FreeBSD/Linux Kernel Cross Reference
sys/kern/vfs_lookup.c
1 /*-
2 * Copyright (c) 1982, 1986, 1989, 1993
3 * The Regents of the University of California. All rights reserved.
4 * (c) UNIX System Laboratories, Inc.
5 * All or some portions of this file are derived from material licensed
6 * to the University of California by American Telephone and Telegraph
7 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
8 * the permission of UNIX System Laboratories, Inc.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 4. Neither the name of the University nor the names of its contributors
19 * may be used to endorse or promote products derived from this software
20 * without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 *
34 * @(#)vfs_lookup.c 8.4 (Berkeley) 2/16/94
35 */
36
37 #include <sys/cdefs.h>
38 __FBSDID("$FreeBSD: releng/9.2/sys/kern/vfs_lookup.c 273415 2014-10-21 20:21:10Z delphij $");
39
40 #include "opt_capsicum.h"
41 #include "opt_kdtrace.h"
42 #include "opt_ktrace.h"
43
44 #include <sys/param.h>
45 #include <sys/systm.h>
46 #include <sys/kernel.h>
47 #include <sys/capability.h>
48 #include <sys/fcntl.h>
49 #include <sys/jail.h>
50 #include <sys/lock.h>
51 #include <sys/mutex.h>
52 #include <sys/namei.h>
53 #include <sys/vnode.h>
54 #include <sys/mount.h>
55 #include <sys/filedesc.h>
56 #include <sys/proc.h>
57 #include <sys/sdt.h>
58 #include <sys/syscallsubr.h>
59 #include <sys/sysctl.h>
60 #ifdef KTRACE
61 #include <sys/ktrace.h>
62 #endif
63
64 #include <security/audit/audit.h>
65 #include <security/mac/mac_framework.h>
66
67 #include <vm/uma.h>
68
69 #define NAMEI_DIAGNOSTIC 1
70 #undef NAMEI_DIAGNOSTIC
71
72 SDT_PROVIDER_DECLARE(vfs);
73 SDT_PROBE_DEFINE3(vfs, namei, lookup, entry, entry, "struct vnode *", "char *",
74 "unsigned long");
75 SDT_PROBE_DEFINE2(vfs, namei, lookup, return, return, "int", "struct vnode *");
76
77 /*
78 * Allocation zone for namei
79 */
80 uma_zone_t namei_zone;
81 /*
82 * Placeholder vnode for mp traversal
83 */
84 static struct vnode *vp_crossmp;
85
86 static void
87 nameiinit(void *dummy __unused)
88 {
89
90 namei_zone = uma_zcreate("NAMEI", MAXPATHLEN, NULL, NULL, NULL, NULL,
91 UMA_ALIGN_PTR, 0);
92 getnewvnode("crossmp", NULL, &dead_vnodeops, &vp_crossmp);
93 vn_lock(vp_crossmp, LK_EXCLUSIVE);
94 VN_LOCK_ASHARE(vp_crossmp);
95 VOP_UNLOCK(vp_crossmp, 0);
96 }
97 SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_SECOND, nameiinit, NULL);
98
99 static int lookup_shared = 1;
100 SYSCTL_INT(_vfs, OID_AUTO, lookup_shared, CTLFLAG_RW, &lookup_shared, 0,
101 "Enables/Disables shared locks for path name translation");
102 TUNABLE_INT("vfs.lookup_shared", &lookup_shared);
103
104 /*
105 * Convert a pathname into a pointer to a locked vnode.
106 *
107 * The FOLLOW flag is set when symbolic links are to be followed
108 * when they occur at the end of the name translation process.
109 * Symbolic links are always followed for all other pathname
110 * components other than the last.
111 *
112 * The segflg defines whether the name is to be copied from user
113 * space or kernel space.
114 *
115 * Overall outline of namei:
116 *
117 * copy in name
118 * get starting directory
119 * while (!done && !error) {
120 * call lookup to search path.
121 * if symbolic link, massage name in buffer and continue
122 * }
123 */
124 static void
125 namei_cleanup_cnp(struct componentname *cnp)
126 {
127 uma_zfree(namei_zone, cnp->cn_pnbuf);
128 #ifdef DIAGNOSTIC
129 cnp->cn_pnbuf = NULL;
130 cnp->cn_nameptr = NULL;
131 #endif
132 }
133
134 int
135 namei(struct nameidata *ndp)
136 {
137 struct filedesc *fdp; /* pointer to file descriptor state */
138 char *cp; /* pointer into pathname argument */
139 struct vnode *dp; /* the directory we are searching */
140 struct iovec aiov; /* uio for reading symbolic links */
141 struct uio auio;
142 int error, linklen;
143 struct componentname *cnp = &ndp->ni_cnd;
144 struct thread *td = cnp->cn_thread;
145 struct proc *p = td->td_proc;
146 int vfslocked;
147
148 KASSERT((cnp->cn_flags & MPSAFE) != 0 || mtx_owned(&Giant) != 0,
149 ("NOT MPSAFE and Giant not held"));
150 ndp->ni_cnd.cn_cred = ndp->ni_cnd.cn_thread->td_ucred;
151 KASSERT(cnp->cn_cred && p, ("namei: bad cred/proc"));
152 KASSERT((cnp->cn_nameiop & (~OPMASK)) == 0,
153 ("namei: nameiop contaminated with flags"));
154 KASSERT((cnp->cn_flags & OPMASK) == 0,
155 ("namei: flags contaminated with nameiops"));
156 if (!lookup_shared)
157 cnp->cn_flags &= ~LOCKSHARED;
158 fdp = p->p_fd;
159
160 /* We will set this ourselves if we need it. */
161 cnp->cn_flags &= ~TRAILINGSLASH;
162
163 /*
164 * Get a buffer for the name to be translated, and copy the
165 * name into the buffer.
166 */
167 if ((cnp->cn_flags & HASBUF) == 0)
168 cnp->cn_pnbuf = uma_zalloc(namei_zone, M_WAITOK);
169 if (ndp->ni_segflg == UIO_SYSSPACE)
170 error = copystr(ndp->ni_dirp, cnp->cn_pnbuf,
171 MAXPATHLEN, (size_t *)&ndp->ni_pathlen);
172 else
173 error = copyinstr(ndp->ni_dirp, cnp->cn_pnbuf,
174 MAXPATHLEN, (size_t *)&ndp->ni_pathlen);
175
176 /*
177 * Don't allow empty pathnames.
178 */
179 if (!error && *cnp->cn_pnbuf == '\0')
180 error = ENOENT;
181
182 #ifdef CAPABILITY_MODE
183 /*
184 * In capability mode, lookups must be "strictly relative" (i.e.
185 * not an absolute path, and not containing '..' components) to
186 * a real file descriptor, not the pseudo-descriptor AT_FDCWD.
187 */
188 if (IN_CAPABILITY_MODE(td)) {
189 ndp->ni_strictrelative = 1;
190 if (ndp->ni_dirfd == AT_FDCWD)
191 error = ECAPMODE;
192 }
193 #endif
194 if (error) {
195 namei_cleanup_cnp(cnp);
196 ndp->ni_vp = NULL;
197 return (error);
198 }
199 ndp->ni_loopcnt = 0;
200 #ifdef KTRACE
201 if (KTRPOINT(td, KTR_NAMEI)) {
202 KASSERT(cnp->cn_thread == curthread,
203 ("namei not using curthread"));
204 ktrnamei(cnp->cn_pnbuf);
205 }
206 #endif
207 /*
208 * Get starting point for the translation.
209 */
210 FILEDESC_SLOCK(fdp);
211 ndp->ni_rootdir = fdp->fd_rdir;
212 ndp->ni_topdir = fdp->fd_jdir;
213
214 /*
215 * If we are auditing the kernel pathname, save the user pathname.
216 */
217 if (cnp->cn_flags & AUDITVNODE1)
218 AUDIT_ARG_UPATH1(td, ndp->ni_dirfd, cnp->cn_pnbuf);
219 if (cnp->cn_flags & AUDITVNODE2)
220 AUDIT_ARG_UPATH2(td, ndp->ni_dirfd, cnp->cn_pnbuf);
221
222 dp = NULL;
223 if (cnp->cn_pnbuf[0] != '/') {
224 if (ndp->ni_startdir != NULL) {
225 dp = ndp->ni_startdir;
226 error = 0;
227 } else if (ndp->ni_dirfd != AT_FDCWD) {
228 if (cnp->cn_flags & AUDITVNODE1)
229 AUDIT_ARG_ATFD1(ndp->ni_dirfd);
230 if (cnp->cn_flags & AUDITVNODE2)
231 AUDIT_ARG_ATFD2(ndp->ni_dirfd);
232 error = fgetvp_rights(td, ndp->ni_dirfd,
233 ndp->ni_rightsneeded | CAP_LOOKUP,
234 &(ndp->ni_baserights), &dp);
235 #ifdef CAPABILITIES
236 /*
237 * Lookups relative to a capability must also be
238 * strictly relative.
239 *
240 * Note that a capability with rights CAP_MASK_VALID
241 * is treated exactly like a regular file descriptor.
242 */
243 if (ndp->ni_baserights != CAP_MASK_VALID)
244 ndp->ni_strictrelative = 1;
245 #endif
246 }
247 if (error != 0 || dp != NULL) {
248 FILEDESC_SUNLOCK(fdp);
249 if (error == 0 && dp->v_type != VDIR) {
250 vfslocked = VFS_LOCK_GIANT(dp->v_mount);
251 vrele(dp);
252 VFS_UNLOCK_GIANT(vfslocked);
253 error = ENOTDIR;
254 }
255 }
256 if (error) {
257 namei_cleanup_cnp(cnp);
258 return (error);
259 }
260 }
261 if (dp == NULL) {
262 dp = fdp->fd_cdir;
263 VREF(dp);
264 FILEDESC_SUNLOCK(fdp);
265 if (ndp->ni_startdir != NULL) {
266 vfslocked = VFS_LOCK_GIANT(ndp->ni_startdir->v_mount);
267 vrele(ndp->ni_startdir);
268 VFS_UNLOCK_GIANT(vfslocked);
269 }
270 }
271 SDT_PROBE(vfs, namei, lookup, entry, dp, cnp->cn_pnbuf,
272 cnp->cn_flags, 0, 0);
273 vfslocked = VFS_LOCK_GIANT(dp->v_mount);
274 for (;;) {
275 /*
276 * Check if root directory should replace current directory.
277 * Done at start of translation and after symbolic link.
278 */
279 cnp->cn_nameptr = cnp->cn_pnbuf;
280 if (*(cnp->cn_nameptr) == '/') {
281 vrele(dp);
282 VFS_UNLOCK_GIANT(vfslocked);
283 if (ndp->ni_strictrelative != 0) {
284 namei_cleanup_cnp(cnp);
285 return (ENOTCAPABLE);
286 }
287 while (*(cnp->cn_nameptr) == '/') {
288 cnp->cn_nameptr++;
289 ndp->ni_pathlen--;
290 }
291 dp = ndp->ni_rootdir;
292 vfslocked = VFS_LOCK_GIANT(dp->v_mount);
293 VREF(dp);
294 }
295 if (vfslocked)
296 ndp->ni_cnd.cn_flags |= GIANTHELD;
297 ndp->ni_startdir = dp;
298 error = lookup(ndp);
299 if (error) {
300 namei_cleanup_cnp(cnp);
301 SDT_PROBE(vfs, namei, lookup, return, error, NULL, 0,
302 0, 0);
303 return (error);
304 }
305 vfslocked = (ndp->ni_cnd.cn_flags & GIANTHELD) != 0;
306 ndp->ni_cnd.cn_flags &= ~GIANTHELD;
307 /*
308 * If not a symbolic link, we're done.
309 */
310 if ((cnp->cn_flags & ISSYMLINK) == 0) {
311 if ((cnp->cn_flags & (SAVENAME | SAVESTART)) == 0) {
312 namei_cleanup_cnp(cnp);
313 } else
314 cnp->cn_flags |= HASBUF;
315
316 if ((cnp->cn_flags & MPSAFE) == 0) {
317 VFS_UNLOCK_GIANT(vfslocked);
318 } else if (vfslocked)
319 ndp->ni_cnd.cn_flags |= GIANTHELD;
320 SDT_PROBE(vfs, namei, lookup, return, 0, ndp->ni_vp,
321 0, 0, 0);
322 return (0);
323 }
324 if (ndp->ni_loopcnt++ >= MAXSYMLINKS) {
325 error = ELOOP;
326 break;
327 }
328 #ifdef MAC
329 if ((cnp->cn_flags & NOMACCHECK) == 0) {
330 error = mac_vnode_check_readlink(td->td_ucred,
331 ndp->ni_vp);
332 if (error)
333 break;
334 }
335 #endif
336 if (ndp->ni_pathlen > 1)
337 cp = uma_zalloc(namei_zone, M_WAITOK);
338 else
339 cp = cnp->cn_pnbuf;
340 aiov.iov_base = cp;
341 aiov.iov_len = MAXPATHLEN;
342 auio.uio_iov = &aiov;
343 auio.uio_iovcnt = 1;
344 auio.uio_offset = 0;
345 auio.uio_rw = UIO_READ;
346 auio.uio_segflg = UIO_SYSSPACE;
347 auio.uio_td = td;
348 auio.uio_resid = MAXPATHLEN;
349 error = VOP_READLINK(ndp->ni_vp, &auio, cnp->cn_cred);
350 if (error) {
351 if (ndp->ni_pathlen > 1)
352 uma_zfree(namei_zone, cp);
353 break;
354 }
355 linklen = MAXPATHLEN - auio.uio_resid;
356 if (linklen == 0) {
357 if (ndp->ni_pathlen > 1)
358 uma_zfree(namei_zone, cp);
359 error = ENOENT;
360 break;
361 }
362 if (linklen + ndp->ni_pathlen >= MAXPATHLEN) {
363 if (ndp->ni_pathlen > 1)
364 uma_zfree(namei_zone, cp);
365 error = ENAMETOOLONG;
366 break;
367 }
368 if (ndp->ni_pathlen > 1) {
369 bcopy(ndp->ni_next, cp + linklen, ndp->ni_pathlen);
370 uma_zfree(namei_zone, cnp->cn_pnbuf);
371 cnp->cn_pnbuf = cp;
372 } else
373 cnp->cn_pnbuf[linklen] = '\0';
374 ndp->ni_pathlen += linklen;
375 vput(ndp->ni_vp);
376 dp = ndp->ni_dvp;
377 }
378 namei_cleanup_cnp(cnp);
379 vput(ndp->ni_vp);
380 ndp->ni_vp = NULL;
381 vrele(ndp->ni_dvp);
382 VFS_UNLOCK_GIANT(vfslocked);
383 SDT_PROBE(vfs, namei, lookup, return, error, NULL, 0, 0, 0);
384 return (error);
385 }
386
387 static int
388 compute_cn_lkflags(struct mount *mp, int lkflags, int cnflags)
389 {
390
391 if (mp == NULL || ((lkflags & LK_SHARED) &&
392 (!(mp->mnt_kern_flag & MNTK_LOOKUP_SHARED) ||
393 ((cnflags & ISDOTDOT) &&
394 (mp->mnt_kern_flag & MNTK_LOOKUP_EXCL_DOTDOT))))) {
395 lkflags &= ~LK_SHARED;
396 lkflags |= LK_EXCLUSIVE;
397 }
398 return (lkflags);
399 }
400
401 static __inline int
402 needs_exclusive_leaf(struct mount *mp, int flags)
403 {
404
405 /*
406 * Intermediate nodes can use shared locks, we only need to
407 * force an exclusive lock for leaf nodes.
408 */
409 if ((flags & (ISLASTCN | LOCKLEAF)) != (ISLASTCN | LOCKLEAF))
410 return (0);
411
412 /* Always use exclusive locks if LOCKSHARED isn't set. */
413 if (!(flags & LOCKSHARED))
414 return (1);
415
416 /*
417 * For lookups during open(), if the mount point supports
418 * extended shared operations, then use a shared lock for the
419 * leaf node, otherwise use an exclusive lock.
420 */
421 if (flags & ISOPEN) {
422 if (mp != NULL &&
423 (mp->mnt_kern_flag & MNTK_EXTENDED_SHARED))
424 return (0);
425 else
426 return (1);
427 }
428
429 /*
430 * Lookup requests outside of open() that specify LOCKSHARED
431 * only need a shared lock on the leaf vnode.
432 */
433 return (0);
434 }
435
436 /*
437 * Search a pathname.
438 * This is a very central and rather complicated routine.
439 *
440 * The pathname is pointed to by ni_ptr and is of length ni_pathlen.
441 * The starting directory is taken from ni_startdir. The pathname is
442 * descended until done, or a symbolic link is encountered. The variable
443 * ni_more is clear if the path is completed; it is set to one if a
444 * symbolic link needing interpretation is encountered.
445 *
446 * The flag argument is LOOKUP, CREATE, RENAME, or DELETE depending on
447 * whether the name is to be looked up, created, renamed, or deleted.
448 * When CREATE, RENAME, or DELETE is specified, information usable in
449 * creating, renaming, or deleting a directory entry may be calculated.
450 * If flag has LOCKPARENT or'ed into it, the parent directory is returned
451 * locked. If flag has WANTPARENT or'ed into it, the parent directory is
452 * returned unlocked. Otherwise the parent directory is not returned. If
453 * the target of the pathname exists and LOCKLEAF is or'ed into the flag
454 * the target is returned locked, otherwise it is returned unlocked.
455 * When creating or renaming and LOCKPARENT is specified, the target may not
456 * be ".". When deleting and LOCKPARENT is specified, the target may be ".".
457 *
458 * Overall outline of lookup:
459 *
460 * dirloop:
461 * identify next component of name at ndp->ni_ptr
462 * handle degenerate case where name is null string
463 * if .. and crossing mount points and on mounted filesys, find parent
464 * call VOP_LOOKUP routine for next component name
465 * directory vnode returned in ni_dvp, unlocked unless LOCKPARENT set
466 * component vnode returned in ni_vp (if it exists), locked.
467 * if result vnode is mounted on and crossing mount points,
468 * find mounted on vnode
469 * if more components of name, do next level at dirloop
470 * return the answer in ni_vp, locked if LOCKLEAF set
471 * if LOCKPARENT set, return locked parent in ni_dvp
472 * if WANTPARENT set, return unlocked parent in ni_dvp
473 */
474 int
475 lookup(struct nameidata *ndp)
476 {
477 char *cp; /* pointer into pathname argument */
478 struct vnode *dp = 0; /* the directory we are searching */
479 struct vnode *tdp; /* saved dp */
480 struct mount *mp; /* mount table entry */
481 struct prison *pr;
482 int docache; /* == 0 do not cache last component */
483 int wantparent; /* 1 => wantparent or lockparent flag */
484 int rdonly; /* lookup read-only flag bit */
485 int error = 0;
486 int dpunlocked = 0; /* dp has already been unlocked */
487 struct componentname *cnp = &ndp->ni_cnd;
488 int vfslocked; /* VFS Giant state for child */
489 int dvfslocked; /* VFS Giant state for parent */
490 int tvfslocked;
491 int lkflags_save;
492 int ni_dvp_unlocked;
493
494 /*
495 * Setup: break out flag bits into variables.
496 */
497 dvfslocked = (ndp->ni_cnd.cn_flags & GIANTHELD) != 0;
498 vfslocked = 0;
499 ni_dvp_unlocked = 0;
500 ndp->ni_cnd.cn_flags &= ~GIANTHELD;
501 wantparent = cnp->cn_flags & (LOCKPARENT | WANTPARENT);
502 KASSERT(cnp->cn_nameiop == LOOKUP || wantparent,
503 ("CREATE, DELETE, RENAME require LOCKPARENT or WANTPARENT."));
504 docache = (cnp->cn_flags & NOCACHE) ^ NOCACHE;
505 if (cnp->cn_nameiop == DELETE ||
506 (wantparent && cnp->cn_nameiop != CREATE &&
507 cnp->cn_nameiop != LOOKUP))
508 docache = 0;
509 rdonly = cnp->cn_flags & RDONLY;
510 cnp->cn_flags &= ~ISSYMLINK;
511 ndp->ni_dvp = NULL;
512 /*
513 * We use shared locks until we hit the parent of the last cn then
514 * we adjust based on the requesting flags.
515 */
516 if (lookup_shared)
517 cnp->cn_lkflags = LK_SHARED;
518 else
519 cnp->cn_lkflags = LK_EXCLUSIVE;
520 dp = ndp->ni_startdir;
521 ndp->ni_startdir = NULLVP;
522 vn_lock(dp,
523 compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags | LK_RETRY,
524 cnp->cn_flags));
525
526 dirloop:
527 /*
528 * Search a new directory.
529 *
530 * The last component of the filename is left accessible via
531 * cnp->cn_nameptr for callers that need the name. Callers needing
532 * the name set the SAVENAME flag. When done, they assume
533 * responsibility for freeing the pathname buffer.
534 */
535 cnp->cn_consume = 0;
536 for (cp = cnp->cn_nameptr; *cp != 0 && *cp != '/'; cp++)
537 continue;
538 cnp->cn_namelen = cp - cnp->cn_nameptr;
539 if (cnp->cn_namelen > NAME_MAX) {
540 error = ENAMETOOLONG;
541 goto bad;
542 }
543 #ifdef NAMEI_DIAGNOSTIC
544 { char c = *cp;
545 *cp = '\0';
546 printf("{%s}: ", cnp->cn_nameptr);
547 *cp = c; }
548 #endif
549 ndp->ni_pathlen -= cnp->cn_namelen;
550 ndp->ni_next = cp;
551
552 /*
553 * Replace multiple slashes by a single slash and trailing slashes
554 * by a null. This must be done before VOP_LOOKUP() because some
555 * fs's don't know about trailing slashes. Remember if there were
556 * trailing slashes to handle symlinks, existing non-directories
557 * and non-existing files that won't be directories specially later.
558 */
559 while (*cp == '/' && (cp[1] == '/' || cp[1] == '\0')) {
560 cp++;
561 ndp->ni_pathlen--;
562 if (*cp == '\0') {
563 *ndp->ni_next = '\0';
564 cnp->cn_flags |= TRAILINGSLASH;
565 }
566 }
567 ndp->ni_next = cp;
568
569 cnp->cn_flags |= MAKEENTRY;
570 if (*cp == '\0' && docache == 0)
571 cnp->cn_flags &= ~MAKEENTRY;
572 if (cnp->cn_namelen == 2 &&
573 cnp->cn_nameptr[1] == '.' && cnp->cn_nameptr[0] == '.')
574 cnp->cn_flags |= ISDOTDOT;
575 else
576 cnp->cn_flags &= ~ISDOTDOT;
577 if (*ndp->ni_next == 0)
578 cnp->cn_flags |= ISLASTCN;
579 else
580 cnp->cn_flags &= ~ISLASTCN;
581
582 if ((cnp->cn_flags & ISLASTCN) != 0 &&
583 cnp->cn_namelen == 1 && cnp->cn_nameptr[0] == '.' &&
584 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) {
585 error = EINVAL;
586 goto bad;
587 }
588
589 /*
590 * Check for degenerate name (e.g. / or "")
591 * which is a way of talking about a directory,
592 * e.g. like "/." or ".".
593 */
594 if (cnp->cn_nameptr[0] == '\0') {
595 if (dp->v_type != VDIR) {
596 error = ENOTDIR;
597 goto bad;
598 }
599 if (cnp->cn_nameiop != LOOKUP) {
600 error = EISDIR;
601 goto bad;
602 }
603 if (wantparent) {
604 ndp->ni_dvp = dp;
605 VREF(dp);
606 }
607 ndp->ni_vp = dp;
608
609 if (cnp->cn_flags & AUDITVNODE1)
610 AUDIT_ARG_VNODE1(dp);
611 else if (cnp->cn_flags & AUDITVNODE2)
612 AUDIT_ARG_VNODE2(dp);
613
614 if (!(cnp->cn_flags & (LOCKPARENT | LOCKLEAF)))
615 VOP_UNLOCK(dp, 0);
616 /* XXX This should probably move to the top of function. */
617 if (cnp->cn_flags & SAVESTART)
618 panic("lookup: SAVESTART");
619 goto success;
620 }
621
622 /*
623 * Handle "..": five special cases.
624 * 0. If doing a capability lookup, return ENOTCAPABLE (this is a
625 * fairly conservative design choice, but it's the only one that we
626 * are satisfied guarantees the property we're looking for).
627 * 1. Return an error if this is the last component of
628 * the name and the operation is DELETE or RENAME.
629 * 2. If at root directory (e.g. after chroot)
630 * or at absolute root directory
631 * then ignore it so can't get out.
632 * 3. If this vnode is the root of a mounted
633 * filesystem, then replace it with the
634 * vnode which was mounted on so we take the
635 * .. in the other filesystem.
636 * 4. If the vnode is the top directory of
637 * the jail or chroot, don't let them out.
638 */
639 if (cnp->cn_flags & ISDOTDOT) {
640 if (ndp->ni_strictrelative != 0) {
641 error = ENOTCAPABLE;
642 goto bad;
643 }
644 if ((cnp->cn_flags & ISLASTCN) != 0 &&
645 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) {
646 error = EINVAL;
647 goto bad;
648 }
649 for (;;) {
650 for (pr = cnp->cn_cred->cr_prison; pr != NULL;
651 pr = pr->pr_parent)
652 if (dp == pr->pr_root)
653 break;
654 if (dp == ndp->ni_rootdir ||
655 dp == ndp->ni_topdir ||
656 dp == rootvnode ||
657 pr != NULL ||
658 ((dp->v_vflag & VV_ROOT) != 0 &&
659 (cnp->cn_flags & NOCROSSMOUNT) != 0)) {
660 ndp->ni_dvp = dp;
661 ndp->ni_vp = dp;
662 vfslocked = VFS_LOCK_GIANT(dp->v_mount);
663 VREF(dp);
664 goto nextname;
665 }
666 if ((dp->v_vflag & VV_ROOT) == 0)
667 break;
668 if (dp->v_iflag & VI_DOOMED) { /* forced unmount */
669 error = ENOENT;
670 goto bad;
671 }
672 tdp = dp;
673 dp = dp->v_mount->mnt_vnodecovered;
674 tvfslocked = dvfslocked;
675 dvfslocked = VFS_LOCK_GIANT(dp->v_mount);
676 VREF(dp);
677 vput(tdp);
678 VFS_UNLOCK_GIANT(tvfslocked);
679 vn_lock(dp,
680 compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags |
681 LK_RETRY, ISDOTDOT));
682 }
683 }
684
685 /*
686 * We now have a segment name to search for, and a directory to search.
687 */
688 unionlookup:
689 #ifdef MAC
690 if ((cnp->cn_flags & NOMACCHECK) == 0) {
691 error = mac_vnode_check_lookup(cnp->cn_thread->td_ucred, dp,
692 cnp);
693 if (error)
694 goto bad;
695 }
696 #endif
697 ndp->ni_dvp = dp;
698 ndp->ni_vp = NULL;
699 ASSERT_VOP_LOCKED(dp, "lookup");
700 VNASSERT(vfslocked == 0, dp, ("lookup: vfslocked %d", vfslocked));
701 /*
702 * If we have a shared lock we may need to upgrade the lock for the
703 * last operation.
704 */
705 if (dp != vp_crossmp &&
706 VOP_ISLOCKED(dp) == LK_SHARED &&
707 (cnp->cn_flags & ISLASTCN) && (cnp->cn_flags & LOCKPARENT))
708 vn_lock(dp, LK_UPGRADE|LK_RETRY);
709 if ((dp->v_iflag & VI_DOOMED) != 0) {
710 error = ENOENT;
711 goto bad;
712 }
713 /*
714 * If we're looking up the last component and we need an exclusive
715 * lock, adjust our lkflags.
716 */
717 if (needs_exclusive_leaf(dp->v_mount, cnp->cn_flags))
718 cnp->cn_lkflags = LK_EXCLUSIVE;
719 #ifdef NAMEI_DIAGNOSTIC
720 vprint("lookup in", dp);
721 #endif
722 lkflags_save = cnp->cn_lkflags;
723 cnp->cn_lkflags = compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags,
724 cnp->cn_flags);
725 if ((error = VOP_LOOKUP(dp, &ndp->ni_vp, cnp)) != 0) {
726 cnp->cn_lkflags = lkflags_save;
727 KASSERT(ndp->ni_vp == NULL, ("leaf should be empty"));
728 #ifdef NAMEI_DIAGNOSTIC
729 printf("not found\n");
730 #endif
731 if ((error == ENOENT) &&
732 (dp->v_vflag & VV_ROOT) && (dp->v_mount != NULL) &&
733 (dp->v_mount->mnt_flag & MNT_UNION)) {
734 tdp = dp;
735 dp = dp->v_mount->mnt_vnodecovered;
736 tvfslocked = dvfslocked;
737 dvfslocked = VFS_LOCK_GIANT(dp->v_mount);
738 VREF(dp);
739 vput(tdp);
740 VFS_UNLOCK_GIANT(tvfslocked);
741 vn_lock(dp,
742 compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags |
743 LK_RETRY, cnp->cn_flags));
744 goto unionlookup;
745 }
746
747 if (error != EJUSTRETURN)
748 goto bad;
749 /*
750 * At this point, we know we're at the end of the
751 * pathname. If creating / renaming, we can consider
752 * allowing the file or directory to be created / renamed,
753 * provided we're not on a read-only filesystem.
754 */
755 if (rdonly) {
756 error = EROFS;
757 goto bad;
758 }
759 /* trailing slash only allowed for directories */
760 if ((cnp->cn_flags & TRAILINGSLASH) &&
761 !(cnp->cn_flags & WILLBEDIR)) {
762 error = ENOENT;
763 goto bad;
764 }
765 if ((cnp->cn_flags & LOCKPARENT) == 0)
766 VOP_UNLOCK(dp, 0);
767 /*
768 * We return with ni_vp NULL to indicate that the entry
769 * doesn't currently exist, leaving a pointer to the
770 * (possibly locked) directory vnode in ndp->ni_dvp.
771 */
772 if (cnp->cn_flags & SAVESTART) {
773 ndp->ni_startdir = ndp->ni_dvp;
774 VREF(ndp->ni_startdir);
775 }
776 goto success;
777 } else
778 cnp->cn_lkflags = lkflags_save;
779 #ifdef NAMEI_DIAGNOSTIC
780 printf("found\n");
781 #endif
782 /*
783 * Take into account any additional components consumed by
784 * the underlying filesystem.
785 */
786 if (cnp->cn_consume > 0) {
787 cnp->cn_nameptr += cnp->cn_consume;
788 ndp->ni_next += cnp->cn_consume;
789 ndp->ni_pathlen -= cnp->cn_consume;
790 cnp->cn_consume = 0;
791 }
792
793 dp = ndp->ni_vp;
794 vfslocked = VFS_LOCK_GIANT(dp->v_mount);
795
796 /*
797 * Check to see if the vnode has been mounted on;
798 * if so find the root of the mounted filesystem.
799 */
800 while (dp->v_type == VDIR && (mp = dp->v_mountedhere) &&
801 (cnp->cn_flags & NOCROSSMOUNT) == 0) {
802 if (vfs_busy(mp, 0))
803 continue;
804 vput(dp);
805 VFS_UNLOCK_GIANT(vfslocked);
806 vfslocked = VFS_LOCK_GIANT(mp);
807 if (dp != ndp->ni_dvp)
808 vput(ndp->ni_dvp);
809 else
810 vrele(ndp->ni_dvp);
811 VFS_UNLOCK_GIANT(dvfslocked);
812 dvfslocked = 0;
813 vref(vp_crossmp);
814 ndp->ni_dvp = vp_crossmp;
815 error = VFS_ROOT(mp, compute_cn_lkflags(mp, cnp->cn_lkflags,
816 cnp->cn_flags), &tdp);
817 vfs_unbusy(mp);
818 if (vn_lock(vp_crossmp, LK_SHARED | LK_NOWAIT))
819 panic("vp_crossmp exclusively locked or reclaimed");
820 if (error) {
821 dpunlocked = 1;
822 goto bad2;
823 }
824 ndp->ni_vp = dp = tdp;
825 }
826
827 /*
828 * Check for symbolic link
829 */
830 if ((dp->v_type == VLNK) &&
831 ((cnp->cn_flags & FOLLOW) || (cnp->cn_flags & TRAILINGSLASH) ||
832 *ndp->ni_next == '/')) {
833 cnp->cn_flags |= ISSYMLINK;
834 if (dp->v_iflag & VI_DOOMED) {
835 /*
836 * We can't know whether the directory was mounted with
837 * NOSYMFOLLOW, so we can't follow safely.
838 */
839 error = ENOENT;
840 goto bad2;
841 }
842 if (dp->v_mount->mnt_flag & MNT_NOSYMFOLLOW) {
843 error = EACCES;
844 goto bad2;
845 }
846 /*
847 * Symlink code always expects an unlocked dvp.
848 */
849 if (ndp->ni_dvp != ndp->ni_vp) {
850 VOP_UNLOCK(ndp->ni_dvp, 0);
851 ni_dvp_unlocked = 1;
852 }
853 goto success;
854 }
855
856 nextname:
857 /*
858 * Not a symbolic link that we will follow. Continue with the
859 * next component if there is any; otherwise, we're done.
860 */
861 KASSERT((cnp->cn_flags & ISLASTCN) || *ndp->ni_next == '/',
862 ("lookup: invalid path state."));
863 if (*ndp->ni_next == '/') {
864 cnp->cn_nameptr = ndp->ni_next;
865 while (*cnp->cn_nameptr == '/') {
866 cnp->cn_nameptr++;
867 ndp->ni_pathlen--;
868 }
869 if (ndp->ni_dvp != dp)
870 vput(ndp->ni_dvp);
871 else
872 vrele(ndp->ni_dvp);
873 VFS_UNLOCK_GIANT(dvfslocked);
874 dvfslocked = vfslocked; /* dp becomes dvp in dirloop */
875 vfslocked = 0;
876 goto dirloop;
877 }
878 /*
879 * If we're processing a path with a trailing slash,
880 * check that the end result is a directory.
881 */
882 if ((cnp->cn_flags & TRAILINGSLASH) && dp->v_type != VDIR) {
883 error = ENOTDIR;
884 goto bad2;
885 }
886 /*
887 * Disallow directory write attempts on read-only filesystems.
888 */
889 if (rdonly &&
890 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) {
891 error = EROFS;
892 goto bad2;
893 }
894 if (cnp->cn_flags & SAVESTART) {
895 ndp->ni_startdir = ndp->ni_dvp;
896 VREF(ndp->ni_startdir);
897 }
898 if (!wantparent) {
899 ni_dvp_unlocked = 2;
900 if (ndp->ni_dvp != dp)
901 vput(ndp->ni_dvp);
902 else
903 vrele(ndp->ni_dvp);
904 VFS_UNLOCK_GIANT(dvfslocked);
905 dvfslocked = 0;
906 } else if ((cnp->cn_flags & LOCKPARENT) == 0 && ndp->ni_dvp != dp) {
907 VOP_UNLOCK(ndp->ni_dvp, 0);
908 ni_dvp_unlocked = 1;
909 }
910
911 if (cnp->cn_flags & AUDITVNODE1)
912 AUDIT_ARG_VNODE1(dp);
913 else if (cnp->cn_flags & AUDITVNODE2)
914 AUDIT_ARG_VNODE2(dp);
915
916 if ((cnp->cn_flags & LOCKLEAF) == 0)
917 VOP_UNLOCK(dp, 0);
918 success:
919 /*
920 * Because of lookup_shared we may have the vnode shared locked, but
921 * the caller may want it to be exclusively locked.
922 */
923 if (needs_exclusive_leaf(dp->v_mount, cnp->cn_flags) &&
924 VOP_ISLOCKED(dp) != LK_EXCLUSIVE) {
925 vn_lock(dp, LK_UPGRADE | LK_RETRY);
926 if (dp->v_iflag & VI_DOOMED) {
927 error = ENOENT;
928 goto bad2;
929 }
930 }
931 if (vfslocked && dvfslocked)
932 VFS_UNLOCK_GIANT(dvfslocked); /* Only need one */
933 if (vfslocked || dvfslocked)
934 ndp->ni_cnd.cn_flags |= GIANTHELD;
935 return (0);
936
937 bad2:
938 if (ni_dvp_unlocked != 2) {
939 if (dp != ndp->ni_dvp && !ni_dvp_unlocked)
940 vput(ndp->ni_dvp);
941 else
942 vrele(ndp->ni_dvp);
943 }
944 bad:
945 if (!dpunlocked)
946 vput(dp);
947 VFS_UNLOCK_GIANT(vfslocked);
948 VFS_UNLOCK_GIANT(dvfslocked);
949 ndp->ni_cnd.cn_flags &= ~GIANTHELD;
950 ndp->ni_vp = NULL;
951 return (error);
952 }
953
954 /*
955 * relookup - lookup a path name component
956 * Used by lookup to re-acquire things.
957 */
958 int
959 relookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp)
960 {
961 struct vnode *dp = 0; /* the directory we are searching */
962 int wantparent; /* 1 => wantparent or lockparent flag */
963 int rdonly; /* lookup read-only flag bit */
964 int error = 0;
965
966 KASSERT(cnp->cn_flags & ISLASTCN,
967 ("relookup: Not given last component."));
968 /*
969 * Setup: break out flag bits into variables.
970 */
971 wantparent = cnp->cn_flags & (LOCKPARENT|WANTPARENT);
972 KASSERT(wantparent, ("relookup: parent not wanted."));
973 rdonly = cnp->cn_flags & RDONLY;
974 cnp->cn_flags &= ~ISSYMLINK;
975 dp = dvp;
976 cnp->cn_lkflags = LK_EXCLUSIVE;
977 vn_lock(dp, LK_EXCLUSIVE | LK_RETRY);
978
979 /*
980 * Search a new directory.
981 *
982 * The last component of the filename is left accessible via
983 * cnp->cn_nameptr for callers that need the name. Callers needing
984 * the name set the SAVENAME flag. When done, they assume
985 * responsibility for freeing the pathname buffer.
986 */
987 #ifdef NAMEI_DIAGNOSTIC
988 printf("{%s}: ", cnp->cn_nameptr);
989 #endif
990
991 /*
992 * Check for "" which represents the root directory after slash
993 * removal.
994 */
995 if (cnp->cn_nameptr[0] == '\0') {
996 /*
997 * Support only LOOKUP for "/" because lookup()
998 * can't succeed for CREATE, DELETE and RENAME.
999 */
1000 KASSERT(cnp->cn_nameiop == LOOKUP, ("nameiop must be LOOKUP"));
1001 KASSERT(dp->v_type == VDIR, ("dp is not a directory"));
1002
1003 if (!(cnp->cn_flags & LOCKLEAF))
1004 VOP_UNLOCK(dp, 0);
1005 *vpp = dp;
1006 /* XXX This should probably move to the top of function. */
1007 if (cnp->cn_flags & SAVESTART)
1008 panic("lookup: SAVESTART");
1009 return (0);
1010 }
1011
1012 if (cnp->cn_flags & ISDOTDOT)
1013 panic ("relookup: lookup on dot-dot");
1014
1015 /*
1016 * We now have a segment name to search for, and a directory to search.
1017 */
1018 #ifdef NAMEI_DIAGNOSTIC
1019 vprint("search in:", dp);
1020 #endif
1021 if ((error = VOP_LOOKUP(dp, vpp, cnp)) != 0) {
1022 KASSERT(*vpp == NULL, ("leaf should be empty"));
1023 if (error != EJUSTRETURN)
1024 goto bad;
1025 /*
1026 * If creating and at end of pathname, then can consider
1027 * allowing file to be created.
1028 */
1029 if (rdonly) {
1030 error = EROFS;
1031 goto bad;
1032 }
1033 /* ASSERT(dvp == ndp->ni_startdir) */
1034 if (cnp->cn_flags & SAVESTART)
1035 VREF(dvp);
1036 if ((cnp->cn_flags & LOCKPARENT) == 0)
1037 VOP_UNLOCK(dp, 0);
1038 /*
1039 * We return with ni_vp NULL to indicate that the entry
1040 * doesn't currently exist, leaving a pointer to the
1041 * (possibly locked) directory vnode in ndp->ni_dvp.
1042 */
1043 return (0);
1044 }
1045
1046 dp = *vpp;
1047
1048 /*
1049 * Disallow directory write attempts on read-only filesystems.
1050 */
1051 if (rdonly &&
1052 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) {
1053 if (dvp == dp)
1054 vrele(dvp);
1055 else
1056 vput(dvp);
1057 error = EROFS;
1058 goto bad;
1059 }
1060 /*
1061 * Set the parent lock/ref state to the requested state.
1062 */
1063 if ((cnp->cn_flags & LOCKPARENT) == 0 && dvp != dp) {
1064 if (wantparent)
1065 VOP_UNLOCK(dvp, 0);
1066 else
1067 vput(dvp);
1068 } else if (!wantparent)
1069 vrele(dvp);
1070 /*
1071 * Check for symbolic link
1072 */
1073 KASSERT(dp->v_type != VLNK || !(cnp->cn_flags & FOLLOW),
1074 ("relookup: symlink found.\n"));
1075
1076 /* ASSERT(dvp == ndp->ni_startdir) */
1077 if (cnp->cn_flags & SAVESTART)
1078 VREF(dvp);
1079
1080 if ((cnp->cn_flags & LOCKLEAF) == 0)
1081 VOP_UNLOCK(dp, 0);
1082 return (0);
1083 bad:
1084 vput(dp);
1085 *vpp = NULL;
1086 return (error);
1087 }
1088
1089 /*
1090 * Free data allocated by namei(); see namei(9) for details.
1091 */
1092 void
1093 NDFREE(struct nameidata *ndp, const u_int flags)
1094 {
1095 int unlock_dvp;
1096 int unlock_vp;
1097
1098 unlock_dvp = 0;
1099 unlock_vp = 0;
1100
1101 if (!(flags & NDF_NO_FREE_PNBUF) &&
1102 (ndp->ni_cnd.cn_flags & HASBUF)) {
1103 uma_zfree(namei_zone, ndp->ni_cnd.cn_pnbuf);
1104 ndp->ni_cnd.cn_flags &= ~HASBUF;
1105 }
1106 if (!(flags & NDF_NO_VP_UNLOCK) &&
1107 (ndp->ni_cnd.cn_flags & LOCKLEAF) && ndp->ni_vp)
1108 unlock_vp = 1;
1109 if (!(flags & NDF_NO_VP_RELE) && ndp->ni_vp) {
1110 if (unlock_vp) {
1111 vput(ndp->ni_vp);
1112 unlock_vp = 0;
1113 } else
1114 vrele(ndp->ni_vp);
1115 ndp->ni_vp = NULL;
1116 }
1117 if (unlock_vp)
1118 VOP_UNLOCK(ndp->ni_vp, 0);
1119 if (!(flags & NDF_NO_DVP_UNLOCK) &&
1120 (ndp->ni_cnd.cn_flags & LOCKPARENT) &&
1121 ndp->ni_dvp != ndp->ni_vp)
1122 unlock_dvp = 1;
1123 if (!(flags & NDF_NO_DVP_RELE) &&
1124 (ndp->ni_cnd.cn_flags & (LOCKPARENT|WANTPARENT))) {
1125 if (unlock_dvp) {
1126 vput(ndp->ni_dvp);
1127 unlock_dvp = 0;
1128 } else
1129 vrele(ndp->ni_dvp);
1130 ndp->ni_dvp = NULL;
1131 }
1132 if (unlock_dvp)
1133 VOP_UNLOCK(ndp->ni_dvp, 0);
1134 if (!(flags & NDF_NO_STARTDIR_RELE) &&
1135 (ndp->ni_cnd.cn_flags & SAVESTART)) {
1136 vrele(ndp->ni_startdir);
1137 ndp->ni_startdir = NULL;
1138 }
1139 }
1140
1141 /*
1142 * Determine if there is a suitable alternate filename under the specified
1143 * prefix for the specified path. If the create flag is set, then the
1144 * alternate prefix will be used so long as the parent directory exists.
1145 * This is used by the various compatiblity ABIs so that Linux binaries prefer
1146 * files under /compat/linux for example. The chosen path (whether under
1147 * the prefix or under /) is returned in a kernel malloc'd buffer pointed
1148 * to by pathbuf. The caller is responsible for free'ing the buffer from
1149 * the M_TEMP bucket if one is returned.
1150 */
1151 int
1152 kern_alternate_path(struct thread *td, const char *prefix, const char *path,
1153 enum uio_seg pathseg, char **pathbuf, int create, int dirfd)
1154 {
1155 struct nameidata nd, ndroot;
1156 char *ptr, *buf, *cp;
1157 size_t len, sz;
1158 int error;
1159
1160 buf = (char *) malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
1161 *pathbuf = buf;
1162
1163 /* Copy the prefix into the new pathname as a starting point. */
1164 len = strlcpy(buf, prefix, MAXPATHLEN);
1165 if (len >= MAXPATHLEN) {
1166 *pathbuf = NULL;
1167 free(buf, M_TEMP);
1168 return (EINVAL);
1169 }
1170 sz = MAXPATHLEN - len;
1171 ptr = buf + len;
1172
1173 /* Append the filename to the prefix. */
1174 if (pathseg == UIO_SYSSPACE)
1175 error = copystr(path, ptr, sz, &len);
1176 else
1177 error = copyinstr(path, ptr, sz, &len);
1178
1179 if (error) {
1180 *pathbuf = NULL;
1181 free(buf, M_TEMP);
1182 return (error);
1183 }
1184
1185 /* Only use a prefix with absolute pathnames. */
1186 if (*ptr != '/') {
1187 error = EINVAL;
1188 goto keeporig;
1189 }
1190
1191 if (dirfd != AT_FDCWD) {
1192 /*
1193 * We want the original because the "prefix" is
1194 * included in the already opened dirfd.
1195 */
1196 bcopy(ptr, buf, len);
1197 return (0);
1198 }
1199
1200 /*
1201 * We know that there is a / somewhere in this pathname.
1202 * Search backwards for it, to find the file's parent dir
1203 * to see if it exists in the alternate tree. If it does,
1204 * and we want to create a file (cflag is set). We don't
1205 * need to worry about the root comparison in this case.
1206 */
1207
1208 if (create) {
1209 for (cp = &ptr[len] - 1; *cp != '/'; cp--);
1210 *cp = '\0';
1211
1212 NDINIT(&nd, LOOKUP, FOLLOW | MPSAFE, UIO_SYSSPACE, buf, td);
1213 error = namei(&nd);
1214 *cp = '/';
1215 if (error != 0)
1216 goto keeporig;
1217 } else {
1218 NDINIT(&nd, LOOKUP, FOLLOW | MPSAFE, UIO_SYSSPACE, buf, td);
1219
1220 error = namei(&nd);
1221 if (error != 0)
1222 goto keeporig;
1223
1224 /*
1225 * We now compare the vnode of the prefix to the one
1226 * vnode asked. If they resolve to be the same, then we
1227 * ignore the match so that the real root gets used.
1228 * This avoids the problem of traversing "../.." to find the
1229 * root directory and never finding it, because "/" resolves
1230 * to the emulation root directory. This is expensive :-(
1231 */
1232 NDINIT(&ndroot, LOOKUP, FOLLOW | MPSAFE, UIO_SYSSPACE, prefix,
1233 td);
1234
1235 /* We shouldn't ever get an error from this namei(). */
1236 error = namei(&ndroot);
1237 if (error == 0) {
1238 if (nd.ni_vp == ndroot.ni_vp)
1239 error = ENOENT;
1240
1241 NDFREE(&ndroot, NDF_ONLY_PNBUF);
1242 vrele(ndroot.ni_vp);
1243 VFS_UNLOCK_GIANT(NDHASGIANT(&ndroot));
1244 }
1245 }
1246
1247 NDFREE(&nd, NDF_ONLY_PNBUF);
1248 vrele(nd.ni_vp);
1249 VFS_UNLOCK_GIANT(NDHASGIANT(&nd));
1250
1251 keeporig:
1252 /* If there was an error, use the original path name. */
1253 if (error)
1254 bcopy(ptr, buf, len);
1255 return (error);
1256 }
Cache object: 88151f6d1fb9894ead6cbbff3fffb52a
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