1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
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
8 * to the University of California by American Telephone and Telegraph
9 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
10 * the permission of UNIX System Laboratories, Inc.
11 *
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
14 * are met:
15 * 1. Redistributions of source code must retain the above copyright
16 * notice, this list of conditions and the following disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 * notice, this list of conditions and the following disclaimer in the
19 * documentation and/or other materials provided with the distribution.
20 * 3. Neither the name of the University nor the names of its contributors
21 * may be used to endorse or promote products derived from this software
22 * without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 *
36 * @(#)vfs_lookup.c 8.4 (Berkeley) 2/16/94
37 */
38
39 #include <sys/cdefs.h>
40 __FBSDID("$FreeBSD$");
41
42 #include "opt_capsicum.h"
43 #include "opt_ktrace.h"
44
45 #include <sys/param.h>
46 #include <sys/systm.h>
47 #include <sys/kernel.h>
48 #include <sys/capsicum.h>
49 #include <sys/fcntl.h>
50 #include <sys/jail.h>
51 #include <sys/lock.h>
52 #include <sys/mutex.h>
53 #include <sys/namei.h>
54 #include <sys/vnode.h>
55 #include <sys/mount.h>
56 #include <sys/filedesc.h>
57 #include <sys/proc.h>
58 #include <sys/sdt.h>
59 #include <sys/syscallsubr.h>
60 #include <sys/sysctl.h>
61 #ifdef KTRACE
62 #include <sys/ktrace.h>
63 #endif
64
65 #include <security/audit/audit.h>
66 #include <security/mac/mac_framework.h>
67
68 #include <vm/uma.h>
69
70 #define NAMEI_DIAGNOSTIC 1
71 #undef NAMEI_DIAGNOSTIC
72
73 SDT_PROVIDER_DECLARE(vfs);
74 SDT_PROBE_DEFINE3(vfs, namei, lookup, entry, "struct vnode *", "char *",
75 "unsigned long");
76 SDT_PROBE_DEFINE2(vfs, namei, lookup, return, "int", "struct vnode *");
77
78 /* Allocation zone for namei. */
79 uma_zone_t namei_zone;
80
81 /* Placeholder vnode for mp traversal. */
82 static struct vnode *vp_crossmp;
83
84 static int
crossmp_vop_islocked(struct vop_islocked_args * ap)85 crossmp_vop_islocked(struct vop_islocked_args *ap)
86 {
87
88 return (LK_SHARED);
89 }
90
91 static int
crossmp_vop_lock1(struct vop_lock1_args * ap)92 crossmp_vop_lock1(struct vop_lock1_args *ap)
93 {
94 struct vnode *vp;
95 struct lock *lk __unused;
96 const char *file __unused;
97 int flags, line __unused;
98
99 vp = ap->a_vp;
100 lk = vp->v_vnlock;
101 flags = ap->a_flags;
102 file = ap->a_file;
103 line = ap->a_line;
104
105 if ((flags & LK_SHARED) == 0)
106 panic("invalid lock request for crossmp");
107
108 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER, file, line,
109 flags & LK_INTERLOCK ? &VI_MTX(vp)->lock_object : NULL);
110 WITNESS_LOCK(&lk->lock_object, 0, file, line);
111 if ((flags & LK_INTERLOCK) != 0)
112 VI_UNLOCK(vp);
113 LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, ap->a_file, line);
114 return (0);
115 }
116
117 static int
crossmp_vop_unlock(struct vop_unlock_args * ap)118 crossmp_vop_unlock(struct vop_unlock_args *ap)
119 {
120 struct vnode *vp;
121 struct lock *lk __unused;
122 int flags;
123
124 vp = ap->a_vp;
125 lk = vp->v_vnlock;
126 flags = ap->a_flags;
127
128 if ((flags & LK_INTERLOCK) != 0)
129 VI_UNLOCK(vp);
130 WITNESS_UNLOCK(&lk->lock_object, 0, LOCK_FILE, LOCK_LINE);
131 LOCK_LOG_LOCK("SUNLOCK", &lk->lock_object, 0, 0, LOCK_FILE,
132 LOCK_LINE);
133 return (0);
134 }
135
136 static struct vop_vector crossmp_vnodeops = {
137 .vop_default = &default_vnodeops,
138 .vop_islocked = crossmp_vop_islocked,
139 .vop_lock1 = crossmp_vop_lock1,
140 .vop_unlock = crossmp_vop_unlock,
141 };
142
143 struct nameicap_tracker {
144 struct vnode *dp;
145 TAILQ_ENTRY(nameicap_tracker) nm_link;
146 };
147
148 /* Zone for cap mode tracker elements used for dotdot capability checks. */
149 static uma_zone_t nt_zone;
150
151 static void
nameiinit(void * dummy __unused)152 nameiinit(void *dummy __unused)
153 {
154
155 namei_zone = uma_zcreate("NAMEI", MAXPATHLEN, NULL, NULL, NULL, NULL,
156 UMA_ALIGN_PTR, 0);
157 nt_zone = uma_zcreate("rentr", sizeof(struct nameicap_tracker),
158 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
159 getnewvnode("crossmp", NULL, &crossmp_vnodeops, &vp_crossmp);
160 }
161 SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_SECOND, nameiinit, NULL);
162
163 static int lookup_cap_dotdot = 1;
164 SYSCTL_INT(_vfs, OID_AUTO, lookup_cap_dotdot, CTLFLAG_RWTUN,
165 &lookup_cap_dotdot, 0,
166 "enables \"..\" components in path lookup in capability mode");
167 static int lookup_cap_dotdot_nonlocal = 1;
168 SYSCTL_INT(_vfs, OID_AUTO, lookup_cap_dotdot_nonlocal, CTLFLAG_RWTUN,
169 &lookup_cap_dotdot_nonlocal, 0,
170 "enables \"..\" components in path lookup in capability mode "
171 "on non-local mount");
172
173 static void
nameicap_tracker_add(struct nameidata * ndp,struct vnode * dp)174 nameicap_tracker_add(struct nameidata *ndp, struct vnode *dp)
175 {
176 struct nameicap_tracker *nt;
177
178 if ((ndp->ni_lcf & NI_LCF_CAP_DOTDOT) == 0 || dp->v_type != VDIR)
179 return;
180 nt = uma_zalloc(nt_zone, M_WAITOK);
181 vhold(dp);
182 nt->dp = dp;
183 TAILQ_INSERT_TAIL(&ndp->ni_cap_tracker, nt, nm_link);
184 }
185
186 static void
nameicap_cleanup(struct nameidata * ndp)187 nameicap_cleanup(struct nameidata *ndp)
188 {
189 struct nameicap_tracker *nt, *nt1;
190
191 KASSERT(TAILQ_EMPTY(&ndp->ni_cap_tracker) ||
192 (ndp->ni_lcf & NI_LCF_CAP_DOTDOT) != 0, ("not strictrelative"));
193 TAILQ_FOREACH_SAFE(nt, &ndp->ni_cap_tracker, nm_link, nt1) {
194 TAILQ_REMOVE(&ndp->ni_cap_tracker, nt, nm_link);
195 vdrop(nt->dp);
196 uma_zfree(nt_zone, nt);
197 }
198 }
199
200 /*
201 * For dotdot lookups in capability mode, only allow the component
202 * lookup to succeed if the resulting directory was already traversed
203 * during the operation. Also fail dotdot lookups for non-local
204 * filesystems, where external agents might assist local lookups to
205 * escape the compartment.
206 */
207 static int
nameicap_check_dotdot(struct nameidata * ndp,struct vnode * dp)208 nameicap_check_dotdot(struct nameidata *ndp, struct vnode *dp)
209 {
210 struct nameicap_tracker *nt;
211 struct mount *mp;
212
213 if ((ndp->ni_lcf & NI_LCF_CAP_DOTDOT) == 0 || dp == NULL ||
214 dp->v_type != VDIR)
215 return (0);
216 mp = dp->v_mount;
217 if (lookup_cap_dotdot_nonlocal == 0 && mp != NULL &&
218 (mp->mnt_flag & MNT_LOCAL) == 0)
219 return (ENOTCAPABLE);
220 TAILQ_FOREACH_REVERSE(nt, &ndp->ni_cap_tracker, nameicap_tracker_head,
221 nm_link) {
222 if (dp == nt->dp)
223 return (0);
224 }
225 return (ENOTCAPABLE);
226 }
227
228 static void
namei_cleanup_cnp(struct componentname * cnp)229 namei_cleanup_cnp(struct componentname *cnp)
230 {
231
232 uma_zfree(namei_zone, cnp->cn_pnbuf);
233 #ifdef DIAGNOSTIC
234 cnp->cn_pnbuf = NULL;
235 cnp->cn_nameptr = NULL;
236 #endif
237 }
238
239 static int
namei_handle_root(struct nameidata * ndp,struct vnode ** dpp)240 namei_handle_root(struct nameidata *ndp, struct vnode **dpp)
241 {
242 struct componentname *cnp;
243
244 cnp = &ndp->ni_cnd;
245 if ((ndp->ni_lcf & NI_LCF_STRICTRELATIVE) != 0) {
246 #ifdef KTRACE
247 if (KTRPOINT(curthread, KTR_CAPFAIL))
248 ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL);
249 #endif
250 return (ENOTCAPABLE);
251 }
252 while (*(cnp->cn_nameptr) == '/') {
253 cnp->cn_nameptr++;
254 ndp->ni_pathlen--;
255 }
256 *dpp = ndp->ni_rootdir;
257 vrefact(*dpp);
258 return (0);
259 }
260
261 /*
262 * Convert a pathname into a pointer to a locked vnode.
263 *
264 * The FOLLOW flag is set when symbolic links are to be followed
265 * when they occur at the end of the name translation process.
266 * Symbolic links are always followed for all other pathname
267 * components other than the last.
268 *
269 * The segflg defines whether the name is to be copied from user
270 * space or kernel space.
271 *
272 * Overall outline of namei:
273 *
274 * copy in name
275 * get starting directory
276 * while (!done && !error) {
277 * call lookup to search path.
278 * if symbolic link, massage name in buffer and continue
279 * }
280 */
281 int
namei(struct nameidata * ndp)282 namei(struct nameidata *ndp)
283 {
284 struct filedesc *fdp; /* pointer to file descriptor state */
285 char *cp; /* pointer into pathname argument */
286 struct vnode *dp; /* the directory we are searching */
287 struct iovec aiov; /* uio for reading symbolic links */
288 struct componentname *cnp;
289 struct thread *td;
290 struct proc *p;
291 cap_rights_t rights;
292 struct uio auio;
293 int error, linklen, startdir_used;
294
295 cnp = &ndp->ni_cnd;
296 td = cnp->cn_thread;
297 p = td->td_proc;
298 ndp->ni_cnd.cn_cred = ndp->ni_cnd.cn_thread->td_ucred;
299 KASSERT(cnp->cn_cred && p, ("namei: bad cred/proc"));
300 KASSERT((cnp->cn_nameiop & (~OPMASK)) == 0,
301 ("namei: nameiop contaminated with flags"));
302 KASSERT((cnp->cn_flags & OPMASK) == 0,
303 ("namei: flags contaminated with nameiops"));
304 MPASS(ndp->ni_startdir == NULL || ndp->ni_startdir->v_type == VDIR ||
305 ndp->ni_startdir->v_type == VBAD);
306 fdp = p->p_fd;
307 TAILQ_INIT(&ndp->ni_cap_tracker);
308 ndp->ni_lcf = 0;
309
310 /* We will set this ourselves if we need it. */
311 cnp->cn_flags &= ~TRAILINGSLASH;
312
313 /*
314 * Get a buffer for the name to be translated, and copy the
315 * name into the buffer.
316 */
317 if ((cnp->cn_flags & HASBUF) == 0)
318 cnp->cn_pnbuf = uma_zalloc(namei_zone, M_WAITOK);
319 if (ndp->ni_segflg == UIO_SYSSPACE)
320 error = copystr(ndp->ni_dirp, cnp->cn_pnbuf, MAXPATHLEN,
321 &ndp->ni_pathlen);
322 else
323 error = copyinstr(ndp->ni_dirp, cnp->cn_pnbuf, MAXPATHLEN,
324 &ndp->ni_pathlen);
325
326 /*
327 * Don't allow empty pathnames.
328 */
329 if (error == 0 && *cnp->cn_pnbuf == '\0')
330 error = ENOENT;
331
332 #ifdef CAPABILITY_MODE
333 /*
334 * In capability mode, lookups must be restricted to happen in
335 * the subtree with the root specified by the file descriptor:
336 * - The root must be real file descriptor, not the pseudo-descriptor
337 * AT_FDCWD.
338 * - The passed path must be relative and not absolute.
339 * - If lookup_cap_dotdot is disabled, path must not contain the
340 * '..' components.
341 * - If lookup_cap_dotdot is enabled, we verify that all '..'
342 * components lookups result in the directories which were
343 * previously walked by us, which prevents an escape from
344 * the relative root.
345 */
346 if (error == 0 && IN_CAPABILITY_MODE(td) &&
347 (cnp->cn_flags & NOCAPCHECK) == 0) {
348 ndp->ni_lcf |= NI_LCF_STRICTRELATIVE;
349 if (ndp->ni_dirfd == AT_FDCWD) {
350 #ifdef KTRACE
351 if (KTRPOINT(td, KTR_CAPFAIL))
352 ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL);
353 #endif
354 error = ECAPMODE;
355 }
356 }
357 #endif
358 if (error != 0) {
359 namei_cleanup_cnp(cnp);
360 ndp->ni_vp = NULL;
361 return (error);
362 }
363 ndp->ni_loopcnt = 0;
364 #ifdef KTRACE
365 if (KTRPOINT(td, KTR_NAMEI)) {
366 KASSERT(cnp->cn_thread == curthread,
367 ("namei not using curthread"));
368 ktrnamei(cnp->cn_pnbuf);
369 }
370 #endif
371 /*
372 * Get starting point for the translation.
373 */
374 FILEDESC_SLOCK(fdp);
375 ndp->ni_rootdir = fdp->fd_rdir;
376 vrefact(ndp->ni_rootdir);
377 ndp->ni_topdir = fdp->fd_jdir;
378
379 /*
380 * If we are auditing the kernel pathname, save the user pathname.
381 */
382 if (cnp->cn_flags & AUDITVNODE1)
383 AUDIT_ARG_UPATH1(td, ndp->ni_dirfd, cnp->cn_pnbuf);
384 if (cnp->cn_flags & AUDITVNODE2)
385 AUDIT_ARG_UPATH2(td, ndp->ni_dirfd, cnp->cn_pnbuf);
386
387 startdir_used = 0;
388 dp = NULL;
389 cnp->cn_nameptr = cnp->cn_pnbuf;
390 if (cnp->cn_pnbuf[0] == '/') {
391 ndp->ni_resflags |= NIRES_ABS;
392 error = namei_handle_root(ndp, &dp);
393 } else {
394 if (ndp->ni_startdir != NULL) {
395 dp = ndp->ni_startdir;
396 startdir_used = 1;
397 } else if (ndp->ni_dirfd == AT_FDCWD) {
398 dp = fdp->fd_cdir;
399 vrefact(dp);
400 } else {
401 rights = ndp->ni_rightsneeded;
402 cap_rights_set(&rights, CAP_LOOKUP);
403
404 if (cnp->cn_flags & AUDITVNODE1)
405 AUDIT_ARG_ATFD1(ndp->ni_dirfd);
406 if (cnp->cn_flags & AUDITVNODE2)
407 AUDIT_ARG_ATFD2(ndp->ni_dirfd);
408 error = fgetvp_rights(td, ndp->ni_dirfd,
409 &rights, &ndp->ni_filecaps, &dp);
410 if (error == EINVAL)
411 error = ENOTDIR;
412 #ifdef CAPABILITIES
413 /*
414 * If file descriptor doesn't have all rights,
415 * all lookups relative to it must also be
416 * strictly relative.
417 */
418 CAP_ALL(&rights);
419 if (!cap_rights_contains(&ndp->ni_filecaps.fc_rights,
420 &rights) ||
421 ndp->ni_filecaps.fc_fcntls != CAP_FCNTL_ALL ||
422 ndp->ni_filecaps.fc_nioctls != -1) {
423 ndp->ni_lcf |= NI_LCF_STRICTRELATIVE;
424 }
425 #endif
426 }
427 if (error == 0 && dp->v_type != VDIR)
428 error = ENOTDIR;
429 }
430 FILEDESC_SUNLOCK(fdp);
431 if (ndp->ni_startdir != NULL && !startdir_used)
432 vrele(ndp->ni_startdir);
433 if (error != 0) {
434 if (dp != NULL)
435 vrele(dp);
436 goto out;
437 }
438 if ((ndp->ni_lcf & NI_LCF_STRICTRELATIVE) != 0 &&
439 lookup_cap_dotdot != 0)
440 ndp->ni_lcf |= NI_LCF_CAP_DOTDOT;
441 SDT_PROBE3(vfs, namei, lookup, entry, dp, cnp->cn_pnbuf,
442 cnp->cn_flags);
443 for (;;) {
444 ndp->ni_startdir = dp;
445 error = lookup(ndp);
446 if (error != 0)
447 goto out;
448 /*
449 * If not a symbolic link, we're done.
450 */
451 if ((cnp->cn_flags & ISSYMLINK) == 0) {
452 vrele(ndp->ni_rootdir);
453 if ((cnp->cn_flags & (SAVENAME | SAVESTART)) == 0) {
454 namei_cleanup_cnp(cnp);
455 } else
456 cnp->cn_flags |= HASBUF;
457 nameicap_cleanup(ndp);
458 SDT_PROBE2(vfs, namei, lookup, return, 0, ndp->ni_vp);
459 return (0);
460 }
461 if (ndp->ni_loopcnt++ >= MAXSYMLINKS) {
462 error = ELOOP;
463 break;
464 }
465 #ifdef MAC
466 if ((cnp->cn_flags & NOMACCHECK) == 0) {
467 error = mac_vnode_check_readlink(td->td_ucred,
468 ndp->ni_vp);
469 if (error != 0)
470 break;
471 }
472 #endif
473 if (ndp->ni_pathlen > 1)
474 cp = uma_zalloc(namei_zone, M_WAITOK);
475 else
476 cp = cnp->cn_pnbuf;
477 aiov.iov_base = cp;
478 aiov.iov_len = MAXPATHLEN;
479 auio.uio_iov = &aiov;
480 auio.uio_iovcnt = 1;
481 auio.uio_offset = 0;
482 auio.uio_rw = UIO_READ;
483 auio.uio_segflg = UIO_SYSSPACE;
484 auio.uio_td = td;
485 auio.uio_resid = MAXPATHLEN;
486 error = VOP_READLINK(ndp->ni_vp, &auio, cnp->cn_cred);
487 if (error != 0) {
488 if (ndp->ni_pathlen > 1)
489 uma_zfree(namei_zone, cp);
490 break;
491 }
492 linklen = MAXPATHLEN - auio.uio_resid;
493 if (linklen == 0) {
494 if (ndp->ni_pathlen > 1)
495 uma_zfree(namei_zone, cp);
496 error = ENOENT;
497 break;
498 }
499 if (linklen + ndp->ni_pathlen > MAXPATHLEN) {
500 if (ndp->ni_pathlen > 1)
501 uma_zfree(namei_zone, cp);
502 error = ENAMETOOLONG;
503 break;
504 }
505 if (ndp->ni_pathlen > 1) {
506 bcopy(ndp->ni_next, cp + linklen, ndp->ni_pathlen);
507 uma_zfree(namei_zone, cnp->cn_pnbuf);
508 cnp->cn_pnbuf = cp;
509 } else
510 cnp->cn_pnbuf[linklen] = '\0';
511 ndp->ni_pathlen += linklen;
512 vput(ndp->ni_vp);
513 dp = ndp->ni_dvp;
514 /*
515 * Check if root directory should replace current directory.
516 */
517 cnp->cn_nameptr = cnp->cn_pnbuf;
518 if (*(cnp->cn_nameptr) == '/') {
519 vrele(dp);
520 error = namei_handle_root(ndp, &dp);
521 if (error != 0)
522 goto out;
523 }
524 }
525 vput(ndp->ni_vp);
526 ndp->ni_vp = NULL;
527 vrele(ndp->ni_dvp);
528 out:
529 vrele(ndp->ni_rootdir);
530 namei_cleanup_cnp(cnp);
531 nameicap_cleanup(ndp);
532 SDT_PROBE2(vfs, namei, lookup, return, error, NULL);
533 return (error);
534 }
535
536 static int
compute_cn_lkflags(struct mount * mp,int lkflags,int cnflags)537 compute_cn_lkflags(struct mount *mp, int lkflags, int cnflags)
538 {
539
540 if (mp == NULL || ((lkflags & LK_SHARED) &&
541 (!(mp->mnt_kern_flag & MNTK_LOOKUP_SHARED) ||
542 ((cnflags & ISDOTDOT) &&
543 (mp->mnt_kern_flag & MNTK_LOOKUP_EXCL_DOTDOT))))) {
544 lkflags &= ~LK_SHARED;
545 lkflags |= LK_EXCLUSIVE;
546 }
547 lkflags |= LK_NODDLKTREAT;
548 return (lkflags);
549 }
550
551 static __inline int
needs_exclusive_leaf(struct mount * mp,int flags)552 needs_exclusive_leaf(struct mount *mp, int flags)
553 {
554
555 /*
556 * Intermediate nodes can use shared locks, we only need to
557 * force an exclusive lock for leaf nodes.
558 */
559 if ((flags & (ISLASTCN | LOCKLEAF)) != (ISLASTCN | LOCKLEAF))
560 return (0);
561
562 /* Always use exclusive locks if LOCKSHARED isn't set. */
563 if (!(flags & LOCKSHARED))
564 return (1);
565
566 /*
567 * For lookups during open(), if the mount point supports
568 * extended shared operations, then use a shared lock for the
569 * leaf node, otherwise use an exclusive lock.
570 */
571 if ((flags & ISOPEN) != 0)
572 return (!MNT_EXTENDED_SHARED(mp));
573
574 /*
575 * Lookup requests outside of open() that specify LOCKSHARED
576 * only need a shared lock on the leaf vnode.
577 */
578 return (0);
579 }
580
581 /*
582 * Search a pathname.
583 * This is a very central and rather complicated routine.
584 *
585 * The pathname is pointed to by ni_ptr and is of length ni_pathlen.
586 * The starting directory is taken from ni_startdir. The pathname is
587 * descended until done, or a symbolic link is encountered. The variable
588 * ni_more is clear if the path is completed; it is set to one if a
589 * symbolic link needing interpretation is encountered.
590 *
591 * The flag argument is LOOKUP, CREATE, RENAME, or DELETE depending on
592 * whether the name is to be looked up, created, renamed, or deleted.
593 * When CREATE, RENAME, or DELETE is specified, information usable in
594 * creating, renaming, or deleting a directory entry may be calculated.
595 * If flag has LOCKPARENT or'ed into it, the parent directory is returned
596 * locked. If flag has WANTPARENT or'ed into it, the parent directory is
597 * returned unlocked. Otherwise the parent directory is not returned. If
598 * the target of the pathname exists and LOCKLEAF is or'ed into the flag
599 * the target is returned locked, otherwise it is returned unlocked.
600 * When creating or renaming and LOCKPARENT is specified, the target may not
601 * be ".". When deleting and LOCKPARENT is specified, the target may be ".".
602 *
603 * Overall outline of lookup:
604 *
605 * dirloop:
606 * identify next component of name at ndp->ni_ptr
607 * handle degenerate case where name is null string
608 * if .. and crossing mount points and on mounted filesys, find parent
609 * call VOP_LOOKUP routine for next component name
610 * directory vnode returned in ni_dvp, unlocked unless LOCKPARENT set
611 * component vnode returned in ni_vp (if it exists), locked.
612 * if result vnode is mounted on and crossing mount points,
613 * find mounted on vnode
614 * if more components of name, do next level at dirloop
615 * return the answer in ni_vp, locked if LOCKLEAF set
616 * if LOCKPARENT set, return locked parent in ni_dvp
617 * if WANTPARENT set, return unlocked parent in ni_dvp
618 */
619 int
lookup(struct nameidata * ndp)620 lookup(struct nameidata *ndp)
621 {
622 char *cp; /* pointer into pathname argument */
623 char *prev_ni_next; /* saved ndp->ni_next */
624 struct vnode *dp = NULL; /* the directory we are searching */
625 struct vnode *tdp; /* saved dp */
626 struct mount *mp; /* mount table entry */
627 struct prison *pr;
628 size_t prev_ni_pathlen; /* saved ndp->ni_pathlen */
629 int docache; /* == 0 do not cache last component */
630 int wantparent; /* 1 => wantparent or lockparent flag */
631 int rdonly; /* lookup read-only flag bit */
632 int error = 0;
633 int dpunlocked = 0; /* dp has already been unlocked */
634 int relookup = 0; /* do not consume the path component */
635 struct componentname *cnp = &ndp->ni_cnd;
636 int lkflags_save;
637 int ni_dvp_unlocked;
638
639 /*
640 * Setup: break out flag bits into variables.
641 */
642 ni_dvp_unlocked = 0;
643 wantparent = cnp->cn_flags & (LOCKPARENT | WANTPARENT);
644 KASSERT(cnp->cn_nameiop == LOOKUP || wantparent,
645 ("CREATE, DELETE, RENAME require LOCKPARENT or WANTPARENT."));
646 docache = (cnp->cn_flags & NOCACHE) ^ NOCACHE;
647 if (cnp->cn_nameiop == DELETE ||
648 (wantparent && cnp->cn_nameiop != CREATE &&
649 cnp->cn_nameiop != LOOKUP))
650 docache = 0;
651 rdonly = cnp->cn_flags & RDONLY;
652 cnp->cn_flags &= ~ISSYMLINK;
653 ndp->ni_dvp = NULL;
654 /*
655 * We use shared locks until we hit the parent of the last cn then
656 * we adjust based on the requesting flags.
657 */
658 cnp->cn_lkflags = LK_SHARED;
659 dp = ndp->ni_startdir;
660 ndp->ni_startdir = NULLVP;
661 vn_lock(dp,
662 compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags | LK_RETRY,
663 cnp->cn_flags));
664
665 dirloop:
666 /*
667 * Search a new directory.
668 *
669 * The last component of the filename is left accessible via
670 * cnp->cn_nameptr for callers that need the name. Callers needing
671 * the name set the SAVENAME flag. When done, they assume
672 * responsibility for freeing the pathname buffer.
673 */
674 for (cp = cnp->cn_nameptr; *cp != 0 && *cp != '/'; cp++)
675 continue;
676 cnp->cn_namelen = cp - cnp->cn_nameptr;
677 if (cnp->cn_namelen > NAME_MAX) {
678 error = ENAMETOOLONG;
679 goto bad;
680 }
681 #ifdef NAMEI_DIAGNOSTIC
682 { char c = *cp;
683 *cp = '\0';
684 printf("{%s}: ", cnp->cn_nameptr);
685 *cp = c; }
686 #endif
687 prev_ni_pathlen = ndp->ni_pathlen;
688 ndp->ni_pathlen -= cnp->cn_namelen;
689 KASSERT(ndp->ni_pathlen <= PATH_MAX,
690 ("%s: ni_pathlen underflow to %zd\n", __func__, ndp->ni_pathlen));
691 prev_ni_next = ndp->ni_next;
692 ndp->ni_next = cp;
693
694 /*
695 * Replace multiple slashes by a single slash and trailing slashes
696 * by a null. This must be done before VOP_LOOKUP() because some
697 * fs's don't know about trailing slashes. Remember if there were
698 * trailing slashes to handle symlinks, existing non-directories
699 * and non-existing files that won't be directories specially later.
700 */
701 while (*cp == '/' && (cp[1] == '/' || cp[1] == '\0')) {
702 cp++;
703 ndp->ni_pathlen--;
704 if (*cp == '\0') {
705 *ndp->ni_next = '\0';
706 cnp->cn_flags |= TRAILINGSLASH;
707 }
708 }
709 ndp->ni_next = cp;
710
711 cnp->cn_flags |= MAKEENTRY;
712 if (*cp == '\0' && docache == 0)
713 cnp->cn_flags &= ~MAKEENTRY;
714 if (cnp->cn_namelen == 2 &&
715 cnp->cn_nameptr[1] == '.' && cnp->cn_nameptr[0] == '.')
716 cnp->cn_flags |= ISDOTDOT;
717 else
718 cnp->cn_flags &= ~ISDOTDOT;
719 if (*ndp->ni_next == 0)
720 cnp->cn_flags |= ISLASTCN;
721 else
722 cnp->cn_flags &= ~ISLASTCN;
723
724 if ((cnp->cn_flags & ISLASTCN) != 0 &&
725 cnp->cn_namelen == 1 && cnp->cn_nameptr[0] == '.' &&
726 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) {
727 error = EINVAL;
728 goto bad;
729 }
730
731 nameicap_tracker_add(ndp, dp);
732
733 /*
734 * Check for degenerate name (e.g. / or "")
735 * which is a way of talking about a directory,
736 * e.g. like "/." or ".".
737 */
738 if (cnp->cn_nameptr[0] == '\0') {
739 if (dp->v_type != VDIR) {
740 error = ENOTDIR;
741 goto bad;
742 }
743 if (cnp->cn_nameiop != LOOKUP) {
744 error = EISDIR;
745 goto bad;
746 }
747 if (wantparent) {
748 ndp->ni_dvp = dp;
749 VREF(dp);
750 }
751 ndp->ni_vp = dp;
752
753 if (cnp->cn_flags & AUDITVNODE1)
754 AUDIT_ARG_VNODE1(dp);
755 else if (cnp->cn_flags & AUDITVNODE2)
756 AUDIT_ARG_VNODE2(dp);
757
758 if (!(cnp->cn_flags & (LOCKPARENT | LOCKLEAF)))
759 VOP_UNLOCK(dp, 0);
760 /* XXX This should probably move to the top of function. */
761 if (cnp->cn_flags & SAVESTART)
762 panic("lookup: SAVESTART");
763 goto success;
764 }
765
766 /*
767 * Handle "..": five special cases.
768 * 0. If doing a capability lookup and lookup_cap_dotdot is
769 * disabled, return ENOTCAPABLE.
770 * 1. Return an error if this is the last component of
771 * the name and the operation is DELETE or RENAME.
772 * 2. If at root directory (e.g. after chroot)
773 * or at absolute root directory
774 * then ignore it so can't get out.
775 * 3. If this vnode is the root of a mounted
776 * filesystem, then replace it with the
777 * vnode which was mounted on so we take the
778 * .. in the other filesystem.
779 * 4. If the vnode is the top directory of
780 * the jail or chroot, don't let them out.
781 * 5. If doing a capability lookup and lookup_cap_dotdot is
782 * enabled, return ENOTCAPABLE if the lookup would escape
783 * from the initial file descriptor directory. Checks are
784 * done by ensuring that namei() already traversed the
785 * result of dotdot lookup.
786 */
787 if (cnp->cn_flags & ISDOTDOT) {
788 if ((ndp->ni_lcf & (NI_LCF_STRICTRELATIVE | NI_LCF_CAP_DOTDOT))
789 == NI_LCF_STRICTRELATIVE) {
790 #ifdef KTRACE
791 if (KTRPOINT(curthread, KTR_CAPFAIL))
792 ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL);
793 #endif
794 error = ENOTCAPABLE;
795 goto bad;
796 }
797 if ((cnp->cn_flags & ISLASTCN) != 0 &&
798 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) {
799 error = EINVAL;
800 goto bad;
801 }
802 for (;;) {
803 for (pr = cnp->cn_cred->cr_prison; pr != NULL;
804 pr = pr->pr_parent)
805 if (dp == pr->pr_root)
806 break;
807 if (dp == ndp->ni_rootdir ||
808 dp == ndp->ni_topdir ||
809 dp == rootvnode ||
810 pr != NULL ||
811 ((dp->v_vflag & VV_ROOT) != 0 &&
812 (cnp->cn_flags & NOCROSSMOUNT) != 0)) {
813 ndp->ni_dvp = dp;
814 ndp->ni_vp = dp;
815 VREF(dp);
816 goto nextname;
817 }
818 if ((dp->v_vflag & VV_ROOT) == 0)
819 break;
820 if (dp->v_iflag & VI_DOOMED) { /* forced unmount */
821 error = ENOENT;
822 goto bad;
823 }
824 tdp = dp;
825 dp = dp->v_mount->mnt_vnodecovered;
826 VREF(dp);
827 vput(tdp);
828 vn_lock(dp,
829 compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags |
830 LK_RETRY, ISDOTDOT));
831 error = nameicap_check_dotdot(ndp, dp);
832 if (error != 0) {
833 #ifdef KTRACE
834 if (KTRPOINT(curthread, KTR_CAPFAIL))
835 ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL);
836 #endif
837 goto bad;
838 }
839 }
840 }
841
842 /*
843 * We now have a segment name to search for, and a directory to search.
844 */
845 unionlookup:
846 #ifdef MAC
847 if ((cnp->cn_flags & NOMACCHECK) == 0) {
848 error = mac_vnode_check_lookup(cnp->cn_thread->td_ucred, dp,
849 cnp);
850 if (error)
851 goto bad;
852 }
853 #endif
854 ndp->ni_dvp = dp;
855 ndp->ni_vp = NULL;
856 ASSERT_VOP_LOCKED(dp, "lookup");
857 /*
858 * If we have a shared lock we may need to upgrade the lock for the
859 * last operation.
860 */
861 if ((cnp->cn_flags & LOCKPARENT) && (cnp->cn_flags & ISLASTCN) &&
862 dp != vp_crossmp && VOP_ISLOCKED(dp) == LK_SHARED)
863 vn_lock(dp, LK_UPGRADE|LK_RETRY);
864 if ((dp->v_iflag & VI_DOOMED) != 0) {
865 error = ENOENT;
866 goto bad;
867 }
868 /*
869 * If we're looking up the last component and we need an exclusive
870 * lock, adjust our lkflags.
871 */
872 if (needs_exclusive_leaf(dp->v_mount, cnp->cn_flags))
873 cnp->cn_lkflags = LK_EXCLUSIVE;
874 #ifdef NAMEI_DIAGNOSTIC
875 vn_printf(dp, "lookup in ");
876 #endif
877 lkflags_save = cnp->cn_lkflags;
878 cnp->cn_lkflags = compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags,
879 cnp->cn_flags);
880 error = VOP_LOOKUP(dp, &ndp->ni_vp, cnp);
881 cnp->cn_lkflags = lkflags_save;
882 if (error != 0) {
883 KASSERT(ndp->ni_vp == NULL, ("leaf should be empty"));
884 #ifdef NAMEI_DIAGNOSTIC
885 printf("not found\n");
886 #endif
887 if ((error == ENOENT) &&
888 (dp->v_vflag & VV_ROOT) && (dp->v_mount != NULL) &&
889 (dp->v_mount->mnt_flag & MNT_UNION)) {
890 tdp = dp;
891 dp = dp->v_mount->mnt_vnodecovered;
892 VREF(dp);
893 vput(tdp);
894 vn_lock(dp,
895 compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags |
896 LK_RETRY, cnp->cn_flags));
897 nameicap_tracker_add(ndp, dp);
898 goto unionlookup;
899 }
900
901 if (error == ERELOOKUP) {
902 vref(dp);
903 ndp->ni_vp = dp;
904 error = 0;
905 relookup = 1;
906 goto good;
907 }
908
909 if (error != EJUSTRETURN)
910 goto bad;
911 /*
912 * At this point, we know we're at the end of the
913 * pathname. If creating / renaming, we can consider
914 * allowing the file or directory to be created / renamed,
915 * provided we're not on a read-only filesystem.
916 */
917 if (rdonly) {
918 error = EROFS;
919 goto bad;
920 }
921 /* trailing slash only allowed for directories */
922 if ((cnp->cn_flags & TRAILINGSLASH) &&
923 !(cnp->cn_flags & WILLBEDIR)) {
924 error = ENOENT;
925 goto bad;
926 }
927 if ((cnp->cn_flags & LOCKPARENT) == 0)
928 VOP_UNLOCK(dp, 0);
929 /*
930 * We return with ni_vp NULL to indicate that the entry
931 * doesn't currently exist, leaving a pointer to the
932 * (possibly locked) directory vnode in ndp->ni_dvp.
933 */
934 if (cnp->cn_flags & SAVESTART) {
935 ndp->ni_startdir = ndp->ni_dvp;
936 VREF(ndp->ni_startdir);
937 }
938 goto success;
939 }
940
941 good:
942 #ifdef NAMEI_DIAGNOSTIC
943 printf("found\n");
944 #endif
945 dp = ndp->ni_vp;
946
947 /*
948 * Check to see if the vnode has been mounted on;
949 * if so find the root of the mounted filesystem.
950 */
951 while (dp->v_type == VDIR && (mp = dp->v_mountedhere) &&
952 (cnp->cn_flags & NOCROSSMOUNT) == 0) {
953 if (vfs_busy(mp, 0))
954 continue;
955 vput(dp);
956 if (dp != ndp->ni_dvp)
957 vput(ndp->ni_dvp);
958 else
959 vrele(ndp->ni_dvp);
960 vrefact(vp_crossmp);
961 ndp->ni_dvp = vp_crossmp;
962 error = VFS_ROOT(mp, compute_cn_lkflags(mp, cnp->cn_lkflags,
963 cnp->cn_flags), &tdp);
964 vfs_unbusy(mp);
965 if (vn_lock(vp_crossmp, LK_SHARED | LK_NOWAIT))
966 panic("vp_crossmp exclusively locked or reclaimed");
967 if (error) {
968 dpunlocked = 1;
969 goto bad2;
970 }
971 ndp->ni_vp = dp = tdp;
972 }
973
974 /*
975 * Check for symbolic link
976 */
977 if ((dp->v_type == VLNK) &&
978 ((cnp->cn_flags & FOLLOW) || (cnp->cn_flags & TRAILINGSLASH) ||
979 *ndp->ni_next == '/')) {
980 cnp->cn_flags |= ISSYMLINK;
981 if (dp->v_iflag & VI_DOOMED) {
982 /*
983 * We can't know whether the directory was mounted with
984 * NOSYMFOLLOW, so we can't follow safely.
985 */
986 error = ENOENT;
987 goto bad2;
988 }
989 if (dp->v_mount->mnt_flag & MNT_NOSYMFOLLOW) {
990 error = EACCES;
991 goto bad2;
992 }
993 /*
994 * Symlink code always expects an unlocked dvp.
995 */
996 if (ndp->ni_dvp != ndp->ni_vp) {
997 VOP_UNLOCK(ndp->ni_dvp, 0);
998 ni_dvp_unlocked = 1;
999 }
1000 goto success;
1001 }
1002
1003 nextname:
1004 /*
1005 * Not a symbolic link that we will follow. Continue with the
1006 * next component if there is any; otherwise, we're done.
1007 */
1008 KASSERT((cnp->cn_flags & ISLASTCN) || *ndp->ni_next == '/',
1009 ("lookup: invalid path state."));
1010 if (relookup) {
1011 relookup = 0;
1012 ndp->ni_pathlen = prev_ni_pathlen;
1013 ndp->ni_next = prev_ni_next;
1014 if (ndp->ni_dvp != dp)
1015 vput(ndp->ni_dvp);
1016 else
1017 vrele(ndp->ni_dvp);
1018 goto dirloop;
1019 }
1020 if (cnp->cn_flags & ISDOTDOT) {
1021 error = nameicap_check_dotdot(ndp, ndp->ni_vp);
1022 if (error != 0) {
1023 #ifdef KTRACE
1024 if (KTRPOINT(curthread, KTR_CAPFAIL))
1025 ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL);
1026 #endif
1027 goto bad2;
1028 }
1029 }
1030 if (*ndp->ni_next == '/') {
1031 cnp->cn_nameptr = ndp->ni_next;
1032 while (*cnp->cn_nameptr == '/') {
1033 cnp->cn_nameptr++;
1034 ndp->ni_pathlen--;
1035 }
1036 if (ndp->ni_dvp != dp)
1037 vput(ndp->ni_dvp);
1038 else
1039 vrele(ndp->ni_dvp);
1040 goto dirloop;
1041 }
1042 /*
1043 * If we're processing a path with a trailing slash,
1044 * check that the end result is a directory.
1045 */
1046 if ((cnp->cn_flags & TRAILINGSLASH) && dp->v_type != VDIR) {
1047 error = ENOTDIR;
1048 goto bad2;
1049 }
1050 /*
1051 * Disallow directory write attempts on read-only filesystems.
1052 */
1053 if (rdonly &&
1054 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) {
1055 error = EROFS;
1056 goto bad2;
1057 }
1058 if (cnp->cn_flags & SAVESTART) {
1059 ndp->ni_startdir = ndp->ni_dvp;
1060 VREF(ndp->ni_startdir);
1061 }
1062 if (!wantparent) {
1063 ni_dvp_unlocked = 2;
1064 if (ndp->ni_dvp != dp)
1065 vput(ndp->ni_dvp);
1066 else
1067 vrele(ndp->ni_dvp);
1068 } else if ((cnp->cn_flags & LOCKPARENT) == 0 && ndp->ni_dvp != dp) {
1069 VOP_UNLOCK(ndp->ni_dvp, 0);
1070 ni_dvp_unlocked = 1;
1071 }
1072
1073 if (cnp->cn_flags & AUDITVNODE1)
1074 AUDIT_ARG_VNODE1(dp);
1075 else if (cnp->cn_flags & AUDITVNODE2)
1076 AUDIT_ARG_VNODE2(dp);
1077
1078 if ((cnp->cn_flags & LOCKLEAF) == 0)
1079 VOP_UNLOCK(dp, 0);
1080 success:
1081 /*
1082 * Because of shared lookup we may have the vnode shared locked, but
1083 * the caller may want it to be exclusively locked.
1084 */
1085 if (needs_exclusive_leaf(dp->v_mount, cnp->cn_flags) &&
1086 VOP_ISLOCKED(dp) != LK_EXCLUSIVE) {
1087 vn_lock(dp, LK_UPGRADE | LK_RETRY);
1088 if (dp->v_iflag & VI_DOOMED) {
1089 error = ENOENT;
1090 goto bad2;
1091 }
1092 }
1093 return (0);
1094
1095 bad2:
1096 if (ni_dvp_unlocked != 2) {
1097 if (dp != ndp->ni_dvp && !ni_dvp_unlocked)
1098 vput(ndp->ni_dvp);
1099 else
1100 vrele(ndp->ni_dvp);
1101 }
1102 bad:
1103 if (!dpunlocked)
1104 vput(dp);
1105 ndp->ni_vp = NULL;
1106 return (error);
1107 }
1108
1109 /*
1110 * relookup - lookup a path name component
1111 * Used by lookup to re-acquire things.
1112 */
1113 int
relookup(struct vnode * dvp,struct vnode ** vpp,struct componentname * cnp)1114 relookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp)
1115 {
1116 struct vnode *dp = NULL; /* the directory we are searching */
1117 int wantparent; /* 1 => wantparent or lockparent flag */
1118 int rdonly; /* lookup read-only flag bit */
1119 int error = 0;
1120
1121 KASSERT(cnp->cn_flags & ISLASTCN,
1122 ("relookup: Not given last component."));
1123 /*
1124 * Setup: break out flag bits into variables.
1125 */
1126 wantparent = cnp->cn_flags & (LOCKPARENT|WANTPARENT);
1127 KASSERT(wantparent, ("relookup: parent not wanted."));
1128 rdonly = cnp->cn_flags & RDONLY;
1129 cnp->cn_flags &= ~ISSYMLINK;
1130 dp = dvp;
1131 cnp->cn_lkflags = LK_EXCLUSIVE;
1132 vn_lock(dp, LK_EXCLUSIVE | LK_RETRY);
1133
1134 /*
1135 * Search a new directory.
1136 *
1137 * The last component of the filename is left accessible via
1138 * cnp->cn_nameptr for callers that need the name. Callers needing
1139 * the name set the SAVENAME flag. When done, they assume
1140 * responsibility for freeing the pathname buffer.
1141 */
1142 #ifdef NAMEI_DIAGNOSTIC
1143 printf("{%s}: ", cnp->cn_nameptr);
1144 #endif
1145
1146 /*
1147 * Check for "" which represents the root directory after slash
1148 * removal.
1149 */
1150 if (cnp->cn_nameptr[0] == '\0') {
1151 /*
1152 * Support only LOOKUP for "/" because lookup()
1153 * can't succeed for CREATE, DELETE and RENAME.
1154 */
1155 KASSERT(cnp->cn_nameiop == LOOKUP, ("nameiop must be LOOKUP"));
1156 KASSERT(dp->v_type == VDIR, ("dp is not a directory"));
1157
1158 if (!(cnp->cn_flags & LOCKLEAF))
1159 VOP_UNLOCK(dp, 0);
1160 *vpp = dp;
1161 /* XXX This should probably move to the top of function. */
1162 if (cnp->cn_flags & SAVESTART)
1163 panic("lookup: SAVESTART");
1164 return (0);
1165 }
1166
1167 if (cnp->cn_flags & ISDOTDOT)
1168 panic ("relookup: lookup on dot-dot");
1169
1170 /*
1171 * We now have a segment name to search for, and a directory to search.
1172 */
1173 #ifdef NAMEI_DIAGNOSTIC
1174 vn_printf(dp, "search in ");
1175 #endif
1176 if ((error = VOP_LOOKUP(dp, vpp, cnp)) != 0) {
1177 KASSERT(*vpp == NULL, ("leaf should be empty"));
1178 if (error != EJUSTRETURN)
1179 goto bad;
1180 /*
1181 * If creating and at end of pathname, then can consider
1182 * allowing file to be created.
1183 */
1184 if (rdonly) {
1185 error = EROFS;
1186 goto bad;
1187 }
1188 /* ASSERT(dvp == ndp->ni_startdir) */
1189 if (cnp->cn_flags & SAVESTART)
1190 VREF(dvp);
1191 if ((cnp->cn_flags & LOCKPARENT) == 0)
1192 VOP_UNLOCK(dp, 0);
1193 /*
1194 * We return with ni_vp NULL to indicate that the entry
1195 * doesn't currently exist, leaving a pointer to the
1196 * (possibly locked) directory vnode in ndp->ni_dvp.
1197 */
1198 return (0);
1199 }
1200
1201 dp = *vpp;
1202
1203 /*
1204 * Disallow directory write attempts on read-only filesystems.
1205 */
1206 if (rdonly &&
1207 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) {
1208 if (dvp == dp)
1209 vrele(dvp);
1210 else
1211 vput(dvp);
1212 error = EROFS;
1213 goto bad;
1214 }
1215 /*
1216 * Set the parent lock/ref state to the requested state.
1217 */
1218 if ((cnp->cn_flags & LOCKPARENT) == 0 && dvp != dp) {
1219 if (wantparent)
1220 VOP_UNLOCK(dvp, 0);
1221 else
1222 vput(dvp);
1223 } else if (!wantparent)
1224 vrele(dvp);
1225 /*
1226 * Check for symbolic link
1227 */
1228 KASSERT(dp->v_type != VLNK || !(cnp->cn_flags & FOLLOW),
1229 ("relookup: symlink found.\n"));
1230
1231 /* ASSERT(dvp == ndp->ni_startdir) */
1232 if (cnp->cn_flags & SAVESTART)
1233 VREF(dvp);
1234
1235 if ((cnp->cn_flags & LOCKLEAF) == 0)
1236 VOP_UNLOCK(dp, 0);
1237 return (0);
1238 bad:
1239 vput(dp);
1240 *vpp = NULL;
1241 return (error);
1242 }
1243
1244 void
NDINIT_ALL(struct nameidata * ndp,u_long op,u_long flags,enum uio_seg segflg,const char * namep,int dirfd,struct vnode * startdir,cap_rights_t * rightsp,struct thread * td)1245 NDINIT_ALL(struct nameidata *ndp, u_long op, u_long flags, enum uio_seg segflg,
1246 const char *namep, int dirfd, struct vnode *startdir, cap_rights_t *rightsp,
1247 struct thread *td)
1248 {
1249
1250 ndp->ni_cnd.cn_nameiop = op;
1251 ndp->ni_cnd.cn_flags = flags;
1252 ndp->ni_segflg = segflg;
1253 ndp->ni_dirp = namep;
1254 ndp->ni_dirfd = dirfd;
1255 ndp->ni_startdir = startdir;
1256 ndp->ni_resflags = 0;
1257 if (rightsp != NULL)
1258 ndp->ni_rightsneeded = *rightsp;
1259 else
1260 cap_rights_init(&ndp->ni_rightsneeded);
1261 filecaps_init(&ndp->ni_filecaps);
1262 ndp->ni_cnd.cn_thread = td;
1263 }
1264
1265 /*
1266 * Free data allocated by namei(); see namei(9) for details.
1267 */
1268 void
NDFREE(struct nameidata * ndp,const u_int flags)1269 NDFREE(struct nameidata *ndp, const u_int flags)
1270 {
1271 int unlock_dvp;
1272 int unlock_vp;
1273
1274 unlock_dvp = 0;
1275 unlock_vp = 0;
1276
1277 if (!(flags & NDF_NO_FREE_PNBUF) &&
1278 (ndp->ni_cnd.cn_flags & HASBUF)) {
1279 uma_zfree(namei_zone, ndp->ni_cnd.cn_pnbuf);
1280 ndp->ni_cnd.cn_flags &= ~HASBUF;
1281 }
1282 if (!(flags & NDF_NO_VP_UNLOCK) &&
1283 (ndp->ni_cnd.cn_flags & LOCKLEAF) && ndp->ni_vp)
1284 unlock_vp = 1;
1285 if (!(flags & NDF_NO_DVP_UNLOCK) &&
1286 (ndp->ni_cnd.cn_flags & LOCKPARENT) &&
1287 ndp->ni_dvp != ndp->ni_vp)
1288 unlock_dvp = 1;
1289 if (!(flags & NDF_NO_VP_RELE) && ndp->ni_vp) {
1290 if (unlock_vp) {
1291 vput(ndp->ni_vp);
1292 unlock_vp = 0;
1293 } else
1294 vrele(ndp->ni_vp);
1295 ndp->ni_vp = NULL;
1296 }
1297 if (unlock_vp)
1298 VOP_UNLOCK(ndp->ni_vp, 0);
1299 if (!(flags & NDF_NO_DVP_RELE) &&
1300 (ndp->ni_cnd.cn_flags & (LOCKPARENT|WANTPARENT))) {
1301 if (unlock_dvp) {
1302 vput(ndp->ni_dvp);
1303 unlock_dvp = 0;
1304 } else
1305 vrele(ndp->ni_dvp);
1306 ndp->ni_dvp = NULL;
1307 }
1308 if (unlock_dvp)
1309 VOP_UNLOCK(ndp->ni_dvp, 0);
1310 if (!(flags & NDF_NO_STARTDIR_RELE) &&
1311 (ndp->ni_cnd.cn_flags & SAVESTART)) {
1312 vrele(ndp->ni_startdir);
1313 ndp->ni_startdir = NULL;
1314 }
1315 }
1316
1317 /*
1318 * Determine if there is a suitable alternate filename under the specified
1319 * prefix for the specified path. If the create flag is set, then the
1320 * alternate prefix will be used so long as the parent directory exists.
1321 * This is used by the various compatibility ABIs so that Linux binaries prefer
1322 * files under /compat/linux for example. The chosen path (whether under
1323 * the prefix or under /) is returned in a kernel malloc'd buffer pointed
1324 * to by pathbuf. The caller is responsible for free'ing the buffer from
1325 * the M_TEMP bucket if one is returned.
1326 */
1327 int
kern_alternate_path(struct thread * td,const char * prefix,const char * path,enum uio_seg pathseg,char ** pathbuf,int create,int dirfd)1328 kern_alternate_path(struct thread *td, const char *prefix, const char *path,
1329 enum uio_seg pathseg, char **pathbuf, int create, int dirfd)
1330 {
1331 struct nameidata nd, ndroot;
1332 char *ptr, *buf, *cp;
1333 size_t len, sz;
1334 int error;
1335
1336 buf = (char *) malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
1337 *pathbuf = buf;
1338
1339 /* Copy the prefix into the new pathname as a starting point. */
1340 len = strlcpy(buf, prefix, MAXPATHLEN);
1341 if (len >= MAXPATHLEN) {
1342 *pathbuf = NULL;
1343 free(buf, M_TEMP);
1344 return (EINVAL);
1345 }
1346 sz = MAXPATHLEN - len;
1347 ptr = buf + len;
1348
1349 /* Append the filename to the prefix. */
1350 if (pathseg == UIO_SYSSPACE)
1351 error = copystr(path, ptr, sz, &len);
1352 else
1353 error = copyinstr(path, ptr, sz, &len);
1354
1355 if (error) {
1356 *pathbuf = NULL;
1357 free(buf, M_TEMP);
1358 return (error);
1359 }
1360
1361 /* Only use a prefix with absolute pathnames. */
1362 if (*ptr != '/') {
1363 error = EINVAL;
1364 goto keeporig;
1365 }
1366
1367 if (dirfd != AT_FDCWD) {
1368 /*
1369 * We want the original because the "prefix" is
1370 * included in the already opened dirfd.
1371 */
1372 bcopy(ptr, buf, len);
1373 return (0);
1374 }
1375
1376 /*
1377 * We know that there is a / somewhere in this pathname.
1378 * Search backwards for it, to find the file's parent dir
1379 * to see if it exists in the alternate tree. If it does,
1380 * and we want to create a file (cflag is set). We don't
1381 * need to worry about the root comparison in this case.
1382 */
1383
1384 if (create) {
1385 for (cp = &ptr[len] - 1; *cp != '/'; cp--);
1386 *cp = '\0';
1387
1388 NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_SYSSPACE, buf, td);
1389 error = namei(&nd);
1390 *cp = '/';
1391 if (error != 0)
1392 goto keeporig;
1393 } else {
1394 NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_SYSSPACE, buf, td);
1395
1396 error = namei(&nd);
1397 if (error != 0)
1398 goto keeporig;
1399
1400 /*
1401 * We now compare the vnode of the prefix to the one
1402 * vnode asked. If they resolve to be the same, then we
1403 * ignore the match so that the real root gets used.
1404 * This avoids the problem of traversing "../.." to find the
1405 * root directory and never finding it, because "/" resolves
1406 * to the emulation root directory. This is expensive :-(
1407 */
1408 NDINIT(&ndroot, LOOKUP, FOLLOW, UIO_SYSSPACE, prefix,
1409 td);
1410
1411 /* We shouldn't ever get an error from this namei(). */
1412 error = namei(&ndroot);
1413 if (error == 0) {
1414 if (nd.ni_vp == ndroot.ni_vp)
1415 error = ENOENT;
1416
1417 NDFREE(&ndroot, NDF_ONLY_PNBUF);
1418 vrele(ndroot.ni_vp);
1419 }
1420 }
1421
1422 NDFREE(&nd, NDF_ONLY_PNBUF);
1423 vrele(nd.ni_vp);
1424
1425 keeporig:
1426 /* If there was an error, use the original path name. */
1427 if (error)
1428 bcopy(ptr, buf, len);
1429 return (error);
1430 }
1431