2 * SPDX-License-Identifier: BSD-3-Clause
4 * Copyright (c) 1982, 1986, 1989, 1993
5 * The Regents of the University of California. All rights reserved.
6 * (c) UNIX System Laboratories, Inc.
7 * All or some portions of this file are derived from material licensed
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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;
301 startdir_used = false;
305 #ifdef CAPABILITY_MODE
307 * In capability mode, lookups must be restricted to happen in
308 * the subtree with the root specified by the file descriptor:
309 * - The root must be real file descriptor, not the pseudo-descriptor
311 * - The passed path must be relative and not absolute.
312 * - If lookup_cap_dotdot is disabled, path must not contain the
314 * - If lookup_cap_dotdot is enabled, we verify that all '..'
315 * components lookups result in the directories which were
316 * previously walked by us, which prevents an escape from
319 if (IN_CAPABILITY_MODE(td) && (cnp->cn_flags & NOCAPCHECK) == 0) {
320 ndp->ni_lcf |= NI_LCF_STRICTRELATIVE;
321 ndp->ni_resflags |= NIRES_STRICTREL;
322 if (ndp->ni_dirfd == AT_FDCWD) {
324 if (KTRPOINT(td, KTR_CAPFAIL))
325 ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL);
334 * Get starting point for the translation.
338 * The reference on ni_rootdir is acquired in the block below to avoid
339 * back-to-back atomics for absolute lookups.
341 ndp->ni_rootdir = pwd->pwd_rdir;
342 ndp->ni_topdir = pwd->pwd_jdir;
344 if (cnp->cn_pnbuf[0] == '/') {
345 ndp->ni_resflags |= NIRES_ABS;
346 error = namei_handle_root(ndp, dpp);
348 if (ndp->ni_startdir != NULL) {
349 *dpp = ndp->ni_startdir;
350 startdir_used = true;
351 } else if (ndp->ni_dirfd == AT_FDCWD) {
352 *dpp = pwd->pwd_cdir;
355 rights = *ndp->ni_rightsneeded;
356 cap_rights_set_one(&rights, CAP_LOOKUP);
358 if (cnp->cn_flags & AUDITVNODE1)
359 AUDIT_ARG_ATFD1(ndp->ni_dirfd);
360 if (cnp->cn_flags & AUDITVNODE2)
361 AUDIT_ARG_ATFD2(ndp->ni_dirfd);
363 * Effectively inlined fgetvp_rights, because
364 * we need to inspect the file as well as
365 * grabbing the vnode. No check for O_PATH,
366 * files to implement its semantic.
368 error = fget_cap(td, ndp->ni_dirfd, &rights,
369 &dfp, &ndp->ni_filecaps);
372 * Preserve the error; it should either be EBADF
373 * or capability-related, both of which can be
374 * safely returned to the caller.
377 if (dfp->f_ops == &badfileops) {
379 } else if (dfp->f_vnode == NULL) {
385 if ((dfp->f_flag & FSEARCH) != 0)
386 cnp->cn_flags |= NOEXECCHECK;
392 * If file descriptor doesn't have all rights,
393 * all lookups relative to it must also be
397 if (!cap_rights_contains(&ndp->ni_filecaps.fc_rights,
399 ndp->ni_filecaps.fc_fcntls != CAP_FCNTL_ALL ||
400 ndp->ni_filecaps.fc_nioctls != -1) {
401 ndp->ni_lcf |= NI_LCF_STRICTRELATIVE;
402 ndp->ni_resflags |= NIRES_STRICTREL;
406 if (error == 0 && (*dpp)->v_type != VDIR &&
407 (cnp->cn_pnbuf[0] != '\0' ||
408 (cnp->cn_flags & EMPTYPATH) == 0))
411 if (error == 0 && (cnp->cn_flags & RBENEATH) != 0) {
412 if (cnp->cn_pnbuf[0] == '/') {
414 } else if ((ndp->ni_lcf & NI_LCF_STRICTRELATIVE) == 0) {
415 ndp->ni_lcf |= NI_LCF_STRICTRELATIVE |
421 * If we are auditing the kernel pathname, save the user pathname.
423 if (cnp->cn_flags & AUDITVNODE1)
424 AUDIT_ARG_UPATH1_VP(td, ndp->ni_rootdir, *dpp, cnp->cn_pnbuf);
425 if (cnp->cn_flags & AUDITVNODE2)
426 AUDIT_ARG_UPATH2_VP(td, ndp->ni_rootdir, *dpp, cnp->cn_pnbuf);
427 if (ndp->ni_startdir != NULL && !startdir_used)
428 vrele(ndp->ni_startdir);
435 if ((ndp->ni_lcf & NI_LCF_STRICTRELATIVE) != 0 &&
436 lookup_cap_dotdot != 0)
437 ndp->ni_lcf |= NI_LCF_CAP_DOTDOT;
438 SDT_PROBE4(vfs, namei, lookup, entry, *dpp, cnp->cn_pnbuf,
439 cnp->cn_flags, false);
445 namei_getpath(struct nameidata *ndp)
447 struct componentname *cnp;
453 * Get a buffer for the name to be translated, and copy the
454 * name into the buffer.
456 cnp->cn_pnbuf = uma_zalloc(namei_zone, M_WAITOK);
457 if (ndp->ni_segflg == UIO_SYSSPACE) {
458 error = copystr(ndp->ni_dirp, cnp->cn_pnbuf, MAXPATHLEN,
461 error = copyinstr(ndp->ni_dirp, cnp->cn_pnbuf, MAXPATHLEN,
465 if (__predict_false(error != 0))
469 * Don't allow empty pathnames unless EMPTYPATH is specified.
470 * Caller checks for ENOENT as an indication for the empty path.
472 if (__predict_false(*cnp->cn_pnbuf == '\0'))
475 cnp->cn_nameptr = cnp->cn_pnbuf;
480 namei_emptypath(struct nameidata *ndp)
482 struct componentname *cnp;
488 MPASS(*cnp->cn_pnbuf == '\0');
489 MPASS((cnp->cn_flags & EMPTYPATH) != 0);
490 MPASS((cnp->cn_flags & (LOCKPARENT | WANTPARENT)) == 0);
492 ndp->ni_resflags |= NIRES_EMPTYPATH;
493 error = namei_setup(ndp, &dp, &pwd);
495 namei_cleanup_cnp(cnp);
500 * Usecount on dp already provided by namei_setup.
503 namei_cleanup_cnp(cnp);
506 if ((cnp->cn_flags & LOCKLEAF) != 0) {
507 VOP_LOCK(dp, (cnp->cn_flags & LOCKSHARED) != 0 ?
508 LK_SHARED : LK_EXCLUSIVE);
509 if (VN_IS_DOOMED(dp)) {
515 SDT_PROBE4(vfs, namei, lookup, return, 0, ndp->ni_vp, false, ndp);
519 SDT_PROBE4(vfs, namei, lookup, return, error, NULL, false, ndp);
524 * Convert a pathname into a pointer to a locked vnode.
526 * The FOLLOW flag is set when symbolic links are to be followed
527 * when they occur at the end of the name translation process.
528 * Symbolic links are always followed for all other pathname
529 * components other than the last.
531 * The segflg defines whether the name is to be copied from user
532 * space or kernel space.
534 * Overall outline of namei:
537 * get starting directory
538 * while (!done && !error) {
539 * call lookup to search path.
540 * if symbolic link, massage name in buffer and continue
544 namei(struct nameidata *ndp)
546 char *cp; /* pointer into pathname argument */
547 struct vnode *dp; /* the directory we are searching */
548 struct iovec aiov; /* uio for reading symbolic links */
549 struct componentname *cnp;
554 enum cache_fpl_status status;
559 KASSERT(cnp->cn_thread == curthread,
560 ("namei not using curthread"));
561 KASSERT((ndp->ni_debugflags & NAMEI_DBG_CALLED) == 0,
562 ("%s: repeated call to namei without NDREINIT", __func__));
563 KASSERT(ndp->ni_debugflags == NAMEI_DBG_INITED,
564 ("%s: bad debugflags %d", __func__, ndp->ni_debugflags));
565 ndp->ni_debugflags |= NAMEI_DBG_CALLED;
566 if (ndp->ni_startdir != NULL)
567 ndp->ni_debugflags |= NAMEI_DBG_HADSTARTDIR;
568 if (cnp->cn_flags & FAILIFEXISTS) {
569 KASSERT(cnp->cn_nameiop == CREATE,
570 ("%s: FAILIFEXISTS passed for op %d", __func__, cnp->cn_nameiop));
572 * The limitation below is to restrict hairy corner cases.
574 KASSERT((cnp->cn_flags & (LOCKPARENT | LOCKLEAF)) == LOCKPARENT,
575 ("%s: FAILIFEXISTS must be passed with LOCKPARENT and without LOCKLEAF",
581 * While NDINIT may seem like a more natural place to do it, there are
582 * callers which directly modify flags past invoking init.
584 cnp->cn_origflags = cnp->cn_flags;
586 ndp->ni_cnd.cn_cred = ndp->ni_cnd.cn_thread->td_ucred;
587 KASSERT(ndp->ni_resflags == 0, ("%s: garbage in ni_resflags: %x\n",
588 __func__, ndp->ni_resflags));
589 KASSERT(cnp->cn_cred && td->td_proc, ("namei: bad cred/proc"));
590 KASSERT((cnp->cn_flags & NAMEI_INTERNAL_FLAGS) == 0,
591 ("namei: unexpected flags: %" PRIx64 "\n",
592 cnp->cn_flags & NAMEI_INTERNAL_FLAGS));
593 if (cnp->cn_flags & NOCACHE)
594 KASSERT(cnp->cn_nameiop != LOOKUP,
595 ("%s: NOCACHE passed with LOOKUP", __func__));
596 MPASS(ndp->ni_startdir == NULL || ndp->ni_startdir->v_type == VDIR ||
597 ndp->ni_startdir->v_type == VBAD);
603 error = namei_getpath(ndp);
604 if (__predict_false(error != 0)) {
605 if (error == ENOENT && (cnp->cn_flags & EMPTYPATH) != 0)
606 return (namei_emptypath(ndp));
607 namei_cleanup_cnp(cnp);
608 SDT_PROBE4(vfs, namei, lookup, return, error, NULL,
614 if (KTRPOINT(td, KTR_NAMEI)) {
615 ktrnamei(cnp->cn_pnbuf);
620 * First try looking up the target without locking any vnodes.
622 * We may need to start from scratch or pick up where it left off.
624 error = cache_fplookup(ndp, &status, &pwd);
626 case CACHE_FPL_STATUS_UNSET:
627 __assert_unreachable();
629 case CACHE_FPL_STATUS_HANDLED:
633 case CACHE_FPL_STATUS_PARTIAL:
634 TAILQ_INIT(&ndp->ni_cap_tracker);
635 dp = ndp->ni_startdir;
637 case CACHE_FPL_STATUS_DESTROYED:
639 error = namei_getpath(ndp);
640 if (__predict_false(error != 0)) {
641 namei_cleanup_cnp(cnp);
645 case CACHE_FPL_STATUS_ABORTED:
646 TAILQ_INIT(&ndp->ni_cap_tracker);
647 MPASS(ndp->ni_lcf == 0);
648 error = namei_setup(ndp, &dp, &pwd);
650 namei_cleanup_cnp(cnp);
660 ndp->ni_startdir = dp;
666 * If not a symbolic link, we're done.
668 if ((cnp->cn_flags & ISSYMLINK) == 0) {
669 SDT_PROBE4(vfs, namei, lookup, return, error,
670 (error == 0 ? ndp->ni_vp : NULL), false, ndp);
671 if ((cnp->cn_flags & (SAVENAME | SAVESTART)) == 0) {
672 namei_cleanup_cnp(cnp);
674 cnp->cn_flags |= HASBUF;
675 nameicap_cleanup(ndp);
681 if (ndp->ni_loopcnt++ >= MAXSYMLINKS) {
686 if ((cnp->cn_flags & NOMACCHECK) == 0) {
687 error = mac_vnode_check_readlink(td->td_ucred,
693 if (ndp->ni_pathlen > 1)
694 cp = uma_zalloc(namei_zone, M_WAITOK);
698 aiov.iov_len = MAXPATHLEN;
699 auio.uio_iov = &aiov;
702 auio.uio_rw = UIO_READ;
703 auio.uio_segflg = UIO_SYSSPACE;
705 auio.uio_resid = MAXPATHLEN;
706 error = VOP_READLINK(ndp->ni_vp, &auio, cnp->cn_cred);
708 if (ndp->ni_pathlen > 1)
709 uma_zfree(namei_zone, cp);
712 linklen = MAXPATHLEN - auio.uio_resid;
714 if (ndp->ni_pathlen > 1)
715 uma_zfree(namei_zone, cp);
719 if (linklen + ndp->ni_pathlen > MAXPATHLEN) {
720 if (ndp->ni_pathlen > 1)
721 uma_zfree(namei_zone, cp);
722 error = ENAMETOOLONG;
725 if (ndp->ni_pathlen > 1) {
726 bcopy(ndp->ni_next, cp + linklen, ndp->ni_pathlen);
727 uma_zfree(namei_zone, cnp->cn_pnbuf);
730 cnp->cn_pnbuf[linklen] = '\0';
731 ndp->ni_pathlen += linklen;
735 * Check if root directory should replace current directory.
737 cnp->cn_nameptr = cnp->cn_pnbuf;
738 if (*(cnp->cn_nameptr) == '/') {
740 error = namei_handle_root(ndp, &dp);
750 SDT_PROBE4(vfs, namei, lookup, return, error, NULL, false, ndp);
751 namei_cleanup_cnp(cnp);
752 nameicap_cleanup(ndp);
758 compute_cn_lkflags(struct mount *mp, int lkflags, int cnflags)
761 if (mp == NULL || ((lkflags & LK_SHARED) &&
762 (!(mp->mnt_kern_flag & MNTK_LOOKUP_SHARED) ||
763 ((cnflags & ISDOTDOT) &&
764 (mp->mnt_kern_flag & MNTK_LOOKUP_EXCL_DOTDOT))))) {
765 lkflags &= ~LK_SHARED;
766 lkflags |= LK_EXCLUSIVE;
768 lkflags |= LK_NODDLKTREAT;
773 needs_exclusive_leaf(struct mount *mp, int flags)
777 * Intermediate nodes can use shared locks, we only need to
778 * force an exclusive lock for leaf nodes.
780 if ((flags & (ISLASTCN | LOCKLEAF)) != (ISLASTCN | LOCKLEAF))
783 /* Always use exclusive locks if LOCKSHARED isn't set. */
784 if (!(flags & LOCKSHARED))
788 * For lookups during open(), if the mount point supports
789 * extended shared operations, then use a shared lock for the
790 * leaf node, otherwise use an exclusive lock.
792 if ((flags & ISOPEN) != 0)
793 return (!MNT_EXTENDED_SHARED(mp));
796 * Lookup requests outside of open() that specify LOCKSHARED
797 * only need a shared lock on the leaf vnode.
803 * Various filesystems expect to be able to copy a name component with length
804 * bounded by NAME_MAX into a directory entry buffer of size MAXNAMLEN. Make
805 * sure that these are the same size.
807 _Static_assert(MAXNAMLEN == NAME_MAX,
808 "MAXNAMLEN and NAME_MAX have different values");
812 * This is a very central and rather complicated routine.
814 * The pathname is pointed to by ni_ptr and is of length ni_pathlen.
815 * The starting directory is taken from ni_startdir. The pathname is
816 * descended until done, or a symbolic link is encountered. The variable
817 * ni_more is clear if the path is completed; it is set to one if a
818 * symbolic link needing interpretation is encountered.
820 * The flag argument is LOOKUP, CREATE, RENAME, or DELETE depending on
821 * whether the name is to be looked up, created, renamed, or deleted.
822 * When CREATE, RENAME, or DELETE is specified, information usable in
823 * creating, renaming, or deleting a directory entry may be calculated.
824 * If flag has LOCKPARENT or'ed into it, the parent directory is returned
825 * locked. If flag has WANTPARENT or'ed into it, the parent directory is
826 * returned unlocked. Otherwise the parent directory is not returned. If
827 * the target of the pathname exists and LOCKLEAF is or'ed into the flag
828 * the target is returned locked, otherwise it is returned unlocked.
829 * When creating or renaming and LOCKPARENT is specified, the target may not
830 * be ".". When deleting and LOCKPARENT is specified, the target may be ".".
832 * Overall outline of lookup:
835 * identify next component of name at ndp->ni_ptr
836 * handle degenerate case where name is null string
837 * if .. and crossing mount points and on mounted filesys, find parent
838 * call VOP_LOOKUP routine for next component name
839 * directory vnode returned in ni_dvp, unlocked unless LOCKPARENT set
840 * component vnode returned in ni_vp (if it exists), locked.
841 * if result vnode is mounted on and crossing mount points,
842 * find mounted on vnode
843 * if more components of name, do next level at dirloop
844 * return the answer in ni_vp, locked if LOCKLEAF set
845 * if LOCKPARENT set, return locked parent in ni_dvp
846 * if WANTPARENT set, return unlocked parent in ni_dvp
849 lookup(struct nameidata *ndp)
851 char *cp; /* pointer into pathname argument */
852 char *prev_ni_next; /* saved ndp->ni_next */
853 char *nulchar; /* location of '\0' in cn_pnbuf */
854 struct vnode *dp = NULL; /* the directory we are searching */
855 struct vnode *tdp; /* saved dp */
856 struct mount *mp; /* mount table entry */
858 size_t prev_ni_pathlen; /* saved ndp->ni_pathlen */
859 int docache; /* == 0 do not cache last component */
860 int wantparent; /* 1 => wantparent or lockparent flag */
861 int rdonly; /* lookup read-only flag bit */
863 int dpunlocked = 0; /* dp has already been unlocked */
864 int relookup = 0; /* do not consume the path component */
865 struct componentname *cnp = &ndp->ni_cnd;
870 * Setup: break out flag bits into variables.
873 wantparent = cnp->cn_flags & (LOCKPARENT | WANTPARENT);
874 KASSERT(cnp->cn_nameiop == LOOKUP || wantparent,
875 ("CREATE, DELETE, RENAME require LOCKPARENT or WANTPARENT."));
877 * When set to zero, docache causes the last component of the
878 * pathname to be deleted from the cache and the full lookup
879 * of the name to be done (via VOP_CACHEDLOOKUP()). Often
880 * filesystems need some pre-computed values that are made
881 * during the full lookup, for instance UFS sets dp->i_offset.
883 * The docache variable is set to zero when requested by the
884 * NOCACHE flag and for all modifying operations except CREATE.
886 docache = (cnp->cn_flags & NOCACHE) ^ NOCACHE;
887 if (cnp->cn_nameiop == DELETE ||
888 (wantparent && cnp->cn_nameiop != CREATE &&
889 cnp->cn_nameiop != LOOKUP))
891 rdonly = cnp->cn_flags & RDONLY;
892 cnp->cn_flags &= ~ISSYMLINK;
895 * We use shared locks until we hit the parent of the last cn then
896 * we adjust based on the requesting flags.
898 cnp->cn_lkflags = LK_SHARED;
899 dp = ndp->ni_startdir;
900 ndp->ni_startdir = NULLVP;
902 compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags | LK_RETRY,
907 * Search a new directory.
909 * The last component of the filename is left accessible via
910 * cnp->cn_nameptr for callers that need the name. Callers needing
911 * the name set the SAVENAME flag. When done, they assume
912 * responsibility for freeing the pathname buffer.
914 * Store / as a temporary sentinel so that we only have one character
915 * to test for. Pathnames tend to be short so this should not be
916 * resulting in cache misses.
918 nulchar = &cnp->cn_nameptr[ndp->ni_pathlen - 1];
919 KASSERT(*nulchar == '\0',
920 ("%s: expected nul at %p; string [%s]\n", __func__, nulchar,
923 for (cp = cnp->cn_nameptr; *cp != '/'; cp++) {
925 ("%s: encountered unexpected nul; string [%s]\n", __func__,
930 cnp->cn_namelen = cp - cnp->cn_nameptr;
931 if (cnp->cn_namelen > NAME_MAX) {
932 error = ENAMETOOLONG;
935 #ifdef NAMEI_DIAGNOSTIC
938 printf("{%s}: ", cnp->cn_nameptr);
941 prev_ni_pathlen = ndp->ni_pathlen;
942 ndp->ni_pathlen -= cnp->cn_namelen;
943 KASSERT(ndp->ni_pathlen <= PATH_MAX,
944 ("%s: ni_pathlen underflow to %zd\n", __func__, ndp->ni_pathlen));
945 prev_ni_next = ndp->ni_next;
949 * Replace multiple slashes by a single slash and trailing slashes
950 * by a null. This must be done before VOP_LOOKUP() because some
951 * fs's don't know about trailing slashes. Remember if there were
952 * trailing slashes to handle symlinks, existing non-directories
953 * and non-existing files that won't be directories specially later.
955 while (*cp == '/' && (cp[1] == '/' || cp[1] == '\0')) {
959 *ndp->ni_next = '\0';
960 cnp->cn_flags |= TRAILINGSLASH;
965 cnp->cn_flags |= MAKEENTRY;
966 if (*cp == '\0' && docache == 0)
967 cnp->cn_flags &= ~MAKEENTRY;
968 if (cnp->cn_namelen == 2 &&
969 cnp->cn_nameptr[1] == '.' && cnp->cn_nameptr[0] == '.')
970 cnp->cn_flags |= ISDOTDOT;
972 cnp->cn_flags &= ~ISDOTDOT;
973 if (*ndp->ni_next == 0)
974 cnp->cn_flags |= ISLASTCN;
976 cnp->cn_flags &= ~ISLASTCN;
978 if ((cnp->cn_flags & ISLASTCN) != 0 &&
979 cnp->cn_namelen == 1 && cnp->cn_nameptr[0] == '.' &&
980 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) {
985 nameicap_tracker_add(ndp, dp);
988 * Check for degenerate name (e.g. / or "")
989 * which is a way of talking about a directory,
990 * e.g. like "/." or ".".
992 if (cnp->cn_nameptr[0] == '\0') {
993 if (dp->v_type != VDIR) {
997 if (cnp->cn_nameiop != LOOKUP) {
1007 if (cnp->cn_flags & AUDITVNODE1)
1008 AUDIT_ARG_VNODE1(dp);
1009 else if (cnp->cn_flags & AUDITVNODE2)
1010 AUDIT_ARG_VNODE2(dp);
1012 if (!(cnp->cn_flags & (LOCKPARENT | LOCKLEAF)))
1014 /* XXX This should probably move to the top of function. */
1015 if (cnp->cn_flags & SAVESTART)
1016 panic("lookup: SAVESTART");
1021 * Handle "..": five special cases.
1022 * 0. If doing a capability lookup and lookup_cap_dotdot is
1023 * disabled, return ENOTCAPABLE.
1024 * 1. Return an error if this is the last component of
1025 * the name and the operation is DELETE or RENAME.
1026 * 2. If at root directory (e.g. after chroot)
1027 * or at absolute root directory
1028 * then ignore it so can't get out.
1029 * 3. If this vnode is the root of a mounted
1030 * filesystem, then replace it with the
1031 * vnode which was mounted on so we take the
1032 * .. in the other filesystem.
1033 * 4. If the vnode is the top directory of
1034 * the jail or chroot, don't let them out.
1035 * 5. If doing a capability lookup and lookup_cap_dotdot is
1036 * enabled, return ENOTCAPABLE if the lookup would escape
1037 * from the initial file descriptor directory. Checks are
1038 * done by ensuring that namei() already traversed the
1039 * result of dotdot lookup.
1041 if (cnp->cn_flags & ISDOTDOT) {
1042 if ((ndp->ni_lcf & (NI_LCF_STRICTRELATIVE | NI_LCF_CAP_DOTDOT))
1043 == NI_LCF_STRICTRELATIVE) {
1045 if (KTRPOINT(curthread, KTR_CAPFAIL))
1046 ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL);
1048 error = ENOTCAPABLE;
1051 if ((cnp->cn_flags & ISLASTCN) != 0 &&
1052 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) {
1057 for (pr = cnp->cn_cred->cr_prison; pr != NULL;
1059 if (dp == pr->pr_root)
1061 if (dp == ndp->ni_rootdir ||
1062 dp == ndp->ni_topdir ||
1065 ((dp->v_vflag & VV_ROOT) != 0 &&
1066 (cnp->cn_flags & NOCROSSMOUNT) != 0)) {
1072 if ((dp->v_vflag & VV_ROOT) == 0)
1074 if (VN_IS_DOOMED(dp)) { /* forced unmount */
1079 dp = dp->v_mount->mnt_vnodecovered;
1083 compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags |
1084 LK_RETRY, ISDOTDOT));
1085 error = nameicap_check_dotdot(ndp, dp);
1088 if (KTRPOINT(curthread, KTR_CAPFAIL))
1089 ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL);
1097 * We now have a segment name to search for, and a directory to search.
1101 error = mac_vnode_check_lookup(cnp->cn_thread->td_ucred, dp, cnp);
1107 ASSERT_VOP_LOCKED(dp, "lookup");
1109 * If we have a shared lock we may need to upgrade the lock for the
1112 if ((cnp->cn_flags & LOCKPARENT) && (cnp->cn_flags & ISLASTCN) &&
1113 dp != vp_crossmp && VOP_ISLOCKED(dp) == LK_SHARED)
1114 vn_lock(dp, LK_UPGRADE|LK_RETRY);
1115 if (VN_IS_DOOMED(dp)) {
1120 * If we're looking up the last component and we need an exclusive
1121 * lock, adjust our lkflags.
1123 if (needs_exclusive_leaf(dp->v_mount, cnp->cn_flags))
1124 cnp->cn_lkflags = LK_EXCLUSIVE;
1125 #ifdef NAMEI_DIAGNOSTIC
1126 vn_printf(dp, "lookup in ");
1128 lkflags_save = cnp->cn_lkflags;
1129 cnp->cn_lkflags = compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags,
1131 error = VOP_LOOKUP(dp, &ndp->ni_vp, cnp);
1132 cnp->cn_lkflags = lkflags_save;
1134 KASSERT(ndp->ni_vp == NULL, ("leaf should be empty"));
1135 #ifdef NAMEI_DIAGNOSTIC
1136 printf("not found\n");
1138 if ((error == ENOENT) &&
1139 (dp->v_vflag & VV_ROOT) && (dp->v_mount != NULL) &&
1140 (dp->v_mount->mnt_flag & MNT_UNION)) {
1142 dp = dp->v_mount->mnt_vnodecovered;
1146 compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags |
1147 LK_RETRY, cnp->cn_flags));
1148 nameicap_tracker_add(ndp, dp);
1152 if (error == ERELOOKUP) {
1160 if (error != EJUSTRETURN)
1163 * At this point, we know we're at the end of the
1164 * pathname. If creating / renaming, we can consider
1165 * allowing the file or directory to be created / renamed,
1166 * provided we're not on a read-only filesystem.
1172 /* trailing slash only allowed for directories */
1173 if ((cnp->cn_flags & TRAILINGSLASH) &&
1174 !(cnp->cn_flags & WILLBEDIR)) {
1178 if ((cnp->cn_flags & LOCKPARENT) == 0)
1181 * We return with ni_vp NULL to indicate that the entry
1182 * doesn't currently exist, leaving a pointer to the
1183 * (possibly locked) directory vnode in ndp->ni_dvp.
1185 if (cnp->cn_flags & SAVESTART) {
1186 ndp->ni_startdir = ndp->ni_dvp;
1187 VREF(ndp->ni_startdir);
1193 #ifdef NAMEI_DIAGNOSTIC
1199 * Check to see if the vnode has been mounted on;
1200 * if so find the root of the mounted filesystem.
1202 while (dp->v_type == VDIR && (mp = dp->v_mountedhere) &&
1203 (cnp->cn_flags & NOCROSSMOUNT) == 0) {
1204 if (vfs_busy(mp, 0))
1207 if (dp != ndp->ni_dvp)
1211 vrefact(vp_crossmp);
1212 ndp->ni_dvp = vp_crossmp;
1213 error = VFS_ROOT(mp, compute_cn_lkflags(mp, cnp->cn_lkflags,
1214 cnp->cn_flags), &tdp);
1216 if (vn_lock(vp_crossmp, LK_SHARED | LK_NOWAIT))
1217 panic("vp_crossmp exclusively locked or reclaimed");
1222 ndp->ni_vp = dp = tdp;
1226 * Check for symbolic link
1228 if ((dp->v_type == VLNK) &&
1229 ((cnp->cn_flags & FOLLOW) || (cnp->cn_flags & TRAILINGSLASH) ||
1230 *ndp->ni_next == '/')) {
1231 cnp->cn_flags |= ISSYMLINK;
1232 if (VN_IS_DOOMED(dp)) {
1234 * We can't know whether the directory was mounted with
1235 * NOSYMFOLLOW, so we can't follow safely.
1240 if (dp->v_mount->mnt_flag & MNT_NOSYMFOLLOW) {
1245 * Symlink code always expects an unlocked dvp.
1247 if (ndp->ni_dvp != ndp->ni_vp) {
1248 VOP_UNLOCK(ndp->ni_dvp);
1249 ni_dvp_unlocked = 1;
1256 * Not a symbolic link that we will follow. Continue with the
1257 * next component if there is any; otherwise, we're done.
1259 KASSERT((cnp->cn_flags & ISLASTCN) || *ndp->ni_next == '/',
1260 ("lookup: invalid path state."));
1263 ndp->ni_pathlen = prev_ni_pathlen;
1264 ndp->ni_next = prev_ni_next;
1265 if (ndp->ni_dvp != dp)
1271 if (cnp->cn_flags & ISDOTDOT) {
1272 error = nameicap_check_dotdot(ndp, ndp->ni_vp);
1275 if (KTRPOINT(curthread, KTR_CAPFAIL))
1276 ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL);
1281 if (*ndp->ni_next == '/') {
1282 cnp->cn_nameptr = ndp->ni_next;
1283 while (*cnp->cn_nameptr == '/') {
1287 if (ndp->ni_dvp != dp)
1294 * If we're processing a path with a trailing slash,
1295 * check that the end result is a directory.
1297 if ((cnp->cn_flags & TRAILINGSLASH) && dp->v_type != VDIR) {
1302 * Disallow directory write attempts on read-only filesystems.
1305 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) {
1309 if (cnp->cn_flags & SAVESTART) {
1310 ndp->ni_startdir = ndp->ni_dvp;
1311 VREF(ndp->ni_startdir);
1314 ni_dvp_unlocked = 2;
1315 if (ndp->ni_dvp != dp)
1319 } else if ((cnp->cn_flags & LOCKPARENT) == 0 && ndp->ni_dvp != dp) {
1320 VOP_UNLOCK(ndp->ni_dvp);
1321 ni_dvp_unlocked = 1;
1324 if (cnp->cn_flags & AUDITVNODE1)
1325 AUDIT_ARG_VNODE1(dp);
1326 else if (cnp->cn_flags & AUDITVNODE2)
1327 AUDIT_ARG_VNODE2(dp);
1329 if ((cnp->cn_flags & LOCKLEAF) == 0)
1333 * FIXME: for lookups which only cross a mount point to fetch the
1334 * root vnode, ni_dvp will be set to vp_crossmp. This can be a problem
1335 * if either WANTPARENT or LOCKPARENT is set.
1338 * Because of shared lookup we may have the vnode shared locked, but
1339 * the caller may want it to be exclusively locked.
1341 if (needs_exclusive_leaf(dp->v_mount, cnp->cn_flags) &&
1342 VOP_ISLOCKED(dp) != LK_EXCLUSIVE) {
1343 vn_lock(dp, LK_UPGRADE | LK_RETRY);
1344 if (VN_IS_DOOMED(dp)) {
1349 if (ndp->ni_vp != NULL) {
1350 if ((cnp->cn_flags & ISDOTDOT) == 0)
1351 nameicap_tracker_add(ndp, ndp->ni_vp);
1352 if ((cnp->cn_flags & (FAILIFEXISTS | ISSYMLINK)) == FAILIFEXISTS)
1358 if (ni_dvp_unlocked != 2) {
1359 if (dp != ndp->ni_dvp && !ni_dvp_unlocked)
1371 * FAILIFEXISTS handling.
1373 * XXX namei called with LOCKPARENT but not LOCKLEAF has the strange
1374 * behaviour of leaving the vnode unlocked if the target is the same
1375 * vnode as the parent.
1377 MPASS((cnp->cn_flags & ISSYMLINK) == 0);
1378 if (ndp->ni_vp == ndp->ni_dvp)
1385 NDFREE(ndp, NDF_ONLY_PNBUF);
1390 * relookup - lookup a path name component
1391 * Used by lookup to re-acquire things.
1394 relookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp)
1396 struct vnode *dp = NULL; /* the directory we are searching */
1397 int rdonly; /* lookup read-only flag bit */
1400 KASSERT(cnp->cn_flags & ISLASTCN,
1401 ("relookup: Not given last component."));
1403 * Setup: break out flag bits into variables.
1405 KASSERT((cnp->cn_flags & (LOCKPARENT | WANTPARENT)) != 0,
1406 ("relookup: parent not wanted"));
1407 rdonly = cnp->cn_flags & RDONLY;
1408 cnp->cn_flags &= ~ISSYMLINK;
1410 cnp->cn_lkflags = LK_EXCLUSIVE;
1411 vn_lock(dp, LK_EXCLUSIVE | LK_RETRY);
1414 * Search a new directory.
1416 * The last component of the filename is left accessible via
1417 * cnp->cn_nameptr for callers that need the name. Callers needing
1418 * the name set the SAVENAME flag. When done, they assume
1419 * responsibility for freeing the pathname buffer.
1421 #ifdef NAMEI_DIAGNOSTIC
1422 printf("{%s}: ", cnp->cn_nameptr);
1426 * Check for "" which represents the root directory after slash
1429 if (cnp->cn_nameptr[0] == '\0') {
1431 * Support only LOOKUP for "/" because lookup()
1432 * can't succeed for CREATE, DELETE and RENAME.
1434 KASSERT(cnp->cn_nameiop == LOOKUP, ("nameiop must be LOOKUP"));
1435 KASSERT(dp->v_type == VDIR, ("dp is not a directory"));
1437 if (!(cnp->cn_flags & LOCKLEAF))
1440 /* XXX This should probably move to the top of function. */
1441 if (cnp->cn_flags & SAVESTART)
1442 panic("lookup: SAVESTART");
1446 if (cnp->cn_flags & ISDOTDOT)
1447 panic ("relookup: lookup on dot-dot");
1450 * We now have a segment name to search for, and a directory to search.
1452 #ifdef NAMEI_DIAGNOSTIC
1453 vn_printf(dp, "search in ");
1455 if ((error = VOP_LOOKUP(dp, vpp, cnp)) != 0) {
1456 KASSERT(*vpp == NULL, ("leaf should be empty"));
1457 if (error != EJUSTRETURN)
1460 * If creating and at end of pathname, then can consider
1461 * allowing file to be created.
1467 /* ASSERT(dvp == ndp->ni_startdir) */
1468 if (cnp->cn_flags & SAVESTART)
1470 if ((cnp->cn_flags & LOCKPARENT) == 0)
1473 * We return with ni_vp NULL to indicate that the entry
1474 * doesn't currently exist, leaving a pointer to the
1475 * (possibly locked) directory vnode in ndp->ni_dvp.
1483 * Disallow directory write attempts on read-only filesystems.
1486 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) {
1495 * Set the parent lock/ref state to the requested state.
1497 if ((cnp->cn_flags & LOCKPARENT) == 0 && dvp != dp)
1500 * Check for symbolic link
1502 KASSERT(dp->v_type != VLNK || !(cnp->cn_flags & FOLLOW),
1503 ("relookup: symlink found.\n"));
1505 /* ASSERT(dvp == ndp->ni_startdir) */
1506 if (cnp->cn_flags & SAVESTART)
1509 if ((cnp->cn_flags & LOCKLEAF) == 0)
1519 * Free data allocated by namei(); see namei(9) for details.
1522 NDFREE_PNBUF(struct nameidata *ndp)
1525 if ((ndp->ni_cnd.cn_flags & HASBUF) != 0) {
1526 MPASS((ndp->ni_cnd.cn_flags & (SAVENAME | SAVESTART)) != 0);
1527 uma_zfree(namei_zone, ndp->ni_cnd.cn_pnbuf);
1528 ndp->ni_cnd.cn_flags &= ~HASBUF;
1533 * NDFREE_PNBUF replacement for callers that know there is no buffer.
1535 * This is a hack. Preferably the VFS layer would not produce anything more
1536 * than it was asked to do. Unfortunately several non-LOOKUP cases can add the
1537 * HASBUF flag to the result. Even then an interface could be implemented where
1538 * the caller specifies what they expected to see in the result and what they
1539 * are going to take care of.
1541 * In the meantime provide this kludge as a trivial replacement for NDFREE_PNBUF
1542 * calls scattered throughout the kernel where we know for a fact the flag must not
1547 NDFREE_NOTHING(struct nameidata *ndp)
1549 struct componentname *cnp;
1552 KASSERT(cnp->cn_nameiop == LOOKUP, ("%s: got non-LOOKUP op %d\n",
1553 __func__, cnp->cn_nameiop));
1554 KASSERT((cnp->cn_flags & (SAVENAME | HASBUF)) == 0,
1555 ("%s: bad flags \%" PRIx64 "\n", __func__, cnp->cn_flags));
1560 (NDFREE)(struct nameidata *ndp, const u_int flags)
1568 if (!(flags & NDF_NO_FREE_PNBUF)) {
1571 if (!(flags & NDF_NO_VP_UNLOCK) &&
1572 (ndp->ni_cnd.cn_flags & LOCKLEAF) && ndp->ni_vp)
1574 if (!(flags & NDF_NO_DVP_UNLOCK) &&
1575 (ndp->ni_cnd.cn_flags & LOCKPARENT) &&
1576 ndp->ni_dvp != ndp->ni_vp)
1578 if (!(flags & NDF_NO_VP_RELE) && ndp->ni_vp) {
1587 VOP_UNLOCK(ndp->ni_vp);
1588 if (!(flags & NDF_NO_DVP_RELE) &&
1589 (ndp->ni_cnd.cn_flags & (LOCKPARENT|WANTPARENT))) {
1598 VOP_UNLOCK(ndp->ni_dvp);
1599 if (!(flags & NDF_NO_STARTDIR_RELE) &&
1600 (ndp->ni_cnd.cn_flags & SAVESTART)) {
1601 vrele(ndp->ni_startdir);
1602 ndp->ni_startdir = NULL;
1608 * Validate the final state of ndp after the lookup.
1610 * Historically filesystems were allowed to modify cn_flags. Most notably they
1611 * can add SAVENAME to the request, resulting in HASBUF and pushing subsequent
1612 * clean up to the consumer. In practice this seems to only concern != LOOKUP
1615 * As a step towards stricter API contract this routine validates the state to
1616 * clean up. Note validation is a work in progress with the intent of becoming
1617 * stricter over time.
1619 #define NDMODIFYINGFLAGS (LOCKLEAF | LOCKPARENT | WANTPARENT | SAVENAME | SAVESTART | HASBUF)
1621 NDVALIDATE(struct nameidata *ndp)
1623 struct componentname *cnp;
1624 u_int64_t used, orig;
1627 orig = cnp->cn_origflags;
1628 used = cnp->cn_flags;
1629 switch (cnp->cn_nameiop) {
1632 * For plain lookup we require strict conformance -- nothing
1633 * to clean up if it was not requested by the caller.
1635 orig &= NDMODIFYINGFLAGS;
1636 used &= NDMODIFYINGFLAGS;
1637 if ((orig & (SAVENAME | SAVESTART)) != 0)
1647 * Some filesystems set SAVENAME to provoke HASBUF, accomodate
1648 * for it until it gets fixed.
1650 orig &= NDMODIFYINGFLAGS;
1651 orig |= (SAVENAME | HASBUF);
1652 used &= NDMODIFYINGFLAGS;
1653 used |= (SAVENAME | HASBUF);
1661 panic("%s: mismatched flags for op %d: added %" PRIx64 ", "
1662 "removed %" PRIx64" (%" PRIx64" != %" PRIx64"; stored %" PRIx64" != %" PRIx64")",
1663 __func__, cnp->cn_nameiop, used & ~orig, orig &~ used,
1664 orig, used, cnp->cn_origflags, cnp->cn_flags);
1669 * Determine if there is a suitable alternate filename under the specified
1670 * prefix for the specified path. If the create flag is set, then the
1671 * alternate prefix will be used so long as the parent directory exists.
1672 * This is used by the various compatibility ABIs so that Linux binaries prefer
1673 * files under /compat/linux for example. The chosen path (whether under
1674 * the prefix or under /) is returned in a kernel malloc'd buffer pointed
1675 * to by pathbuf. The caller is responsible for free'ing the buffer from
1676 * the M_TEMP bucket if one is returned.
1679 kern_alternate_path(struct thread *td, const char *prefix, const char *path,
1680 enum uio_seg pathseg, char **pathbuf, int create, int dirfd)
1682 struct nameidata nd, ndroot;
1683 char *ptr, *buf, *cp;
1687 buf = (char *) malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
1690 /* Copy the prefix into the new pathname as a starting point. */
1691 len = strlcpy(buf, prefix, MAXPATHLEN);
1692 if (len >= MAXPATHLEN) {
1697 sz = MAXPATHLEN - len;
1700 /* Append the filename to the prefix. */
1701 if (pathseg == UIO_SYSSPACE)
1702 error = copystr(path, ptr, sz, &len);
1704 error = copyinstr(path, ptr, sz, &len);
1712 /* Only use a prefix with absolute pathnames. */
1718 if (dirfd != AT_FDCWD) {
1720 * We want the original because the "prefix" is
1721 * included in the already opened dirfd.
1723 bcopy(ptr, buf, len);
1728 * We know that there is a / somewhere in this pathname.
1729 * Search backwards for it, to find the file's parent dir
1730 * to see if it exists in the alternate tree. If it does,
1731 * and we want to create a file (cflag is set). We don't
1732 * need to worry about the root comparison in this case.
1736 for (cp = &ptr[len] - 1; *cp != '/'; cp--);
1739 NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_SYSSPACE, buf, td);
1745 NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_SYSSPACE, buf, td);
1752 * We now compare the vnode of the prefix to the one
1753 * vnode asked. If they resolve to be the same, then we
1754 * ignore the match so that the real root gets used.
1755 * This avoids the problem of traversing "../.." to find the
1756 * root directory and never finding it, because "/" resolves
1757 * to the emulation root directory. This is expensive :-(
1759 NDINIT(&ndroot, LOOKUP, FOLLOW, UIO_SYSSPACE, prefix,
1762 /* We shouldn't ever get an error from this namei(). */
1763 error = namei(&ndroot);
1765 if (nd.ni_vp == ndroot.ni_vp)
1768 NDFREE(&ndroot, NDF_ONLY_PNBUF);
1769 vrele(ndroot.ni_vp);
1773 NDFREE(&nd, NDF_ONLY_PNBUF);
1777 /* If there was an error, use the original path name. */
1779 bcopy(ptr, buf, len);