FreeBSD/Linux Kernel Cross Reference
sys/kern/vfs_lookup.c
1 /*-
2 * Copyright (c) 1982, 1986, 1989, 1993
3 * The Regents of the University of California. All rights reserved.
4 * (c) UNIX System Laboratories, Inc.
5 * All or some portions of this file are derived from material licensed
6 * to the University of California by American Telephone and Telegraph
7 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
8 * the permission of UNIX System Laboratories, Inc.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 4. Neither the name of the University nor the names of its contributors
19 * may be used to endorse or promote products derived from this software
20 * without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 *
34 * @(#)vfs_lookup.c 8.4 (Berkeley) 2/16/94
35 */
36
37 #include <sys/cdefs.h>
38 __FBSDID("$FreeBSD: releng/10.2/sys/kern/vfs_lookup.c 280258 2015-03-19 13:37:36Z rwatson $");
39
40 #include "opt_capsicum.h"
41 #include "opt_kdtrace.h"
42 #include "opt_ktrace.h"
43
44 #include <sys/param.h>
45 #include <sys/systm.h>
46 #include <sys/kernel.h>
47 #include <sys/capsicum.h>
48 #include <sys/fcntl.h>
49 #include <sys/jail.h>
50 #include <sys/lock.h>
51 #include <sys/mutex.h>
52 #include <sys/namei.h>
53 #include <sys/vnode.h>
54 #include <sys/mount.h>
55 #include <sys/filedesc.h>
56 #include <sys/proc.h>
57 #include <sys/sdt.h>
58 #include <sys/syscallsubr.h>
59 #include <sys/sysctl.h>
60 #ifdef KTRACE
61 #include <sys/ktrace.h>
62 #endif
63
64 #include <security/audit/audit.h>
65 #include <security/mac/mac_framework.h>
66
67 #include <vm/uma.h>
68
69 #define NAMEI_DIAGNOSTIC 1
70 #undef NAMEI_DIAGNOSTIC
71
72 SDT_PROVIDER_DECLARE(vfs);
73 SDT_PROBE_DEFINE3(vfs, namei, lookup, entry, "struct vnode *", "char *",
74 "unsigned long");
75 SDT_PROBE_DEFINE2(vfs, namei, lookup, return, "int", "struct vnode *");
76
77 /*
78 * Allocation zone for namei
79 */
80 uma_zone_t namei_zone;
81 /*
82 * Placeholder vnode for mp traversal
83 */
84 static struct vnode *vp_crossmp;
85
86 static void
87 nameiinit(void *dummy __unused)
88 {
89
90 namei_zone = uma_zcreate("NAMEI", MAXPATHLEN, NULL, NULL, NULL, NULL,
91 UMA_ALIGN_PTR, 0);
92 getnewvnode("crossmp", NULL, &dead_vnodeops, &vp_crossmp);
93 vn_lock(vp_crossmp, LK_EXCLUSIVE);
94 VN_LOCK_ASHARE(vp_crossmp);
95 VOP_UNLOCK(vp_crossmp, 0);
96 }
97 SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_SECOND, nameiinit, NULL);
98
99 static int lookup_shared = 1;
100 SYSCTL_INT(_vfs, OID_AUTO, lookup_shared, CTLFLAG_RW, &lookup_shared, 0,
101 "Enables/Disables shared locks for path name translation");
102 TUNABLE_INT("vfs.lookup_shared", &lookup_shared);
103
104 /*
105 * Convert a pathname into a pointer to a locked vnode.
106 *
107 * The FOLLOW flag is set when symbolic links are to be followed
108 * when they occur at the end of the name translation process.
109 * Symbolic links are always followed for all other pathname
110 * components other than the last.
111 *
112 * The segflg defines whether the name is to be copied from user
113 * space or kernel space.
114 *
115 * Overall outline of namei:
116 *
117 * copy in name
118 * get starting directory
119 * while (!done && !error) {
120 * call lookup to search path.
121 * if symbolic link, massage name in buffer and continue
122 * }
123 */
124 static void
125 namei_cleanup_cnp(struct componentname *cnp)
126 {
127 uma_zfree(namei_zone, cnp->cn_pnbuf);
128 #ifdef DIAGNOSTIC
129 cnp->cn_pnbuf = NULL;
130 cnp->cn_nameptr = NULL;
131 #endif
132 }
133
134 int
135 namei(struct nameidata *ndp)
136 {
137 struct filedesc *fdp; /* pointer to file descriptor state */
138 char *cp; /* pointer into pathname argument */
139 struct vnode *dp; /* the directory we are searching */
140 struct iovec aiov; /* uio for reading symbolic links */
141 struct uio auio;
142 int error, linklen;
143 struct componentname *cnp = &ndp->ni_cnd;
144 struct thread *td = cnp->cn_thread;
145 struct proc *p = td->td_proc;
146
147 ndp->ni_cnd.cn_cred = ndp->ni_cnd.cn_thread->td_ucred;
148 KASSERT(cnp->cn_cred && p, ("namei: bad cred/proc"));
149 KASSERT((cnp->cn_nameiop & (~OPMASK)) == 0,
150 ("namei: nameiop contaminated with flags"));
151 KASSERT((cnp->cn_flags & OPMASK) == 0,
152 ("namei: flags contaminated with nameiops"));
153 if (!lookup_shared)
154 cnp->cn_flags &= ~LOCKSHARED;
155 fdp = p->p_fd;
156
157 /* We will set this ourselves if we need it. */
158 cnp->cn_flags &= ~TRAILINGSLASH;
159
160 /*
161 * Get a buffer for the name to be translated, and copy the
162 * name into the buffer.
163 */
164 if ((cnp->cn_flags & HASBUF) == 0)
165 cnp->cn_pnbuf = uma_zalloc(namei_zone, M_WAITOK);
166 if (ndp->ni_segflg == UIO_SYSSPACE)
167 error = copystr(ndp->ni_dirp, cnp->cn_pnbuf,
168 MAXPATHLEN, (size_t *)&ndp->ni_pathlen);
169 else
170 error = copyinstr(ndp->ni_dirp, cnp->cn_pnbuf,
171 MAXPATHLEN, (size_t *)&ndp->ni_pathlen);
172
173 /*
174 * Don't allow empty pathnames.
175 */
176 if (!error && *cnp->cn_pnbuf == '\0')
177 error = ENOENT;
178
179 #ifdef CAPABILITY_MODE
180 /*
181 * In capability mode, lookups must be "strictly relative" (i.e.
182 * not an absolute path, and not containing '..' components) to
183 * a real file descriptor, not the pseudo-descriptor AT_FDCWD.
184 */
185 if (error == 0 && IN_CAPABILITY_MODE(td) &&
186 (cnp->cn_flags & NOCAPCHECK) == 0) {
187 ndp->ni_strictrelative = 1;
188 if (ndp->ni_dirfd == AT_FDCWD) {
189 #ifdef KTRACE
190 if (KTRPOINT(td, KTR_CAPFAIL))
191 ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL);
192 #endif
193 error = ECAPMODE;
194 }
195 }
196 #endif
197 if (error) {
198 namei_cleanup_cnp(cnp);
199 ndp->ni_vp = NULL;
200 return (error);
201 }
202 ndp->ni_loopcnt = 0;
203 #ifdef KTRACE
204 if (KTRPOINT(td, KTR_NAMEI)) {
205 KASSERT(cnp->cn_thread == curthread,
206 ("namei not using curthread"));
207 ktrnamei(cnp->cn_pnbuf);
208 }
209 #endif
210 /*
211 * Get starting point for the translation.
212 */
213 FILEDESC_SLOCK(fdp);
214 ndp->ni_rootdir = fdp->fd_rdir;
215 ndp->ni_topdir = fdp->fd_jdir;
216
217 /*
218 * If we are auditing the kernel pathname, save the user pathname.
219 */
220 if (cnp->cn_flags & AUDITVNODE1)
221 AUDIT_ARG_UPATH1(td, ndp->ni_dirfd, cnp->cn_pnbuf);
222 if (cnp->cn_flags & AUDITVNODE2)
223 AUDIT_ARG_UPATH2(td, ndp->ni_dirfd, cnp->cn_pnbuf);
224
225 dp = NULL;
226 if (cnp->cn_pnbuf[0] != '/') {
227 if (ndp->ni_startdir != NULL) {
228 dp = ndp->ni_startdir;
229 error = 0;
230 } else if (ndp->ni_dirfd != AT_FDCWD) {
231 cap_rights_t rights;
232
233 rights = ndp->ni_rightsneeded;
234 cap_rights_set(&rights, CAP_LOOKUP);
235
236 if (cnp->cn_flags & AUDITVNODE1)
237 AUDIT_ARG_ATFD1(ndp->ni_dirfd);
238 if (cnp->cn_flags & AUDITVNODE2)
239 AUDIT_ARG_ATFD2(ndp->ni_dirfd);
240 error = fgetvp_rights(td, ndp->ni_dirfd,
241 &rights, &ndp->ni_filecaps, &dp);
242 #ifdef CAPABILITIES
243 /*
244 * If file descriptor doesn't have all rights,
245 * all lookups relative to it must also be
246 * strictly relative.
247 */
248 CAP_ALL(&rights);
249 if (!cap_rights_contains(&ndp->ni_filecaps.fc_rights,
250 &rights) ||
251 ndp->ni_filecaps.fc_fcntls != CAP_FCNTL_ALL ||
252 ndp->ni_filecaps.fc_nioctls != -1) {
253 ndp->ni_strictrelative = 1;
254 }
255 #endif
256 }
257 if (error != 0 || dp != NULL) {
258 FILEDESC_SUNLOCK(fdp);
259 if (error == 0 && dp->v_type != VDIR) {
260 vrele(dp);
261 error = ENOTDIR;
262 }
263 }
264 if (error) {
265 namei_cleanup_cnp(cnp);
266 return (error);
267 }
268 }
269 if (dp == NULL) {
270 dp = fdp->fd_cdir;
271 VREF(dp);
272 FILEDESC_SUNLOCK(fdp);
273 if (ndp->ni_startdir != NULL)
274 vrele(ndp->ni_startdir);
275 }
276 SDT_PROBE(vfs, namei, lookup, entry, dp, cnp->cn_pnbuf,
277 cnp->cn_flags, 0, 0);
278 for (;;) {
279 /*
280 * Check if root directory should replace current directory.
281 * Done at start of translation and after symbolic link.
282 */
283 cnp->cn_nameptr = cnp->cn_pnbuf;
284 if (*(cnp->cn_nameptr) == '/') {
285 vrele(dp);
286 if (ndp->ni_strictrelative != 0) {
287 #ifdef KTRACE
288 if (KTRPOINT(curthread, KTR_CAPFAIL))
289 ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL);
290 #endif
291 namei_cleanup_cnp(cnp);
292 return (ENOTCAPABLE);
293 }
294 while (*(cnp->cn_nameptr) == '/') {
295 cnp->cn_nameptr++;
296 ndp->ni_pathlen--;
297 }
298 dp = ndp->ni_rootdir;
299 VREF(dp);
300 }
301 ndp->ni_startdir = dp;
302 error = lookup(ndp);
303 if (error) {
304 namei_cleanup_cnp(cnp);
305 SDT_PROBE(vfs, namei, lookup, return, error, NULL, 0,
306 0, 0);
307 return (error);
308 }
309 /*
310 * If not a symbolic link, we're done.
311 */
312 if ((cnp->cn_flags & ISSYMLINK) == 0) {
313 if ((cnp->cn_flags & (SAVENAME | SAVESTART)) == 0) {
314 namei_cleanup_cnp(cnp);
315 } else
316 cnp->cn_flags |= HASBUF;
317
318 SDT_PROBE(vfs, namei, lookup, return, 0, ndp->ni_vp,
319 0, 0, 0);
320 return (0);
321 }
322 if (ndp->ni_loopcnt++ >= MAXSYMLINKS) {
323 error = ELOOP;
324 break;
325 }
326 #ifdef MAC
327 if ((cnp->cn_flags & NOMACCHECK) == 0) {
328 error = mac_vnode_check_readlink(td->td_ucred,
329 ndp->ni_vp);
330 if (error)
331 break;
332 }
333 #endif
334 if (ndp->ni_pathlen > 1)
335 cp = uma_zalloc(namei_zone, M_WAITOK);
336 else
337 cp = cnp->cn_pnbuf;
338 aiov.iov_base = cp;
339 aiov.iov_len = MAXPATHLEN;
340 auio.uio_iov = &aiov;
341 auio.uio_iovcnt = 1;
342 auio.uio_offset = 0;
343 auio.uio_rw = UIO_READ;
344 auio.uio_segflg = UIO_SYSSPACE;
345 auio.uio_td = td;
346 auio.uio_resid = MAXPATHLEN;
347 error = VOP_READLINK(ndp->ni_vp, &auio, cnp->cn_cred);
348 if (error) {
349 if (ndp->ni_pathlen > 1)
350 uma_zfree(namei_zone, cp);
351 break;
352 }
353 linklen = MAXPATHLEN - auio.uio_resid;
354 if (linklen == 0) {
355 if (ndp->ni_pathlen > 1)
356 uma_zfree(namei_zone, cp);
357 error = ENOENT;
358 break;
359 }
360 if (linklen + ndp->ni_pathlen >= MAXPATHLEN) {
361 if (ndp->ni_pathlen > 1)
362 uma_zfree(namei_zone, cp);
363 error = ENAMETOOLONG;
364 break;
365 }
366 if (ndp->ni_pathlen > 1) {
367 bcopy(ndp->ni_next, cp + linklen, ndp->ni_pathlen);
368 uma_zfree(namei_zone, cnp->cn_pnbuf);
369 cnp->cn_pnbuf = cp;
370 } else
371 cnp->cn_pnbuf[linklen] = '\0';
372 ndp->ni_pathlen += linklen;
373 vput(ndp->ni_vp);
374 dp = ndp->ni_dvp;
375 }
376 namei_cleanup_cnp(cnp);
377 vput(ndp->ni_vp);
378 ndp->ni_vp = NULL;
379 vrele(ndp->ni_dvp);
380 SDT_PROBE(vfs, namei, lookup, return, error, NULL, 0, 0, 0);
381 return (error);
382 }
383
384 static int
385 compute_cn_lkflags(struct mount *mp, int lkflags, int cnflags)
386 {
387
388 if (mp == NULL || ((lkflags & LK_SHARED) &&
389 (!(mp->mnt_kern_flag & MNTK_LOOKUP_SHARED) ||
390 ((cnflags & ISDOTDOT) &&
391 (mp->mnt_kern_flag & MNTK_LOOKUP_EXCL_DOTDOT))))) {
392 lkflags &= ~LK_SHARED;
393 lkflags |= LK_EXCLUSIVE;
394 }
395 lkflags |= LK_NODDLKTREAT;
396 return (lkflags);
397 }
398
399 static __inline int
400 needs_exclusive_leaf(struct mount *mp, int flags)
401 {
402
403 /*
404 * Intermediate nodes can use shared locks, we only need to
405 * force an exclusive lock for leaf nodes.
406 */
407 if ((flags & (ISLASTCN | LOCKLEAF)) != (ISLASTCN | LOCKLEAF))
408 return (0);
409
410 /* Always use exclusive locks if LOCKSHARED isn't set. */
411 if (!(flags & LOCKSHARED))
412 return (1);
413
414 /*
415 * For lookups during open(), if the mount point supports
416 * extended shared operations, then use a shared lock for the
417 * leaf node, otherwise use an exclusive lock.
418 */
419 if ((flags & ISOPEN) != 0)
420 return (!MNT_EXTENDED_SHARED(mp));
421
422 /*
423 * Lookup requests outside of open() that specify LOCKSHARED
424 * only need a shared lock on the leaf vnode.
425 */
426 return (0);
427 }
428
429 /*
430 * Search a pathname.
431 * This is a very central and rather complicated routine.
432 *
433 * The pathname is pointed to by ni_ptr and is of length ni_pathlen.
434 * The starting directory is taken from ni_startdir. The pathname is
435 * descended until done, or a symbolic link is encountered. The variable
436 * ni_more is clear if the path is completed; it is set to one if a
437 * symbolic link needing interpretation is encountered.
438 *
439 * The flag argument is LOOKUP, CREATE, RENAME, or DELETE depending on
440 * whether the name is to be looked up, created, renamed, or deleted.
441 * When CREATE, RENAME, or DELETE is specified, information usable in
442 * creating, renaming, or deleting a directory entry may be calculated.
443 * If flag has LOCKPARENT or'ed into it, the parent directory is returned
444 * locked. If flag has WANTPARENT or'ed into it, the parent directory is
445 * returned unlocked. Otherwise the parent directory is not returned. If
446 * the target of the pathname exists and LOCKLEAF is or'ed into the flag
447 * the target is returned locked, otherwise it is returned unlocked.
448 * When creating or renaming and LOCKPARENT is specified, the target may not
449 * be ".". When deleting and LOCKPARENT is specified, the target may be ".".
450 *
451 * Overall outline of lookup:
452 *
453 * dirloop:
454 * identify next component of name at ndp->ni_ptr
455 * handle degenerate case where name is null string
456 * if .. and crossing mount points and on mounted filesys, find parent
457 * call VOP_LOOKUP routine for next component name
458 * directory vnode returned in ni_dvp, unlocked unless LOCKPARENT set
459 * component vnode returned in ni_vp (if it exists), locked.
460 * if result vnode is mounted on and crossing mount points,
461 * find mounted on vnode
462 * if more components of name, do next level at dirloop
463 * return the answer in ni_vp, locked if LOCKLEAF set
464 * if LOCKPARENT set, return locked parent in ni_dvp
465 * if WANTPARENT set, return unlocked parent in ni_dvp
466 */
467 int
468 lookup(struct nameidata *ndp)
469 {
470 char *cp; /* pointer into pathname argument */
471 struct vnode *dp = 0; /* the directory we are searching */
472 struct vnode *tdp; /* saved dp */
473 struct mount *mp; /* mount table entry */
474 struct prison *pr;
475 int docache; /* == 0 do not cache last component */
476 int wantparent; /* 1 => wantparent or lockparent flag */
477 int rdonly; /* lookup read-only flag bit */
478 int error = 0;
479 int dpunlocked = 0; /* dp has already been unlocked */
480 struct componentname *cnp = &ndp->ni_cnd;
481 int lkflags_save;
482 int ni_dvp_unlocked;
483
484 /*
485 * Setup: break out flag bits into variables.
486 */
487 ni_dvp_unlocked = 0;
488 wantparent = cnp->cn_flags & (LOCKPARENT | WANTPARENT);
489 KASSERT(cnp->cn_nameiop == LOOKUP || wantparent,
490 ("CREATE, DELETE, RENAME require LOCKPARENT or WANTPARENT."));
491 docache = (cnp->cn_flags & NOCACHE) ^ NOCACHE;
492 if (cnp->cn_nameiop == DELETE ||
493 (wantparent && cnp->cn_nameiop != CREATE &&
494 cnp->cn_nameiop != LOOKUP))
495 docache = 0;
496 rdonly = cnp->cn_flags & RDONLY;
497 cnp->cn_flags &= ~ISSYMLINK;
498 ndp->ni_dvp = NULL;
499 /*
500 * We use shared locks until we hit the parent of the last cn then
501 * we adjust based on the requesting flags.
502 */
503 if (lookup_shared)
504 cnp->cn_lkflags = LK_SHARED;
505 else
506 cnp->cn_lkflags = LK_EXCLUSIVE;
507 dp = ndp->ni_startdir;
508 ndp->ni_startdir = NULLVP;
509 vn_lock(dp,
510 compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags | LK_RETRY,
511 cnp->cn_flags));
512
513 dirloop:
514 /*
515 * Search a new directory.
516 *
517 * The last component of the filename is left accessible via
518 * cnp->cn_nameptr for callers that need the name. Callers needing
519 * the name set the SAVENAME flag. When done, they assume
520 * responsibility for freeing the pathname buffer.
521 */
522 cnp->cn_consume = 0;
523 for (cp = cnp->cn_nameptr; *cp != 0 && *cp != '/'; cp++)
524 continue;
525 cnp->cn_namelen = cp - cnp->cn_nameptr;
526 if (cnp->cn_namelen > NAME_MAX) {
527 error = ENAMETOOLONG;
528 goto bad;
529 }
530 #ifdef NAMEI_DIAGNOSTIC
531 { char c = *cp;
532 *cp = '\0';
533 printf("{%s}: ", cnp->cn_nameptr);
534 *cp = c; }
535 #endif
536 ndp->ni_pathlen -= cnp->cn_namelen;
537 ndp->ni_next = cp;
538
539 /*
540 * Replace multiple slashes by a single slash and trailing slashes
541 * by a null. This must be done before VOP_LOOKUP() because some
542 * fs's don't know about trailing slashes. Remember if there were
543 * trailing slashes to handle symlinks, existing non-directories
544 * and non-existing files that won't be directories specially later.
545 */
546 while (*cp == '/' && (cp[1] == '/' || cp[1] == '\0')) {
547 cp++;
548 ndp->ni_pathlen--;
549 if (*cp == '\0') {
550 *ndp->ni_next = '\0';
551 cnp->cn_flags |= TRAILINGSLASH;
552 }
553 }
554 ndp->ni_next = cp;
555
556 cnp->cn_flags |= MAKEENTRY;
557 if (*cp == '\0' && docache == 0)
558 cnp->cn_flags &= ~MAKEENTRY;
559 if (cnp->cn_namelen == 2 &&
560 cnp->cn_nameptr[1] == '.' && cnp->cn_nameptr[0] == '.')
561 cnp->cn_flags |= ISDOTDOT;
562 else
563 cnp->cn_flags &= ~ISDOTDOT;
564 if (*ndp->ni_next == 0)
565 cnp->cn_flags |= ISLASTCN;
566 else
567 cnp->cn_flags &= ~ISLASTCN;
568
569 if ((cnp->cn_flags & ISLASTCN) != 0 &&
570 cnp->cn_namelen == 1 && cnp->cn_nameptr[0] == '.' &&
571 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) {
572 error = EINVAL;
573 goto bad;
574 }
575
576 /*
577 * Check for degenerate name (e.g. / or "")
578 * which is a way of talking about a directory,
579 * e.g. like "/." or ".".
580 */
581 if (cnp->cn_nameptr[0] == '\0') {
582 if (dp->v_type != VDIR) {
583 error = ENOTDIR;
584 goto bad;
585 }
586 if (cnp->cn_nameiop != LOOKUP) {
587 error = EISDIR;
588 goto bad;
589 }
590 if (wantparent) {
591 ndp->ni_dvp = dp;
592 VREF(dp);
593 }
594 ndp->ni_vp = dp;
595
596 if (cnp->cn_flags & AUDITVNODE1)
597 AUDIT_ARG_VNODE1(dp);
598 else if (cnp->cn_flags & AUDITVNODE2)
599 AUDIT_ARG_VNODE2(dp);
600
601 if (!(cnp->cn_flags & (LOCKPARENT | LOCKLEAF)))
602 VOP_UNLOCK(dp, 0);
603 /* XXX This should probably move to the top of function. */
604 if (cnp->cn_flags & SAVESTART)
605 panic("lookup: SAVESTART");
606 goto success;
607 }
608
609 /*
610 * Handle "..": five special cases.
611 * 0. If doing a capability lookup, return ENOTCAPABLE (this is a
612 * fairly conservative design choice, but it's the only one that we
613 * are satisfied guarantees the property we're looking for).
614 * 1. Return an error if this is the last component of
615 * the name and the operation is DELETE or RENAME.
616 * 2. If at root directory (e.g. after chroot)
617 * or at absolute root directory
618 * then ignore it so can't get out.
619 * 3. If this vnode is the root of a mounted
620 * filesystem, then replace it with the
621 * vnode which was mounted on so we take the
622 * .. in the other filesystem.
623 * 4. If the vnode is the top directory of
624 * the jail or chroot, don't let them out.
625 */
626 if (cnp->cn_flags & ISDOTDOT) {
627 if (ndp->ni_strictrelative != 0) {
628 #ifdef KTRACE
629 if (KTRPOINT(curthread, KTR_CAPFAIL))
630 ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL);
631 #endif
632 error = ENOTCAPABLE;
633 goto bad;
634 }
635 if ((cnp->cn_flags & ISLASTCN) != 0 &&
636 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) {
637 error = EINVAL;
638 goto bad;
639 }
640 for (;;) {
641 for (pr = cnp->cn_cred->cr_prison; pr != NULL;
642 pr = pr->pr_parent)
643 if (dp == pr->pr_root)
644 break;
645 if (dp == ndp->ni_rootdir ||
646 dp == ndp->ni_topdir ||
647 dp == rootvnode ||
648 pr != NULL ||
649 ((dp->v_vflag & VV_ROOT) != 0 &&
650 (cnp->cn_flags & NOCROSSMOUNT) != 0)) {
651 ndp->ni_dvp = dp;
652 ndp->ni_vp = dp;
653 VREF(dp);
654 goto nextname;
655 }
656 if ((dp->v_vflag & VV_ROOT) == 0)
657 break;
658 if (dp->v_iflag & VI_DOOMED) { /* forced unmount */
659 error = ENOENT;
660 goto bad;
661 }
662 tdp = dp;
663 dp = dp->v_mount->mnt_vnodecovered;
664 VREF(dp);
665 vput(tdp);
666 vn_lock(dp,
667 compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags |
668 LK_RETRY, ISDOTDOT));
669 }
670 }
671
672 /*
673 * We now have a segment name to search for, and a directory to search.
674 */
675 unionlookup:
676 #ifdef MAC
677 if ((cnp->cn_flags & NOMACCHECK) == 0) {
678 error = mac_vnode_check_lookup(cnp->cn_thread->td_ucred, dp,
679 cnp);
680 if (error)
681 goto bad;
682 }
683 #endif
684 ndp->ni_dvp = dp;
685 ndp->ni_vp = NULL;
686 ASSERT_VOP_LOCKED(dp, "lookup");
687 /*
688 * If we have a shared lock we may need to upgrade the lock for the
689 * last operation.
690 */
691 if (dp != vp_crossmp &&
692 VOP_ISLOCKED(dp) == LK_SHARED &&
693 (cnp->cn_flags & ISLASTCN) && (cnp->cn_flags & LOCKPARENT))
694 vn_lock(dp, LK_UPGRADE|LK_RETRY);
695 if ((dp->v_iflag & VI_DOOMED) != 0) {
696 error = ENOENT;
697 goto bad;
698 }
699 /*
700 * If we're looking up the last component and we need an exclusive
701 * lock, adjust our lkflags.
702 */
703 if (needs_exclusive_leaf(dp->v_mount, cnp->cn_flags))
704 cnp->cn_lkflags = LK_EXCLUSIVE;
705 #ifdef NAMEI_DIAGNOSTIC
706 vprint("lookup in", dp);
707 #endif
708 lkflags_save = cnp->cn_lkflags;
709 cnp->cn_lkflags = compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags,
710 cnp->cn_flags);
711 if ((error = VOP_LOOKUP(dp, &ndp->ni_vp, cnp)) != 0) {
712 cnp->cn_lkflags = lkflags_save;
713 KASSERT(ndp->ni_vp == NULL, ("leaf should be empty"));
714 #ifdef NAMEI_DIAGNOSTIC
715 printf("not found\n");
716 #endif
717 if ((error == ENOENT) &&
718 (dp->v_vflag & VV_ROOT) && (dp->v_mount != NULL) &&
719 (dp->v_mount->mnt_flag & MNT_UNION)) {
720 tdp = dp;
721 dp = dp->v_mount->mnt_vnodecovered;
722 VREF(dp);
723 vput(tdp);
724 vn_lock(dp,
725 compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags |
726 LK_RETRY, cnp->cn_flags));
727 goto unionlookup;
728 }
729
730 if (error != EJUSTRETURN)
731 goto bad;
732 /*
733 * At this point, we know we're at the end of the
734 * pathname. If creating / renaming, we can consider
735 * allowing the file or directory to be created / renamed,
736 * provided we're not on a read-only filesystem.
737 */
738 if (rdonly) {
739 error = EROFS;
740 goto bad;
741 }
742 /* trailing slash only allowed for directories */
743 if ((cnp->cn_flags & TRAILINGSLASH) &&
744 !(cnp->cn_flags & WILLBEDIR)) {
745 error = ENOENT;
746 goto bad;
747 }
748 if ((cnp->cn_flags & LOCKPARENT) == 0)
749 VOP_UNLOCK(dp, 0);
750 /*
751 * We return with ni_vp NULL to indicate that the entry
752 * doesn't currently exist, leaving a pointer to the
753 * (possibly locked) directory vnode in ndp->ni_dvp.
754 */
755 if (cnp->cn_flags & SAVESTART) {
756 ndp->ni_startdir = ndp->ni_dvp;
757 VREF(ndp->ni_startdir);
758 }
759 goto success;
760 } else
761 cnp->cn_lkflags = lkflags_save;
762 #ifdef NAMEI_DIAGNOSTIC
763 printf("found\n");
764 #endif
765 /*
766 * Take into account any additional components consumed by
767 * the underlying filesystem.
768 */
769 if (cnp->cn_consume > 0) {
770 cnp->cn_nameptr += cnp->cn_consume;
771 ndp->ni_next += cnp->cn_consume;
772 ndp->ni_pathlen -= cnp->cn_consume;
773 cnp->cn_consume = 0;
774 }
775
776 dp = ndp->ni_vp;
777
778 /*
779 * Check to see if the vnode has been mounted on;
780 * if so find the root of the mounted filesystem.
781 */
782 while (dp->v_type == VDIR && (mp = dp->v_mountedhere) &&
783 (cnp->cn_flags & NOCROSSMOUNT) == 0) {
784 if (vfs_busy(mp, 0))
785 continue;
786 vput(dp);
787 if (dp != ndp->ni_dvp)
788 vput(ndp->ni_dvp);
789 else
790 vrele(ndp->ni_dvp);
791 vref(vp_crossmp);
792 ndp->ni_dvp = vp_crossmp;
793 error = VFS_ROOT(mp, compute_cn_lkflags(mp, cnp->cn_lkflags,
794 cnp->cn_flags), &tdp);
795 vfs_unbusy(mp);
796 if (vn_lock(vp_crossmp, LK_SHARED | LK_NOWAIT))
797 panic("vp_crossmp exclusively locked or reclaimed");
798 if (error) {
799 dpunlocked = 1;
800 goto bad2;
801 }
802 ndp->ni_vp = dp = tdp;
803 }
804
805 /*
806 * Check for symbolic link
807 */
808 if ((dp->v_type == VLNK) &&
809 ((cnp->cn_flags & FOLLOW) || (cnp->cn_flags & TRAILINGSLASH) ||
810 *ndp->ni_next == '/')) {
811 cnp->cn_flags |= ISSYMLINK;
812 if (dp->v_iflag & VI_DOOMED) {
813 /*
814 * We can't know whether the directory was mounted with
815 * NOSYMFOLLOW, so we can't follow safely.
816 */
817 error = ENOENT;
818 goto bad2;
819 }
820 if (dp->v_mount->mnt_flag & MNT_NOSYMFOLLOW) {
821 error = EACCES;
822 goto bad2;
823 }
824 /*
825 * Symlink code always expects an unlocked dvp.
826 */
827 if (ndp->ni_dvp != ndp->ni_vp) {
828 VOP_UNLOCK(ndp->ni_dvp, 0);
829 ni_dvp_unlocked = 1;
830 }
831 goto success;
832 }
833
834 nextname:
835 /*
836 * Not a symbolic link that we will follow. Continue with the
837 * next component if there is any; otherwise, we're done.
838 */
839 KASSERT((cnp->cn_flags & ISLASTCN) || *ndp->ni_next == '/',
840 ("lookup: invalid path state."));
841 if (*ndp->ni_next == '/') {
842 cnp->cn_nameptr = ndp->ni_next;
843 while (*cnp->cn_nameptr == '/') {
844 cnp->cn_nameptr++;
845 ndp->ni_pathlen--;
846 }
847 if (ndp->ni_dvp != dp)
848 vput(ndp->ni_dvp);
849 else
850 vrele(ndp->ni_dvp);
851 goto dirloop;
852 }
853 /*
854 * If we're processing a path with a trailing slash,
855 * check that the end result is a directory.
856 */
857 if ((cnp->cn_flags & TRAILINGSLASH) && dp->v_type != VDIR) {
858 error = ENOTDIR;
859 goto bad2;
860 }
861 /*
862 * Disallow directory write attempts on read-only filesystems.
863 */
864 if (rdonly &&
865 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) {
866 error = EROFS;
867 goto bad2;
868 }
869 if (cnp->cn_flags & SAVESTART) {
870 ndp->ni_startdir = ndp->ni_dvp;
871 VREF(ndp->ni_startdir);
872 }
873 if (!wantparent) {
874 ni_dvp_unlocked = 2;
875 if (ndp->ni_dvp != dp)
876 vput(ndp->ni_dvp);
877 else
878 vrele(ndp->ni_dvp);
879 } else if ((cnp->cn_flags & LOCKPARENT) == 0 && ndp->ni_dvp != dp) {
880 VOP_UNLOCK(ndp->ni_dvp, 0);
881 ni_dvp_unlocked = 1;
882 }
883
884 if (cnp->cn_flags & AUDITVNODE1)
885 AUDIT_ARG_VNODE1(dp);
886 else if (cnp->cn_flags & AUDITVNODE2)
887 AUDIT_ARG_VNODE2(dp);
888
889 if ((cnp->cn_flags & LOCKLEAF) == 0)
890 VOP_UNLOCK(dp, 0);
891 success:
892 /*
893 * Because of lookup_shared we may have the vnode shared locked, but
894 * the caller may want it to be exclusively locked.
895 */
896 if (needs_exclusive_leaf(dp->v_mount, cnp->cn_flags) &&
897 VOP_ISLOCKED(dp) != LK_EXCLUSIVE) {
898 vn_lock(dp, LK_UPGRADE | LK_RETRY);
899 if (dp->v_iflag & VI_DOOMED) {
900 error = ENOENT;
901 goto bad2;
902 }
903 }
904 return (0);
905
906 bad2:
907 if (ni_dvp_unlocked != 2) {
908 if (dp != ndp->ni_dvp && !ni_dvp_unlocked)
909 vput(ndp->ni_dvp);
910 else
911 vrele(ndp->ni_dvp);
912 }
913 bad:
914 if (!dpunlocked)
915 vput(dp);
916 ndp->ni_vp = NULL;
917 return (error);
918 }
919
920 /*
921 * relookup - lookup a path name component
922 * Used by lookup to re-acquire things.
923 */
924 int
925 relookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp)
926 {
927 struct vnode *dp = 0; /* the directory we are searching */
928 int wantparent; /* 1 => wantparent or lockparent flag */
929 int rdonly; /* lookup read-only flag bit */
930 int error = 0;
931
932 KASSERT(cnp->cn_flags & ISLASTCN,
933 ("relookup: Not given last component."));
934 /*
935 * Setup: break out flag bits into variables.
936 */
937 wantparent = cnp->cn_flags & (LOCKPARENT|WANTPARENT);
938 KASSERT(wantparent, ("relookup: parent not wanted."));
939 rdonly = cnp->cn_flags & RDONLY;
940 cnp->cn_flags &= ~ISSYMLINK;
941 dp = dvp;
942 cnp->cn_lkflags = LK_EXCLUSIVE;
943 vn_lock(dp, LK_EXCLUSIVE | LK_RETRY);
944
945 /*
946 * Search a new directory.
947 *
948 * The last component of the filename is left accessible via
949 * cnp->cn_nameptr for callers that need the name. Callers needing
950 * the name set the SAVENAME flag. When done, they assume
951 * responsibility for freeing the pathname buffer.
952 */
953 #ifdef NAMEI_DIAGNOSTIC
954 printf("{%s}: ", cnp->cn_nameptr);
955 #endif
956
957 /*
958 * Check for "" which represents the root directory after slash
959 * removal.
960 */
961 if (cnp->cn_nameptr[0] == '\0') {
962 /*
963 * Support only LOOKUP for "/" because lookup()
964 * can't succeed for CREATE, DELETE and RENAME.
965 */
966 KASSERT(cnp->cn_nameiop == LOOKUP, ("nameiop must be LOOKUP"));
967 KASSERT(dp->v_type == VDIR, ("dp is not a directory"));
968
969 if (!(cnp->cn_flags & LOCKLEAF))
970 VOP_UNLOCK(dp, 0);
971 *vpp = dp;
972 /* XXX This should probably move to the top of function. */
973 if (cnp->cn_flags & SAVESTART)
974 panic("lookup: SAVESTART");
975 return (0);
976 }
977
978 if (cnp->cn_flags & ISDOTDOT)
979 panic ("relookup: lookup on dot-dot");
980
981 /*
982 * We now have a segment name to search for, and a directory to search.
983 */
984 #ifdef NAMEI_DIAGNOSTIC
985 vprint("search in:", dp);
986 #endif
987 if ((error = VOP_LOOKUP(dp, vpp, cnp)) != 0) {
988 KASSERT(*vpp == NULL, ("leaf should be empty"));
989 if (error != EJUSTRETURN)
990 goto bad;
991 /*
992 * If creating and at end of pathname, then can consider
993 * allowing file to be created.
994 */
995 if (rdonly) {
996 error = EROFS;
997 goto bad;
998 }
999 /* ASSERT(dvp == ndp->ni_startdir) */
1000 if (cnp->cn_flags & SAVESTART)
1001 VREF(dvp);
1002 if ((cnp->cn_flags & LOCKPARENT) == 0)
1003 VOP_UNLOCK(dp, 0);
1004 /*
1005 * We return with ni_vp NULL to indicate that the entry
1006 * doesn't currently exist, leaving a pointer to the
1007 * (possibly locked) directory vnode in ndp->ni_dvp.
1008 */
1009 return (0);
1010 }
1011
1012 dp = *vpp;
1013
1014 /*
1015 * Disallow directory write attempts on read-only filesystems.
1016 */
1017 if (rdonly &&
1018 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) {
1019 if (dvp == dp)
1020 vrele(dvp);
1021 else
1022 vput(dvp);
1023 error = EROFS;
1024 goto bad;
1025 }
1026 /*
1027 * Set the parent lock/ref state to the requested state.
1028 */
1029 if ((cnp->cn_flags & LOCKPARENT) == 0 && dvp != dp) {
1030 if (wantparent)
1031 VOP_UNLOCK(dvp, 0);
1032 else
1033 vput(dvp);
1034 } else if (!wantparent)
1035 vrele(dvp);
1036 /*
1037 * Check for symbolic link
1038 */
1039 KASSERT(dp->v_type != VLNK || !(cnp->cn_flags & FOLLOW),
1040 ("relookup: symlink found.\n"));
1041
1042 /* ASSERT(dvp == ndp->ni_startdir) */
1043 if (cnp->cn_flags & SAVESTART)
1044 VREF(dvp);
1045
1046 if ((cnp->cn_flags & LOCKLEAF) == 0)
1047 VOP_UNLOCK(dp, 0);
1048 return (0);
1049 bad:
1050 vput(dp);
1051 *vpp = NULL;
1052 return (error);
1053 }
1054
1055 void
1056 NDINIT_ALL(struct nameidata *ndp, u_long op, u_long flags, enum uio_seg segflg,
1057 const char *namep, int dirfd, struct vnode *startdir, cap_rights_t *rightsp,
1058 struct thread *td)
1059 {
1060
1061 ndp->ni_cnd.cn_nameiop = op;
1062 ndp->ni_cnd.cn_flags = flags;
1063 ndp->ni_segflg = segflg;
1064 ndp->ni_dirp = namep;
1065 ndp->ni_dirfd = dirfd;
1066 ndp->ni_startdir = startdir;
1067 ndp->ni_strictrelative = 0;
1068 if (rightsp != NULL)
1069 ndp->ni_rightsneeded = *rightsp;
1070 else
1071 cap_rights_init(&ndp->ni_rightsneeded);
1072 filecaps_init(&ndp->ni_filecaps);
1073 ndp->ni_cnd.cn_thread = td;
1074 }
1075
1076 /*
1077 * Free data allocated by namei(); see namei(9) for details.
1078 */
1079 void
1080 NDFREE(struct nameidata *ndp, const u_int flags)
1081 {
1082 int unlock_dvp;
1083 int unlock_vp;
1084
1085 unlock_dvp = 0;
1086 unlock_vp = 0;
1087
1088 if (!(flags & NDF_NO_FREE_PNBUF) &&
1089 (ndp->ni_cnd.cn_flags & HASBUF)) {
1090 uma_zfree(namei_zone, ndp->ni_cnd.cn_pnbuf);
1091 ndp->ni_cnd.cn_flags &= ~HASBUF;
1092 }
1093 if (!(flags & NDF_NO_VP_UNLOCK) &&
1094 (ndp->ni_cnd.cn_flags & LOCKLEAF) && ndp->ni_vp)
1095 unlock_vp = 1;
1096 if (!(flags & NDF_NO_VP_RELE) && ndp->ni_vp) {
1097 if (unlock_vp) {
1098 vput(ndp->ni_vp);
1099 unlock_vp = 0;
1100 } else
1101 vrele(ndp->ni_vp);
1102 ndp->ni_vp = NULL;
1103 }
1104 if (unlock_vp)
1105 VOP_UNLOCK(ndp->ni_vp, 0);
1106 if (!(flags & NDF_NO_DVP_UNLOCK) &&
1107 (ndp->ni_cnd.cn_flags & LOCKPARENT) &&
1108 ndp->ni_dvp != ndp->ni_vp)
1109 unlock_dvp = 1;
1110 if (!(flags & NDF_NO_DVP_RELE) &&
1111 (ndp->ni_cnd.cn_flags & (LOCKPARENT|WANTPARENT))) {
1112 if (unlock_dvp) {
1113 vput(ndp->ni_dvp);
1114 unlock_dvp = 0;
1115 } else
1116 vrele(ndp->ni_dvp);
1117 ndp->ni_dvp = NULL;
1118 }
1119 if (unlock_dvp)
1120 VOP_UNLOCK(ndp->ni_dvp, 0);
1121 if (!(flags & NDF_NO_STARTDIR_RELE) &&
1122 (ndp->ni_cnd.cn_flags & SAVESTART)) {
1123 vrele(ndp->ni_startdir);
1124 ndp->ni_startdir = NULL;
1125 }
1126 }
1127
1128 /*
1129 * Determine if there is a suitable alternate filename under the specified
1130 * prefix for the specified path. If the create flag is set, then the
1131 * alternate prefix will be used so long as the parent directory exists.
1132 * This is used by the various compatiblity ABIs so that Linux binaries prefer
1133 * files under /compat/linux for example. The chosen path (whether under
1134 * the prefix or under /) is returned in a kernel malloc'd buffer pointed
1135 * to by pathbuf. The caller is responsible for free'ing the buffer from
1136 * the M_TEMP bucket if one is returned.
1137 */
1138 int
1139 kern_alternate_path(struct thread *td, const char *prefix, const char *path,
1140 enum uio_seg pathseg, char **pathbuf, int create, int dirfd)
1141 {
1142 struct nameidata nd, ndroot;
1143 char *ptr, *buf, *cp;
1144 size_t len, sz;
1145 int error;
1146
1147 buf = (char *) malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
1148 *pathbuf = buf;
1149
1150 /* Copy the prefix into the new pathname as a starting point. */
1151 len = strlcpy(buf, prefix, MAXPATHLEN);
1152 if (len >= MAXPATHLEN) {
1153 *pathbuf = NULL;
1154 free(buf, M_TEMP);
1155 return (EINVAL);
1156 }
1157 sz = MAXPATHLEN - len;
1158 ptr = buf + len;
1159
1160 /* Append the filename to the prefix. */
1161 if (pathseg == UIO_SYSSPACE)
1162 error = copystr(path, ptr, sz, &len);
1163 else
1164 error = copyinstr(path, ptr, sz, &len);
1165
1166 if (error) {
1167 *pathbuf = NULL;
1168 free(buf, M_TEMP);
1169 return (error);
1170 }
1171
1172 /* Only use a prefix with absolute pathnames. */
1173 if (*ptr != '/') {
1174 error = EINVAL;
1175 goto keeporig;
1176 }
1177
1178 if (dirfd != AT_FDCWD) {
1179 /*
1180 * We want the original because the "prefix" is
1181 * included in the already opened dirfd.
1182 */
1183 bcopy(ptr, buf, len);
1184 return (0);
1185 }
1186
1187 /*
1188 * We know that there is a / somewhere in this pathname.
1189 * Search backwards for it, to find the file's parent dir
1190 * to see if it exists in the alternate tree. If it does,
1191 * and we want to create a file (cflag is set). We don't
1192 * need to worry about the root comparison in this case.
1193 */
1194
1195 if (create) {
1196 for (cp = &ptr[len] - 1; *cp != '/'; cp--);
1197 *cp = '\0';
1198
1199 NDINIT(&nd, LOOKUP, FOLLOW, UIO_SYSSPACE, buf, td);
1200 error = namei(&nd);
1201 *cp = '/';
1202 if (error != 0)
1203 goto keeporig;
1204 } else {
1205 NDINIT(&nd, LOOKUP, FOLLOW, UIO_SYSSPACE, buf, td);
1206
1207 error = namei(&nd);
1208 if (error != 0)
1209 goto keeporig;
1210
1211 /*
1212 * We now compare the vnode of the prefix to the one
1213 * vnode asked. If they resolve to be the same, then we
1214 * ignore the match so that the real root gets used.
1215 * This avoids the problem of traversing "../.." to find the
1216 * root directory and never finding it, because "/" resolves
1217 * to the emulation root directory. This is expensive :-(
1218 */
1219 NDINIT(&ndroot, LOOKUP, FOLLOW, UIO_SYSSPACE, prefix,
1220 td);
1221
1222 /* We shouldn't ever get an error from this namei(). */
1223 error = namei(&ndroot);
1224 if (error == 0) {
1225 if (nd.ni_vp == ndroot.ni_vp)
1226 error = ENOENT;
1227
1228 NDFREE(&ndroot, NDF_ONLY_PNBUF);
1229 vrele(ndroot.ni_vp);
1230 }
1231 }
1232
1233 NDFREE(&nd, NDF_ONLY_PNBUF);
1234 vrele(nd.ni_vp);
1235
1236 keeporig:
1237 /* If there was an error, use the original path name. */
1238 if (error)
1239 bcopy(ptr, buf, len);
1240 return (error);
1241 }
Cache object: e251c2385bbd8dd295a56c4f2654bd0a
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