2 * SPDX-License-Identifier: BSD-3-Clause
4 * Copyright (c) 1982, 1986, 1989, 1993
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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 __diagused;
101 const char *file __diagused;
102 int flags, line __diagused;
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 __diagused;
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;
182 if ((ndp->ni_lcf & NI_LCF_CAP_DOTDOT) == 0 || dp->v_type != VDIR)
184 nt = TAILQ_LAST(&ndp->ni_cap_tracker, nameicap_tracker_head);
185 if (nt != NULL && nt->dp == dp)
187 nt = malloc(sizeof(*nt), M_NAMEITRACKER, M_WAITOK);
190 TAILQ_INSERT_TAIL(&ndp->ni_cap_tracker, nt, nm_link);
194 nameicap_cleanup_from(struct nameidata *ndp, struct nameicap_tracker *first)
196 struct nameicap_tracker *nt, *nt1;
199 TAILQ_FOREACH_FROM_SAFE(nt, &ndp->ni_cap_tracker, nm_link, nt1) {
200 TAILQ_REMOVE(&ndp->ni_cap_tracker, nt, nm_link);
202 free(nt, M_NAMEITRACKER);
207 nameicap_cleanup(struct nameidata *ndp)
209 KASSERT(TAILQ_EMPTY(&ndp->ni_cap_tracker) ||
210 (ndp->ni_lcf & NI_LCF_CAP_DOTDOT) != 0, ("not strictrelative"));
211 nameicap_cleanup_from(ndp, NULL);
215 * For dotdot lookups in capability mode, only allow the component
216 * lookup to succeed if the resulting directory was already traversed
217 * during the operation. This catches situations where already
218 * traversed directory is moved to different parent, and then we walk
219 * over it with dotdots.
221 * Also allow to force failure of dotdot lookups for non-local
222 * filesystems, where external agents might assist local lookups to
223 * escape the compartment.
226 nameicap_check_dotdot(struct nameidata *ndp, struct vnode *dp)
228 struct nameicap_tracker *nt;
231 if (dp == NULL || dp->v_type != VDIR || (ndp->ni_lcf &
232 NI_LCF_STRICTRELATIVE) == 0)
234 if ((ndp->ni_lcf & NI_LCF_CAP_DOTDOT) == 0)
235 return (ENOTCAPABLE);
237 if (lookup_cap_dotdot_nonlocal == 0 && mp != NULL &&
238 (mp->mnt_flag & MNT_LOCAL) == 0)
239 return (ENOTCAPABLE);
240 TAILQ_FOREACH_REVERSE(nt, &ndp->ni_cap_tracker, nameicap_tracker_head,
243 nt = TAILQ_NEXT(nt, nm_link);
245 nameicap_cleanup_from(ndp, nt);
249 return (ENOTCAPABLE);
253 namei_cleanup_cnp(struct componentname *cnp)
256 uma_zfree(namei_zone, cnp->cn_pnbuf);
258 cnp->cn_pnbuf = NULL;
259 cnp->cn_nameptr = NULL;
264 namei_handle_root(struct nameidata *ndp, struct vnode **dpp)
266 struct componentname *cnp;
269 if ((ndp->ni_lcf & NI_LCF_STRICTRELATIVE) != 0) {
271 if (KTRPOINT(curthread, KTR_CAPFAIL))
272 ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL);
274 return (ENOTCAPABLE);
276 while (*(cnp->cn_nameptr) == '/') {
280 *dpp = ndp->ni_rootdir;
286 namei_setup(struct nameidata *ndp, struct vnode **dpp, struct pwd **pwdp)
288 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 rights = *ndp->ni_rightsneeded;
354 cap_rights_set_one(&rights, CAP_LOOKUP);
356 if (cnp->cn_flags & AUDITVNODE1)
357 AUDIT_ARG_ATFD1(ndp->ni_dirfd);
358 if (cnp->cn_flags & AUDITVNODE2)
359 AUDIT_ARG_ATFD2(ndp->ni_dirfd);
361 * Effectively inlined fgetvp_rights, because
362 * we need to inspect the file as well as
363 * grabbing the vnode. No check for O_PATH,
364 * files to implement its semantic.
366 error = fget_cap(td, ndp->ni_dirfd, &rights,
367 &dfp, &ndp->ni_filecaps);
370 * Preserve the error; it should either be EBADF
371 * or capability-related, both of which can be
372 * safely returned to the caller.
375 if (dfp->f_ops == &badfileops) {
377 } else if (dfp->f_vnode == NULL) {
383 if ((dfp->f_flag & FSEARCH) != 0)
384 cnp->cn_flags |= NOEXECCHECK;
390 * If file descriptor doesn't have all rights,
391 * all lookups relative to it must also be
395 if (!cap_rights_contains(&ndp->ni_filecaps.fc_rights,
397 ndp->ni_filecaps.fc_fcntls != CAP_FCNTL_ALL ||
398 ndp->ni_filecaps.fc_nioctls != -1) {
399 ndp->ni_lcf |= NI_LCF_STRICTRELATIVE;
400 ndp->ni_resflags |= NIRES_STRICTREL;
404 if (error == 0 && (*dpp)->v_type != VDIR &&
405 (cnp->cn_pnbuf[0] != '\0' ||
406 (cnp->cn_flags & EMPTYPATH) == 0))
409 if (error == 0 && (cnp->cn_flags & RBENEATH) != 0) {
410 if (cnp->cn_pnbuf[0] == '/') {
412 } else if ((ndp->ni_lcf & NI_LCF_STRICTRELATIVE) == 0) {
413 ndp->ni_lcf |= NI_LCF_STRICTRELATIVE |
419 * If we are auditing the kernel pathname, save the user pathname.
421 if (cnp->cn_flags & AUDITVNODE1)
422 AUDIT_ARG_UPATH1_VP(td, ndp->ni_rootdir, *dpp, cnp->cn_pnbuf);
423 if (cnp->cn_flags & AUDITVNODE2)
424 AUDIT_ARG_UPATH2_VP(td, ndp->ni_rootdir, *dpp, cnp->cn_pnbuf);
425 if (ndp->ni_startdir != NULL && !startdir_used)
426 vrele(ndp->ni_startdir);
433 if ((ndp->ni_lcf & NI_LCF_STRICTRELATIVE) != 0 &&
434 lookup_cap_dotdot != 0)
435 ndp->ni_lcf |= NI_LCF_CAP_DOTDOT;
436 SDT_PROBE4(vfs, namei, lookup, entry, *dpp, cnp->cn_pnbuf,
437 cnp->cn_flags, false);
443 namei_getpath(struct nameidata *ndp)
445 struct componentname *cnp;
451 * Get a buffer for the name to be translated, and copy the
452 * name into the buffer.
454 cnp->cn_pnbuf = uma_zalloc(namei_zone, M_WAITOK);
455 if (ndp->ni_segflg == UIO_SYSSPACE) {
456 error = copystr(ndp->ni_dirp, cnp->cn_pnbuf, MAXPATHLEN,
459 error = copyinstr(ndp->ni_dirp, cnp->cn_pnbuf, MAXPATHLEN,
463 if (__predict_false(error != 0))
467 * Don't allow empty pathnames unless EMPTYPATH is specified.
468 * Caller checks for ENOENT as an indication for the empty path.
470 if (__predict_false(*cnp->cn_pnbuf == '\0'))
473 cnp->cn_nameptr = cnp->cn_pnbuf;
478 namei_emptypath(struct nameidata *ndp)
480 struct componentname *cnp;
486 MPASS(*cnp->cn_pnbuf == '\0');
487 MPASS((cnp->cn_flags & EMPTYPATH) != 0);
488 MPASS((cnp->cn_flags & (LOCKPARENT | WANTPARENT)) == 0);
490 ndp->ni_resflags |= NIRES_EMPTYPATH;
491 error = namei_setup(ndp, &dp, &pwd);
493 namei_cleanup_cnp(cnp);
498 * Usecount on dp already provided by namei_setup.
501 namei_cleanup_cnp(cnp);
504 if ((cnp->cn_flags & LOCKLEAF) != 0) {
505 VOP_LOCK(dp, (cnp->cn_flags & LOCKSHARED) != 0 ?
506 LK_SHARED : LK_EXCLUSIVE);
507 if (VN_IS_DOOMED(dp)) {
513 SDT_PROBE4(vfs, namei, lookup, return, 0, ndp->ni_vp, false, ndp);
517 SDT_PROBE4(vfs, namei, lookup, return, error, NULL, false, ndp);
522 * Convert a pathname into a pointer to a locked vnode.
524 * The FOLLOW flag is set when symbolic links are to be followed
525 * when they occur at the end of the name translation process.
526 * Symbolic links are always followed for all other pathname
527 * components other than the last.
529 * The segflg defines whether the name is to be copied from user
530 * space or kernel space.
532 * Overall outline of namei:
535 * get starting directory
536 * while (!done && !error) {
537 * call lookup to search path.
538 * if symbolic link, massage name in buffer and continue
542 namei(struct nameidata *ndp)
544 char *cp; /* pointer into pathname argument */
545 struct vnode *dp; /* the directory we are searching */
546 struct iovec aiov; /* uio for reading symbolic links */
547 struct componentname *cnp;
552 enum cache_fpl_status status;
557 KASSERT((ndp->ni_debugflags & NAMEI_DBG_CALLED) == 0,
558 ("%s: repeated call to namei without NDREINIT", __func__));
559 KASSERT(ndp->ni_debugflags == NAMEI_DBG_INITED,
560 ("%s: bad debugflags %d", __func__, ndp->ni_debugflags));
561 ndp->ni_debugflags |= NAMEI_DBG_CALLED;
562 if (ndp->ni_startdir != NULL)
563 ndp->ni_debugflags |= NAMEI_DBG_HADSTARTDIR;
564 if (cnp->cn_flags & FAILIFEXISTS) {
565 KASSERT(cnp->cn_nameiop == CREATE,
566 ("%s: FAILIFEXISTS passed for op %d", __func__, cnp->cn_nameiop));
568 * The limitation below is to restrict hairy corner cases.
570 KASSERT((cnp->cn_flags & (LOCKPARENT | LOCKLEAF)) == LOCKPARENT,
571 ("%s: FAILIFEXISTS must be passed with LOCKPARENT and without LOCKLEAF",
577 * While NDINIT may seem like a more natural place to do it, there are
578 * callers which directly modify flags past invoking init.
580 cnp->cn_origflags = cnp->cn_flags;
582 ndp->ni_cnd.cn_cred = ndp->ni_cnd.cn_thread->td_ucred;
583 KASSERT(ndp->ni_resflags == 0, ("%s: garbage in ni_resflags: %x\n",
584 __func__, ndp->ni_resflags));
585 KASSERT(cnp->cn_cred && td->td_proc, ("namei: bad cred/proc"));
586 KASSERT((cnp->cn_flags & NAMEI_INTERNAL_FLAGS) == 0,
587 ("namei: unexpected flags: %" PRIx64 "\n",
588 cnp->cn_flags & NAMEI_INTERNAL_FLAGS));
589 if (cnp->cn_flags & NOCACHE)
590 KASSERT(cnp->cn_nameiop != LOOKUP,
591 ("%s: NOCACHE passed with LOOKUP", __func__));
592 MPASS(ndp->ni_startdir == NULL || ndp->ni_startdir->v_type == VDIR ||
593 ndp->ni_startdir->v_type == VBAD);
599 error = namei_getpath(ndp);
600 if (__predict_false(error != 0)) {
601 if (error == ENOENT && (cnp->cn_flags & EMPTYPATH) != 0)
602 return (namei_emptypath(ndp));
603 namei_cleanup_cnp(cnp);
604 SDT_PROBE4(vfs, namei, lookup, return, error, NULL,
610 if (KTRPOINT(td, KTR_NAMEI)) {
611 KASSERT(cnp->cn_thread == curthread,
612 ("namei not using curthread"));
613 ktrnamei(cnp->cn_pnbuf);
618 * First try looking up the target without locking any vnodes.
620 * We may need to start from scratch or pick up where it left off.
622 error = cache_fplookup(ndp, &status, &pwd);
624 case CACHE_FPL_STATUS_UNSET:
625 __assert_unreachable();
627 case CACHE_FPL_STATUS_HANDLED:
631 case CACHE_FPL_STATUS_PARTIAL:
632 TAILQ_INIT(&ndp->ni_cap_tracker);
633 dp = ndp->ni_startdir;
635 case CACHE_FPL_STATUS_DESTROYED:
637 error = namei_getpath(ndp);
638 if (__predict_false(error != 0)) {
639 namei_cleanup_cnp(cnp);
643 case CACHE_FPL_STATUS_ABORTED:
644 TAILQ_INIT(&ndp->ni_cap_tracker);
645 MPASS(ndp->ni_lcf == 0);
646 error = namei_setup(ndp, &dp, &pwd);
648 namei_cleanup_cnp(cnp);
658 ndp->ni_startdir = dp;
664 * If not a symbolic link, we're done.
666 if ((cnp->cn_flags & ISSYMLINK) == 0) {
667 SDT_PROBE4(vfs, namei, lookup, return, error,
668 (error == 0 ? ndp->ni_vp : NULL), false, ndp);
669 if ((cnp->cn_flags & (SAVENAME | SAVESTART)) == 0) {
670 namei_cleanup_cnp(cnp);
672 cnp->cn_flags |= HASBUF;
673 nameicap_cleanup(ndp);
679 if (ndp->ni_loopcnt++ >= MAXSYMLINKS) {
684 if ((cnp->cn_flags & NOMACCHECK) == 0) {
685 error = mac_vnode_check_readlink(td->td_ucred,
691 if (ndp->ni_pathlen > 1)
692 cp = uma_zalloc(namei_zone, M_WAITOK);
696 aiov.iov_len = MAXPATHLEN;
697 auio.uio_iov = &aiov;
700 auio.uio_rw = UIO_READ;
701 auio.uio_segflg = UIO_SYSSPACE;
703 auio.uio_resid = MAXPATHLEN;
704 error = VOP_READLINK(ndp->ni_vp, &auio, cnp->cn_cred);
706 if (ndp->ni_pathlen > 1)
707 uma_zfree(namei_zone, cp);
710 linklen = MAXPATHLEN - auio.uio_resid;
712 if (ndp->ni_pathlen > 1)
713 uma_zfree(namei_zone, cp);
717 if (linklen + ndp->ni_pathlen > MAXPATHLEN) {
718 if (ndp->ni_pathlen > 1)
719 uma_zfree(namei_zone, cp);
720 error = ENAMETOOLONG;
723 if (ndp->ni_pathlen > 1) {
724 bcopy(ndp->ni_next, cp + linklen, ndp->ni_pathlen);
725 uma_zfree(namei_zone, cnp->cn_pnbuf);
728 cnp->cn_pnbuf[linklen] = '\0';
729 ndp->ni_pathlen += linklen;
733 * Check if root directory should replace current directory.
735 cnp->cn_nameptr = cnp->cn_pnbuf;
736 if (*(cnp->cn_nameptr) == '/') {
738 error = namei_handle_root(ndp, &dp);
748 SDT_PROBE4(vfs, namei, lookup, return, error, NULL, false, ndp);
749 namei_cleanup_cnp(cnp);
750 nameicap_cleanup(ndp);
756 compute_cn_lkflags(struct mount *mp, int lkflags, int cnflags)
759 if (mp == NULL || ((lkflags & LK_SHARED) &&
760 (!(mp->mnt_kern_flag & MNTK_LOOKUP_SHARED) ||
761 ((cnflags & ISDOTDOT) &&
762 (mp->mnt_kern_flag & MNTK_LOOKUP_EXCL_DOTDOT))))) {
763 lkflags &= ~LK_SHARED;
764 lkflags |= LK_EXCLUSIVE;
766 lkflags |= LK_NODDLKTREAT;
771 needs_exclusive_leaf(struct mount *mp, int flags)
775 * Intermediate nodes can use shared locks, we only need to
776 * force an exclusive lock for leaf nodes.
778 if ((flags & (ISLASTCN | LOCKLEAF)) != (ISLASTCN | LOCKLEAF))
781 /* Always use exclusive locks if LOCKSHARED isn't set. */
782 if (!(flags & LOCKSHARED))
786 * For lookups during open(), if the mount point supports
787 * extended shared operations, then use a shared lock for the
788 * leaf node, otherwise use an exclusive lock.
790 if ((flags & ISOPEN) != 0)
791 return (!MNT_EXTENDED_SHARED(mp));
794 * Lookup requests outside of open() that specify LOCKSHARED
795 * only need a shared lock on the leaf vnode.
801 * Various filesystems expect to be able to copy a name component with length
802 * bounded by NAME_MAX into a directory entry buffer of size MAXNAMLEN. Make
803 * sure that these are the same size.
805 _Static_assert(MAXNAMLEN == NAME_MAX,
806 "MAXNAMLEN and NAME_MAX have different values");
810 * This is a very central and rather complicated routine.
812 * The pathname is pointed to by ni_ptr and is of length ni_pathlen.
813 * The starting directory is taken from ni_startdir. The pathname is
814 * descended until done, or a symbolic link is encountered. The variable
815 * ni_more is clear if the path is completed; it is set to one if a
816 * symbolic link needing interpretation is encountered.
818 * The flag argument is LOOKUP, CREATE, RENAME, or DELETE depending on
819 * whether the name is to be looked up, created, renamed, or deleted.
820 * When CREATE, RENAME, or DELETE is specified, information usable in
821 * creating, renaming, or deleting a directory entry may be calculated.
822 * If flag has LOCKPARENT or'ed into it, the parent directory is returned
823 * locked. If flag has WANTPARENT or'ed into it, the parent directory is
824 * returned unlocked. Otherwise the parent directory is not returned. If
825 * the target of the pathname exists and LOCKLEAF is or'ed into the flag
826 * the target is returned locked, otherwise it is returned unlocked.
827 * When creating or renaming and LOCKPARENT is specified, the target may not
828 * be ".". When deleting and LOCKPARENT is specified, the target may be ".".
830 * Overall outline of lookup:
833 * identify next component of name at ndp->ni_ptr
834 * handle degenerate case where name is null string
835 * if .. and crossing mount points and on mounted filesys, find parent
836 * call VOP_LOOKUP routine for next component name
837 * directory vnode returned in ni_dvp, unlocked unless LOCKPARENT set
838 * component vnode returned in ni_vp (if it exists), locked.
839 * if result vnode is mounted on and crossing mount points,
840 * find mounted on vnode
841 * if more components of name, do next level at dirloop
842 * return the answer in ni_vp, locked if LOCKLEAF set
843 * if LOCKPARENT set, return locked parent in ni_dvp
844 * if WANTPARENT set, return unlocked parent in ni_dvp
847 lookup(struct nameidata *ndp)
849 char *cp; /* pointer into pathname argument */
850 char *prev_ni_next; /* saved ndp->ni_next */
851 char *nulchar; /* location of '\0' in cn_pnbuf */
852 struct vnode *dp = NULL; /* the directory we are searching */
853 struct vnode *tdp; /* saved dp */
854 struct mount *mp; /* mount table entry */
856 size_t prev_ni_pathlen; /* saved ndp->ni_pathlen */
857 int docache; /* == 0 do not cache last component */
858 int wantparent; /* 1 => wantparent or lockparent flag */
859 int rdonly; /* lookup read-only flag bit */
861 int dpunlocked = 0; /* dp has already been unlocked */
862 int relookup = 0; /* do not consume the path component */
863 struct componentname *cnp = &ndp->ni_cnd;
868 * Setup: break out flag bits into variables.
871 wantparent = cnp->cn_flags & (LOCKPARENT | WANTPARENT);
872 KASSERT(cnp->cn_nameiop == LOOKUP || wantparent,
873 ("CREATE, DELETE, RENAME require LOCKPARENT or WANTPARENT."));
875 * When set to zero, docache causes the last component of the
876 * pathname to be deleted from the cache and the full lookup
877 * of the name to be done (via VOP_CACHEDLOOKUP()). Often
878 * filesystems need some pre-computed values that are made
879 * during the full lookup, for instance UFS sets dp->i_offset.
881 * The docache variable is set to zero when requested by the
882 * NOCACHE flag and for all modifying operations except CREATE.
884 docache = (cnp->cn_flags & NOCACHE) ^ NOCACHE;
885 if (cnp->cn_nameiop == DELETE ||
886 (wantparent && cnp->cn_nameiop != CREATE &&
887 cnp->cn_nameiop != LOOKUP))
889 rdonly = cnp->cn_flags & RDONLY;
890 cnp->cn_flags &= ~ISSYMLINK;
893 * We use shared locks until we hit the parent of the last cn then
894 * we adjust based on the requesting flags.
896 cnp->cn_lkflags = LK_SHARED;
897 dp = ndp->ni_startdir;
898 ndp->ni_startdir = NULLVP;
900 compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags | LK_RETRY,
905 * Search a new directory.
907 * The last component of the filename is left accessible via
908 * cnp->cn_nameptr for callers that need the name. Callers needing
909 * the name set the SAVENAME flag. When done, they assume
910 * responsibility for freeing the pathname buffer.
912 * Store / as a temporary sentinel so that we only have one character
913 * to test for. Pathnames tend to be short so this should not be
914 * resulting in cache misses.
916 nulchar = &cnp->cn_nameptr[ndp->ni_pathlen - 1];
917 KASSERT(*nulchar == '\0',
918 ("%s: expected nul at %p; string [%s]\n", __func__, nulchar,
921 for (cp = cnp->cn_nameptr; *cp != '/'; cp++) {
923 ("%s: encountered unexpected nul; string [%s]\n", __func__,
928 cnp->cn_namelen = cp - cnp->cn_nameptr;
929 if (cnp->cn_namelen > NAME_MAX) {
930 error = ENAMETOOLONG;
933 #ifdef NAMEI_DIAGNOSTIC
936 printf("{%s}: ", cnp->cn_nameptr);
939 prev_ni_pathlen = ndp->ni_pathlen;
940 ndp->ni_pathlen -= cnp->cn_namelen;
941 KASSERT(ndp->ni_pathlen <= PATH_MAX,
942 ("%s: ni_pathlen underflow to %zd\n", __func__, ndp->ni_pathlen));
943 prev_ni_next = ndp->ni_next;
947 * Replace multiple slashes by a single slash and trailing slashes
948 * by a null. This must be done before VOP_LOOKUP() because some
949 * fs's don't know about trailing slashes. Remember if there were
950 * trailing slashes to handle symlinks, existing non-directories
951 * and non-existing files that won't be directories specially later.
953 while (*cp == '/' && (cp[1] == '/' || cp[1] == '\0')) {
957 *ndp->ni_next = '\0';
958 cnp->cn_flags |= TRAILINGSLASH;
963 cnp->cn_flags |= MAKEENTRY;
964 if (*cp == '\0' && docache == 0)
965 cnp->cn_flags &= ~MAKEENTRY;
966 if (cnp->cn_namelen == 2 &&
967 cnp->cn_nameptr[1] == '.' && cnp->cn_nameptr[0] == '.')
968 cnp->cn_flags |= ISDOTDOT;
970 cnp->cn_flags &= ~ISDOTDOT;
971 if (*ndp->ni_next == 0)
972 cnp->cn_flags |= ISLASTCN;
974 cnp->cn_flags &= ~ISLASTCN;
976 if ((cnp->cn_flags & ISLASTCN) != 0 &&
977 cnp->cn_namelen == 1 && cnp->cn_nameptr[0] == '.' &&
978 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) {
983 nameicap_tracker_add(ndp, dp);
986 * Check for degenerate name (e.g. / or "")
987 * which is a way of talking about a directory,
988 * e.g. like "/." or ".".
990 if (cnp->cn_nameptr[0] == '\0') {
991 if (dp->v_type != VDIR) {
995 if (cnp->cn_nameiop != LOOKUP) {
1005 if (cnp->cn_flags & AUDITVNODE1)
1006 AUDIT_ARG_VNODE1(dp);
1007 else if (cnp->cn_flags & AUDITVNODE2)
1008 AUDIT_ARG_VNODE2(dp);
1010 if (!(cnp->cn_flags & (LOCKPARENT | LOCKLEAF)))
1012 /* XXX This should probably move to the top of function. */
1013 if (cnp->cn_flags & SAVESTART)
1014 panic("lookup: SAVESTART");
1019 * Handle "..": five special cases.
1020 * 0. If doing a capability lookup and lookup_cap_dotdot is
1021 * disabled, return ENOTCAPABLE.
1022 * 1. Return an error if this is the last component of
1023 * the name and the operation is DELETE or RENAME.
1024 * 2. If at root directory (e.g. after chroot)
1025 * or at absolute root directory
1026 * then ignore it so can't get out.
1027 * 3. If this vnode is the root of a mounted
1028 * filesystem, then replace it with the
1029 * vnode which was mounted on so we take the
1030 * .. in the other filesystem.
1031 * 4. If the vnode is the top directory of
1032 * the jail or chroot, don't let them out.
1033 * 5. If doing a capability lookup and lookup_cap_dotdot is
1034 * enabled, return ENOTCAPABLE if the lookup would escape
1035 * from the initial file descriptor directory. Checks are
1036 * done by ensuring that namei() already traversed the
1037 * result of dotdot lookup.
1039 if (cnp->cn_flags & ISDOTDOT) {
1040 if ((ndp->ni_lcf & (NI_LCF_STRICTRELATIVE | NI_LCF_CAP_DOTDOT))
1041 == NI_LCF_STRICTRELATIVE) {
1043 if (KTRPOINT(curthread, KTR_CAPFAIL))
1044 ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL);
1046 error = ENOTCAPABLE;
1049 if ((cnp->cn_flags & ISLASTCN) != 0 &&
1050 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) {
1055 for (pr = cnp->cn_cred->cr_prison; pr != NULL;
1057 if (dp == pr->pr_root)
1059 if (dp == ndp->ni_rootdir ||
1060 dp == ndp->ni_topdir ||
1063 ((dp->v_vflag & VV_ROOT) != 0 &&
1064 (cnp->cn_flags & NOCROSSMOUNT) != 0)) {
1070 if ((dp->v_vflag & VV_ROOT) == 0)
1072 if (VN_IS_DOOMED(dp)) { /* forced unmount */
1077 dp = dp->v_mount->mnt_vnodecovered;
1081 compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags |
1082 LK_RETRY, ISDOTDOT));
1083 error = nameicap_check_dotdot(ndp, dp);
1086 if (KTRPOINT(curthread, KTR_CAPFAIL))
1087 ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL);
1095 * We now have a segment name to search for, and a directory to search.
1099 error = mac_vnode_check_lookup(cnp->cn_thread->td_ucred, dp, cnp);
1105 ASSERT_VOP_LOCKED(dp, "lookup");
1107 * If we have a shared lock we may need to upgrade the lock for the
1110 if ((cnp->cn_flags & LOCKPARENT) && (cnp->cn_flags & ISLASTCN) &&
1111 dp != vp_crossmp && VOP_ISLOCKED(dp) == LK_SHARED)
1112 vn_lock(dp, LK_UPGRADE|LK_RETRY);
1113 if (VN_IS_DOOMED(dp)) {
1118 * If we're looking up the last component and we need an exclusive
1119 * lock, adjust our lkflags.
1121 if (needs_exclusive_leaf(dp->v_mount, cnp->cn_flags))
1122 cnp->cn_lkflags = LK_EXCLUSIVE;
1123 #ifdef NAMEI_DIAGNOSTIC
1124 vn_printf(dp, "lookup in ");
1126 lkflags_save = cnp->cn_lkflags;
1127 cnp->cn_lkflags = compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags,
1129 error = VOP_LOOKUP(dp, &ndp->ni_vp, cnp);
1130 cnp->cn_lkflags = lkflags_save;
1132 KASSERT(ndp->ni_vp == NULL, ("leaf should be empty"));
1133 #ifdef NAMEI_DIAGNOSTIC
1134 printf("not found\n");
1136 if ((error == ENOENT) &&
1137 (dp->v_vflag & VV_ROOT) && (dp->v_mount != NULL) &&
1138 (dp->v_mount->mnt_flag & MNT_UNION)) {
1140 dp = dp->v_mount->mnt_vnodecovered;
1144 compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags |
1145 LK_RETRY, cnp->cn_flags));
1146 nameicap_tracker_add(ndp, dp);
1150 if (error == ERELOOKUP) {
1158 if (error != EJUSTRETURN)
1161 * At this point, we know we're at the end of the
1162 * pathname. If creating / renaming, we can consider
1163 * allowing the file or directory to be created / renamed,
1164 * provided we're not on a read-only filesystem.
1170 /* trailing slash only allowed for directories */
1171 if ((cnp->cn_flags & TRAILINGSLASH) &&
1172 !(cnp->cn_flags & WILLBEDIR)) {
1176 if ((cnp->cn_flags & LOCKPARENT) == 0)
1179 * We return with ni_vp NULL to indicate that the entry
1180 * doesn't currently exist, leaving a pointer to the
1181 * (possibly locked) directory vnode in ndp->ni_dvp.
1183 if (cnp->cn_flags & SAVESTART) {
1184 ndp->ni_startdir = ndp->ni_dvp;
1185 VREF(ndp->ni_startdir);
1191 #ifdef NAMEI_DIAGNOSTIC
1197 * Check to see if the vnode has been mounted on;
1198 * if so find the root of the mounted filesystem.
1200 while (dp->v_type == VDIR && (mp = dp->v_mountedhere) &&
1201 (cnp->cn_flags & NOCROSSMOUNT) == 0) {
1202 if (vfs_busy(mp, 0))
1205 if (dp != ndp->ni_dvp)
1209 vrefact(vp_crossmp);
1210 ndp->ni_dvp = vp_crossmp;
1211 error = VFS_ROOT(mp, compute_cn_lkflags(mp, cnp->cn_lkflags,
1212 cnp->cn_flags), &tdp);
1214 if (vn_lock(vp_crossmp, LK_SHARED | LK_NOWAIT))
1215 panic("vp_crossmp exclusively locked or reclaimed");
1220 ndp->ni_vp = dp = tdp;
1224 * Check for symbolic link
1226 if ((dp->v_type == VLNK) &&
1227 ((cnp->cn_flags & FOLLOW) || (cnp->cn_flags & TRAILINGSLASH) ||
1228 *ndp->ni_next == '/')) {
1229 cnp->cn_flags |= ISSYMLINK;
1230 if (VN_IS_DOOMED(dp)) {
1232 * We can't know whether the directory was mounted with
1233 * NOSYMFOLLOW, so we can't follow safely.
1238 if (dp->v_mount->mnt_flag & MNT_NOSYMFOLLOW) {
1243 * Symlink code always expects an unlocked dvp.
1245 if (ndp->ni_dvp != ndp->ni_vp) {
1246 VOP_UNLOCK(ndp->ni_dvp);
1247 ni_dvp_unlocked = 1;
1254 * Not a symbolic link that we will follow. Continue with the
1255 * next component if there is any; otherwise, we're done.
1257 KASSERT((cnp->cn_flags & ISLASTCN) || *ndp->ni_next == '/',
1258 ("lookup: invalid path state."));
1261 ndp->ni_pathlen = prev_ni_pathlen;
1262 ndp->ni_next = prev_ni_next;
1263 if (ndp->ni_dvp != dp)
1269 if (cnp->cn_flags & ISDOTDOT) {
1270 error = nameicap_check_dotdot(ndp, ndp->ni_vp);
1273 if (KTRPOINT(curthread, KTR_CAPFAIL))
1274 ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL);
1279 if (*ndp->ni_next == '/') {
1280 cnp->cn_nameptr = ndp->ni_next;
1281 while (*cnp->cn_nameptr == '/') {
1285 if (ndp->ni_dvp != dp)
1292 * If we're processing a path with a trailing slash,
1293 * check that the end result is a directory.
1295 if ((cnp->cn_flags & TRAILINGSLASH) && dp->v_type != VDIR) {
1300 * Disallow directory write attempts on read-only filesystems.
1303 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) {
1307 if (cnp->cn_flags & SAVESTART) {
1308 ndp->ni_startdir = ndp->ni_dvp;
1309 VREF(ndp->ni_startdir);
1312 ni_dvp_unlocked = 2;
1313 if (ndp->ni_dvp != dp)
1317 } else if ((cnp->cn_flags & LOCKPARENT) == 0 && ndp->ni_dvp != dp) {
1318 VOP_UNLOCK(ndp->ni_dvp);
1319 ni_dvp_unlocked = 1;
1322 if (cnp->cn_flags & AUDITVNODE1)
1323 AUDIT_ARG_VNODE1(dp);
1324 else if (cnp->cn_flags & AUDITVNODE2)
1325 AUDIT_ARG_VNODE2(dp);
1327 if ((cnp->cn_flags & LOCKLEAF) == 0)
1331 * FIXME: for lookups which only cross a mount point to fetch the
1332 * root vnode, ni_dvp will be set to vp_crossmp. This can be a problem
1333 * if either WANTPARENT or LOCKPARENT is set.
1336 * Because of shared lookup we may have the vnode shared locked, but
1337 * the caller may want it to be exclusively locked.
1339 if (needs_exclusive_leaf(dp->v_mount, cnp->cn_flags) &&
1340 VOP_ISLOCKED(dp) != LK_EXCLUSIVE) {
1341 vn_lock(dp, LK_UPGRADE | LK_RETRY);
1342 if (VN_IS_DOOMED(dp)) {
1347 if (ndp->ni_vp != NULL) {
1348 if ((cnp->cn_flags & ISDOTDOT) == 0)
1349 nameicap_tracker_add(ndp, ndp->ni_vp);
1350 if ((cnp->cn_flags & (FAILIFEXISTS | ISSYMLINK)) == FAILIFEXISTS)
1356 if (ni_dvp_unlocked != 2) {
1357 if (dp != ndp->ni_dvp && !ni_dvp_unlocked)
1369 * FAILIFEXISTS handling.
1371 * XXX namei called with LOCKPARENT but not LOCKLEAF has the strange
1372 * behaviour of leaving the vnode unlocked if the target is the same
1373 * vnode as the parent.
1375 MPASS((cnp->cn_flags & ISSYMLINK) == 0);
1376 if (ndp->ni_vp == ndp->ni_dvp)
1383 NDFREE(ndp, NDF_ONLY_PNBUF);
1388 * relookup - lookup a path name component
1389 * Used by lookup to re-acquire things.
1392 relookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp)
1394 struct vnode *dp = NULL; /* the directory we are searching */
1395 int rdonly; /* lookup read-only flag bit */
1398 KASSERT(cnp->cn_flags & ISLASTCN,
1399 ("relookup: Not given last component."));
1401 * Setup: break out flag bits into variables.
1403 KASSERT((cnp->cn_flags & (LOCKPARENT | WANTPARENT)) != 0,
1404 ("relookup: parent not wanted"));
1405 rdonly = cnp->cn_flags & RDONLY;
1406 cnp->cn_flags &= ~ISSYMLINK;
1408 cnp->cn_lkflags = LK_EXCLUSIVE;
1409 vn_lock(dp, LK_EXCLUSIVE | LK_RETRY);
1412 * Search a new directory.
1414 * The last component of the filename is left accessible via
1415 * cnp->cn_nameptr for callers that need the name. Callers needing
1416 * the name set the SAVENAME flag. When done, they assume
1417 * responsibility for freeing the pathname buffer.
1419 #ifdef NAMEI_DIAGNOSTIC
1420 printf("{%s}: ", cnp->cn_nameptr);
1424 * Check for "" which represents the root directory after slash
1427 if (cnp->cn_nameptr[0] == '\0') {
1429 * Support only LOOKUP for "/" because lookup()
1430 * can't succeed for CREATE, DELETE and RENAME.
1432 KASSERT(cnp->cn_nameiop == LOOKUP, ("nameiop must be LOOKUP"));
1433 KASSERT(dp->v_type == VDIR, ("dp is not a directory"));
1435 if (!(cnp->cn_flags & LOCKLEAF))
1438 /* XXX This should probably move to the top of function. */
1439 if (cnp->cn_flags & SAVESTART)
1440 panic("lookup: SAVESTART");
1444 if (cnp->cn_flags & ISDOTDOT)
1445 panic ("relookup: lookup on dot-dot");
1448 * We now have a segment name to search for, and a directory to search.
1450 #ifdef NAMEI_DIAGNOSTIC
1451 vn_printf(dp, "search in ");
1453 if ((error = VOP_LOOKUP(dp, vpp, cnp)) != 0) {
1454 KASSERT(*vpp == NULL, ("leaf should be empty"));
1455 if (error != EJUSTRETURN)
1458 * If creating and at end of pathname, then can consider
1459 * allowing file to be created.
1465 /* ASSERT(dvp == ndp->ni_startdir) */
1466 if (cnp->cn_flags & SAVESTART)
1468 if ((cnp->cn_flags & LOCKPARENT) == 0)
1471 * We return with ni_vp NULL to indicate that the entry
1472 * doesn't currently exist, leaving a pointer to the
1473 * (possibly locked) directory vnode in ndp->ni_dvp.
1481 * Disallow directory write attempts on read-only filesystems.
1484 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) {
1493 * Set the parent lock/ref state to the requested state.
1495 if ((cnp->cn_flags & LOCKPARENT) == 0 && dvp != dp)
1498 * Check for symbolic link
1500 KASSERT(dp->v_type != VLNK || !(cnp->cn_flags & FOLLOW),
1501 ("relookup: symlink found.\n"));
1503 /* ASSERT(dvp == ndp->ni_startdir) */
1504 if (cnp->cn_flags & SAVESTART)
1507 if ((cnp->cn_flags & LOCKLEAF) == 0)
1517 * Free data allocated by namei(); see namei(9) for details.
1520 NDFREE_PNBUF(struct nameidata *ndp)
1523 if ((ndp->ni_cnd.cn_flags & HASBUF) != 0) {
1524 MPASS((ndp->ni_cnd.cn_flags & (SAVENAME | SAVESTART)) != 0);
1525 uma_zfree(namei_zone, ndp->ni_cnd.cn_pnbuf);
1526 ndp->ni_cnd.cn_flags &= ~HASBUF;
1531 * NDFREE_PNBUF replacement for callers that know there is no buffer.
1533 * This is a hack. Preferably the VFS layer would not produce anything more
1534 * than it was asked to do. Unfortunately several non-LOOKUP cases can add the
1535 * HASBUF flag to the result. Even then an interface could be implemented where
1536 * the caller specifies what they expected to see in the result and what they
1537 * are going to take care of.
1539 * In the meantime provide this kludge as a trivial replacement for NDFREE_PNBUF
1540 * calls scattered throughout the kernel where we know for a fact the flag must not
1545 NDFREE_NOTHING(struct nameidata *ndp)
1547 struct componentname *cnp;
1550 KASSERT(cnp->cn_nameiop == LOOKUP, ("%s: got non-LOOKUP op %d\n",
1551 __func__, cnp->cn_nameiop));
1552 KASSERT((cnp->cn_flags & (SAVENAME | HASBUF)) == 0,
1553 ("%s: bad flags \%" PRIx64 "\n", __func__, cnp->cn_flags));
1558 (NDFREE)(struct nameidata *ndp, const u_int flags)
1566 if (!(flags & NDF_NO_FREE_PNBUF)) {
1569 if (!(flags & NDF_NO_VP_UNLOCK) &&
1570 (ndp->ni_cnd.cn_flags & LOCKLEAF) && ndp->ni_vp)
1572 if (!(flags & NDF_NO_DVP_UNLOCK) &&
1573 (ndp->ni_cnd.cn_flags & LOCKPARENT) &&
1574 ndp->ni_dvp != ndp->ni_vp)
1576 if (!(flags & NDF_NO_VP_RELE) && ndp->ni_vp) {
1585 VOP_UNLOCK(ndp->ni_vp);
1586 if (!(flags & NDF_NO_DVP_RELE) &&
1587 (ndp->ni_cnd.cn_flags & (LOCKPARENT|WANTPARENT))) {
1596 VOP_UNLOCK(ndp->ni_dvp);
1597 if (!(flags & NDF_NO_STARTDIR_RELE) &&
1598 (ndp->ni_cnd.cn_flags & SAVESTART)) {
1599 vrele(ndp->ni_startdir);
1600 ndp->ni_startdir = NULL;
1606 * Validate the final state of ndp after the lookup.
1608 * Historically filesystems were allowed to modify cn_flags. Most notably they
1609 * can add SAVENAME to the request, resulting in HASBUF and pushing subsequent
1610 * clean up to the consumer. In practice this seems to only concern != LOOKUP
1613 * As a step towards stricter API contract this routine validates the state to
1614 * clean up. Note validation is a work in progress with the intent of becoming
1615 * stricter over time.
1617 #define NDMODIFYINGFLAGS (LOCKLEAF | LOCKPARENT | WANTPARENT | SAVENAME | SAVESTART | HASBUF)
1619 NDVALIDATE(struct nameidata *ndp)
1621 struct componentname *cnp;
1622 u_int64_t used, orig;
1625 orig = cnp->cn_origflags;
1626 used = cnp->cn_flags;
1627 switch (cnp->cn_nameiop) {
1630 * For plain lookup we require strict conformance -- nothing
1631 * to clean up if it was not requested by the caller.
1633 orig &= NDMODIFYINGFLAGS;
1634 used &= NDMODIFYINGFLAGS;
1635 if ((orig & (SAVENAME | SAVESTART)) != 0)
1645 * Some filesystems set SAVENAME to provoke HASBUF, accomodate
1646 * for it until it gets fixed.
1648 orig &= NDMODIFYINGFLAGS;
1649 orig |= (SAVENAME | HASBUF);
1650 used &= NDMODIFYINGFLAGS;
1651 used |= (SAVENAME | HASBUF);
1659 panic("%s: mismatched flags for op %d: added %" PRIx64 ", "
1660 "removed %" PRIx64" (%" PRIx64" != %" PRIx64"; stored %" PRIx64" != %" PRIx64")",
1661 __func__, cnp->cn_nameiop, used & ~orig, orig &~ used,
1662 orig, used, cnp->cn_origflags, cnp->cn_flags);
1667 * Determine if there is a suitable alternate filename under the specified
1668 * prefix for the specified path. If the create flag is set, then the
1669 * alternate prefix will be used so long as the parent directory exists.
1670 * This is used by the various compatibility ABIs so that Linux binaries prefer
1671 * files under /compat/linux for example. The chosen path (whether under
1672 * the prefix or under /) is returned in a kernel malloc'd buffer pointed
1673 * to by pathbuf. The caller is responsible for free'ing the buffer from
1674 * the M_TEMP bucket if one is returned.
1677 kern_alternate_path(struct thread *td, const char *prefix, const char *path,
1678 enum uio_seg pathseg, char **pathbuf, int create, int dirfd)
1680 struct nameidata nd, ndroot;
1681 char *ptr, *buf, *cp;
1685 buf = (char *) malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
1688 /* Copy the prefix into the new pathname as a starting point. */
1689 len = strlcpy(buf, prefix, MAXPATHLEN);
1690 if (len >= MAXPATHLEN) {
1695 sz = MAXPATHLEN - len;
1698 /* Append the filename to the prefix. */
1699 if (pathseg == UIO_SYSSPACE)
1700 error = copystr(path, ptr, sz, &len);
1702 error = copyinstr(path, ptr, sz, &len);
1710 /* Only use a prefix with absolute pathnames. */
1716 if (dirfd != AT_FDCWD) {
1718 * We want the original because the "prefix" is
1719 * included in the already opened dirfd.
1721 bcopy(ptr, buf, len);
1726 * We know that there is a / somewhere in this pathname.
1727 * Search backwards for it, to find the file's parent dir
1728 * to see if it exists in the alternate tree. If it does,
1729 * and we want to create a file (cflag is set). We don't
1730 * need to worry about the root comparison in this case.
1734 for (cp = &ptr[len] - 1; *cp != '/'; cp--);
1737 NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_SYSSPACE, buf, td);
1743 NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_SYSSPACE, buf, td);
1750 * We now compare the vnode of the prefix to the one
1751 * vnode asked. If they resolve to be the same, then we
1752 * ignore the match so that the real root gets used.
1753 * This avoids the problem of traversing "../.." to find the
1754 * root directory and never finding it, because "/" resolves
1755 * to the emulation root directory. This is expensive :-(
1757 NDINIT(&ndroot, LOOKUP, FOLLOW, UIO_SYSSPACE, prefix,
1760 /* We shouldn't ever get an error from this namei(). */
1761 error = namei(&ndroot);
1763 if (nd.ni_vp == ndroot.ni_vp)
1766 NDFREE(&ndroot, NDF_ONLY_PNBUF);
1767 vrele(ndroot.ni_vp);
1771 NDFREE(&nd, NDF_ONLY_PNBUF);
1775 /* If there was an error, use the original path name. */
1777 bcopy(ptr, buf, len);