2 * SPDX-License-Identifier: BSD-3-Clause
4 * Copyright (c) 1982, 1986, 1989, 1993
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6 * (c) UNIX System Laboratories, Inc.
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36 * @(#)vfs_lookup.c 8.4 (Berkeley) 2/16/94
39 #include <sys/cdefs.h>
40 __FBSDID("$FreeBSD$");
42 #include "opt_capsicum.h"
43 #include "opt_ktrace.h"
45 #include <sys/param.h>
46 #include <sys/systm.h>
47 #include <sys/dirent.h>
48 #include <sys/kernel.h>
49 #include <sys/capsicum.h>
50 #include <sys/fcntl.h>
53 #include <sys/mutex.h>
54 #include <sys/namei.h>
55 #include <sys/vnode.h>
56 #include <sys/mount.h>
57 #include <sys/filedesc.h>
60 #include <sys/syscallsubr.h>
61 #include <sys/sysctl.h>
63 #include <sys/ktrace.h>
66 #include <machine/_inttypes.h>
69 #include <security/audit/audit.h>
70 #include <security/mac/mac_framework.h>
74 #define NAMEI_DIAGNOSTIC 1
75 #undef NAMEI_DIAGNOSTIC
77 SDT_PROVIDER_DEFINE(vfs);
78 SDT_PROBE_DEFINE4(vfs, namei, lookup, entry, "struct vnode *", "char *",
79 "unsigned long", "bool");
80 SDT_PROBE_DEFINE4(vfs, namei, lookup, return, "int", "struct vnode *", "bool",
83 /* Allocation zone for namei. */
84 uma_zone_t namei_zone;
86 /* Placeholder vnode for mp traversal. */
87 static struct vnode *vp_crossmp;
90 crossmp_vop_islocked(struct vop_islocked_args *ap)
97 crossmp_vop_lock1(struct vop_lock1_args *ap)
100 struct lock *lk __unused;
101 const char *file __unused;
102 int flags, line __unused;
110 if ((flags & LK_SHARED) == 0)
111 panic("invalid lock request for crossmp");
113 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER, file, line,
114 flags & LK_INTERLOCK ? &VI_MTX(vp)->lock_object : NULL);
115 WITNESS_LOCK(&lk->lock_object, 0, file, line);
116 if ((flags & LK_INTERLOCK) != 0)
118 LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, ap->a_file, line);
123 crossmp_vop_unlock(struct vop_unlock_args *ap)
126 struct lock *lk __unused;
131 WITNESS_UNLOCK(&lk->lock_object, 0, LOCK_FILE, LOCK_LINE);
132 LOCK_LOG_LOCK("SUNLOCK", &lk->lock_object, 0, 0, LOCK_FILE,
137 static struct vop_vector crossmp_vnodeops = {
138 .vop_default = &default_vnodeops,
139 .vop_islocked = crossmp_vop_islocked,
140 .vop_lock1 = crossmp_vop_lock1,
141 .vop_unlock = crossmp_vop_unlock,
144 * VFS_VOP_VECTOR_REGISTER(crossmp_vnodeops) is not used here since the vnode
145 * gets allocated early. See nameiinit for the direct call below.
148 struct nameicap_tracker {
150 TAILQ_ENTRY(nameicap_tracker) nm_link;
153 /* Zone for cap mode tracker elements used for dotdot capability checks. */
154 MALLOC_DEFINE(M_NAMEITRACKER, "namei_tracker", "namei tracking for dotdot");
157 nameiinit(void *dummy __unused)
160 namei_zone = uma_zcreate("NAMEI", MAXPATHLEN, NULL, NULL, NULL, NULL,
162 vfs_vector_op_register(&crossmp_vnodeops);
163 getnewvnode("crossmp", NULL, &crossmp_vnodeops, &vp_crossmp);
165 SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_SECOND, nameiinit, NULL);
167 static int lookup_cap_dotdot = 1;
168 SYSCTL_INT(_vfs, OID_AUTO, lookup_cap_dotdot, CTLFLAG_RWTUN,
169 &lookup_cap_dotdot, 0,
170 "enables \"..\" components in path lookup in capability mode");
171 static int lookup_cap_dotdot_nonlocal = 1;
172 SYSCTL_INT(_vfs, OID_AUTO, lookup_cap_dotdot_nonlocal, CTLFLAG_RWTUN,
173 &lookup_cap_dotdot_nonlocal, 0,
174 "enables \"..\" components in path lookup in capability mode "
175 "on non-local mount");
178 nameicap_tracker_add(struct nameidata *ndp, struct vnode *dp)
180 struct nameicap_tracker *nt;
181 struct componentname *cnp;
183 if ((ndp->ni_lcf & NI_LCF_CAP_DOTDOT) == 0 || dp->v_type != VDIR)
186 nt = TAILQ_LAST(&ndp->ni_cap_tracker, nameicap_tracker_head);
187 if (nt != NULL && nt->dp == dp)
189 nt = malloc(sizeof(*nt), M_NAMEITRACKER, M_WAITOK);
192 TAILQ_INSERT_TAIL(&ndp->ni_cap_tracker, nt, nm_link);
196 nameicap_cleanup_from(struct nameidata *ndp, struct nameicap_tracker *first)
198 struct nameicap_tracker *nt, *nt1;
201 TAILQ_FOREACH_FROM_SAFE(nt, &ndp->ni_cap_tracker, nm_link, nt1) {
202 TAILQ_REMOVE(&ndp->ni_cap_tracker, nt, nm_link);
204 free(nt, M_NAMEITRACKER);
209 nameicap_cleanup(struct nameidata *ndp)
211 KASSERT(TAILQ_EMPTY(&ndp->ni_cap_tracker) ||
212 (ndp->ni_lcf & NI_LCF_CAP_DOTDOT) != 0, ("not strictrelative"));
213 nameicap_cleanup_from(ndp, NULL);
217 * For dotdot lookups in capability mode, only allow the component
218 * lookup to succeed if the resulting directory was already traversed
219 * during the operation. This catches situations where already
220 * traversed directory is moved to different parent, and then we walk
221 * over it with dotdots.
223 * Also allow to force failure of dotdot lookups for non-local
224 * filesystems, where external agents might assist local lookups to
225 * escape the compartment.
228 nameicap_check_dotdot(struct nameidata *ndp, struct vnode *dp)
230 struct nameicap_tracker *nt;
233 if (dp == NULL || dp->v_type != VDIR || (ndp->ni_lcf &
234 NI_LCF_STRICTRELATIVE) == 0)
236 if ((ndp->ni_lcf & NI_LCF_CAP_DOTDOT) == 0)
237 return (ENOTCAPABLE);
239 if (lookup_cap_dotdot_nonlocal == 0 && mp != NULL &&
240 (mp->mnt_flag & MNT_LOCAL) == 0)
241 return (ENOTCAPABLE);
242 TAILQ_FOREACH_REVERSE(nt, &ndp->ni_cap_tracker, nameicap_tracker_head,
245 nt = TAILQ_NEXT(nt, nm_link);
247 nameicap_cleanup_from(ndp, nt);
251 return (ENOTCAPABLE);
255 namei_cleanup_cnp(struct componentname *cnp)
258 uma_zfree(namei_zone, cnp->cn_pnbuf);
260 cnp->cn_pnbuf = NULL;
261 cnp->cn_nameptr = NULL;
266 namei_handle_root(struct nameidata *ndp, struct vnode **dpp)
268 struct componentname *cnp;
271 if ((ndp->ni_lcf & NI_LCF_STRICTRELATIVE) != 0) {
273 if (KTRPOINT(curthread, KTR_CAPFAIL))
274 ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL);
276 return (ENOTCAPABLE);
278 while (*(cnp->cn_nameptr) == '/') {
282 *dpp = ndp->ni_rootdir;
288 namei_setup(struct nameidata *ndp, struct vnode **dpp, struct pwd **pwdp)
290 struct componentname *cnp;
299 startdir_used = false;
303 #ifdef CAPABILITY_MODE
305 * In capability mode, lookups must be restricted to happen in
306 * the subtree with the root specified by the file descriptor:
307 * - The root must be real file descriptor, not the pseudo-descriptor
309 * - The passed path must be relative and not absolute.
310 * - If lookup_cap_dotdot is disabled, path must not contain the
312 * - If lookup_cap_dotdot is enabled, we verify that all '..'
313 * components lookups result in the directories which were
314 * previously walked by us, which prevents an escape from
317 if (IN_CAPABILITY_MODE(td) && (cnp->cn_flags & NOCAPCHECK) == 0) {
318 ndp->ni_lcf |= NI_LCF_STRICTRELATIVE;
319 ndp->ni_resflags |= NIRES_STRICTREL;
320 if (ndp->ni_dirfd == AT_FDCWD) {
322 if (KTRPOINT(td, KTR_CAPFAIL))
323 ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL);
332 * Get starting point for the translation.
336 * The reference on ni_rootdir is acquired in the block below to avoid
337 * back-to-back atomics for absolute lookups.
339 ndp->ni_rootdir = pwd->pwd_rdir;
340 ndp->ni_topdir = pwd->pwd_jdir;
342 if (cnp->cn_pnbuf[0] == '/') {
343 ndp->ni_resflags |= NIRES_ABS;
344 error = namei_handle_root(ndp, dpp);
346 if (ndp->ni_startdir != NULL) {
347 *dpp = ndp->ni_startdir;
348 startdir_used = true;
349 } else if (ndp->ni_dirfd == AT_FDCWD) {
350 *dpp = pwd->pwd_cdir;
353 if (cnp->cn_flags & AUDITVNODE1)
354 AUDIT_ARG_ATFD1(ndp->ni_dirfd);
355 if (cnp->cn_flags & AUDITVNODE2)
356 AUDIT_ARG_ATFD2(ndp->ni_dirfd);
358 error = fgetvp_lookup(ndp->ni_dirfd, ndp, dpp);
360 if (error == 0 && (*dpp)->v_type != VDIR &&
361 (cnp->cn_pnbuf[0] != '\0' ||
362 (cnp->cn_flags & EMPTYPATH) == 0))
365 if (error == 0 && (cnp->cn_flags & RBENEATH) != 0) {
366 if (cnp->cn_pnbuf[0] == '/') {
368 } else if ((ndp->ni_lcf & NI_LCF_STRICTRELATIVE) == 0) {
369 ndp->ni_lcf |= NI_LCF_STRICTRELATIVE |
375 * If we are auditing the kernel pathname, save the user pathname.
377 if (cnp->cn_flags & AUDITVNODE1)
378 AUDIT_ARG_UPATH1_VP(td, ndp->ni_rootdir, *dpp, cnp->cn_pnbuf);
379 if (cnp->cn_flags & AUDITVNODE2)
380 AUDIT_ARG_UPATH2_VP(td, ndp->ni_rootdir, *dpp, cnp->cn_pnbuf);
381 if (ndp->ni_startdir != NULL && !startdir_used)
382 vrele(ndp->ni_startdir);
389 if ((ndp->ni_lcf & NI_LCF_STRICTRELATIVE) != 0 &&
390 lookup_cap_dotdot != 0)
391 ndp->ni_lcf |= NI_LCF_CAP_DOTDOT;
392 SDT_PROBE4(vfs, namei, lookup, entry, *dpp, cnp->cn_pnbuf,
393 cnp->cn_flags, false);
399 namei_getpath(struct nameidata *ndp)
401 struct componentname *cnp;
407 * Get a buffer for the name to be translated, and copy the
408 * name into the buffer.
410 cnp->cn_pnbuf = uma_zalloc(namei_zone, M_WAITOK);
411 if (ndp->ni_segflg == UIO_SYSSPACE) {
412 error = copystr(ndp->ni_dirp, cnp->cn_pnbuf, MAXPATHLEN,
415 error = copyinstr(ndp->ni_dirp, cnp->cn_pnbuf, MAXPATHLEN,
419 if (__predict_false(error != 0))
422 cnp->cn_nameptr = cnp->cn_pnbuf;
427 namei_emptypath(struct nameidata *ndp)
429 struct componentname *cnp;
435 MPASS(*cnp->cn_pnbuf == '\0');
436 MPASS((cnp->cn_flags & EMPTYPATH) != 0);
437 MPASS((cnp->cn_flags & (LOCKPARENT | WANTPARENT)) == 0);
439 ndp->ni_resflags |= NIRES_EMPTYPATH;
440 error = namei_setup(ndp, &dp, &pwd);
442 namei_cleanup_cnp(cnp);
447 * Usecount on dp already provided by namei_setup.
450 namei_cleanup_cnp(cnp);
453 if ((cnp->cn_flags & LOCKLEAF) != 0) {
454 VOP_LOCK(dp, (cnp->cn_flags & LOCKSHARED) != 0 ?
455 LK_SHARED : LK_EXCLUSIVE);
456 if (VN_IS_DOOMED(dp)) {
462 SDT_PROBE4(vfs, namei, lookup, return, 0, ndp->ni_vp, false, ndp);
466 SDT_PROBE4(vfs, namei, lookup, return, error, NULL, false, ndp);
471 * Convert a pathname into a pointer to a locked vnode.
473 * The FOLLOW flag is set when symbolic links are to be followed
474 * when they occur at the end of the name translation process.
475 * Symbolic links are always followed for all other pathname
476 * components other than the last.
478 * The segflg defines whether the name is to be copied from user
479 * space or kernel space.
481 * Overall outline of namei:
484 * get starting directory
485 * while (!done && !error) {
486 * call lookup to search path.
487 * if symbolic link, massage name in buffer and continue
491 namei(struct nameidata *ndp)
493 char *cp; /* pointer into pathname argument */
494 struct vnode *dp; /* the directory we are searching */
495 struct iovec aiov; /* uio for reading symbolic links */
496 struct componentname *cnp;
501 enum cache_fpl_status status;
506 KASSERT(cnp->cn_thread == curthread,
507 ("namei not using curthread"));
508 KASSERT((ndp->ni_debugflags & NAMEI_DBG_CALLED) == 0,
509 ("%s: repeated call to namei without NDREINIT", __func__));
510 KASSERT(ndp->ni_debugflags == NAMEI_DBG_INITED,
511 ("%s: bad debugflags %d", __func__, ndp->ni_debugflags));
512 ndp->ni_debugflags |= NAMEI_DBG_CALLED;
513 if (ndp->ni_startdir != NULL)
514 ndp->ni_debugflags |= NAMEI_DBG_HADSTARTDIR;
515 if (cnp->cn_flags & FAILIFEXISTS) {
516 KASSERT(cnp->cn_nameiop == CREATE,
517 ("%s: FAILIFEXISTS passed for op %d", __func__, cnp->cn_nameiop));
519 * The limitation below is to restrict hairy corner cases.
521 KASSERT((cnp->cn_flags & (LOCKPARENT | LOCKLEAF)) == LOCKPARENT,
522 ("%s: FAILIFEXISTS must be passed with LOCKPARENT and without LOCKLEAF",
528 * While NDINIT may seem like a more natural place to do it, there are
529 * callers which directly modify flags past invoking init.
531 cnp->cn_origflags = cnp->cn_flags;
533 ndp->ni_cnd.cn_cred = ndp->ni_cnd.cn_thread->td_ucred;
534 KASSERT(ndp->ni_resflags == 0, ("%s: garbage in ni_resflags: %x\n",
535 __func__, ndp->ni_resflags));
536 KASSERT(cnp->cn_cred && td->td_proc, ("namei: bad cred/proc"));
537 KASSERT((cnp->cn_flags & NAMEI_INTERNAL_FLAGS) == 0,
538 ("namei: unexpected flags: %" PRIx64 "\n",
539 cnp->cn_flags & NAMEI_INTERNAL_FLAGS));
540 if (cnp->cn_flags & NOCACHE)
541 KASSERT(cnp->cn_nameiop != LOOKUP,
542 ("%s: NOCACHE passed with LOOKUP", __func__));
543 MPASS(ndp->ni_startdir == NULL || ndp->ni_startdir->v_type == VDIR ||
544 ndp->ni_startdir->v_type == VBAD);
550 error = namei_getpath(ndp);
551 if (__predict_false(error != 0)) {
552 namei_cleanup_cnp(cnp);
553 SDT_PROBE4(vfs, namei, lookup, return, error, NULL,
559 if (KTRPOINT(td, KTR_NAMEI)) {
560 ktrnamei(cnp->cn_pnbuf);
563 TSNAMEI(curthread->td_proc->p_pid, cnp->cn_pnbuf);
566 * First try looking up the target without locking any vnodes.
568 * We may need to start from scratch or pick up where it left off.
570 error = cache_fplookup(ndp, &status, &pwd);
572 case CACHE_FPL_STATUS_UNSET:
573 __assert_unreachable();
575 case CACHE_FPL_STATUS_HANDLED:
579 case CACHE_FPL_STATUS_PARTIAL:
580 TAILQ_INIT(&ndp->ni_cap_tracker);
581 dp = ndp->ni_startdir;
583 case CACHE_FPL_STATUS_DESTROYED:
585 error = namei_getpath(ndp);
586 if (__predict_false(error != 0)) {
587 namei_cleanup_cnp(cnp);
591 case CACHE_FPL_STATUS_ABORTED:
592 TAILQ_INIT(&ndp->ni_cap_tracker);
593 MPASS(ndp->ni_lcf == 0);
594 if (*cnp->cn_pnbuf == '\0') {
595 if ((cnp->cn_flags & EMPTYPATH) != 0) {
596 return (namei_emptypath(ndp));
598 namei_cleanup_cnp(cnp);
599 SDT_PROBE4(vfs, namei, lookup, return, ENOENT, NULL,
603 error = namei_setup(ndp, &dp, &pwd);
605 namei_cleanup_cnp(cnp);
615 ndp->ni_startdir = dp;
621 * If not a symbolic link, we're done.
623 if ((cnp->cn_flags & ISSYMLINK) == 0) {
624 SDT_PROBE4(vfs, namei, lookup, return, error,
625 (error == 0 ? ndp->ni_vp : NULL), false, ndp);
626 if ((cnp->cn_flags & (SAVENAME | SAVESTART)) == 0) {
627 namei_cleanup_cnp(cnp);
629 cnp->cn_flags |= HASBUF;
630 nameicap_cleanup(ndp);
636 if (ndp->ni_loopcnt++ >= MAXSYMLINKS) {
641 if ((cnp->cn_flags & NOMACCHECK) == 0) {
642 error = mac_vnode_check_readlink(td->td_ucred,
648 if (ndp->ni_pathlen > 1)
649 cp = uma_zalloc(namei_zone, M_WAITOK);
653 aiov.iov_len = MAXPATHLEN;
654 auio.uio_iov = &aiov;
657 auio.uio_rw = UIO_READ;
658 auio.uio_segflg = UIO_SYSSPACE;
660 auio.uio_resid = MAXPATHLEN;
661 error = VOP_READLINK(ndp->ni_vp, &auio, cnp->cn_cred);
663 if (ndp->ni_pathlen > 1)
664 uma_zfree(namei_zone, cp);
667 linklen = MAXPATHLEN - auio.uio_resid;
669 if (ndp->ni_pathlen > 1)
670 uma_zfree(namei_zone, cp);
674 if (linklen + ndp->ni_pathlen > MAXPATHLEN) {
675 if (ndp->ni_pathlen > 1)
676 uma_zfree(namei_zone, cp);
677 error = ENAMETOOLONG;
680 if (ndp->ni_pathlen > 1) {
681 bcopy(ndp->ni_next, cp + linklen, ndp->ni_pathlen);
682 uma_zfree(namei_zone, cnp->cn_pnbuf);
685 cnp->cn_pnbuf[linklen] = '\0';
686 ndp->ni_pathlen += linklen;
690 * Check if root directory should replace current directory.
692 cnp->cn_nameptr = cnp->cn_pnbuf;
693 if (*(cnp->cn_nameptr) == '/') {
695 error = namei_handle_root(ndp, &dp);
705 SDT_PROBE4(vfs, namei, lookup, return, error, NULL, false, ndp);
706 namei_cleanup_cnp(cnp);
707 nameicap_cleanup(ndp);
713 compute_cn_lkflags(struct mount *mp, int lkflags, int cnflags)
716 if (mp == NULL || ((lkflags & LK_SHARED) &&
717 (!(mp->mnt_kern_flag & MNTK_LOOKUP_SHARED) ||
718 ((cnflags & ISDOTDOT) &&
719 (mp->mnt_kern_flag & MNTK_LOOKUP_EXCL_DOTDOT))))) {
720 lkflags &= ~LK_SHARED;
721 lkflags |= LK_EXCLUSIVE;
723 lkflags |= LK_NODDLKTREAT;
728 needs_exclusive_leaf(struct mount *mp, int flags)
732 * Intermediate nodes can use shared locks, we only need to
733 * force an exclusive lock for leaf nodes.
735 if ((flags & (ISLASTCN | LOCKLEAF)) != (ISLASTCN | LOCKLEAF))
738 /* Always use exclusive locks if LOCKSHARED isn't set. */
739 if (!(flags & LOCKSHARED))
743 * For lookups during open(), if the mount point supports
744 * extended shared operations, then use a shared lock for the
745 * leaf node, otherwise use an exclusive lock.
747 if ((flags & ISOPEN) != 0)
748 return (!MNT_EXTENDED_SHARED(mp));
751 * Lookup requests outside of open() that specify LOCKSHARED
752 * only need a shared lock on the leaf vnode.
758 * Various filesystems expect to be able to copy a name component with length
759 * bounded by NAME_MAX into a directory entry buffer of size MAXNAMLEN. Make
760 * sure that these are the same size.
762 _Static_assert(MAXNAMLEN == NAME_MAX,
763 "MAXNAMLEN and NAME_MAX have different values");
767 * This is a very central and rather complicated routine.
769 * The pathname is pointed to by ni_ptr and is of length ni_pathlen.
770 * The starting directory is taken from ni_startdir. The pathname is
771 * descended until done, or a symbolic link is encountered. The variable
772 * ni_more is clear if the path is completed; it is set to one if a
773 * symbolic link needing interpretation is encountered.
775 * The flag argument is LOOKUP, CREATE, RENAME, or DELETE depending on
776 * whether the name is to be looked up, created, renamed, or deleted.
777 * When CREATE, RENAME, or DELETE is specified, information usable in
778 * creating, renaming, or deleting a directory entry may be calculated.
779 * If flag has LOCKPARENT or'ed into it, the parent directory is returned
780 * locked. If flag has WANTPARENT or'ed into it, the parent directory is
781 * returned unlocked. Otherwise the parent directory is not returned. If
782 * the target of the pathname exists and LOCKLEAF is or'ed into the flag
783 * the target is returned locked, otherwise it is returned unlocked.
784 * When creating or renaming and LOCKPARENT is specified, the target may not
785 * be ".". When deleting and LOCKPARENT is specified, the target may be ".".
787 * Overall outline of lookup:
790 * identify next component of name at ndp->ni_ptr
791 * handle degenerate case where name is null string
792 * if .. and crossing mount points and on mounted filesys, find parent
793 * call VOP_LOOKUP routine for next component name
794 * directory vnode returned in ni_dvp, unlocked unless LOCKPARENT set
795 * component vnode returned in ni_vp (if it exists), locked.
796 * if result vnode is mounted on and crossing mount points,
797 * find mounted on vnode
798 * if more components of name, do next level at dirloop
799 * return the answer in ni_vp, locked if LOCKLEAF set
800 * if LOCKPARENT set, return locked parent in ni_dvp
801 * if WANTPARENT set, return unlocked parent in ni_dvp
804 lookup(struct nameidata *ndp)
806 char *cp; /* pointer into pathname argument */
807 char *prev_ni_next; /* saved ndp->ni_next */
808 char *nulchar; /* location of '\0' in cn_pnbuf */
809 struct vnode *dp = NULL; /* the directory we are searching */
810 struct vnode *tdp; /* saved dp */
811 struct mount *mp; /* mount table entry */
813 size_t prev_ni_pathlen; /* saved ndp->ni_pathlen */
814 int docache; /* == 0 do not cache last component */
815 int wantparent; /* 1 => wantparent or lockparent flag */
816 int rdonly; /* lookup read-only flag bit */
818 int dpunlocked = 0; /* dp has already been unlocked */
819 int relookup = 0; /* do not consume the path component */
820 struct componentname *cnp = &ndp->ni_cnd;
825 * Setup: break out flag bits into variables.
828 wantparent = cnp->cn_flags & (LOCKPARENT | WANTPARENT);
829 KASSERT(cnp->cn_nameiop == LOOKUP || wantparent,
830 ("CREATE, DELETE, RENAME require LOCKPARENT or WANTPARENT."));
832 * When set to zero, docache causes the last component of the
833 * pathname to be deleted from the cache and the full lookup
834 * of the name to be done (via VOP_CACHEDLOOKUP()). Often
835 * filesystems need some pre-computed values that are made
836 * during the full lookup, for instance UFS sets dp->i_offset.
838 * The docache variable is set to zero when requested by the
839 * NOCACHE flag and for all modifying operations except CREATE.
841 docache = (cnp->cn_flags & NOCACHE) ^ NOCACHE;
842 if (cnp->cn_nameiop == DELETE ||
843 (wantparent && cnp->cn_nameiop != CREATE &&
844 cnp->cn_nameiop != LOOKUP))
846 rdonly = cnp->cn_flags & RDONLY;
847 cnp->cn_flags &= ~ISSYMLINK;
850 * We use shared locks until we hit the parent of the last cn then
851 * we adjust based on the requesting flags.
853 cnp->cn_lkflags = LK_SHARED;
854 dp = ndp->ni_startdir;
855 ndp->ni_startdir = NULLVP;
857 compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags | LK_RETRY,
862 * Search a new directory.
864 * The last component of the filename is left accessible via
865 * cnp->cn_nameptr for callers that need the name. Callers needing
866 * the name set the SAVENAME flag. When done, they assume
867 * responsibility for freeing the pathname buffer.
869 * Store / as a temporary sentinel so that we only have one character
870 * to test for. Pathnames tend to be short so this should not be
871 * resulting in cache misses.
873 nulchar = &cnp->cn_nameptr[ndp->ni_pathlen - 1];
874 KASSERT(*nulchar == '\0',
875 ("%s: expected nul at %p; string [%s]\n", __func__, nulchar,
878 for (cp = cnp->cn_nameptr; *cp != '/'; cp++) {
880 ("%s: encountered unexpected nul; string [%s]\n", __func__,
885 cnp->cn_namelen = cp - cnp->cn_nameptr;
886 if (cnp->cn_namelen > NAME_MAX) {
887 error = ENAMETOOLONG;
890 #ifdef NAMEI_DIAGNOSTIC
893 printf("{%s}: ", cnp->cn_nameptr);
896 prev_ni_pathlen = ndp->ni_pathlen;
897 ndp->ni_pathlen -= cnp->cn_namelen;
898 KASSERT(ndp->ni_pathlen <= PATH_MAX,
899 ("%s: ni_pathlen underflow to %zd\n", __func__, ndp->ni_pathlen));
900 prev_ni_next = ndp->ni_next;
904 * Replace multiple slashes by a single slash and trailing slashes
905 * by a null. This must be done before VOP_LOOKUP() because some
906 * fs's don't know about trailing slashes. Remember if there were
907 * trailing slashes to handle symlinks, existing non-directories
908 * and non-existing files that won't be directories specially later.
910 while (*cp == '/' && (cp[1] == '/' || cp[1] == '\0')) {
914 *ndp->ni_next = '\0';
915 cnp->cn_flags |= TRAILINGSLASH;
920 cnp->cn_flags |= MAKEENTRY;
921 if (*cp == '\0' && docache == 0)
922 cnp->cn_flags &= ~MAKEENTRY;
923 if (cnp->cn_namelen == 2 &&
924 cnp->cn_nameptr[1] == '.' && cnp->cn_nameptr[0] == '.')
925 cnp->cn_flags |= ISDOTDOT;
927 cnp->cn_flags &= ~ISDOTDOT;
928 if (*ndp->ni_next == 0)
929 cnp->cn_flags |= ISLASTCN;
931 cnp->cn_flags &= ~ISLASTCN;
933 if ((cnp->cn_flags & ISLASTCN) != 0 &&
934 cnp->cn_namelen == 1 && cnp->cn_nameptr[0] == '.' &&
935 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) {
940 nameicap_tracker_add(ndp, dp);
943 * Check for degenerate name (e.g. / or "")
944 * which is a way of talking about a directory,
945 * e.g. like "/." or ".".
947 if (cnp->cn_nameptr[0] == '\0') {
948 if (dp->v_type != VDIR) {
952 if (cnp->cn_nameiop != LOOKUP) {
962 if (cnp->cn_flags & AUDITVNODE1)
963 AUDIT_ARG_VNODE1(dp);
964 else if (cnp->cn_flags & AUDITVNODE2)
965 AUDIT_ARG_VNODE2(dp);
967 if (!(cnp->cn_flags & (LOCKPARENT | LOCKLEAF)))
969 /* XXX This should probably move to the top of function. */
970 if (cnp->cn_flags & SAVESTART)
971 panic("lookup: SAVESTART");
976 * Handle "..": five special cases.
977 * 0. If doing a capability lookup and lookup_cap_dotdot is
978 * disabled, return ENOTCAPABLE.
979 * 1. Return an error if this is the last component of
980 * the name and the operation is DELETE or RENAME.
981 * 2. If at root directory (e.g. after chroot)
982 * or at absolute root directory
983 * then ignore it so can't get out.
984 * 3. If this vnode is the root of a mounted
985 * filesystem, then replace it with the
986 * vnode which was mounted on so we take the
987 * .. in the other filesystem.
988 * 4. If the vnode is the top directory of
989 * the jail or chroot, don't let them out.
990 * 5. If doing a capability lookup and lookup_cap_dotdot is
991 * enabled, return ENOTCAPABLE if the lookup would escape
992 * from the initial file descriptor directory. Checks are
993 * done by ensuring that namei() already traversed the
994 * result of dotdot lookup.
996 if (cnp->cn_flags & ISDOTDOT) {
997 if ((ndp->ni_lcf & (NI_LCF_STRICTRELATIVE | NI_LCF_CAP_DOTDOT))
998 == NI_LCF_STRICTRELATIVE) {
1000 if (KTRPOINT(curthread, KTR_CAPFAIL))
1001 ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL);
1003 error = ENOTCAPABLE;
1006 if ((cnp->cn_flags & ISLASTCN) != 0 &&
1007 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) {
1012 for (pr = cnp->cn_cred->cr_prison; pr != NULL;
1014 if (dp == pr->pr_root)
1016 if (dp == ndp->ni_rootdir ||
1017 dp == ndp->ni_topdir ||
1020 ((dp->v_vflag & VV_ROOT) != 0 &&
1021 (cnp->cn_flags & NOCROSSMOUNT) != 0)) {
1027 if ((dp->v_vflag & VV_ROOT) == 0)
1029 if (VN_IS_DOOMED(dp)) { /* forced unmount */
1034 dp = dp->v_mount->mnt_vnodecovered;
1038 compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags |
1039 LK_RETRY, ISDOTDOT));
1040 error = nameicap_check_dotdot(ndp, dp);
1043 if (KTRPOINT(curthread, KTR_CAPFAIL))
1044 ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL);
1052 * We now have a segment name to search for, and a directory to search.
1056 error = mac_vnode_check_lookup(cnp->cn_thread->td_ucred, dp, cnp);
1062 ASSERT_VOP_LOCKED(dp, "lookup");
1064 * If we have a shared lock we may need to upgrade the lock for the
1067 if ((cnp->cn_flags & LOCKPARENT) && (cnp->cn_flags & ISLASTCN) &&
1068 dp != vp_crossmp && VOP_ISLOCKED(dp) == LK_SHARED)
1069 vn_lock(dp, LK_UPGRADE|LK_RETRY);
1070 if (VN_IS_DOOMED(dp)) {
1075 * If we're looking up the last component and we need an exclusive
1076 * lock, adjust our lkflags.
1078 if (needs_exclusive_leaf(dp->v_mount, cnp->cn_flags))
1079 cnp->cn_lkflags = LK_EXCLUSIVE;
1080 #ifdef NAMEI_DIAGNOSTIC
1081 vn_printf(dp, "lookup in ");
1083 lkflags_save = cnp->cn_lkflags;
1084 cnp->cn_lkflags = compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags,
1086 error = VOP_LOOKUP(dp, &ndp->ni_vp, cnp);
1087 cnp->cn_lkflags = lkflags_save;
1089 KASSERT(ndp->ni_vp == NULL, ("leaf should be empty"));
1090 #ifdef NAMEI_DIAGNOSTIC
1091 printf("not found\n");
1093 if ((error == ENOENT) &&
1094 (dp->v_vflag & VV_ROOT) && (dp->v_mount != NULL) &&
1095 (dp->v_mount->mnt_flag & MNT_UNION)) {
1097 dp = dp->v_mount->mnt_vnodecovered;
1101 compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags |
1102 LK_RETRY, cnp->cn_flags));
1103 nameicap_tracker_add(ndp, dp);
1107 if (error == ERELOOKUP) {
1115 if (error != EJUSTRETURN)
1118 * At this point, we know we're at the end of the
1119 * pathname. If creating / renaming, we can consider
1120 * allowing the file or directory to be created / renamed,
1121 * provided we're not on a read-only filesystem.
1127 /* trailing slash only allowed for directories */
1128 if ((cnp->cn_flags & TRAILINGSLASH) &&
1129 !(cnp->cn_flags & WILLBEDIR)) {
1133 if ((cnp->cn_flags & LOCKPARENT) == 0)
1136 * We return with ni_vp NULL to indicate that the entry
1137 * doesn't currently exist, leaving a pointer to the
1138 * (possibly locked) directory vnode in ndp->ni_dvp.
1140 if (cnp->cn_flags & SAVESTART) {
1141 ndp->ni_startdir = ndp->ni_dvp;
1142 VREF(ndp->ni_startdir);
1148 #ifdef NAMEI_DIAGNOSTIC
1154 * Check to see if the vnode has been mounted on;
1155 * if so find the root of the mounted filesystem.
1157 while (dp->v_type == VDIR && (mp = dp->v_mountedhere) &&
1158 (cnp->cn_flags & NOCROSSMOUNT) == 0) {
1159 if (vfs_busy(mp, 0))
1162 if (dp != ndp->ni_dvp)
1166 vrefact(vp_crossmp);
1167 ndp->ni_dvp = vp_crossmp;
1168 error = VFS_ROOT(mp, compute_cn_lkflags(mp, cnp->cn_lkflags,
1169 cnp->cn_flags), &tdp);
1171 if (vn_lock(vp_crossmp, LK_SHARED | LK_NOWAIT))
1172 panic("vp_crossmp exclusively locked or reclaimed");
1177 ndp->ni_vp = dp = tdp;
1181 * Check for symbolic link
1183 if ((dp->v_type == VLNK) &&
1184 ((cnp->cn_flags & FOLLOW) || (cnp->cn_flags & TRAILINGSLASH) ||
1185 *ndp->ni_next == '/')) {
1186 cnp->cn_flags |= ISSYMLINK;
1187 if (VN_IS_DOOMED(dp)) {
1189 * We can't know whether the directory was mounted with
1190 * NOSYMFOLLOW, so we can't follow safely.
1195 if (dp->v_mount->mnt_flag & MNT_NOSYMFOLLOW) {
1200 * Symlink code always expects an unlocked dvp.
1202 if (ndp->ni_dvp != ndp->ni_vp) {
1203 VOP_UNLOCK(ndp->ni_dvp);
1204 ni_dvp_unlocked = 1;
1211 * Not a symbolic link that we will follow. Continue with the
1212 * next component if there is any; otherwise, we're done.
1214 KASSERT((cnp->cn_flags & ISLASTCN) || *ndp->ni_next == '/',
1215 ("lookup: invalid path state."));
1218 ndp->ni_pathlen = prev_ni_pathlen;
1219 ndp->ni_next = prev_ni_next;
1220 if (ndp->ni_dvp != dp)
1226 if (cnp->cn_flags & ISDOTDOT) {
1227 error = nameicap_check_dotdot(ndp, ndp->ni_vp);
1230 if (KTRPOINT(curthread, KTR_CAPFAIL))
1231 ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL);
1236 if (*ndp->ni_next == '/') {
1237 cnp->cn_nameptr = ndp->ni_next;
1238 while (*cnp->cn_nameptr == '/') {
1242 if (ndp->ni_dvp != dp)
1249 * If we're processing a path with a trailing slash,
1250 * check that the end result is a directory.
1252 if ((cnp->cn_flags & TRAILINGSLASH) && dp->v_type != VDIR) {
1257 * Disallow directory write attempts on read-only filesystems.
1260 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) {
1264 if (cnp->cn_flags & SAVESTART) {
1265 ndp->ni_startdir = ndp->ni_dvp;
1266 VREF(ndp->ni_startdir);
1269 ni_dvp_unlocked = 2;
1270 if (ndp->ni_dvp != dp)
1274 } else if ((cnp->cn_flags & LOCKPARENT) == 0 && ndp->ni_dvp != dp) {
1275 VOP_UNLOCK(ndp->ni_dvp);
1276 ni_dvp_unlocked = 1;
1279 if (cnp->cn_flags & AUDITVNODE1)
1280 AUDIT_ARG_VNODE1(dp);
1281 else if (cnp->cn_flags & AUDITVNODE2)
1282 AUDIT_ARG_VNODE2(dp);
1284 if ((cnp->cn_flags & LOCKLEAF) == 0)
1288 * FIXME: for lookups which only cross a mount point to fetch the
1289 * root vnode, ni_dvp will be set to vp_crossmp. This can be a problem
1290 * if either WANTPARENT or LOCKPARENT is set.
1293 * Because of shared lookup we may have the vnode shared locked, but
1294 * the caller may want it to be exclusively locked.
1296 if (needs_exclusive_leaf(dp->v_mount, cnp->cn_flags) &&
1297 VOP_ISLOCKED(dp) != LK_EXCLUSIVE) {
1298 vn_lock(dp, LK_UPGRADE | LK_RETRY);
1299 if (VN_IS_DOOMED(dp)) {
1304 if (ndp->ni_vp != NULL) {
1305 if ((cnp->cn_flags & ISDOTDOT) == 0)
1306 nameicap_tracker_add(ndp, ndp->ni_vp);
1307 if ((cnp->cn_flags & (FAILIFEXISTS | ISSYMLINK)) == FAILIFEXISTS)
1313 if (ni_dvp_unlocked != 2) {
1314 if (dp != ndp->ni_dvp && !ni_dvp_unlocked)
1326 * FAILIFEXISTS handling.
1328 * XXX namei called with LOCKPARENT but not LOCKLEAF has the strange
1329 * behaviour of leaving the vnode unlocked if the target is the same
1330 * vnode as the parent.
1332 MPASS((cnp->cn_flags & ISSYMLINK) == 0);
1333 if (ndp->ni_vp == ndp->ni_dvp)
1340 NDFREE(ndp, NDF_ONLY_PNBUF);
1345 * relookup - lookup a path name component
1346 * Used by lookup to re-acquire things.
1349 relookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp)
1351 struct vnode *dp = NULL; /* the directory we are searching */
1352 int rdonly; /* lookup read-only flag bit */
1355 KASSERT(cnp->cn_flags & ISLASTCN,
1356 ("relookup: Not given last component."));
1358 * Setup: break out flag bits into variables.
1360 KASSERT((cnp->cn_flags & (LOCKPARENT | WANTPARENT)) != 0,
1361 ("relookup: parent not wanted"));
1362 rdonly = cnp->cn_flags & RDONLY;
1363 cnp->cn_flags &= ~ISSYMLINK;
1365 cnp->cn_lkflags = LK_EXCLUSIVE;
1366 vn_lock(dp, LK_EXCLUSIVE | LK_RETRY);
1369 * Search a new directory.
1371 * The last component of the filename is left accessible via
1372 * cnp->cn_nameptr for callers that need the name. Callers needing
1373 * the name set the SAVENAME flag. When done, they assume
1374 * responsibility for freeing the pathname buffer.
1376 #ifdef NAMEI_DIAGNOSTIC
1377 printf("{%s}: ", cnp->cn_nameptr);
1381 * Check for "" which represents the root directory after slash
1384 if (cnp->cn_nameptr[0] == '\0') {
1386 * Support only LOOKUP for "/" because lookup()
1387 * can't succeed for CREATE, DELETE and RENAME.
1389 KASSERT(cnp->cn_nameiop == LOOKUP, ("nameiop must be LOOKUP"));
1390 KASSERT(dp->v_type == VDIR, ("dp is not a directory"));
1392 if (!(cnp->cn_flags & LOCKLEAF))
1395 /* XXX This should probably move to the top of function. */
1396 if (cnp->cn_flags & SAVESTART)
1397 panic("lookup: SAVESTART");
1401 if (cnp->cn_flags & ISDOTDOT)
1402 panic ("relookup: lookup on dot-dot");
1405 * We now have a segment name to search for, and a directory to search.
1407 #ifdef NAMEI_DIAGNOSTIC
1408 vn_printf(dp, "search in ");
1410 if ((error = VOP_LOOKUP(dp, vpp, cnp)) != 0) {
1411 KASSERT(*vpp == NULL, ("leaf should be empty"));
1412 if (error != EJUSTRETURN)
1415 * If creating and at end of pathname, then can consider
1416 * allowing file to be created.
1422 /* ASSERT(dvp == ndp->ni_startdir) */
1423 if (cnp->cn_flags & SAVESTART)
1425 if ((cnp->cn_flags & LOCKPARENT) == 0)
1428 * We return with ni_vp NULL to indicate that the entry
1429 * doesn't currently exist, leaving a pointer to the
1430 * (possibly locked) directory vnode in ndp->ni_dvp.
1438 * Disallow directory write attempts on read-only filesystems.
1441 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) {
1450 * Set the parent lock/ref state to the requested state.
1452 if ((cnp->cn_flags & LOCKPARENT) == 0 && dvp != dp)
1455 * Check for symbolic link
1457 KASSERT(dp->v_type != VLNK || !(cnp->cn_flags & FOLLOW),
1458 ("relookup: symlink found.\n"));
1460 /* ASSERT(dvp == ndp->ni_startdir) */
1461 if (cnp->cn_flags & SAVESTART)
1464 if ((cnp->cn_flags & LOCKLEAF) == 0)
1474 * Free data allocated by namei(); see namei(9) for details.
1477 NDFREE_PNBUF(struct nameidata *ndp)
1480 if ((ndp->ni_cnd.cn_flags & HASBUF) != 0) {
1481 MPASS((ndp->ni_cnd.cn_flags & (SAVENAME | SAVESTART)) != 0);
1482 uma_zfree(namei_zone, ndp->ni_cnd.cn_pnbuf);
1483 ndp->ni_cnd.cn_flags &= ~HASBUF;
1488 * NDFREE_PNBUF replacement for callers that know there is no buffer.
1490 * This is a hack. Preferably the VFS layer would not produce anything more
1491 * than it was asked to do. Unfortunately several non-LOOKUP cases can add the
1492 * HASBUF flag to the result. Even then an interface could be implemented where
1493 * the caller specifies what they expected to see in the result and what they
1494 * are going to take care of.
1496 * In the meantime provide this kludge as a trivial replacement for NDFREE_PNBUF
1497 * calls scattered throughout the kernel where we know for a fact the flag must not
1502 NDFREE_NOTHING(struct nameidata *ndp)
1504 struct componentname *cnp;
1507 KASSERT(cnp->cn_nameiop == LOOKUP, ("%s: got non-LOOKUP op %d\n",
1508 __func__, cnp->cn_nameiop));
1509 KASSERT((cnp->cn_flags & (SAVENAME | HASBUF)) == 0,
1510 ("%s: bad flags \%" PRIx64 "\n", __func__, cnp->cn_flags));
1515 (NDFREE)(struct nameidata *ndp, const u_int flags)
1523 if (!(flags & NDF_NO_FREE_PNBUF)) {
1526 if (!(flags & NDF_NO_VP_UNLOCK) &&
1527 (ndp->ni_cnd.cn_flags & LOCKLEAF) && ndp->ni_vp)
1529 if (!(flags & NDF_NO_DVP_UNLOCK) &&
1530 (ndp->ni_cnd.cn_flags & LOCKPARENT) &&
1531 ndp->ni_dvp != ndp->ni_vp)
1533 if (!(flags & NDF_NO_VP_RELE) && ndp->ni_vp) {
1542 VOP_UNLOCK(ndp->ni_vp);
1543 if (!(flags & NDF_NO_DVP_RELE) &&
1544 (ndp->ni_cnd.cn_flags & (LOCKPARENT|WANTPARENT))) {
1553 VOP_UNLOCK(ndp->ni_dvp);
1554 if (!(flags & NDF_NO_STARTDIR_RELE) &&
1555 (ndp->ni_cnd.cn_flags & SAVESTART)) {
1556 vrele(ndp->ni_startdir);
1557 ndp->ni_startdir = NULL;
1563 * Validate the final state of ndp after the lookup.
1565 * Historically filesystems were allowed to modify cn_flags. Most notably they
1566 * can add SAVENAME to the request, resulting in HASBUF and pushing subsequent
1567 * clean up to the consumer. In practice this seems to only concern != LOOKUP
1570 * As a step towards stricter API contract this routine validates the state to
1571 * clean up. Note validation is a work in progress with the intent of becoming
1572 * stricter over time.
1574 #define NDMODIFYINGFLAGS (LOCKLEAF | LOCKPARENT | WANTPARENT | SAVENAME | SAVESTART | HASBUF)
1576 NDVALIDATE(struct nameidata *ndp)
1578 struct componentname *cnp;
1579 u_int64_t used, orig;
1582 orig = cnp->cn_origflags;
1583 used = cnp->cn_flags;
1584 switch (cnp->cn_nameiop) {
1587 * For plain lookup we require strict conformance -- nothing
1588 * to clean up if it was not requested by the caller.
1590 orig &= NDMODIFYINGFLAGS;
1591 used &= NDMODIFYINGFLAGS;
1592 if ((orig & (SAVENAME | SAVESTART)) != 0)
1602 * Some filesystems set SAVENAME to provoke HASBUF, accomodate
1603 * for it until it gets fixed.
1605 orig &= NDMODIFYINGFLAGS;
1606 orig |= (SAVENAME | HASBUF);
1607 used &= NDMODIFYINGFLAGS;
1608 used |= (SAVENAME | HASBUF);
1616 panic("%s: mismatched flags for op %d: added %" PRIx64 ", "
1617 "removed %" PRIx64" (%" PRIx64" != %" PRIx64"; stored %" PRIx64" != %" PRIx64")",
1618 __func__, cnp->cn_nameiop, used & ~orig, orig &~ used,
1619 orig, used, cnp->cn_origflags, cnp->cn_flags);
1624 * Determine if there is a suitable alternate filename under the specified
1625 * prefix for the specified path. If the create flag is set, then the
1626 * alternate prefix will be used so long as the parent directory exists.
1627 * This is used by the various compatibility ABIs so that Linux binaries prefer
1628 * files under /compat/linux for example. The chosen path (whether under
1629 * the prefix or under /) is returned in a kernel malloc'd buffer pointed
1630 * to by pathbuf. The caller is responsible for free'ing the buffer from
1631 * the M_TEMP bucket if one is returned.
1634 kern_alternate_path(struct thread *td, const char *prefix, const char *path,
1635 enum uio_seg pathseg, char **pathbuf, int create, int dirfd)
1637 struct nameidata nd, ndroot;
1638 char *ptr, *buf, *cp;
1642 buf = (char *) malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
1645 /* Copy the prefix into the new pathname as a starting point. */
1646 len = strlcpy(buf, prefix, MAXPATHLEN);
1647 if (len >= MAXPATHLEN) {
1652 sz = MAXPATHLEN - len;
1655 /* Append the filename to the prefix. */
1656 if (pathseg == UIO_SYSSPACE)
1657 error = copystr(path, ptr, sz, &len);
1659 error = copyinstr(path, ptr, sz, &len);
1667 /* Only use a prefix with absolute pathnames. */
1673 if (dirfd != AT_FDCWD) {
1675 * We want the original because the "prefix" is
1676 * included in the already opened dirfd.
1678 bcopy(ptr, buf, len);
1683 * We know that there is a / somewhere in this pathname.
1684 * Search backwards for it, to find the file's parent dir
1685 * to see if it exists in the alternate tree. If it does,
1686 * and we want to create a file (cflag is set). We don't
1687 * need to worry about the root comparison in this case.
1691 for (cp = &ptr[len] - 1; *cp != '/'; cp--);
1694 NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_SYSSPACE, buf, td);
1700 NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_SYSSPACE, buf, td);
1707 * We now compare the vnode of the prefix to the one
1708 * vnode asked. If they resolve to be the same, then we
1709 * ignore the match so that the real root gets used.
1710 * This avoids the problem of traversing "../.." to find the
1711 * root directory and never finding it, because "/" resolves
1712 * to the emulation root directory. This is expensive :-(
1714 NDINIT(&ndroot, LOOKUP, FOLLOW, UIO_SYSSPACE, prefix,
1717 /* We shouldn't ever get an error from this namei(). */
1718 error = namei(&ndroot);
1720 if (nd.ni_vp == ndroot.ni_vp)
1723 NDFREE(&ndroot, NDF_ONLY_PNBUF);
1724 vrele(ndroot.ni_vp);
1728 NDFREE(&nd, NDF_ONLY_PNBUF);
1732 /* If there was an error, use the original path name. */
1734 bcopy(ptr, buf, len);