG;
1012 goto fail;
1013 }
1014 }
1015 cp[linklen] = 0;
1016 nlc->nlc_nameptr = cp;
1017 nlc->nlc_namelen = linklen;
1018 vput(vp);
1019 return(0);
1020 fail:
1021 objcache_put(namei_oc, cp);
1022 vput(vp);
1023 return(error);
1024 }
1025
1026 /*
1027 * Check access [XXX cache vattr!] [XXX quota]
1028 *
1029 * Generally check the NLC_* access bits. All specified bits must pass
1030 * for this function to return 0.
1031 *
1032 * The file does not have to exist when checking NLC_CREATE or NLC_RENAME_DST
1033 * access, otherwise it must exist. No error is returned in this case.
1034 *
1035 * The file must not exist if NLC_EXCL is specified.
1036 *
1037 * Directory permissions in general are tested for NLC_CREATE if the file
1038 * does not exist, NLC_DELETE if the file does exist, and NLC_RENAME_DST
1039 * whether the file exists or not.
1040 *
1041 * The directory sticky bit is tested for NLC_DELETE and NLC_RENAME_DST,
1042 * the latter is only tested if the target exists.
1043 *
1044 * The passed ncp must be referenced and locked. If it is already resolved
1045 * it may be locked shared but otherwise should be locked exclusively.
1046 */
1047 static int
1048 naccess(struct nchandle *nch, int nflags, struct ucred *cred, int *nflagsp)
1049 {
1050 struct vnode *vp;
1051 struct vattr va;
1052 struct namecache *ncp;
1053 int error;
1054 int cflags;
1055
1056 KKASSERT(cache_lockstatus(nch) > 0);
1057
1058 ncp = nch->ncp;
1059 if (ncp->nc_flag & NCF_UNRESOLVED) {
1060 cache_resolve(nch, cred);
1061 ncp = nch->ncp;
1062 }
1063 error = ncp->nc_error;
1064
1065 /*
1066 * Directory permissions checks. Silently ignore ENOENT if these
1067 * tests pass. It isn't an error.
1068 *
1069 * We can safely resolve ncp->nc_parent because ncp is currently
1070 * locked.
1071 */
1072 if (nflags & (NLC_CREATE | NLC_DELETE | NLC_RENAME_SRC | NLC_RENAME_DST)) {
1073 if (((nflags & NLC_CREATE) && ncp->nc_vp == NULL) ||
1074 ((nflags & NLC_DELETE) && ncp->nc_vp != NULL) ||
1075 ((nflags & NLC_RENAME_SRC) && ncp->nc_vp != NULL) ||
1076 (nflags & NLC_RENAME_DST)
1077 ) {
1078 struct nchandle par;
1079
1080 if ((par.ncp = ncp->nc_parent) == NULL) {
1081 if (error != EAGAIN)
1082 error = EINVAL;
1083 } else if (error == 0 || error == ENOENT) {
1084 par.mount = nch->mount;
1085 cache_hold(&par);
1086 cache_lock_maybe_shared(&par, 0);
1087 error = naccess(&par, NLC_WRITE, cred, NULL);
1088 cache_put(&par);
1089 }
1090 }
1091 }
1092
1093 /*
1094 * NLC_EXCL check. Target file must not exist.
1095 */
1096 if (error == 0 && (nflags & NLC_EXCL) && ncp->nc_vp != NULL)
1097 error = EEXIST;
1098
1099 /*
1100 * Get the vnode attributes so we can do the rest of our checks.
1101 *
1102 * NOTE: We only call naccess_va() if the target exists.
1103 */
1104 if (error == 0) {
1105 error = cache_vget(nch, cred, LK_SHARED, &vp);
1106 if (error == ENOENT) {
1107 /*
1108 * Silently zero-out ENOENT if creating or renaming
1109 * (rename target). It isn't an error.
1110 */
1111 if (nflags & (NLC_CREATE | NLC_RENAME_DST))
1112 error = 0;
1113 } else if (error == 0) {
1114 /*
1115 * Get the vnode attributes and check for illegal O_TRUNC
1116 * requests and read-only mounts.
1117 *
1118 * NOTE: You can still open devices on read-only mounts for
1119 * writing.
1120 *
1121 * NOTE: creates/deletes/renames are handled by the NLC_WRITE
1122 * check on the parent directory above.
1123 *
1124 * XXX cache the va in the namecache or in the vnode
1125 */
1126 error = VOP_GETATTR(vp, &va);
1127 if (error == 0 && (nflags & NLC_TRUNCATE)) {
1128 switch(va.va_type) {
1129 case VREG:
1130 case VDATABASE:
1131 case VCHR:
1132 case VBLK:
1133 case VFIFO:
1134 break;
1135 case VDIR:
1136 error = EISDIR;
1137 break;
1138 default:
1139 error = EINVAL;
1140 break;
1141 }
1142 }
1143 if (error == 0 && (nflags & NLC_WRITE) && vp->v_mount &&
1144 (vp->v_mount->mnt_flag & MNT_RDONLY)
1145 ) {
1146 switch(va.va_type) {
1147 case VDIR:
1148 case VLNK:
1149 case VREG:
1150 case VDATABASE:
1151 error = EROFS;
1152 break;
1153 default:
1154 break;
1155 }
1156 }
1157 vput(vp);
1158
1159 /*
1160 * Check permissions based on file attributes. The passed
1161 * flags (*nflagsp) are modified with feedback based on
1162 * special attributes and requirements.
1163 */
1164 if (error == 0) {
1165 /*
1166 * Adjust the returned (*nflagsp) if non-NULL.
1167 */
1168 if (nflagsp) {
1169 if ((va.va_mode & VSVTX) && va.va_uid != cred->cr_uid)
1170 *nflagsp |= NLC_STICKY;
1171 if (va.va_flags & APPEND)
1172 *nflagsp |= NLC_APPENDONLY;
1173 if (va.va_flags & IMMUTABLE)
1174 *nflagsp |= NLC_IMMUTABLE;
1175 }
1176
1177 /*
1178 * Track swapcache management flags in the namecache.
1179 *
1180 * Calculate the flags based on the current vattr info
1181 * and recalculate the inherited flags from the parent
1182 * (the original cache linkage may have occurred without
1183 * getattrs and thus have stale flags).
1184 */
1185 cflags = 0;
1186 if (va.va_flags & SF_NOCACHE)
1187 cflags |= NCF_SF_NOCACHE;
1188 if (va.va_flags & UF_CACHE)
1189 cflags |= NCF_UF_CACHE;
1190 if (ncp->nc_parent) {
1191 if (ncp->nc_parent->nc_flag &
1192 (NCF_SF_NOCACHE | NCF_SF_PNOCACHE)) {
1193 cflags |= NCF_SF_PNOCACHE;
1194 }
1195 if (ncp->nc_parent->nc_flag &
1196 (NCF_UF_CACHE | NCF_UF_PCACHE)) {
1197 cflags |= NCF_UF_PCACHE;
1198 }
1199 }
1200
1201 /*
1202 * XXX we're not supposed to update nc_flag when holding
1203 * a shared lock.
1204 */
1205 atomic_clear_short(&ncp->nc_flag,
1206 (NCF_SF_NOCACHE | NCF_UF_CACHE |
1207 NCF_SF_PNOCACHE | NCF_UF_PCACHE) & ~cflags);
1208 atomic_set_short(&ncp->nc_flag, cflags);
1209
1210 /*
1211 * Process general access.
1212 */
1213 error = naccess_va(&va, nflags, cred);
1214 }
1215 }
1216 }
1217 return(error);
1218 }
1219
1220 /*
1221 * Check the requested access against the given vattr using cred.
1222 */
1223 int
1224 naccess_va(struct vattr *va, int nflags, struct ucred *cred)
1225 {
1226 int i;
1227 int vmode;
1228
1229 /*
1230 * Test the immutable bit. Creations, deletions, renames (source
1231 * or destination) are not allowed. chown/chmod/other is also not
1232 * allowed but is handled by SETATTR. Hardlinks to the immutable
1233 * file are allowed.
1234 *
1235 * If the directory is set to immutable then creations, deletions,
1236 * renames (source or dest) and hardlinks to files within the directory
1237 * are not allowed, and regular files opened through the directory may
1238 * not be written to or truncated (unless a special device).
1239 *
1240 * NOTE! New hardlinks to immutable files work but new hardlinks to
1241 * files, immutable or not, sitting inside an immutable directory are
1242 * not allowed. As always if the file is hardlinked via some other
1243 * path additional hardlinks may be possible even if the file is marked
1244 * immutable. The sysop needs to create a closure by checking the hard
1245 * link count. Once closure is achieved you are good, and security
1246 * scripts should check link counts anyway.
1247 *
1248 * Writes and truncations are only allowed on special devices.
1249 */
1250 if ((va->va_flags & IMMUTABLE) || (nflags & NLC_IMMUTABLE)) {
1251 if ((nflags & NLC_IMMUTABLE) && (nflags & NLC_HLINK))
1252 return (EPERM);
1253 if (nflags & (NLC_CREATE | NLC_DELETE |
1254 NLC_RENAME_SRC | NLC_RENAME_DST)) {
1255 return (EPERM);
1256 }
1257 if (nflags & (NLC_WRITE | NLC_TRUNCATE)) {
1258 switch(va->va_type) {
1259 case VDIR:
1260 return (EISDIR);
1261 case VLNK:
1262 case VREG:
1263 case VDATABASE:
1264 return (EPERM);
1265 default:
1266 break;
1267 }
1268 }
1269 }
1270
1271 /*
1272 * Test the no-unlink and append-only bits for opens, rename targets,
1273 * and deletions. These bits are not tested for creations or
1274 * rename sources.
1275 *
1276 * Unlike FreeBSD we allow a file with APPEND set to be renamed.
1277 * If you do not wish this you must also set NOUNLINK.
1278 *
1279 * If the governing directory is marked APPEND-only it implies
1280 * NOUNLINK for all entries in the directory.
1281 */
1282 if (((va->va_flags & NOUNLINK) || (nflags & NLC_APPENDONLY)) &&
1283 (nflags & (NLC_DELETE | NLC_RENAME_SRC | NLC_RENAME_DST))
1284 ) {
1285 return (EPERM);
1286 }
1287
1288 /*
1289 * A file marked append-only may not be deleted but can be renamed.
1290 */
1291 if ((va->va_flags & APPEND) &&
1292 (nflags & (NLC_DELETE | NLC_RENAME_DST))
1293 ) {
1294 return (EPERM);
1295 }
1296
1297 /*
1298 * A file marked append-only which is opened for writing must also
1299 * be opened O_APPEND.
1300 */
1301 if ((va->va_flags & APPEND) && (nflags & (NLC_OPEN | NLC_TRUNCATE))) {
1302 if (nflags & NLC_TRUNCATE)
1303 return (EPERM);
1304 if ((nflags & (NLC_OPEN | NLC_WRITE)) == (NLC_OPEN | NLC_WRITE)) {
1305 if ((nflags & NLC_APPEND) == 0)
1306 return (EPERM);
1307 }
1308 }
1309
1310 /*
1311 * root gets universal access
1312 */
1313 if (cred->cr_uid == 0)
1314 return(0);
1315
1316 /*
1317 * Check owner perms.
1318 *
1319 * If NLC_OWN is set the owner of the file is allowed no matter when
1320 * the owner-mode bits say (utimes).
1321 */
1322 vmode = 0;
1323 if (nflags & NLC_READ)
1324 vmode |= S_IRUSR;
1325 if (nflags & NLC_WRITE)
1326 vmode |= S_IWUSR;
1327 if (nflags & NLC_EXEC)
1328 vmode |= S_IXUSR;
1329
1330 if (cred->cr_uid == va->va_uid) {
1331 if ((nflags & NLC_OWN) == 0) {
1332 if ((vmode & va->va_mode) != vmode)
1333 return(EACCES);
1334 }
1335 return(0);
1336 }
1337
1338 /*
1339 * If NLC_STICKY is set only the owner may delete or rename a file.
1340 * This bit is typically set on /tmp.
1341 *
1342 * Note that the NLC_READ/WRITE/EXEC bits are not typically set in
1343 * the specific delete or rename case. For deletions and renames we
1344 * usually just care about directory permissions, not file permissions.
1345 */
1346 if ((nflags & NLC_STICKY) &&
1347 (nflags & (NLC_RENAME_SRC | NLC_RENAME_DST | NLC_DELETE))) {
1348 return(EACCES);
1349 }
1350
1351 /*
1352 * Check group perms
1353 */
1354 vmode >>= 3;
1355 for (i = 0; i < cred->cr_ngroups; ++i) {
1356 if (va->va_gid == cred->cr_groups[i]) {
1357 if ((vmode & va->va_mode) != vmode)
1358 return(EACCES);
1359 return(0);
1360 }
1361 }
1362
1363 /*
1364 * Check world perms
1365 */
1366 vmode >>= 3;
1367 if ((vmode & va->va_mode) != vmode)
1368 return(EACCES);
1369 return(0);
1370 }
1371
Cache object: 2a6b2039b2f34bad6b7334c327d2cd90
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