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FreeBSD/Linux Kernel Cross Reference
sys/kern/vfs_lookup.c
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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: releng/12.0/sys/kern/vfs_lookup.c 338835 2018-09-20 18:25:26Z mjg $"); 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 85 crossmp_vop_islocked(struct vop_islocked_args *ap) 86 { 87 88 return (LK_SHARED); 89 } 90 91 static int 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 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 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 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 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 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 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 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 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 error = namei_handle_root(ndp, &dp); 392 } else { 393 if (ndp->ni_startdir != NULL) { 394 dp = ndp->ni_startdir; 395 startdir_used = 1; 396 } else if (ndp->ni_dirfd == AT_FDCWD) { 397 dp = fdp->fd_cdir; 398 vrefact(dp); 399 } else { 400 rights = ndp->ni_rightsneeded; 401 cap_rights_set(&rights, CAP_LOOKUP); 402 403 if (cnp->cn_flags & AUDITVNODE1) 404 AUDIT_ARG_ATFD1(ndp->ni_dirfd); 405 if (cnp->cn_flags & AUDITVNODE2) 406 AUDIT_ARG_ATFD2(ndp->ni_dirfd); 407 error = fgetvp_rights(td, ndp->ni_dirfd, 408 &rights, &ndp->ni_filecaps, &dp); 409 if (error == EINVAL) 410 error = ENOTDIR; 411 #ifdef CAPABILITIES 412 /* 413 * If file descriptor doesn't have all rights, 414 * all lookups relative to it must also be 415 * strictly relative. 416 */ 417 CAP_ALL(&rights); 418 if (!cap_rights_contains(&ndp->ni_filecaps.fc_rights, 419 &rights) || 420 ndp->ni_filecaps.fc_fcntls != CAP_FCNTL_ALL || 421 ndp->ni_filecaps.fc_nioctls != -1) { 422 ndp->ni_lcf |= NI_LCF_STRICTRELATIVE; 423 } 424 #endif 425 } 426 if (error == 0 && dp->v_type != VDIR) 427 error = ENOTDIR; 428 } 429 FILEDESC_SUNLOCK(fdp); 430 if (ndp->ni_startdir != NULL && !startdir_used) 431 vrele(ndp->ni_startdir); 432 if (error != 0) { 433 if (dp != NULL) 434 vrele(dp); 435 goto out; 436 } 437 if ((ndp->ni_lcf & NI_LCF_STRICTRELATIVE) != 0 && 438 lookup_cap_dotdot != 0) 439 ndp->ni_lcf |= NI_LCF_CAP_DOTDOT; 440 SDT_PROBE3(vfs, namei, lookup, entry, dp, cnp->cn_pnbuf, 441 cnp->cn_flags); 442 for (;;) { 443 ndp->ni_startdir = dp; 444 error = lookup(ndp); 445 if (error != 0) 446 goto out; 447 /* 448 * If not a symbolic link, we're done. 449 */ 450 if ((cnp->cn_flags & ISSYMLINK) == 0) { 451 vrele(ndp->ni_rootdir); 452 if ((cnp->cn_flags & (SAVENAME | SAVESTART)) == 0) { 453 namei_cleanup_cnp(cnp); 454 } else 455 cnp->cn_flags |= HASBUF; 456 nameicap_cleanup(ndp); 457 SDT_PROBE2(vfs, namei, lookup, return, 0, ndp->ni_vp); 458 return (0); 459 } 460 if (ndp->ni_loopcnt++ >= MAXSYMLINKS) { 461 error = ELOOP; 462 break; 463 } 464 #ifdef MAC 465 if ((cnp->cn_flags & NOMACCHECK) == 0) { 466 error = mac_vnode_check_readlink(td->td_ucred, 467 ndp->ni_vp); 468 if (error != 0) 469 break; 470 } 471 #endif 472 if (ndp->ni_pathlen > 1) 473 cp = uma_zalloc(namei_zone, M_WAITOK); 474 else 475 cp = cnp->cn_pnbuf; 476 aiov.iov_base = cp; 477 aiov.iov_len = MAXPATHLEN; 478 auio.uio_iov = &aiov; 479 auio.uio_iovcnt = 1; 480 auio.uio_offset = 0; 481 auio.uio_rw = UIO_READ; 482 auio.uio_segflg = UIO_SYSSPACE; 483 auio.uio_td = td; 484 auio.uio_resid = MAXPATHLEN; 485 error = VOP_READLINK(ndp->ni_vp, &auio, cnp->cn_cred); 486 if (error != 0) { 487 if (ndp->ni_pathlen > 1) 488 uma_zfree(namei_zone, cp); 489 break; 490 } 491 linklen = MAXPATHLEN - auio.uio_resid; 492 if (linklen == 0) { 493 if (ndp->ni_pathlen > 1) 494 uma_zfree(namei_zone, cp); 495 error = ENOENT; 496 break; 497 } 498 if (linklen + ndp->ni_pathlen > MAXPATHLEN) { 499 if (ndp->ni_pathlen > 1) 500 uma_zfree(namei_zone, cp); 501 error = ENAMETOOLONG; 502 break; 503 } 504 if (ndp->ni_pathlen > 1) { 505 bcopy(ndp->ni_next, cp + linklen, ndp->ni_pathlen); 506 uma_zfree(namei_zone, cnp->cn_pnbuf); 507 cnp->cn_pnbuf = cp; 508 } else 509 cnp->cn_pnbuf[linklen] = '\0'; 510 ndp->ni_pathlen += linklen; 511 vput(ndp->ni_vp); 512 dp = ndp->ni_dvp; 513 /* 514 * Check if root directory should replace current directory. 515 */ 516 cnp->cn_nameptr = cnp->cn_pnbuf; 517 if (*(cnp->cn_nameptr) == '/') { 518 vrele(dp); 519 error = namei_handle_root(ndp, &dp); 520 if (error != 0) 521 goto out; 522 } 523 } 524 vput(ndp->ni_vp); 525 ndp->ni_vp = NULL; 526 vrele(ndp->ni_dvp); 527 out: 528 vrele(ndp->ni_rootdir); 529 namei_cleanup_cnp(cnp); 530 nameicap_cleanup(ndp); 531 SDT_PROBE2(vfs, namei, lookup, return, error, NULL); 532 return (error); 533 } 534 535 static int 536 compute_cn_lkflags(struct mount *mp, int lkflags, int cnflags) 537 { 538 539 if (mp == NULL || ((lkflags & LK_SHARED) && 540 (!(mp->mnt_kern_flag & MNTK_LOOKUP_SHARED) || 541 ((cnflags & ISDOTDOT) && 542 (mp->mnt_kern_flag & MNTK_LOOKUP_EXCL_DOTDOT))))) { 543 lkflags &= ~LK_SHARED; 544 lkflags |= LK_EXCLUSIVE; 545 } 546 lkflags |= LK_NODDLKTREAT; 547 return (lkflags); 548 } 549 550 static __inline int 551 needs_exclusive_leaf(struct mount *mp, int flags) 552 { 553 554 /* 555 * Intermediate nodes can use shared locks, we only need to 556 * force an exclusive lock for leaf nodes. 557 */ 558 if ((flags & (ISLASTCN | LOCKLEAF)) != (ISLASTCN | LOCKLEAF)) 559 return (0); 560 561 /* Always use exclusive locks if LOCKSHARED isn't set. */ 562 if (!(flags & LOCKSHARED)) 563 return (1); 564 565 /* 566 * For lookups during open(), if the mount point supports 567 * extended shared operations, then use a shared lock for the 568 * leaf node, otherwise use an exclusive lock. 569 */ 570 if ((flags & ISOPEN) != 0) 571 return (!MNT_EXTENDED_SHARED(mp)); 572 573 /* 574 * Lookup requests outside of open() that specify LOCKSHARED 575 * only need a shared lock on the leaf vnode. 576 */ 577 return (0); 578 } 579 580 /* 581 * Search a pathname. 582 * This is a very central and rather complicated routine. 583 * 584 * The pathname is pointed to by ni_ptr and is of length ni_pathlen. 585 * The starting directory is taken from ni_startdir. The pathname is 586 * descended until done, or a symbolic link is encountered. The variable 587 * ni_more is clear if the path is completed; it is set to one if a 588 * symbolic link needing interpretation is encountered. 589 * 590 * The flag argument is LOOKUP, CREATE, RENAME, or DELETE depending on 591 * whether the name is to be looked up, created, renamed, or deleted. 592 * When CREATE, RENAME, or DELETE is specified, information usable in 593 * creating, renaming, or deleting a directory entry may be calculated. 594 * If flag has LOCKPARENT or'ed into it, the parent directory is returned 595 * locked. If flag has WANTPARENT or'ed into it, the parent directory is 596 * returned unlocked. Otherwise the parent directory is not returned. If 597 * the target of the pathname exists and LOCKLEAF is or'ed into the flag 598 * the target is returned locked, otherwise it is returned unlocked. 599 * When creating or renaming and LOCKPARENT is specified, the target may not 600 * be ".". When deleting and LOCKPARENT is specified, the target may be ".". 601 * 602 * Overall outline of lookup: 603 * 604 * dirloop: 605 * identify next component of name at ndp->ni_ptr 606 * handle degenerate case where name is null string 607 * if .. and crossing mount points and on mounted filesys, find parent 608 * call VOP_LOOKUP routine for next component name 609 * directory vnode returned in ni_dvp, unlocked unless LOCKPARENT set 610 * component vnode returned in ni_vp (if it exists), locked. 611 * if result vnode is mounted on and crossing mount points, 612 * find mounted on vnode 613 * if more components of name, do next level at dirloop 614 * return the answer in ni_vp, locked if LOCKLEAF set 615 * if LOCKPARENT set, return locked parent in ni_dvp 616 * if WANTPARENT set, return unlocked parent in ni_dvp 617 */ 618 int 619 lookup(struct nameidata *ndp) 620 { 621 char *cp; /* pointer into pathname argument */ 622 char *prev_ni_next; /* saved ndp->ni_next */ 623 struct vnode *dp = NULL; /* the directory we are searching */ 624 struct vnode *tdp; /* saved dp */ 625 struct mount *mp; /* mount table entry */ 626 struct prison *pr; 627 size_t prev_ni_pathlen; /* saved ndp->ni_pathlen */ 628 int docache; /* == 0 do not cache last component */ 629 int wantparent; /* 1 => wantparent or lockparent flag */ 630 int rdonly; /* lookup read-only flag bit */ 631 int error = 0; 632 int dpunlocked = 0; /* dp has already been unlocked */ 633 int relookup = 0; /* do not consume the path component */ 634 struct componentname *cnp = &ndp->ni_cnd; 635 int lkflags_save; 636 int ni_dvp_unlocked; 637 638 /* 639 * Setup: break out flag bits into variables. 640 */ 641 ni_dvp_unlocked = 0; 642 wantparent = cnp->cn_flags & (LOCKPARENT | WANTPARENT); 643 KASSERT(cnp->cn_nameiop == LOOKUP || wantparent, 644 ("CREATE, DELETE, RENAME require LOCKPARENT or WANTPARENT.")); 645 docache = (cnp->cn_flags & NOCACHE) ^ NOCACHE; 646 if (cnp->cn_nameiop == DELETE || 647 (wantparent && cnp->cn_nameiop != CREATE && 648 cnp->cn_nameiop != LOOKUP)) 649 docache = 0; 650 rdonly = cnp->cn_flags & RDONLY; 651 cnp->cn_flags &= ~ISSYMLINK; 652 ndp->ni_dvp = NULL; 653 /* 654 * We use shared locks until we hit the parent of the last cn then 655 * we adjust based on the requesting flags. 656 */ 657 cnp->cn_lkflags = LK_SHARED; 658 dp = ndp->ni_startdir; 659 ndp->ni_startdir = NULLVP; 660 vn_lock(dp, 661 compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags | LK_RETRY, 662 cnp->cn_flags)); 663 664 dirloop: 665 /* 666 * Search a new directory. 667 * 668 * The last component of the filename is left accessible via 669 * cnp->cn_nameptr for callers that need the name. Callers needing 670 * the name set the SAVENAME flag. When done, they assume 671 * responsibility for freeing the pathname buffer. 672 */ 673 for (cp = cnp->cn_nameptr; *cp != 0 && *cp != '/'; cp++) 674 continue; 675 cnp->cn_namelen = cp - cnp->cn_nameptr; 676 if (cnp->cn_namelen > NAME_MAX) { 677 error = ENAMETOOLONG; 678 goto bad; 679 } 680 #ifdef NAMEI_DIAGNOSTIC 681 { char c = *cp; 682 *cp = '\0'; 683 printf("{%s}: ", cnp->cn_nameptr); 684 *cp = c; } 685 #endif 686 prev_ni_pathlen = ndp->ni_pathlen; 687 ndp->ni_pathlen -= cnp->cn_namelen; 688 KASSERT(ndp->ni_pathlen <= PATH_MAX, 689 ("%s: ni_pathlen underflow to %zd\n", __func__, ndp->ni_pathlen)); 690 prev_ni_next = ndp->ni_next; 691 ndp->ni_next = cp; 692 693 /* 694 * Replace multiple slashes by a single slash and trailing slashes 695 * by a null. This must be done before VOP_LOOKUP() because some 696 * fs's don't know about trailing slashes. Remember if there were 697 * trailing slashes to handle symlinks, existing non-directories 698 * and non-existing files that won't be directories specially later. 699 */ 700 while (*cp == '/' && (cp[1] == '/' || cp[1] == '\0')) { 701 cp++; 702 ndp->ni_pathlen--; 703 if (*cp == '\0') { 704 *ndp->ni_next = '\0'; 705 cnp->cn_flags |= TRAILINGSLASH; 706 } 707 } 708 ndp->ni_next = cp; 709 710 cnp->cn_flags |= MAKEENTRY; 711 if (*cp == '\0' && docache == 0) 712 cnp->cn_flags &= ~MAKEENTRY; 713 if (cnp->cn_namelen == 2 && 714 cnp->cn_nameptr[1] == '.' && cnp->cn_nameptr[0] == '.') 715 cnp->cn_flags |= ISDOTDOT; 716 else 717 cnp->cn_flags &= ~ISDOTDOT; 718 if (*ndp->ni_next == 0) 719 cnp->cn_flags |= ISLASTCN; 720 else 721 cnp->cn_flags &= ~ISLASTCN; 722 723 if ((cnp->cn_flags & ISLASTCN) != 0 && 724 cnp->cn_namelen == 1 && cnp->cn_nameptr[0] == '.' && 725 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) { 726 error = EINVAL; 727 goto bad; 728 } 729 730 nameicap_tracker_add(ndp, dp); 731 732 /* 733 * Check for degenerate name (e.g. / or "") 734 * which is a way of talking about a directory, 735 * e.g. like "/." or ".". 736 */ 737 if (cnp->cn_nameptr[0] == '\0') { 738 if (dp->v_type != VDIR) { 739 error = ENOTDIR; 740 goto bad; 741 } 742 if (cnp->cn_nameiop != LOOKUP) { 743 error = EISDIR; 744 goto bad; 745 } 746 if (wantparent) { 747 ndp->ni_dvp = dp; 748 VREF(dp); 749 } 750 ndp->ni_vp = dp; 751 752 if (cnp->cn_flags & AUDITVNODE1) 753 AUDIT_ARG_VNODE1(dp); 754 else if (cnp->cn_flags & AUDITVNODE2) 755 AUDIT_ARG_VNODE2(dp); 756 757 if (!(cnp->cn_flags & (LOCKPARENT | LOCKLEAF))) 758 VOP_UNLOCK(dp, 0); 759 /* XXX This should probably move to the top of function. */ 760 if (cnp->cn_flags & SAVESTART) 761 panic("lookup: SAVESTART"); 762 goto success; 763 } 764 765 /* 766 * Handle "..": five special cases. 767 * 0. If doing a capability lookup and lookup_cap_dotdot is 768 * disabled, return ENOTCAPABLE. 769 * 1. Return an error if this is the last component of 770 * the name and the operation is DELETE or RENAME. 771 * 2. If at root directory (e.g. after chroot) 772 * or at absolute root directory 773 * then ignore it so can't get out. 774 * 3. If this vnode is the root of a mounted 775 * filesystem, then replace it with the 776 * vnode which was mounted on so we take the 777 * .. in the other filesystem. 778 * 4. If the vnode is the top directory of 779 * the jail or chroot, don't let them out. 780 * 5. If doing a capability lookup and lookup_cap_dotdot is 781 * enabled, return ENOTCAPABLE if the lookup would escape 782 * from the initial file descriptor directory. Checks are 783 * done by ensuring that namei() already traversed the 784 * result of dotdot lookup. 785 */ 786 if (cnp->cn_flags & ISDOTDOT) { 787 if ((ndp->ni_lcf & (NI_LCF_STRICTRELATIVE | NI_LCF_CAP_DOTDOT)) 788 == NI_LCF_STRICTRELATIVE) { 789 #ifdef KTRACE 790 if (KTRPOINT(curthread, KTR_CAPFAIL)) 791 ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL); 792 #endif 793 error = ENOTCAPABLE; 794 goto bad; 795 } 796 if ((cnp->cn_flags & ISLASTCN) != 0 && 797 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) { 798 error = EINVAL; 799 goto bad; 800 } 801 for (;;) { 802 for (pr = cnp->cn_cred->cr_prison; pr != NULL; 803 pr = pr->pr_parent) 804 if (dp == pr->pr_root) 805 break; 806 if (dp == ndp->ni_rootdir || 807 dp == ndp->ni_topdir || 808 dp == rootvnode || 809 pr != NULL || 810 ((dp->v_vflag & VV_ROOT) != 0 && 811 (cnp->cn_flags & NOCROSSMOUNT) != 0)) { 812 ndp->ni_dvp = dp; 813 ndp->ni_vp = dp; 814 VREF(dp); 815 goto nextname; 816 } 817 if ((dp->v_vflag & VV_ROOT) == 0) 818 break; 819 if (dp->v_iflag & VI_DOOMED) { /* forced unmount */ 820 error = ENOENT; 821 goto bad; 822 } 823 tdp = dp; 824 dp = dp->v_mount->mnt_vnodecovered; 825 VREF(dp); 826 vput(tdp); 827 vn_lock(dp, 828 compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags | 829 LK_RETRY, ISDOTDOT)); 830 error = nameicap_check_dotdot(ndp, dp); 831 if (error != 0) { 832 #ifdef KTRACE 833 if (KTRPOINT(curthread, KTR_CAPFAIL)) 834 ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL); 835 #endif 836 goto bad; 837 } 838 } 839 } 840 841 /* 842 * We now have a segment name to search for, and a directory to search. 843 */ 844 unionlookup: 845 #ifdef MAC 846 if ((cnp->cn_flags & NOMACCHECK) == 0) { 847 error = mac_vnode_check_lookup(cnp->cn_thread->td_ucred, dp, 848 cnp); 849 if (error) 850 goto bad; 851 } 852 #endif 853 ndp->ni_dvp = dp; 854 ndp->ni_vp = NULL; 855 ASSERT_VOP_LOCKED(dp, "lookup"); 856 /* 857 * If we have a shared lock we may need to upgrade the lock for the 858 * last operation. 859 */ 860 if ((cnp->cn_flags & LOCKPARENT) && (cnp->cn_flags & ISLASTCN) && 861 dp != vp_crossmp && VOP_ISLOCKED(dp) == LK_SHARED) 862 vn_lock(dp, LK_UPGRADE|LK_RETRY); 863 if ((dp->v_iflag & VI_DOOMED) != 0) { 864 error = ENOENT; 865 goto bad; 866 } 867 /* 868 * If we're looking up the last component and we need an exclusive 869 * lock, adjust our lkflags. 870 */ 871 if (needs_exclusive_leaf(dp->v_mount, cnp->cn_flags)) 872 cnp->cn_lkflags = LK_EXCLUSIVE; 873 #ifdef NAMEI_DIAGNOSTIC 874 vn_printf(dp, "lookup in "); 875 #endif 876 lkflags_save = cnp->cn_lkflags; 877 cnp->cn_lkflags = compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags, 878 cnp->cn_flags); 879 error = VOP_LOOKUP(dp, &ndp->ni_vp, cnp); 880 cnp->cn_lkflags = lkflags_save; 881 if (error != 0) { 882 KASSERT(ndp->ni_vp == NULL, ("leaf should be empty")); 883 #ifdef NAMEI_DIAGNOSTIC 884 printf("not found\n"); 885 #endif 886 if ((error == ENOENT) && 887 (dp->v_vflag & VV_ROOT) && (dp->v_mount != NULL) && 888 (dp->v_mount->mnt_flag & MNT_UNION)) { 889 tdp = dp; 890 dp = dp->v_mount->mnt_vnodecovered; 891 VREF(dp); 892 vput(tdp); 893 vn_lock(dp, 894 compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags | 895 LK_RETRY, cnp->cn_flags)); 896 nameicap_tracker_add(ndp, dp); 897 goto unionlookup; 898 } 899 900 if (error == ERELOOKUP) { 901 vref(dp); 902 ndp->ni_vp = dp; 903 error = 0; 904 relookup = 1; 905 goto good; 906 } 907 908 if (error != EJUSTRETURN) 909 goto bad; 910 /* 911 * At this point, we know we're at the end of the 912 * pathname. If creating / renaming, we can consider 913 * allowing the file or directory to be created / renamed, 914 * provided we're not on a read-only filesystem. 915 */ 916 if (rdonly) { 917 error = EROFS; 918 goto bad; 919 } 920 /* trailing slash only allowed for directories */ 921 if ((cnp->cn_flags & TRAILINGSLASH) && 922 !(cnp->cn_flags & WILLBEDIR)) { 923 error = ENOENT; 924 goto bad; 925 } 926 if ((cnp->cn_flags & LOCKPARENT) == 0) 927 VOP_UNLOCK(dp, 0); 928 /* 929 * We return with ni_vp NULL to indicate that the entry 930 * doesn't currently exist, leaving a pointer to the 931 * (possibly locked) directory vnode in ndp->ni_dvp. 932 */ 933 if (cnp->cn_flags & SAVESTART) { 934 ndp->ni_startdir = ndp->ni_dvp; 935 VREF(ndp->ni_startdir); 936 } 937 goto success; 938 } 939 940 good: 941 #ifdef NAMEI_DIAGNOSTIC 942 printf("found\n"); 943 #endif 944 dp = ndp->ni_vp; 945 946 /* 947 * Check to see if the vnode has been mounted on; 948 * if so find the root of the mounted filesystem. 949 */ 950 while (dp->v_type == VDIR && (mp = dp->v_mountedhere) && 951 (cnp->cn_flags & NOCROSSMOUNT) == 0) { 952 if (vfs_busy(mp, 0)) 953 continue; 954 vput(dp); 955 if (dp != ndp->ni_dvp) 956 vput(ndp->ni_dvp); 957 else 958 vrele(ndp->ni_dvp); 959 vrefact(vp_crossmp); 960 ndp->ni_dvp = vp_crossmp; 961 error = VFS_ROOT(mp, compute_cn_lkflags(mp, cnp->cn_lkflags, 962 cnp->cn_flags), &tdp); 963 vfs_unbusy(mp); 964 if (vn_lock(vp_crossmp, LK_SHARED | LK_NOWAIT)) 965 panic("vp_crossmp exclusively locked or reclaimed"); 966 if (error) { 967 dpunlocked = 1; 968 goto bad2; 969 } 970 ndp->ni_vp = dp = tdp; 971 } 972 973 /* 974 * Check for symbolic link 975 */ 976 if ((dp->v_type == VLNK) && 977 ((cnp->cn_flags & FOLLOW) || (cnp->cn_flags & TRAILINGSLASH) || 978 *ndp->ni_next == '/')) { 979 cnp->cn_flags |= ISSYMLINK; 980 if (dp->v_iflag & VI_DOOMED) { 981 /* 982 * We can't know whether the directory was mounted with 983 * NOSYMFOLLOW, so we can't follow safely. 984 */ 985 error = ENOENT; 986 goto bad2; 987 } 988 if (dp->v_mount->mnt_flag & MNT_NOSYMFOLLOW) { 989 error = EACCES; 990 goto bad2; 991 } 992 /* 993 * Symlink code always expects an unlocked dvp. 994 */ 995 if (ndp->ni_dvp != ndp->ni_vp) { 996 VOP_UNLOCK(ndp->ni_dvp, 0); 997 ni_dvp_unlocked = 1; 998 } 999 goto success; 1000 } 1001 1002 nextname: 1003 /* 1004 * Not a symbolic link that we will follow. Continue with the 1005 * next component if there is any; otherwise, we're done. 1006 */ 1007 KASSERT((cnp->cn_flags & ISLASTCN) || *ndp->ni_next == '/', 1008 ("lookup: invalid path state.")); 1009 if (relookup) { 1010 relookup = 0; 1011 ndp->ni_pathlen = prev_ni_pathlen; 1012 ndp->ni_next = prev_ni_next; 1013 if (ndp->ni_dvp != dp) 1014 vput(ndp->ni_dvp); 1015 else 1016 vrele(ndp->ni_dvp); 1017 goto dirloop; 1018 } 1019 if (cnp->cn_flags & ISDOTDOT) { 1020 error = nameicap_check_dotdot(ndp, ndp->ni_vp); 1021 if (error != 0) { 1022 #ifdef KTRACE 1023 if (KTRPOINT(curthread, KTR_CAPFAIL)) 1024 ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL); 1025 #endif 1026 goto bad2; 1027 } 1028 } 1029 if (*ndp->ni_next == '/') { 1030 cnp->cn_nameptr = ndp->ni_next; 1031 while (*cnp->cn_nameptr == '/') { 1032 cnp->cn_nameptr++; 1033 ndp->ni_pathlen--; 1034 } 1035 if (ndp->ni_dvp != dp) 1036 vput(ndp->ni_dvp); 1037 else 1038 vrele(ndp->ni_dvp); 1039 goto dirloop; 1040 } 1041 /* 1042 * If we're processing a path with a trailing slash, 1043 * check that the end result is a directory. 1044 */ 1045 if ((cnp->cn_flags & TRAILINGSLASH) && dp->v_type != VDIR) { 1046 error = ENOTDIR; 1047 goto bad2; 1048 } 1049 /* 1050 * Disallow directory write attempts on read-only filesystems. 1051 */ 1052 if (rdonly && 1053 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) { 1054 error = EROFS; 1055 goto bad2; 1056 } 1057 if (cnp->cn_flags & SAVESTART) { 1058 ndp->ni_startdir = ndp->ni_dvp; 1059 VREF(ndp->ni_startdir); 1060 } 1061 if (!wantparent) { 1062 ni_dvp_unlocked = 2; 1063 if (ndp->ni_dvp != dp) 1064 vput(ndp->ni_dvp); 1065 else 1066 vrele(ndp->ni_dvp); 1067 } else if ((cnp->cn_flags & LOCKPARENT) == 0 && ndp->ni_dvp != dp) { 1068 VOP_UNLOCK(ndp->ni_dvp, 0); 1069 ni_dvp_unlocked = 1; 1070 } 1071 1072 if (cnp->cn_flags & AUDITVNODE1) 1073 AUDIT_ARG_VNODE1(dp); 1074 else if (cnp->cn_flags & AUDITVNODE2) 1075 AUDIT_ARG_VNODE2(dp); 1076 1077 if ((cnp->cn_flags & LOCKLEAF) == 0) 1078 VOP_UNLOCK(dp, 0); 1079 success: 1080 /* 1081 * Because of shared lookup we may have the vnode shared locked, but 1082 * the caller may want it to be exclusively locked. 1083 */ 1084 if (needs_exclusive_leaf(dp->v_mount, cnp->cn_flags) && 1085 VOP_ISLOCKED(dp) != LK_EXCLUSIVE) { 1086 vn_lock(dp, LK_UPGRADE | LK_RETRY); 1087 if (dp->v_iflag & VI_DOOMED) { 1088 error = ENOENT; 1089 goto bad2; 1090 } 1091 } 1092 return (0); 1093 1094 bad2: 1095 if (ni_dvp_unlocked != 2) { 1096 if (dp != ndp->ni_dvp && !ni_dvp_unlocked) 1097 vput(ndp->ni_dvp); 1098 else 1099 vrele(ndp->ni_dvp); 1100 } 1101 bad: 1102 if (!dpunlocked) 1103 vput(dp); 1104 ndp->ni_vp = NULL; 1105 return (error); 1106 } 1107 1108 /* 1109 * relookup - lookup a path name component 1110 * Used by lookup to re-acquire things. 1111 */ 1112 int 1113 relookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp) 1114 { 1115 struct vnode *dp = NULL; /* the directory we are searching */ 1116 int wantparent; /* 1 => wantparent or lockparent flag */ 1117 int rdonly; /* lookup read-only flag bit */ 1118 int error = 0; 1119 1120 KASSERT(cnp->cn_flags & ISLASTCN, 1121 ("relookup: Not given last component.")); 1122 /* 1123 * Setup: break out flag bits into variables. 1124 */ 1125 wantparent = cnp->cn_flags & (LOCKPARENT|WANTPARENT); 1126 KASSERT(wantparent, ("relookup: parent not wanted.")); 1127 rdonly = cnp->cn_flags & RDONLY; 1128 cnp->cn_flags &= ~ISSYMLINK; 1129 dp = dvp; 1130 cnp->cn_lkflags = LK_EXCLUSIVE; 1131 vn_lock(dp, LK_EXCLUSIVE | LK_RETRY); 1132 1133 /* 1134 * Search a new directory. 1135 * 1136 * The last component of the filename is left accessible via 1137 * cnp->cn_nameptr for callers that need the name. Callers needing 1138 * the name set the SAVENAME flag. When done, they assume 1139 * responsibility for freeing the pathname buffer. 1140 */ 1141 #ifdef NAMEI_DIAGNOSTIC 1142 printf("{%s}: ", cnp->cn_nameptr); 1143 #endif 1144 1145 /* 1146 * Check for "" which represents the root directory after slash 1147 * removal. 1148 */ 1149 if (cnp->cn_nameptr[0] == '\0') { 1150 /* 1151 * Support only LOOKUP for "/" because lookup() 1152 * can't succeed for CREATE, DELETE and RENAME. 1153 */ 1154 KASSERT(cnp->cn_nameiop == LOOKUP, ("nameiop must be LOOKUP")); 1155 KASSERT(dp->v_type == VDIR, ("dp is not a directory")); 1156 1157 if (!(cnp->cn_flags & LOCKLEAF)) 1158 VOP_UNLOCK(dp, 0); 1159 *vpp = dp; 1160 /* XXX This should probably move to the top of function. */ 1161 if (cnp->cn_flags & SAVESTART) 1162 panic("lookup: SAVESTART"); 1163 return (0); 1164 } 1165 1166 if (cnp->cn_flags & ISDOTDOT) 1167 panic ("relookup: lookup on dot-dot"); 1168 1169 /* 1170 * We now have a segment name to search for, and a directory to search. 1171 */ 1172 #ifdef NAMEI_DIAGNOSTIC 1173 vn_printf(dp, "search in "); 1174 #endif 1175 if ((error = VOP_LOOKUP(dp, vpp, cnp)) != 0) { 1176 KASSERT(*vpp == NULL, ("leaf should be empty")); 1177 if (error != EJUSTRETURN) 1178 goto bad; 1179 /* 1180 * If creating and at end of pathname, then can consider 1181 * allowing file to be created. 1182 */ 1183 if (rdonly) { 1184 error = EROFS; 1185 goto bad; 1186 } 1187 /* ASSERT(dvp == ndp->ni_startdir) */ 1188 if (cnp->cn_flags & SAVESTART) 1189 VREF(dvp); 1190 if ((cnp->cn_flags & LOCKPARENT) == 0) 1191 VOP_UNLOCK(dp, 0); 1192 /* 1193 * We return with ni_vp NULL to indicate that the entry 1194 * doesn't currently exist, leaving a pointer to the 1195 * (possibly locked) directory vnode in ndp->ni_dvp. 1196 */ 1197 return (0); 1198 } 1199 1200 dp = *vpp; 1201 1202 /* 1203 * Disallow directory write attempts on read-only filesystems. 1204 */ 1205 if (rdonly && 1206 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) { 1207 if (dvp == dp) 1208 vrele(dvp); 1209 else 1210 vput(dvp); 1211 error = EROFS; 1212 goto bad; 1213 } 1214 /* 1215 * Set the parent lock/ref state to the requested state. 1216 */ 1217 if ((cnp->cn_flags & LOCKPARENT) == 0 && dvp != dp) { 1218 if (wantparent) 1219 VOP_UNLOCK(dvp, 0); 1220 else 1221 vput(dvp); 1222 } else if (!wantparent) 1223 vrele(dvp); 1224 /* 1225 * Check for symbolic link 1226 */ 1227 KASSERT(dp->v_type != VLNK || !(cnp->cn_flags & FOLLOW), 1228 ("relookup: symlink found.\n")); 1229 1230 /* ASSERT(dvp == ndp->ni_startdir) */ 1231 if (cnp->cn_flags & SAVESTART) 1232 VREF(dvp); 1233 1234 if ((cnp->cn_flags & LOCKLEAF) == 0) 1235 VOP_UNLOCK(dp, 0); 1236 return (0); 1237 bad: 1238 vput(dp); 1239 *vpp = NULL; 1240 return (error); 1241 } 1242 1243 void 1244 NDINIT_ALL(struct nameidata *ndp, u_long op, u_long flags, enum uio_seg segflg, 1245 const char *namep, int dirfd, struct vnode *startdir, cap_rights_t *rightsp, 1246 struct thread *td) 1247 { 1248 1249 ndp->ni_cnd.cn_nameiop = op; 1250 ndp->ni_cnd.cn_flags = flags; 1251 ndp->ni_segflg = segflg; 1252 ndp->ni_dirp = namep; 1253 ndp->ni_dirfd = dirfd; 1254 ndp->ni_startdir = startdir; 1255 if (rightsp != NULL) 1256 ndp->ni_rightsneeded = *rightsp; 1257 else 1258 cap_rights_init(&ndp->ni_rightsneeded); 1259 filecaps_init(&ndp->ni_filecaps); 1260 ndp->ni_cnd.cn_thread = td; 1261 } 1262 1263 /* 1264 * Free data allocated by namei(); see namei(9) for details. 1265 */ 1266 void 1267 NDFREE(struct nameidata *ndp, const u_int flags) 1268 { 1269 int unlock_dvp; 1270 int unlock_vp; 1271 1272 unlock_dvp = 0; 1273 unlock_vp = 0; 1274 1275 if (!(flags & NDF_NO_FREE_PNBUF) && 1276 (ndp->ni_cnd.cn_flags & HASBUF)) { 1277 uma_zfree(namei_zone, ndp->ni_cnd.cn_pnbuf); 1278 ndp->ni_cnd.cn_flags &= ~HASBUF; 1279 } 1280 if (!(flags & NDF_NO_VP_UNLOCK) && 1281 (ndp->ni_cnd.cn_flags & LOCKLEAF) && ndp->ni_vp) 1282 unlock_vp = 1; 1283 if (!(flags & NDF_NO_VP_RELE) && ndp->ni_vp) { 1284 if (unlock_vp) { 1285 vput(ndp->ni_vp); 1286 unlock_vp = 0; 1287 } else 1288 vrele(ndp->ni_vp); 1289 ndp->ni_vp = NULL; 1290 } 1291 if (unlock_vp) 1292 VOP_UNLOCK(ndp->ni_vp, 0); 1293 if (!(flags & NDF_NO_DVP_UNLOCK) && 1294 (ndp->ni_cnd.cn_flags & LOCKPARENT) && 1295 ndp->ni_dvp != ndp->ni_vp) 1296 unlock_dvp = 1; 1297 if (!(flags & NDF_NO_DVP_RELE) && 1298 (ndp->ni_cnd.cn_flags & (LOCKPARENT|WANTPARENT))) { 1299 if (unlock_dvp) { 1300 vput(ndp->ni_dvp); 1301 unlock_dvp = 0; 1302 } else 1303 vrele(ndp->ni_dvp); 1304 ndp->ni_dvp = NULL; 1305 } 1306 if (unlock_dvp) 1307 VOP_UNLOCK(ndp->ni_dvp, 0); 1308 if (!(flags & NDF_NO_STARTDIR_RELE) && 1309 (ndp->ni_cnd.cn_flags & SAVESTART)) { 1310 vrele(ndp->ni_startdir); 1311 ndp->ni_startdir = NULL; 1312 } 1313 } 1314 1315 /* 1316 * Determine if there is a suitable alternate filename under the specified 1317 * prefix for the specified path. If the create flag is set, then the 1318 * alternate prefix will be used so long as the parent directory exists. 1319 * This is used by the various compatibility ABIs so that Linux binaries prefer 1320 * files under /compat/linux for example. The chosen path (whether under 1321 * the prefix or under /) is returned in a kernel malloc'd buffer pointed 1322 * to by pathbuf. The caller is responsible for free'ing the buffer from 1323 * the M_TEMP bucket if one is returned. 1324 */ 1325 int 1326 kern_alternate_path(struct thread *td, const char *prefix, const char *path, 1327 enum uio_seg pathseg, char **pathbuf, int create, int dirfd) 1328 { 1329 struct nameidata nd, ndroot; 1330 char *ptr, *buf, *cp; 1331 size_t len, sz; 1332 int error; 1333 1334 buf = (char *) malloc(MAXPATHLEN, M_TEMP, M_WAITOK); 1335 *pathbuf = buf; 1336 1337 /* Copy the prefix into the new pathname as a starting point. */ 1338 len = strlcpy(buf, prefix, MAXPATHLEN); 1339 if (len >= MAXPATHLEN) { 1340 *pathbuf = NULL; 1341 free(buf, M_TEMP); 1342 return (EINVAL); 1343 } 1344 sz = MAXPATHLEN - len; 1345 ptr = buf + len; 1346 1347 /* Append the filename to the prefix. */ 1348 if (pathseg == UIO_SYSSPACE) 1349 error = copystr(path, ptr, sz, &len); 1350 else 1351 error = copyinstr(path, ptr, sz, &len); 1352 1353 if (error) { 1354 *pathbuf = NULL; 1355 free(buf, M_TEMP); 1356 return (error); 1357 } 1358 1359 /* Only use a prefix with absolute pathnames. */ 1360 if (*ptr != '/') { 1361 error = EINVAL; 1362 goto keeporig; 1363 } 1364 1365 if (dirfd != AT_FDCWD) { 1366 /* 1367 * We want the original because the "prefix" is 1368 * included in the already opened dirfd. 1369 */ 1370 bcopy(ptr, buf, len); 1371 return (0); 1372 } 1373 1374 /* 1375 * We know that there is a / somewhere in this pathname. 1376 * Search backwards for it, to find the file's parent dir 1377 * to see if it exists in the alternate tree. If it does, 1378 * and we want to create a file (cflag is set). We don't 1379 * need to worry about the root comparison in this case. 1380 */ 1381 1382 if (create) { 1383 for (cp = &ptr[len] - 1; *cp != '/'; cp--); 1384 *cp = '\0'; 1385 1386 NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_SYSSPACE, buf, td); 1387 error = namei(&nd); 1388 *cp = '/'; 1389 if (error != 0) 1390 goto keeporig; 1391 } else { 1392 NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_SYSSPACE, buf, td); 1393 1394 error = namei(&nd); 1395 if (error != 0) 1396 goto keeporig; 1397 1398 /* 1399 * We now compare the vnode of the prefix to the one 1400 * vnode asked. If they resolve to be the same, then we 1401 * ignore the match so that the real root gets used. 1402 * This avoids the problem of traversing "../.." to find the 1403 * root directory and never finding it, because "/" resolves 1404 * to the emulation root directory. This is expensive :-( 1405 */ 1406 NDINIT(&ndroot, LOOKUP, FOLLOW, UIO_SYSSPACE, prefix, 1407 td); 1408 1409 /* We shouldn't ever get an error from this namei(). */ 1410 error = namei(&ndroot); 1411 if (error == 0) { 1412 if (nd.ni_vp == ndroot.ni_vp) 1413 error = ENOENT; 1414 1415 NDFREE(&ndroot, NDF_ONLY_PNBUF); 1416 vrele(ndroot.ni_vp); 1417 } 1418 } 1419 1420 NDFREE(&nd, NDF_ONLY_PNBUF); 1421 vrele(nd.ni_vp); 1422 1423 keeporig: 1424 /* If there was an error, use the original path name. */ 1425 if (error) 1426 bcopy(ptr, buf, len); 1427 return (error); 1428 }
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