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38 * @(#)vfs_lookup.c 8.4 (Berkeley) 2/16/94
39 * $FreeBSD: src/sys/kern/vfs_lookup.c,v 1.38.2.3 2001/08/31 19:36:49 dillon Exp $
42 #include "opt_ktrace.h"
44 #include <sys/param.h>
45 #include <sys/systm.h>
46 #include <sys/namei.h>
47 #include <sys/vnode.h>
48 #include <sys/mount.h>
49 #include <sys/filedesc.h>
53 #include <sys/ktrace.h>
56 #include <vm/vm_zone.h>
59 * Convert a pathname into a pointer to a locked inode.
61 * The FOLLOW flag is set when symbolic links are to be followed
62 * when they occur at the end of the name translation process.
63 * Symbolic links are always followed for all other pathname
64 * components other than the last.
66 * The segflg defines whether the name is to be copied from user
67 * space or kernel space.
69 * Overall outline of namei:
72 * get starting directory
73 * while (!done && !error) {
74 * call lookup to search path.
75 * if symbolic link, massage name in buffer and continue
80 register struct nameidata *ndp;
82 register struct filedesc *fdp; /* pointer to file descriptor state */
83 register char *cp; /* pointer into pathname argument */
84 register struct vnode *dp; /* the directory we are searching */
85 struct iovec aiov; /* uio for reading symbolic links */
88 struct componentname *cnp = &ndp->ni_cnd;
89 struct proc *p = cnp->cn_proc;
91 ndp->ni_cnd.cn_cred = ndp->ni_cnd.cn_proc->p_ucred;
92 KASSERT(cnp->cn_cred && cnp->cn_proc, ("namei: bad cred/proc"));
93 KASSERT((cnp->cn_nameiop & (~OPMASK)) == 0,
94 ("namei: nameiop contaminated with flags"));
95 KASSERT((cnp->cn_flags & OPMASK) == 0,
96 ("namei: flags contaminated with nameiops"));
97 fdp = cnp->cn_proc->p_fd;
100 * Get a buffer for the name to be translated, and copy the
101 * name into the buffer.
103 if ((cnp->cn_flags & HASBUF) == 0)
104 cnp->cn_pnbuf = zalloc(namei_zone);
105 if (ndp->ni_segflg == UIO_SYSSPACE)
106 error = copystr(ndp->ni_dirp, cnp->cn_pnbuf,
107 MAXPATHLEN, (size_t *)&ndp->ni_pathlen);
109 error = copyinstr(ndp->ni_dirp, cnp->cn_pnbuf,
110 MAXPATHLEN, (size_t *)&ndp->ni_pathlen);
113 * Don't allow empty pathnames.
115 if (!error && *cnp->cn_pnbuf == '\0')
119 zfree(namei_zone, cnp->cn_pnbuf);
125 if (KTRPOINT(cnp->cn_proc, KTR_NAMEI))
126 ktrnamei(cnp->cn_proc->p_tracep, cnp->cn_pnbuf);
130 * Get starting point for the translation.
132 ndp->ni_rootdir = fdp->fd_rdir;
133 ndp->ni_topdir = fdp->fd_jdir;
139 * Check if root directory should replace current directory.
140 * Done at start of translation and after symbolic link.
142 cnp->cn_nameptr = cnp->cn_pnbuf;
143 if (*(cnp->cn_nameptr) == '/') {
145 while (*(cnp->cn_nameptr) == '/') {
149 dp = ndp->ni_rootdir;
152 ndp->ni_startdir = dp;
155 zfree(namei_zone, cnp->cn_pnbuf);
159 * Check for symbolic link
161 if ((cnp->cn_flags & ISSYMLINK) == 0) {
162 if ((cnp->cn_flags & (SAVENAME | SAVESTART)) == 0)
163 zfree(namei_zone, cnp->cn_pnbuf);
165 cnp->cn_flags |= HASBUF;
167 if (vn_canvmio(ndp->ni_vp) == TRUE &&
168 (cnp->cn_nameiop != DELETE) &&
169 ((cnp->cn_flags & (NOOBJ|LOCKLEAF)) ==
171 vfs_object_create(ndp->ni_vp,
173 ndp->ni_cnd.cn_cred);
177 if ((cnp->cn_flags & LOCKPARENT) && ndp->ni_pathlen == 1)
178 VOP_UNLOCK(ndp->ni_dvp, 0, p);
179 if (ndp->ni_loopcnt++ >= MAXSYMLINKS) {
183 if (ndp->ni_pathlen > 1)
184 cp = zalloc(namei_zone);
188 aiov.iov_len = MAXPATHLEN;
189 auio.uio_iov = &aiov;
192 auio.uio_rw = UIO_READ;
193 auio.uio_segflg = UIO_SYSSPACE;
194 auio.uio_procp = (struct proc *)0;
195 auio.uio_resid = MAXPATHLEN;
196 error = VOP_READLINK(ndp->ni_vp, &auio, cnp->cn_cred);
198 if (ndp->ni_pathlen > 1)
199 zfree(namei_zone, cp);
202 linklen = MAXPATHLEN - auio.uio_resid;
204 if (ndp->ni_pathlen > 1)
205 zfree(namei_zone, cp);
209 if (linklen + ndp->ni_pathlen >= MAXPATHLEN) {
210 if (ndp->ni_pathlen > 1)
211 zfree(namei_zone, cp);
212 error = ENAMETOOLONG;
215 if (ndp->ni_pathlen > 1) {
216 bcopy(ndp->ni_next, cp + linklen, ndp->ni_pathlen);
217 zfree(namei_zone, cnp->cn_pnbuf);
220 cnp->cn_pnbuf[linklen] = '\0';
221 ndp->ni_pathlen += linklen;
225 zfree(namei_zone, cnp->cn_pnbuf);
234 * This is a very central and rather complicated routine.
236 * The pathname is pointed to by ni_ptr and is of length ni_pathlen.
237 * The starting directory is taken from ni_startdir. The pathname is
238 * descended until done, or a symbolic link is encountered. The variable
239 * ni_more is clear if the path is completed; it is set to one if a
240 * symbolic link needing interpretation is encountered.
242 * The flag argument is LOOKUP, CREATE, RENAME, or DELETE depending on
243 * whether the name is to be looked up, created, renamed, or deleted.
244 * When CREATE, RENAME, or DELETE is specified, information usable in
245 * creating, renaming, or deleting a directory entry may be calculated.
246 * If flag has LOCKPARENT or'ed into it, the parent directory is returned
247 * locked. If flag has WANTPARENT or'ed into it, the parent directory is
248 * returned unlocked. Otherwise the parent directory is not returned. If
249 * the target of the pathname exists and LOCKLEAF is or'ed into the flag
250 * the target is returned locked, otherwise it is returned unlocked.
251 * When creating or renaming and LOCKPARENT is specified, the target may not
252 * be ".". When deleting and LOCKPARENT is specified, the target may be ".".
254 * Overall outline of lookup:
257 * identify next component of name at ndp->ni_ptr
258 * handle degenerate case where name is null string
259 * if .. and crossing mount points and on mounted filesys, find parent
260 * call VOP_LOOKUP routine for next component name
261 * directory vnode returned in ni_dvp, unlocked unless LOCKPARENT set
262 * component vnode returned in ni_vp (if it exists), locked.
263 * if result vnode is mounted on and crossing mount points,
264 * find mounted on vnode
265 * if more components of name, do next level at dirloop
266 * return the answer in ni_vp, locked if LOCKLEAF set
267 * if LOCKPARENT set, return locked parent in ni_dvp
268 * if WANTPARENT set, return unlocked parent in ni_dvp
272 register struct nameidata *ndp;
274 register char *cp; /* pointer into pathname argument */
275 register struct vnode *dp = 0; /* the directory we are searching */
276 struct vnode *tdp; /* saved dp */
277 struct mount *mp; /* mount table entry */
278 int docache; /* == 0 do not cache last component */
279 int wantparent; /* 1 => wantparent or lockparent flag */
280 int rdonly; /* lookup read-only flag bit */
283 int dpunlocked = 0; /* dp has already been unlocked */
284 struct componentname *cnp = &ndp->ni_cnd;
285 struct proc *p = cnp->cn_proc;
288 * Setup: break out flag bits into variables.
290 wantparent = cnp->cn_flags & (LOCKPARENT | WANTPARENT);
291 docache = (cnp->cn_flags & NOCACHE) ^ NOCACHE;
292 if (cnp->cn_nameiop == DELETE ||
293 (wantparent && cnp->cn_nameiop != CREATE &&
294 cnp->cn_nameiop != LOOKUP))
296 rdonly = cnp->cn_flags & RDONLY;
298 cnp->cn_flags &= ~ISSYMLINK;
299 dp = ndp->ni_startdir;
300 ndp->ni_startdir = NULLVP;
301 vn_lock(dp, LK_EXCLUSIVE | LK_RETRY, p);
305 * Search a new directory.
307 * The last component of the filename is left accessible via
308 * cnp->cn_nameptr for callers that need the name. Callers needing
309 * the name set the SAVENAME flag. When done, they assume
310 * responsibility for freeing the pathname buffer.
313 for (cp = cnp->cn_nameptr; *cp != 0 && *cp != '/'; cp++)
315 cnp->cn_namelen = cp - cnp->cn_nameptr;
316 if (cnp->cn_namelen > NAME_MAX) {
317 error = ENAMETOOLONG;
320 #ifdef NAMEI_DIAGNOSTIC
323 printf("{%s}: ", cnp->cn_nameptr);
326 ndp->ni_pathlen -= cnp->cn_namelen;
330 * Replace multiple slashes by a single slash and trailing slashes
331 * by a null. This must be done before VOP_LOOKUP() because some
332 * fs's don't know about trailing slashes. Remember if there were
333 * trailing slashes to handle symlinks, existing non-directories
334 * and non-existing files that won't be directories specially later.
337 while (*cp == '/' && (cp[1] == '/' || cp[1] == '\0')) {
342 *ndp->ni_next = '\0'; /* XXX for direnter() ... */
347 cnp->cn_flags |= MAKEENTRY;
348 if (*cp == '\0' && docache == 0)
349 cnp->cn_flags &= ~MAKEENTRY;
350 if (cnp->cn_namelen == 2 &&
351 cnp->cn_nameptr[1] == '.' && cnp->cn_nameptr[0] == '.')
352 cnp->cn_flags |= ISDOTDOT;
354 cnp->cn_flags &= ~ISDOTDOT;
355 if (*ndp->ni_next == 0)
356 cnp->cn_flags |= ISLASTCN;
358 cnp->cn_flags &= ~ISLASTCN;
362 * Check for degenerate name (e.g. / or "")
363 * which is a way of talking about a directory,
364 * e.g. like "/." or ".".
366 if (cnp->cn_nameptr[0] == '\0') {
367 if (dp->v_type != VDIR) {
371 if (cnp->cn_nameiop != LOOKUP) {
380 if (!(cnp->cn_flags & (LOCKPARENT | LOCKLEAF)))
381 VOP_UNLOCK(dp, 0, p);
382 /* XXX This should probably move to the top of function. */
383 if (cnp->cn_flags & SAVESTART)
384 panic("lookup: SAVESTART");
389 * Handle "..": two special cases.
390 * 1. If at root directory (e.g. after chroot)
391 * or at absolute root directory
392 * then ignore it so can't get out.
393 * 2. If this vnode is the root of a mounted
394 * filesystem, then replace it with the
395 * vnode which was mounted on so we take the
396 * .. in the other file system.
397 * 3. If the vnode is the top directory of
398 * the jail or chroot, don't let them out.
400 if (cnp->cn_flags & ISDOTDOT) {
402 if (dp == ndp->ni_rootdir ||
403 dp == ndp->ni_topdir ||
410 if ((dp->v_flag & VROOT) == 0 ||
411 (cnp->cn_flags & NOCROSSMOUNT))
413 if (dp->v_mount == NULL) { /* forced unmount */
418 dp = dp->v_mount->mnt_vnodecovered;
421 vn_lock(dp, LK_EXCLUSIVE | LK_RETRY, p);
426 * We now have a segment name to search for, and a directory to search.
431 cnp->cn_flags &= ~PDIRUNLOCK;
432 ASSERT_VOP_LOCKED(dp, "lookup");
433 if ((error = VOP_LOOKUP(dp, &ndp->ni_vp, cnp)) != 0) {
434 KASSERT(ndp->ni_vp == NULL, ("leaf should be empty"));
435 #ifdef NAMEI_DIAGNOSTIC
436 printf("not found\n");
438 if ((error == ENOENT) &&
439 (dp->v_flag & VROOT) && (dp->v_mount != NULL) &&
440 (dp->v_mount->mnt_flag & MNT_UNION)) {
442 dp = dp->v_mount->mnt_vnodecovered;
443 if (cnp->cn_flags & PDIRUNLOCK)
448 vn_lock(dp, LK_EXCLUSIVE | LK_RETRY, p);
452 if (error != EJUSTRETURN)
455 * If creating and at end of pathname, then can consider
456 * allowing file to be created.
462 if (*cp == '\0' && trailing_slash &&
463 !(cnp->cn_flags & WILLBEDIR)) {
468 * We return with ni_vp NULL to indicate that the entry
469 * doesn't currently exist, leaving a pointer to the
470 * (possibly locked) directory inode in ndp->ni_dvp.
472 if (cnp->cn_flags & SAVESTART) {
473 ndp->ni_startdir = ndp->ni_dvp;
474 VREF(ndp->ni_startdir);
478 #ifdef NAMEI_DIAGNOSTIC
482 ASSERT_VOP_LOCKED(ndp->ni_vp, "lookup");
485 * Take into account any additional components consumed by
486 * the underlying filesystem.
488 if (cnp->cn_consume > 0) {
489 cnp->cn_nameptr += cnp->cn_consume;
490 ndp->ni_next += cnp->cn_consume;
491 ndp->ni_pathlen -= cnp->cn_consume;
498 * Check to see if the vnode has been mounted on;
499 * if so find the root of the mounted file system.
501 while (dp->v_type == VDIR && (mp = dp->v_mountedhere) &&
502 (cnp->cn_flags & NOCROSSMOUNT) == 0) {
503 if (vfs_busy(mp, 0, 0, p))
505 VOP_UNLOCK(dp, 0, p);
506 error = VFS_ROOT(mp, &tdp);
513 ndp->ni_vp = dp = tdp;
517 * Check for symbolic link
519 if ((dp->v_type == VLNK) &&
520 ((cnp->cn_flags & FOLLOW) || trailing_slash ||
521 *ndp->ni_next == '/')) {
522 cnp->cn_flags |= ISSYMLINK;
523 if (dp->v_mount == NULL) {
524 /* We can't know whether the directory was mounted with
525 * NOSYMFOLLOW, so we can't follow safely. */
529 if (dp->v_mount->mnt_flag & MNT_NOSYMFOLLOW) {
537 * Check for bogus trailing slashes.
539 if (trailing_slash && dp->v_type != VDIR) {
546 * Not a symbolic link. If more pathname,
547 * continue at next component, else return.
549 if (*ndp->ni_next == '/') {
550 cnp->cn_nameptr = ndp->ni_next;
551 while (*cnp->cn_nameptr == '/') {
555 if (ndp->ni_dvp != ndp->ni_vp)
556 ASSERT_VOP_UNLOCKED(ndp->ni_dvp, "lookup");
561 * Disallow directory write attempts on read-only file systems.
564 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) {
568 if (cnp->cn_flags & SAVESTART) {
569 ndp->ni_startdir = ndp->ni_dvp;
570 VREF(ndp->ni_startdir);
575 if ((cnp->cn_flags & LOCKLEAF) == 0)
576 VOP_UNLOCK(dp, 0, p);
580 if ((cnp->cn_flags & (LOCKPARENT | PDIRUNLOCK)) == LOCKPARENT &&
581 *ndp->ni_next == '\0')
582 VOP_UNLOCK(ndp->ni_dvp, 0, p);
594 * relookup - lookup a path name component
595 * Used by lookup to re-aquire things.
598 relookup(dvp, vpp, cnp)
599 struct vnode *dvp, **vpp;
600 struct componentname *cnp;
602 struct proc *p = cnp->cn_proc;
603 struct vnode *dp = 0; /* the directory we are searching */
604 int docache; /* == 0 do not cache last component */
605 int wantparent; /* 1 => wantparent or lockparent flag */
606 int rdonly; /* lookup read-only flag bit */
608 #ifdef NAMEI_DIAGNOSTIC
609 int newhash; /* DEBUG: check name hash */
610 char *cp; /* DEBUG: check name ptr/len */
614 * Setup: break out flag bits into variables.
616 wantparent = cnp->cn_flags & (LOCKPARENT|WANTPARENT);
617 docache = (cnp->cn_flags & NOCACHE) ^ NOCACHE;
618 if (cnp->cn_nameiop == DELETE ||
619 (wantparent && cnp->cn_nameiop != CREATE))
621 rdonly = cnp->cn_flags & RDONLY;
622 cnp->cn_flags &= ~ISSYMLINK;
624 vn_lock(dp, LK_EXCLUSIVE | LK_RETRY, p);
628 * Search a new directory.
630 * The last component of the filename is left accessible via
631 * cnp->cn_nameptr for callers that need the name. Callers needing
632 * the name set the SAVENAME flag. When done, they assume
633 * responsibility for freeing the pathname buffer.
635 #ifdef NAMEI_DIAGNOSTIC
636 if (cnp->cn_namelen != cp - cnp->cn_nameptr)
637 panic ("relookup: bad len");
639 panic("relookup: not last component");
640 printf("{%s}: ", cnp->cn_nameptr);
644 * Check for degenerate name (e.g. / or "")
645 * which is a way of talking about a directory,
646 * e.g. like "/." or ".".
648 if (cnp->cn_nameptr[0] == '\0') {
649 if (cnp->cn_nameiop != LOOKUP || wantparent) {
653 if (dp->v_type != VDIR) {
657 if (!(cnp->cn_flags & LOCKLEAF))
658 VOP_UNLOCK(dp, 0, p);
660 /* XXX This should probably move to the top of function. */
661 if (cnp->cn_flags & SAVESTART)
662 panic("lookup: SAVESTART");
666 if (cnp->cn_flags & ISDOTDOT)
667 panic ("relookup: lookup on dot-dot");
670 * We now have a segment name to search for, and a directory to search.
672 if ((error = VOP_LOOKUP(dp, vpp, cnp)) != 0) {
673 KASSERT(*vpp == NULL, ("leaf should be empty"));
674 if (error != EJUSTRETURN)
677 * If creating and at end of pathname, then can consider
678 * allowing file to be created.
684 /* ASSERT(dvp == ndp->ni_startdir) */
685 if (cnp->cn_flags & SAVESTART)
688 * We return with ni_vp NULL to indicate that the entry
689 * doesn't currently exist, leaving a pointer to the
690 * (possibly locked) directory inode in ndp->ni_dvp.
697 * Check for symbolic link
699 KASSERT(dp->v_type != VLNK || !(cnp->cn_flags & FOLLOW),
700 ("relookup: symlink found.\n"));
703 * Disallow directory write attempts on read-only file systems.
706 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) {
710 /* ASSERT(dvp == ndp->ni_startdir) */
711 if (cnp->cn_flags & SAVESTART)
717 if (vn_canvmio(dp) == TRUE &&
718 ((cnp->cn_flags & (NOOBJ|LOCKLEAF)) == LOCKLEAF))
719 vfs_object_create(dp, cnp->cn_proc, cnp->cn_cred);
721 if ((cnp->cn_flags & LOCKLEAF) == 0)
722 VOP_UNLOCK(dp, 0, p);
726 if ((cnp->cn_flags & LOCKPARENT) && (cnp->cn_flags & ISLASTCN))
727 VOP_UNLOCK(dvp, 0, p);