Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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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("$FreeBSD$"); 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 #ifdef INVARIANTS 65 #include <machine/_inttypes.h> 66 #endif 67 68 #include <security/audit/audit.h> 69 #include <security/mac/mac_framework.h> 70 71 #include <vm/uma.h> 72 73 #define NAMEI_DIAGNOSTIC 1 74 #undef NAMEI_DIAGNOSTIC 75 76 SDT_PROVIDER_DEFINE(vfs); 77 SDT_PROBE_DEFINE4(vfs, namei, lookup, entry, "struct vnode *", "char *", 78 "unsigned long", "bool"); 79 SDT_PROBE_DEFINE4(vfs, namei, lookup, return, "int", "struct vnode *", "bool", 80 "struct nameidata"); 81 82 /* Allocation zone for namei. */ 83 uma_zone_t namei_zone; 84 85 /* Placeholder vnode for mp traversal. */ 86 static struct vnode *vp_crossmp; 87 88 static int 89 crossmp_vop_islocked(struct vop_islocked_args *ap) 90 { 91 92 return (LK_SHARED); 93 } 94 95 static int 96 crossmp_vop_lock1(struct vop_lock1_args *ap) 97 { 98 struct vnode *vp; 99 struct lock *lk __unused; 100 const char *file __unused; 101 int flags, line __unused; 102 103 vp = ap->a_vp; 104 lk = vp->v_vnlock; 105 flags = ap->a_flags; 106 file = ap->a_file; 107 line = ap->a_line; 108 109 if ((flags & LK_SHARED) == 0) 110 panic("invalid lock request for crossmp"); 111 112 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER, file, line, 113 flags & LK_INTERLOCK ? &VI_MTX(vp)->lock_object : NULL); 114 WITNESS_LOCK(&lk->lock_object, 0, file, line); 115 if ((flags & LK_INTERLOCK) != 0) 116 VI_UNLOCK(vp); 117 LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, ap->a_file, line); 118 return (0); 119 } 120 121 static int 122 crossmp_vop_unlock(struct vop_unlock_args *ap) 123 { 124 struct vnode *vp; 125 struct lock *lk __unused; 126 127 vp = ap->a_vp; 128 lk = vp->v_vnlock; 129 130 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 * VFS_VOP_VECTOR_REGISTER(crossmp_vnodeops) is not used here since the vnode 144 * gets allocated early. See nameiinit for the direct call below. 145 */ 146 147 struct nameicap_tracker { 148 struct vnode *dp; 149 TAILQ_ENTRY(nameicap_tracker) nm_link; 150 }; 151 152 /* Zone for cap mode tracker elements used for dotdot capability checks. */ 153 MALLOC_DEFINE(M_NAMEITRACKER, "namei_tracker", "namei tracking for dotdot"); 154 155 static void 156 nameiinit(void *dummy __unused) 157 { 158 159 namei_zone = uma_zcreate("NAMEI", MAXPATHLEN, NULL, NULL, NULL, NULL, 160 UMA_ALIGN_PTR, 0); 161 vfs_vector_op_register(&crossmp_vnodeops); 162 getnewvnode("crossmp", NULL, &crossmp_vnodeops, &vp_crossmp); 163 } 164 SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_SECOND, nameiinit, NULL); 165 166 static int lookup_cap_dotdot = 1; 167 SYSCTL_INT(_vfs, OID_AUTO, lookup_cap_dotdot, CTLFLAG_RWTUN, 168 &lookup_cap_dotdot, 0, 169 "enables \"..\" components in path lookup in capability mode"); 170 static int lookup_cap_dotdot_nonlocal = 1; 171 SYSCTL_INT(_vfs, OID_AUTO, lookup_cap_dotdot_nonlocal, CTLFLAG_RWTUN, 172 &lookup_cap_dotdot_nonlocal, 0, 173 "enables \"..\" components in path lookup in capability mode " 174 "on non-local mount"); 175 176 static void 177 nameicap_tracker_add(struct nameidata *ndp, struct vnode *dp) 178 { 179 struct nameicap_tracker *nt; 180 struct componentname *cnp; 181 182 if ((ndp->ni_lcf & NI_LCF_CAP_DOTDOT) == 0 || dp->v_type != VDIR) 183 return; 184 cnp = &ndp->ni_cnd; 185 nt = TAILQ_LAST(&ndp->ni_cap_tracker, nameicap_tracker_head); 186 if (nt != NULL && nt->dp == dp) 187 return; 188 nt = malloc(sizeof(*nt), M_NAMEITRACKER, M_WAITOK); 189 vhold(dp); 190 nt->dp = dp; 191 TAILQ_INSERT_TAIL(&ndp->ni_cap_tracker, nt, nm_link); 192 } 193 194 static void 195 nameicap_cleanup_from(struct nameidata *ndp, struct nameicap_tracker *first) 196 { 197 struct nameicap_tracker *nt, *nt1; 198 199 nt = first; 200 TAILQ_FOREACH_FROM_SAFE(nt, &ndp->ni_cap_tracker, nm_link, nt1) { 201 TAILQ_REMOVE(&ndp->ni_cap_tracker, nt, nm_link); 202 vdrop(nt->dp); 203 free(nt, M_NAMEITRACKER); 204 } 205 } 206 207 static void 208 nameicap_cleanup(struct nameidata *ndp) 209 { 210 KASSERT(TAILQ_EMPTY(&ndp->ni_cap_tracker) || 211 (ndp->ni_lcf & NI_LCF_CAP_DOTDOT) != 0, ("not strictrelative")); 212 nameicap_cleanup_from(ndp, NULL); 213 } 214 215 /* 216 * For dotdot lookups in capability mode, only allow the component 217 * lookup to succeed if the resulting directory was already traversed 218 * during the operation. This catches situations where already 219 * traversed directory is moved to different parent, and then we walk 220 * over it with dotdots. 221 * 222 * Also allow to force failure of dotdot lookups for non-local 223 * filesystems, where external agents might assist local lookups to 224 * escape the compartment. 225 */ 226 static int 227 nameicap_check_dotdot(struct nameidata *ndp, struct vnode *dp) 228 { 229 struct nameicap_tracker *nt; 230 struct mount *mp; 231 232 if (dp == NULL || dp->v_type != VDIR || (ndp->ni_lcf & 233 NI_LCF_STRICTRELATIVE) == 0) 234 return (0); 235 if ((ndp->ni_lcf & NI_LCF_CAP_DOTDOT) == 0) 236 return (ENOTCAPABLE); 237 mp = dp->v_mount; 238 if (lookup_cap_dotdot_nonlocal == 0 && mp != NULL && 239 (mp->mnt_flag & MNT_LOCAL) == 0) 240 return (ENOTCAPABLE); 241 TAILQ_FOREACH_REVERSE(nt, &ndp->ni_cap_tracker, nameicap_tracker_head, 242 nm_link) { 243 if (dp == nt->dp) { 244 nt = TAILQ_NEXT(nt, nm_link); 245 if (nt != NULL) 246 nameicap_cleanup_from(ndp, nt); 247 return (0); 248 } 249 } 250 return (ENOTCAPABLE); 251 } 252 253 static void 254 namei_cleanup_cnp(struct componentname *cnp) 255 { 256 257 uma_zfree(namei_zone, cnp->cn_pnbuf); 258 #ifdef DIAGNOSTIC 259 cnp->cn_pnbuf = NULL; 260 cnp->cn_nameptr = NULL; 261 #endif 262 } 263 264 static int 265 namei_handle_root(struct nameidata *ndp, struct vnode **dpp) 266 { 267 struct componentname *cnp; 268 269 cnp = &ndp->ni_cnd; 270 if ((ndp->ni_lcf & NI_LCF_STRICTRELATIVE) != 0) { 271 #ifdef KTRACE 272 if (KTRPOINT(curthread, KTR_CAPFAIL)) 273 ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL); 274 #endif 275 return (ENOTCAPABLE); 276 } 277 while (*(cnp->cn_nameptr) == '/') { 278 cnp->cn_nameptr++; 279 ndp->ni_pathlen--; 280 } 281 *dpp = ndp->ni_rootdir; 282 vrefact(*dpp); 283 return (0); 284 } 285 286 static int 287 namei_setup(struct nameidata *ndp, struct vnode **dpp, struct pwd **pwdp) 288 { 289 struct componentname *cnp; 290 struct file *dfp; 291 struct thread *td; 292 struct pwd *pwd; 293 cap_rights_t rights; 294 int error; 295 bool startdir_used; 296 297 cnp = &ndp->ni_cnd; 298 td = cnp->cn_thread; 299 300 startdir_used = false; 301 *pwdp = NULL; 302 *dpp = NULL; 303 304 #ifdef CAPABILITY_MODE 305 /* 306 * In capability mode, lookups must be restricted to happen in 307 * the subtree with the root specified by the file descriptor: 308 * - The root must be real file descriptor, not the pseudo-descriptor 309 * AT_FDCWD. 310 * - The passed path must be relative and not absolute. 311 * - If lookup_cap_dotdot is disabled, path must not contain the 312 * '..' components. 313 * - If lookup_cap_dotdot is enabled, we verify that all '..' 314 * components lookups result in the directories which were 315 * previously walked by us, which prevents an escape from 316 * the relative root. 317 */ 318 if (IN_CAPABILITY_MODE(td) && (cnp->cn_flags & NOCAPCHECK) == 0) { 319 ndp->ni_lcf |= NI_LCF_STRICTRELATIVE; 320 ndp->ni_resflags |= NIRES_STRICTREL; 321 if (ndp->ni_dirfd == AT_FDCWD) { 322 #ifdef KTRACE 323 if (KTRPOINT(td, KTR_CAPFAIL)) 324 ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL); 325 #endif 326 return (ECAPMODE); 327 } 328 } 329 #endif 330 error = 0; 331 332 /* 333 * Get starting point for the translation. 334 */ 335 pwd = pwd_hold(td); 336 /* 337 * The reference on ni_rootdir is acquired in the block below to avoid 338 * back-to-back atomics for absolute lookups. 339 */ 340 ndp->ni_rootdir = pwd->pwd_rdir; 341 ndp->ni_topdir = pwd->pwd_jdir; 342 343 if (cnp->cn_pnbuf[0] == '/') { 344 ndp->ni_resflags |= NIRES_ABS; 345 error = namei_handle_root(ndp, dpp); 346 } else { 347 if (ndp->ni_startdir != NULL) { 348 *dpp = ndp->ni_startdir; 349 startdir_used = true; 350 } else if (ndp->ni_dirfd == AT_FDCWD) { 351 *dpp = pwd->pwd_cdir; 352 vrefact(*dpp); 353 } else { 354 rights = *ndp->ni_rightsneeded; 355 cap_rights_set_one(&rights, CAP_LOOKUP); 356 357 if (cnp->cn_flags & AUDITVNODE1) 358 AUDIT_ARG_ATFD1(ndp->ni_dirfd); 359 if (cnp->cn_flags & AUDITVNODE2) 360 AUDIT_ARG_ATFD2(ndp->ni_dirfd); 361 /* 362 * Effectively inlined fgetvp_rights, because we need to 363 * inspect the file as well as grabbing the vnode. 364 */ 365 error = fget_cap(td, ndp->ni_dirfd, &rights, 366 &dfp, &ndp->ni_filecaps); 367 if (error != 0) { 368 /* 369 * Preserve the error; it should either be EBADF 370 * or capability-related, both of which can be 371 * safely returned to the caller. 372 */ 373 } else { 374 if (dfp->f_ops == &badfileops) { 375 error = EBADF; 376 } else if (dfp->f_vnode == NULL) { 377 error = ENOTDIR; 378 } else { 379 *dpp = dfp->f_vnode; 380 vrefact(*dpp); 381 382 if ((dfp->f_flag & FSEARCH) != 0) 383 cnp->cn_flags |= NOEXECCHECK; 384 } 385 fdrop(dfp, td); 386 } 387 #ifdef CAPABILITIES 388 /* 389 * If file descriptor doesn't have all rights, 390 * all lookups relative to it must also be 391 * strictly relative. 392 */ 393 CAP_ALL(&rights); 394 if (!cap_rights_contains(&ndp->ni_filecaps.fc_rights, 395 &rights) || 396 ndp->ni_filecaps.fc_fcntls != CAP_FCNTL_ALL || 397 ndp->ni_filecaps.fc_nioctls != -1) { 398 ndp->ni_lcf |= NI_LCF_STRICTRELATIVE; 399 ndp->ni_resflags |= NIRES_STRICTREL; 400 } 401 #endif 402 } 403 if (error == 0 && (*dpp)->v_type != VDIR) 404 error = ENOTDIR; 405 } 406 if (error == 0 && (cnp->cn_flags & RBENEATH) != 0) { 407 if (cnp->cn_pnbuf[0] == '/') { 408 error = ENOTCAPABLE; 409 } else if ((ndp->ni_lcf & NI_LCF_STRICTRELATIVE) == 0) { 410 ndp->ni_lcf |= NI_LCF_STRICTRELATIVE | 411 NI_LCF_CAP_DOTDOT; 412 } 413 } 414 415 /* 416 * If we are auditing the kernel pathname, save the user pathname. 417 */ 418 if (cnp->cn_flags & AUDITVNODE1) 419 AUDIT_ARG_UPATH1_VP(td, ndp->ni_rootdir, *dpp, cnp->cn_pnbuf); 420 if (cnp->cn_flags & AUDITVNODE2) 421 AUDIT_ARG_UPATH2_VP(td, ndp->ni_rootdir, *dpp, cnp->cn_pnbuf); 422 if (ndp->ni_startdir != NULL && !startdir_used) 423 vrele(ndp->ni_startdir); 424 if (error != 0) { 425 if (*dpp != NULL) 426 vrele(*dpp); 427 pwd_drop(pwd); 428 return (error); 429 } 430 if ((ndp->ni_lcf & NI_LCF_STRICTRELATIVE) != 0 && 431 lookup_cap_dotdot != 0) 432 ndp->ni_lcf |= NI_LCF_CAP_DOTDOT; 433 SDT_PROBE4(vfs, namei, lookup, entry, *dpp, cnp->cn_pnbuf, 434 cnp->cn_flags, false); 435 *pwdp = pwd; 436 return (0); 437 } 438 439 static int 440 namei_getpath(struct nameidata *ndp) 441 { 442 struct componentname *cnp; 443 int error; 444 445 cnp = &ndp->ni_cnd; 446 447 /* 448 * Get a buffer for the name to be translated, and copy the 449 * name into the buffer. 450 */ 451 cnp->cn_pnbuf = uma_zalloc(namei_zone, M_WAITOK); 452 if (ndp->ni_segflg == UIO_SYSSPACE) { 453 error = copystr(ndp->ni_dirp, cnp->cn_pnbuf, MAXPATHLEN, 454 &ndp->ni_pathlen); 455 } else { 456 error = copyinstr(ndp->ni_dirp, cnp->cn_pnbuf, MAXPATHLEN, 457 &ndp->ni_pathlen); 458 } 459 460 if (__predict_false(error != 0)) { 461 namei_cleanup_cnp(cnp); 462 return (error); 463 } 464 465 /* 466 * Don't allow empty pathnames. 467 */ 468 if (__predict_false(*cnp->cn_pnbuf == '\0')) { 469 namei_cleanup_cnp(cnp); 470 return (ENOENT); 471 } 472 473 cnp->cn_nameptr = cnp->cn_pnbuf; 474 return (0); 475 } 476 477 /* 478 * Convert a pathname into a pointer to a locked vnode. 479 * 480 * The FOLLOW flag is set when symbolic links are to be followed 481 * when they occur at the end of the name translation process. 482 * Symbolic links are always followed for all other pathname 483 * components other than the last. 484 * 485 * The segflg defines whether the name is to be copied from user 486 * space or kernel space. 487 * 488 * Overall outline of namei: 489 * 490 * copy in name 491 * get starting directory 492 * while (!done && !error) { 493 * call lookup to search path. 494 * if symbolic link, massage name in buffer and continue 495 * } 496 */ 497 int 498 namei(struct nameidata *ndp) 499 { 500 char *cp; /* pointer into pathname argument */ 501 struct vnode *dp; /* the directory we are searching */ 502 struct iovec aiov; /* uio for reading symbolic links */ 503 struct componentname *cnp; 504 struct thread *td; 505 struct pwd *pwd; 506 struct uio auio; 507 int error, linklen; 508 enum cache_fpl_status status; 509 510 cnp = &ndp->ni_cnd; 511 td = cnp->cn_thread; 512 #ifdef INVARIANTS 513 KASSERT((ndp->ni_debugflags & NAMEI_DBG_CALLED) == 0, 514 ("%s: repeated call to namei without NDREINIT", __func__)); 515 KASSERT(ndp->ni_debugflags == NAMEI_DBG_INITED, 516 ("%s: bad debugflags %d", __func__, ndp->ni_debugflags)); 517 ndp->ni_debugflags |= NAMEI_DBG_CALLED; 518 if (ndp->ni_startdir != NULL) 519 ndp->ni_debugflags |= NAMEI_DBG_HADSTARTDIR; 520 if (cnp->cn_flags & FAILIFEXISTS) { 521 KASSERT(cnp->cn_nameiop == CREATE, 522 ("%s: FAILIFEXISTS passed for op %d", __func__, cnp->cn_nameiop)); 523 /* 524 * The limitation below is to restrict hairy corner cases. 525 */ 526 KASSERT((cnp->cn_flags & (LOCKPARENT | LOCKLEAF)) == LOCKPARENT, 527 ("%s: FAILIFEXISTS must be passed with LOCKPARENT and without LOCKLEAF", 528 __func__)); 529 } 530 /* 531 * For NDVALIDATE. 532 * 533 * While NDINIT may seem like a more natural place to do it, there are 534 * callers which directly modify flags past invoking init. 535 */ 536 cnp->cn_origflags = cnp->cn_flags; 537 #endif 538 ndp->ni_cnd.cn_cred = ndp->ni_cnd.cn_thread->td_ucred; 539 KASSERT(ndp->ni_resflags == 0, ("%s: garbage in ni_resflags: %x\n", 540 __func__, ndp->ni_resflags)); 541 KASSERT(cnp->cn_cred && td->td_proc, ("namei: bad cred/proc")); 542 KASSERT((cnp->cn_flags & NAMEI_INTERNAL_FLAGS) == 0, 543 ("namei: unexpected flags: %" PRIx64 "\n", 544 cnp->cn_flags & NAMEI_INTERNAL_FLAGS)); 545 if (cnp->cn_flags & NOCACHE) 546 KASSERT(cnp->cn_nameiop != LOOKUP, 547 ("%s: NOCACHE passed with LOOKUP", __func__)); 548 MPASS(ndp->ni_startdir == NULL || ndp->ni_startdir->v_type == VDIR || 549 ndp->ni_startdir->v_type == VBAD); 550 551 ndp->ni_lcf = 0; 552 ndp->ni_loopcnt = 0; 553 ndp->ni_vp = NULL; 554 555 error = namei_getpath(ndp); 556 if (__predict_false(error != 0)) { 557 return (error); 558 } 559 560 #ifdef KTRACE 561 if (KTRPOINT(td, KTR_NAMEI)) { 562 KASSERT(cnp->cn_thread == curthread, 563 ("namei not using curthread")); 564 ktrnamei(cnp->cn_pnbuf); 565 } 566 #endif 567 568 /* 569 * First try looking up the target without locking any vnodes. 570 * 571 * We may need to start from scratch or pick up where it left off. 572 */ 573 error = cache_fplookup(ndp, &status, &pwd); 574 switch (status) { 575 case CACHE_FPL_STATUS_UNSET: 576 __assert_unreachable(); 577 break; 578 case CACHE_FPL_STATUS_HANDLED: 579 if (error == 0) 580 NDVALIDATE(ndp); 581 return (error); 582 case CACHE_FPL_STATUS_PARTIAL: 583 TAILQ_INIT(&ndp->ni_cap_tracker); 584 dp = ndp->ni_startdir; 585 break; 586 case CACHE_FPL_STATUS_DESTROYED: 587 ndp->ni_loopcnt = 0; 588 error = namei_getpath(ndp); 589 if (__predict_false(error != 0)) { 590 return (error); 591 } 592 /* FALLTHROUGH */ 593 case CACHE_FPL_STATUS_ABORTED: 594 TAILQ_INIT(&ndp->ni_cap_tracker); 595 MPASS(ndp->ni_lcf == 0); 596 error = namei_setup(ndp, &dp, &pwd); 597 if (error != 0) { 598 namei_cleanup_cnp(cnp); 599 return (error); 600 } 601 break; 602 } 603 604 /* 605 * Locked lookup. 606 */ 607 for (;;) { 608 ndp->ni_startdir = dp; 609 error = lookup(ndp); 610 if (error != 0) 611 goto out; 612 613 /* 614 * If not a symbolic link, we're done. 615 */ 616 if ((cnp->cn_flags & ISSYMLINK) == 0) { 617 SDT_PROBE4(vfs, namei, lookup, return, error, 618 (error == 0 ? ndp->ni_vp : NULL), false, ndp); 619 if ((cnp->cn_flags & (SAVENAME | SAVESTART)) == 0) { 620 namei_cleanup_cnp(cnp); 621 } else 622 cnp->cn_flags |= HASBUF; 623 nameicap_cleanup(ndp); 624 pwd_drop(pwd); 625 if (error == 0) 626 NDVALIDATE(ndp); 627 return (error); 628 } 629 if (ndp->ni_loopcnt++ >= MAXSYMLINKS) { 630 error = ELOOP; 631 break; 632 } 633 #ifdef MAC 634 if ((cnp->cn_flags & NOMACCHECK) == 0) { 635 error = mac_vnode_check_readlink(td->td_ucred, 636 ndp->ni_vp); 637 if (error != 0) 638 break; 639 } 640 #endif 641 if (ndp->ni_pathlen > 1) 642 cp = uma_zalloc(namei_zone, M_WAITOK); 643 else 644 cp = cnp->cn_pnbuf; 645 aiov.iov_base = cp; 646 aiov.iov_len = MAXPATHLEN; 647 auio.uio_iov = &aiov; 648 auio.uio_iovcnt = 1; 649 auio.uio_offset = 0; 650 auio.uio_rw = UIO_READ; 651 auio.uio_segflg = UIO_SYSSPACE; 652 auio.uio_td = td; 653 auio.uio_resid = MAXPATHLEN; 654 error = VOP_READLINK(ndp->ni_vp, &auio, cnp->cn_cred); 655 if (error != 0) { 656 if (ndp->ni_pathlen > 1) 657 uma_zfree(namei_zone, cp); 658 break; 659 } 660 linklen = MAXPATHLEN - auio.uio_resid; 661 if (linklen == 0) { 662 if (ndp->ni_pathlen > 1) 663 uma_zfree(namei_zone, cp); 664 error = ENOENT; 665 break; 666 } 667 if (linklen + ndp->ni_pathlen > MAXPATHLEN) { 668 if (ndp->ni_pathlen > 1) 669 uma_zfree(namei_zone, cp); 670 error = ENAMETOOLONG; 671 break; 672 } 673 if (ndp->ni_pathlen > 1) { 674 bcopy(ndp->ni_next, cp + linklen, ndp->ni_pathlen); 675 uma_zfree(namei_zone, cnp->cn_pnbuf); 676 cnp->cn_pnbuf = cp; 677 } else 678 cnp->cn_pnbuf[linklen] = '\0'; 679 ndp->ni_pathlen += linklen; 680 vput(ndp->ni_vp); 681 dp = ndp->ni_dvp; 682 /* 683 * Check if root directory should replace current directory. 684 */ 685 cnp->cn_nameptr = cnp->cn_pnbuf; 686 if (*(cnp->cn_nameptr) == '/') { 687 vrele(dp); 688 error = namei_handle_root(ndp, &dp); 689 if (error != 0) 690 goto out; 691 } 692 } 693 vput(ndp->ni_vp); 694 ndp->ni_vp = NULL; 695 vrele(ndp->ni_dvp); 696 out: 697 MPASS(error != 0); 698 SDT_PROBE4(vfs, namei, lookup, return, error, NULL, false, ndp); 699 namei_cleanup_cnp(cnp); 700 nameicap_cleanup(ndp); 701 pwd_drop(pwd); 702 return (error); 703 } 704 705 static int 706 compute_cn_lkflags(struct mount *mp, int lkflags, int cnflags) 707 { 708 709 if (mp == NULL || ((lkflags & LK_SHARED) && 710 (!(mp->mnt_kern_flag & MNTK_LOOKUP_SHARED) || 711 ((cnflags & ISDOTDOT) && 712 (mp->mnt_kern_flag & MNTK_LOOKUP_EXCL_DOTDOT))))) { 713 lkflags &= ~LK_SHARED; 714 lkflags |= LK_EXCLUSIVE; 715 } 716 lkflags |= LK_NODDLKTREAT; 717 return (lkflags); 718 } 719 720 static __inline int 721 needs_exclusive_leaf(struct mount *mp, int flags) 722 { 723 724 /* 725 * Intermediate nodes can use shared locks, we only need to 726 * force an exclusive lock for leaf nodes. 727 */ 728 if ((flags & (ISLASTCN | LOCKLEAF)) != (ISLASTCN | LOCKLEAF)) 729 return (0); 730 731 /* Always use exclusive locks if LOCKSHARED isn't set. */ 732 if (!(flags & LOCKSHARED)) 733 return (1); 734 735 /* 736 * For lookups during open(), if the mount point supports 737 * extended shared operations, then use a shared lock for the 738 * leaf node, otherwise use an exclusive lock. 739 */ 740 if ((flags & ISOPEN) != 0) 741 return (!MNT_EXTENDED_SHARED(mp)); 742 743 /* 744 * Lookup requests outside of open() that specify LOCKSHARED 745 * only need a shared lock on the leaf vnode. 746 */ 747 return (0); 748 } 749 750 /* 751 * Search a pathname. 752 * This is a very central and rather complicated routine. 753 * 754 * The pathname is pointed to by ni_ptr and is of length ni_pathlen. 755 * The starting directory is taken from ni_startdir. The pathname is 756 * descended until done, or a symbolic link is encountered. The variable 757 * ni_more is clear if the path is completed; it is set to one if a 758 * symbolic link needing interpretation is encountered. 759 * 760 * The flag argument is LOOKUP, CREATE, RENAME, or DELETE depending on 761 * whether the name is to be looked up, created, renamed, or deleted. 762 * When CREATE, RENAME, or DELETE is specified, information usable in 763 * creating, renaming, or deleting a directory entry may be calculated. 764 * If flag has LOCKPARENT or'ed into it, the parent directory is returned 765 * locked. If flag has WANTPARENT or'ed into it, the parent directory is 766 * returned unlocked. Otherwise the parent directory is not returned. If 767 * the target of the pathname exists and LOCKLEAF is or'ed into the flag 768 * the target is returned locked, otherwise it is returned unlocked. 769 * When creating or renaming and LOCKPARENT is specified, the target may not 770 * be ".". When deleting and LOCKPARENT is specified, the target may be ".". 771 * 772 * Overall outline of lookup: 773 * 774 * dirloop: 775 * identify next component of name at ndp->ni_ptr 776 * handle degenerate case where name is null string 777 * if .. and crossing mount points and on mounted filesys, find parent 778 * call VOP_LOOKUP routine for next component name 779 * directory vnode returned in ni_dvp, unlocked unless LOCKPARENT set 780 * component vnode returned in ni_vp (if it exists), locked. 781 * if result vnode is mounted on and crossing mount points, 782 * find mounted on vnode 783 * if more components of name, do next level at dirloop 784 * return the answer in ni_vp, locked if LOCKLEAF set 785 * if LOCKPARENT set, return locked parent in ni_dvp 786 * if WANTPARENT set, return unlocked parent in ni_dvp 787 */ 788 int 789 lookup(struct nameidata *ndp) 790 { 791 char *cp; /* pointer into pathname argument */ 792 char *prev_ni_next; /* saved ndp->ni_next */ 793 struct vnode *dp = NULL; /* the directory we are searching */ 794 struct vnode *tdp; /* saved dp */ 795 struct mount *mp; /* mount table entry */ 796 struct prison *pr; 797 size_t prev_ni_pathlen; /* saved ndp->ni_pathlen */ 798 int docache; /* == 0 do not cache last component */ 799 int wantparent; /* 1 => wantparent or lockparent flag */ 800 int rdonly; /* lookup read-only flag bit */ 801 int error = 0; 802 int dpunlocked = 0; /* dp has already been unlocked */ 803 int relookup = 0; /* do not consume the path component */ 804 struct componentname *cnp = &ndp->ni_cnd; 805 int lkflags_save; 806 int ni_dvp_unlocked; 807 808 /* 809 * Setup: break out flag bits into variables. 810 */ 811 ni_dvp_unlocked = 0; 812 wantparent = cnp->cn_flags & (LOCKPARENT | WANTPARENT); 813 KASSERT(cnp->cn_nameiop == LOOKUP || wantparent, 814 ("CREATE, DELETE, RENAME require LOCKPARENT or WANTPARENT.")); 815 /* 816 * When set to zero, docache causes the last component of the 817 * pathname to be deleted from the cache and the full lookup 818 * of the name to be done (via VOP_CACHEDLOOKUP()). Often 819 * filesystems need some pre-computed values that are made 820 * during the full lookup, for instance UFS sets dp->i_offset. 821 * 822 * The docache variable is set to zero when requested by the 823 * NOCACHE flag and for all modifying operations except CREATE. 824 */ 825 docache = (cnp->cn_flags & NOCACHE) ^ NOCACHE; 826 if (cnp->cn_nameiop == DELETE || 827 (wantparent && cnp->cn_nameiop != CREATE && 828 cnp->cn_nameiop != LOOKUP)) 829 docache = 0; 830 rdonly = cnp->cn_flags & RDONLY; 831 cnp->cn_flags &= ~ISSYMLINK; 832 ndp->ni_dvp = NULL; 833 /* 834 * We use shared locks until we hit the parent of the last cn then 835 * we adjust based on the requesting flags. 836 */ 837 cnp->cn_lkflags = LK_SHARED; 838 dp = ndp->ni_startdir; 839 ndp->ni_startdir = NULLVP; 840 vn_lock(dp, 841 compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags | LK_RETRY, 842 cnp->cn_flags)); 843 844 dirloop: 845 /* 846 * Search a new directory. 847 * 848 * The last component of the filename is left accessible via 849 * cnp->cn_nameptr for callers that need the name. Callers needing 850 * the name set the SAVENAME flag. When done, they assume 851 * responsibility for freeing the pathname buffer. 852 */ 853 for (cp = cnp->cn_nameptr; *cp != 0 && *cp != '/'; cp++) 854 continue; 855 cnp->cn_namelen = cp - cnp->cn_nameptr; 856 if (cnp->cn_namelen > NAME_MAX) { 857 error = ENAMETOOLONG; 858 goto bad; 859 } 860 #ifdef NAMEI_DIAGNOSTIC 861 { char c = *cp; 862 *cp = '\0'; 863 printf("{%s}: ", cnp->cn_nameptr); 864 *cp = c; } 865 #endif 866 prev_ni_pathlen = ndp->ni_pathlen; 867 ndp->ni_pathlen -= cnp->cn_namelen; 868 KASSERT(ndp->ni_pathlen <= PATH_MAX, 869 ("%s: ni_pathlen underflow to %zd\n", __func__, ndp->ni_pathlen)); 870 prev_ni_next = ndp->ni_next; 871 ndp->ni_next = cp; 872 873 /* 874 * Replace multiple slashes by a single slash and trailing slashes 875 * by a null. This must be done before VOP_LOOKUP() because some 876 * fs's don't know about trailing slashes. Remember if there were 877 * trailing slashes to handle symlinks, existing non-directories 878 * and non-existing files that won't be directories specially later. 879 */ 880 while (*cp == '/' && (cp[1] == '/' || cp[1] == '\0')) { 881 cp++; 882 ndp->ni_pathlen--; 883 if (*cp == '\0') { 884 *ndp->ni_next = '\0'; 885 cnp->cn_flags |= TRAILINGSLASH; 886 } 887 } 888 ndp->ni_next = cp; 889 890 cnp->cn_flags |= MAKEENTRY; 891 if (*cp == '\0' && docache == 0) 892 cnp->cn_flags &= ~MAKEENTRY; 893 if (cnp->cn_namelen == 2 && 894 cnp->cn_nameptr[1] == '.' && cnp->cn_nameptr[0] == '.') 895 cnp->cn_flags |= ISDOTDOT; 896 else 897 cnp->cn_flags &= ~ISDOTDOT; 898 if (*ndp->ni_next == 0) 899 cnp->cn_flags |= ISLASTCN; 900 else 901 cnp->cn_flags &= ~ISLASTCN; 902 903 if ((cnp->cn_flags & ISLASTCN) != 0 && 904 cnp->cn_namelen == 1 && cnp->cn_nameptr[0] == '.' && 905 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) { 906 error = EINVAL; 907 goto bad; 908 } 909 910 nameicap_tracker_add(ndp, dp); 911 912 /* 913 * Check for degenerate name (e.g. / or "") 914 * which is a way of talking about a directory, 915 * e.g. like "/." or ".". 916 */ 917 if (cnp->cn_nameptr[0] == '\0') { 918 if (dp->v_type != VDIR) { 919 error = ENOTDIR; 920 goto bad; 921 } 922 if (cnp->cn_nameiop != LOOKUP) { 923 error = EISDIR; 924 goto bad; 925 } 926 if (wantparent) { 927 ndp->ni_dvp = dp; 928 VREF(dp); 929 } 930 ndp->ni_vp = dp; 931 932 if (cnp->cn_flags & AUDITVNODE1) 933 AUDIT_ARG_VNODE1(dp); 934 else if (cnp->cn_flags & AUDITVNODE2) 935 AUDIT_ARG_VNODE2(dp); 936 937 if (!(cnp->cn_flags & (LOCKPARENT | LOCKLEAF))) 938 VOP_UNLOCK(dp); 939 /* XXX This should probably move to the top of function. */ 940 if (cnp->cn_flags & SAVESTART) 941 panic("lookup: SAVESTART"); 942 goto success; 943 } 944 945 /* 946 * Handle "..": five special cases. 947 * 0. If doing a capability lookup and lookup_cap_dotdot is 948 * disabled, return ENOTCAPABLE. 949 * 1. Return an error if this is the last component of 950 * the name and the operation is DELETE or RENAME. 951 * 2. If at root directory (e.g. after chroot) 952 * or at absolute root directory 953 * then ignore it so can't get out. 954 * 3. If this vnode is the root of a mounted 955 * filesystem, then replace it with the 956 * vnode which was mounted on so we take the 957 * .. in the other filesystem. 958 * 4. If the vnode is the top directory of 959 * the jail or chroot, don't let them out. 960 * 5. If doing a capability lookup and lookup_cap_dotdot is 961 * enabled, return ENOTCAPABLE if the lookup would escape 962 * from the initial file descriptor directory. Checks are 963 * done by ensuring that namei() already traversed the 964 * result of dotdot lookup. 965 */ 966 if (cnp->cn_flags & ISDOTDOT) { 967 if ((ndp->ni_lcf & (NI_LCF_STRICTRELATIVE | NI_LCF_CAP_DOTDOT)) 968 == NI_LCF_STRICTRELATIVE) { 969 #ifdef KTRACE 970 if (KTRPOINT(curthread, KTR_CAPFAIL)) 971 ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL); 972 #endif 973 error = ENOTCAPABLE; 974 goto bad; 975 } 976 if ((cnp->cn_flags & ISLASTCN) != 0 && 977 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) { 978 error = EINVAL; 979 goto bad; 980 } 981 for (;;) { 982 for (pr = cnp->cn_cred->cr_prison; pr != NULL; 983 pr = pr->pr_parent) 984 if (dp == pr->pr_root) 985 break; 986 if (dp == ndp->ni_rootdir || 987 dp == ndp->ni_topdir || 988 dp == rootvnode || 989 pr != NULL || 990 ((dp->v_vflag & VV_ROOT) != 0 && 991 (cnp->cn_flags & NOCROSSMOUNT) != 0)) { 992 ndp->ni_dvp = dp; 993 ndp->ni_vp = dp; 994 VREF(dp); 995 goto nextname; 996 } 997 if ((dp->v_vflag & VV_ROOT) == 0) 998 break; 999 if (VN_IS_DOOMED(dp)) { /* forced unmount */ 1000 error = ENOENT; 1001 goto bad; 1002 } 1003 tdp = dp; 1004 dp = dp->v_mount->mnt_vnodecovered; 1005 VREF(dp); 1006 vput(tdp); 1007 vn_lock(dp, 1008 compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags | 1009 LK_RETRY, ISDOTDOT)); 1010 error = nameicap_check_dotdot(ndp, dp); 1011 if (error != 0) { 1012 #ifdef KTRACE 1013 if (KTRPOINT(curthread, KTR_CAPFAIL)) 1014 ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL); 1015 #endif 1016 goto bad; 1017 } 1018 } 1019 } 1020 1021 /* 1022 * We now have a segment name to search for, and a directory to search. 1023 */ 1024 unionlookup: 1025 #ifdef MAC 1026 error = mac_vnode_check_lookup(cnp->cn_thread->td_ucred, dp, cnp); 1027 if (error) 1028 goto bad; 1029 #endif 1030 ndp->ni_dvp = dp; 1031 ndp->ni_vp = NULL; 1032 ASSERT_VOP_LOCKED(dp, "lookup"); 1033 /* 1034 * If we have a shared lock we may need to upgrade the lock for the 1035 * last operation. 1036 */ 1037 if ((cnp->cn_flags & LOCKPARENT) && (cnp->cn_flags & ISLASTCN) && 1038 dp != vp_crossmp && VOP_ISLOCKED(dp) == LK_SHARED) 1039 vn_lock(dp, LK_UPGRADE|LK_RETRY); 1040 if (VN_IS_DOOMED(dp)) { 1041 error = ENOENT; 1042 goto bad; 1043 } 1044 /* 1045 * If we're looking up the last component and we need an exclusive 1046 * lock, adjust our lkflags. 1047 */ 1048 if (needs_exclusive_leaf(dp->v_mount, cnp->cn_flags)) 1049 cnp->cn_lkflags = LK_EXCLUSIVE; 1050 #ifdef NAMEI_DIAGNOSTIC 1051 vn_printf(dp, "lookup in "); 1052 #endif 1053 lkflags_save = cnp->cn_lkflags; 1054 cnp->cn_lkflags = compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags, 1055 cnp->cn_flags); 1056 error = VOP_LOOKUP(dp, &ndp->ni_vp, cnp); 1057 cnp->cn_lkflags = lkflags_save; 1058 if (error != 0) { 1059 KASSERT(ndp->ni_vp == NULL, ("leaf should be empty")); 1060 #ifdef NAMEI_DIAGNOSTIC 1061 printf("not found\n"); 1062 #endif 1063 if ((error == ENOENT) && 1064 (dp->v_vflag & VV_ROOT) && (dp->v_mount != NULL) && 1065 (dp->v_mount->mnt_flag & MNT_UNION)) { 1066 tdp = dp; 1067 dp = dp->v_mount->mnt_vnodecovered; 1068 VREF(dp); 1069 vput(tdp); 1070 vn_lock(dp, 1071 compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags | 1072 LK_RETRY, cnp->cn_flags)); 1073 nameicap_tracker_add(ndp, dp); 1074 goto unionlookup; 1075 } 1076 1077 if (error == ERELOOKUP) { 1078 vref(dp); 1079 ndp->ni_vp = dp; 1080 error = 0; 1081 relookup = 1; 1082 goto good; 1083 } 1084 1085 if (error != EJUSTRETURN) 1086 goto bad; 1087 /* 1088 * At this point, we know we're at the end of the 1089 * pathname. If creating / renaming, we can consider 1090 * allowing the file or directory to be created / renamed, 1091 * provided we're not on a read-only filesystem. 1092 */ 1093 if (rdonly) { 1094 error = EROFS; 1095 goto bad; 1096 } 1097 /* trailing slash only allowed for directories */ 1098 if ((cnp->cn_flags & TRAILINGSLASH) && 1099 !(cnp->cn_flags & WILLBEDIR)) { 1100 error = ENOENT; 1101 goto bad; 1102 } 1103 if ((cnp->cn_flags & LOCKPARENT) == 0) 1104 VOP_UNLOCK(dp); 1105 /* 1106 * We return with ni_vp NULL to indicate that the entry 1107 * doesn't currently exist, leaving a pointer to the 1108 * (possibly locked) directory vnode in ndp->ni_dvp. 1109 */ 1110 if (cnp->cn_flags & SAVESTART) { 1111 ndp->ni_startdir = ndp->ni_dvp; 1112 VREF(ndp->ni_startdir); 1113 } 1114 goto success; 1115 } 1116 1117 good: 1118 #ifdef NAMEI_DIAGNOSTIC 1119 printf("found\n"); 1120 #endif 1121 dp = ndp->ni_vp; 1122 1123 /* 1124 * Check to see if the vnode has been mounted on; 1125 * if so find the root of the mounted filesystem. 1126 */ 1127 while (dp->v_type == VDIR && (mp = dp->v_mountedhere) && 1128 (cnp->cn_flags & NOCROSSMOUNT) == 0) { 1129 if (vfs_busy(mp, 0)) 1130 continue; 1131 vput(dp); 1132 if (dp != ndp->ni_dvp) 1133 vput(ndp->ni_dvp); 1134 else 1135 vrele(ndp->ni_dvp); 1136 vrefact(vp_crossmp); 1137 ndp->ni_dvp = vp_crossmp; 1138 error = VFS_ROOT(mp, compute_cn_lkflags(mp, cnp->cn_lkflags, 1139 cnp->cn_flags), &tdp); 1140 vfs_unbusy(mp); 1141 if (vn_lock(vp_crossmp, LK_SHARED | LK_NOWAIT)) 1142 panic("vp_crossmp exclusively locked or reclaimed"); 1143 if (error) { 1144 dpunlocked = 1; 1145 goto bad2; 1146 } 1147 ndp->ni_vp = dp = tdp; 1148 } 1149 1150 /* 1151 * Check for symbolic link 1152 */ 1153 if ((dp->v_type == VLNK) && 1154 ((cnp->cn_flags & FOLLOW) || (cnp->cn_flags & TRAILINGSLASH) || 1155 *ndp->ni_next == '/')) { 1156 cnp->cn_flags |= ISSYMLINK; 1157 if (VN_IS_DOOMED(dp)) { 1158 /* 1159 * We can't know whether the directory was mounted with 1160 * NOSYMFOLLOW, so we can't follow safely. 1161 */ 1162 error = ENOENT; 1163 goto bad2; 1164 } 1165 if (dp->v_mount->mnt_flag & MNT_NOSYMFOLLOW) { 1166 error = EACCES; 1167 goto bad2; 1168 } 1169 /* 1170 * Symlink code always expects an unlocked dvp. 1171 */ 1172 if (ndp->ni_dvp != ndp->ni_vp) { 1173 VOP_UNLOCK(ndp->ni_dvp); 1174 ni_dvp_unlocked = 1; 1175 } 1176 goto success; 1177 } 1178 1179 nextname: 1180 /* 1181 * Not a symbolic link that we will follow. Continue with the 1182 * next component if there is any; otherwise, we're done. 1183 */ 1184 KASSERT((cnp->cn_flags & ISLASTCN) || *ndp->ni_next == '/', 1185 ("lookup: invalid path state.")); 1186 if (relookup) { 1187 relookup = 0; 1188 ndp->ni_pathlen = prev_ni_pathlen; 1189 ndp->ni_next = prev_ni_next; 1190 if (ndp->ni_dvp != dp) 1191 vput(ndp->ni_dvp); 1192 else 1193 vrele(ndp->ni_dvp); 1194 goto dirloop; 1195 } 1196 if (cnp->cn_flags & ISDOTDOT) { 1197 error = nameicap_check_dotdot(ndp, ndp->ni_vp); 1198 if (error != 0) { 1199 #ifdef KTRACE 1200 if (KTRPOINT(curthread, KTR_CAPFAIL)) 1201 ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL); 1202 #endif 1203 goto bad2; 1204 } 1205 } 1206 if (*ndp->ni_next == '/') { 1207 cnp->cn_nameptr = ndp->ni_next; 1208 while (*cnp->cn_nameptr == '/') { 1209 cnp->cn_nameptr++; 1210 ndp->ni_pathlen--; 1211 } 1212 if (ndp->ni_dvp != dp) 1213 vput(ndp->ni_dvp); 1214 else 1215 vrele(ndp->ni_dvp); 1216 goto dirloop; 1217 } 1218 /* 1219 * If we're processing a path with a trailing slash, 1220 * check that the end result is a directory. 1221 */ 1222 if ((cnp->cn_flags & TRAILINGSLASH) && dp->v_type != VDIR) { 1223 error = ENOTDIR; 1224 goto bad2; 1225 } 1226 /* 1227 * Disallow directory write attempts on read-only filesystems. 1228 */ 1229 if (rdonly && 1230 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) { 1231 error = EROFS; 1232 goto bad2; 1233 } 1234 if (cnp->cn_flags & SAVESTART) { 1235 ndp->ni_startdir = ndp->ni_dvp; 1236 VREF(ndp->ni_startdir); 1237 } 1238 if (!wantparent) { 1239 ni_dvp_unlocked = 2; 1240 if (ndp->ni_dvp != dp) 1241 vput(ndp->ni_dvp); 1242 else 1243 vrele(ndp->ni_dvp); 1244 } else if ((cnp->cn_flags & LOCKPARENT) == 0 && ndp->ni_dvp != dp) { 1245 VOP_UNLOCK(ndp->ni_dvp); 1246 ni_dvp_unlocked = 1; 1247 } 1248 1249 if (cnp->cn_flags & AUDITVNODE1) 1250 AUDIT_ARG_VNODE1(dp); 1251 else if (cnp->cn_flags & AUDITVNODE2) 1252 AUDIT_ARG_VNODE2(dp); 1253 1254 if ((cnp->cn_flags & LOCKLEAF) == 0) 1255 VOP_UNLOCK(dp); 1256 success: 1257 /* 1258 * FIXME: for lookups which only cross a mount point to fetch the 1259 * root vnode, ni_dvp will be set to vp_crossmp. This can be a problem 1260 * if either WANTPARENT or LOCKPARENT is set. 1261 */ 1262 /* 1263 * Because of shared lookup we may have the vnode shared locked, but 1264 * the caller may want it to be exclusively locked. 1265 */ 1266 if (needs_exclusive_leaf(dp->v_mount, cnp->cn_flags) && 1267 VOP_ISLOCKED(dp) != LK_EXCLUSIVE) { 1268 vn_lock(dp, LK_UPGRADE | LK_RETRY); 1269 if (VN_IS_DOOMED(dp)) { 1270 error = ENOENT; 1271 goto bad2; 1272 } 1273 } 1274 if (ndp->ni_vp != NULL) { 1275 if ((cnp->cn_flags & ISDOTDOT) == 0) 1276 nameicap_tracker_add(ndp, ndp->ni_vp); 1277 if ((cnp->cn_flags & (FAILIFEXISTS | ISSYMLINK)) == FAILIFEXISTS) 1278 goto bad_eexist; 1279 } 1280 return (0); 1281 1282 bad2: 1283 if (ni_dvp_unlocked != 2) { 1284 if (dp != ndp->ni_dvp && !ni_dvp_unlocked) 1285 vput(ndp->ni_dvp); 1286 else 1287 vrele(ndp->ni_dvp); 1288 } 1289 bad: 1290 if (!dpunlocked) 1291 vput(dp); 1292 ndp->ni_vp = NULL; 1293 return (error); 1294 bad_eexist: 1295 /* 1296 * FAILIFEXISTS handling. 1297 * 1298 * XXX namei called with LOCKPARENT but not LOCKLEAF has the strange 1299 * behaviour of leaving the vnode unlocked if the target is the same 1300 * vnode as the parent. 1301 */ 1302 MPASS((cnp->cn_flags & ISSYMLINK) == 0); 1303 if (ndp->ni_vp == ndp->ni_dvp) 1304 vrele(ndp->ni_dvp); 1305 else 1306 vput(ndp->ni_dvp); 1307 vrele(ndp->ni_vp); 1308 ndp->ni_dvp = NULL; 1309 ndp->ni_vp = NULL; 1310 NDFREE(ndp, NDF_ONLY_PNBUF); 1311 return (EEXIST); 1312 } 1313 1314 /* 1315 * relookup - lookup a path name component 1316 * Used by lookup to re-acquire things. 1317 */ 1318 int 1319 relookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp) 1320 { 1321 struct vnode *dp = NULL; /* the directory we are searching */ 1322 int rdonly; /* lookup read-only flag bit */ 1323 int error = 0; 1324 1325 KASSERT(cnp->cn_flags & ISLASTCN, 1326 ("relookup: Not given last component.")); 1327 /* 1328 * Setup: break out flag bits into variables. 1329 */ 1330 KASSERT((cnp->cn_flags & (LOCKPARENT | WANTPARENT)) != 0, 1331 ("relookup: parent not wanted")); 1332 rdonly = cnp->cn_flags & RDONLY; 1333 cnp->cn_flags &= ~ISSYMLINK; 1334 dp = dvp; 1335 cnp->cn_lkflags = LK_EXCLUSIVE; 1336 vn_lock(dp, LK_EXCLUSIVE | LK_RETRY); 1337 1338 /* 1339 * Search a new directory. 1340 * 1341 * The last component of the filename is left accessible via 1342 * cnp->cn_nameptr for callers that need the name. Callers needing 1343 * the name set the SAVENAME flag. When done, they assume 1344 * responsibility for freeing the pathname buffer. 1345 */ 1346 #ifdef NAMEI_DIAGNOSTIC 1347 printf("{%s}: ", cnp->cn_nameptr); 1348 #endif 1349 1350 /* 1351 * Check for "" which represents the root directory after slash 1352 * removal. 1353 */ 1354 if (cnp->cn_nameptr[0] == '\0') { 1355 /* 1356 * Support only LOOKUP for "/" because lookup() 1357 * can't succeed for CREATE, DELETE and RENAME. 1358 */ 1359 KASSERT(cnp->cn_nameiop == LOOKUP, ("nameiop must be LOOKUP")); 1360 KASSERT(dp->v_type == VDIR, ("dp is not a directory")); 1361 1362 if (!(cnp->cn_flags & LOCKLEAF)) 1363 VOP_UNLOCK(dp); 1364 *vpp = dp; 1365 /* XXX This should probably move to the top of function. */ 1366 if (cnp->cn_flags & SAVESTART) 1367 panic("lookup: SAVESTART"); 1368 return (0); 1369 } 1370 1371 if (cnp->cn_flags & ISDOTDOT) 1372 panic ("relookup: lookup on dot-dot"); 1373 1374 /* 1375 * We now have a segment name to search for, and a directory to search. 1376 */ 1377 #ifdef NAMEI_DIAGNOSTIC 1378 vn_printf(dp, "search in "); 1379 #endif 1380 if ((error = VOP_LOOKUP(dp, vpp, cnp)) != 0) { 1381 KASSERT(*vpp == NULL, ("leaf should be empty")); 1382 if (error != EJUSTRETURN) 1383 goto bad; 1384 /* 1385 * If creating and at end of pathname, then can consider 1386 * allowing file to be created. 1387 */ 1388 if (rdonly) { 1389 error = EROFS; 1390 goto bad; 1391 } 1392 /* ASSERT(dvp == ndp->ni_startdir) */ 1393 if (cnp->cn_flags & SAVESTART) 1394 VREF(dvp); 1395 if ((cnp->cn_flags & LOCKPARENT) == 0) 1396 VOP_UNLOCK(dp); 1397 /* 1398 * We return with ni_vp NULL to indicate that the entry 1399 * doesn't currently exist, leaving a pointer to the 1400 * (possibly locked) directory vnode in ndp->ni_dvp. 1401 */ 1402 return (0); 1403 } 1404 1405 dp = *vpp; 1406 1407 /* 1408 * Disallow directory write attempts on read-only filesystems. 1409 */ 1410 if (rdonly && 1411 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) { 1412 if (dvp == dp) 1413 vrele(dvp); 1414 else 1415 vput(dvp); 1416 error = EROFS; 1417 goto bad; 1418 } 1419 /* 1420 * Set the parent lock/ref state to the requested state. 1421 */ 1422 if ((cnp->cn_flags & LOCKPARENT) == 0 && dvp != dp) 1423 VOP_UNLOCK(dvp); 1424 /* 1425 * Check for symbolic link 1426 */ 1427 KASSERT(dp->v_type != VLNK || !(cnp->cn_flags & FOLLOW), 1428 ("relookup: symlink found.\n")); 1429 1430 /* ASSERT(dvp == ndp->ni_startdir) */ 1431 if (cnp->cn_flags & SAVESTART) 1432 VREF(dvp); 1433 1434 if ((cnp->cn_flags & LOCKLEAF) == 0) 1435 VOP_UNLOCK(dp); 1436 return (0); 1437 bad: 1438 vput(dp); 1439 *vpp = NULL; 1440 return (error); 1441 } 1442 1443 /* 1444 * Free data allocated by namei(); see namei(9) for details. 1445 */ 1446 void 1447 NDFREE_PNBUF(struct nameidata *ndp) 1448 { 1449 1450 if ((ndp->ni_cnd.cn_flags & HASBUF) != 0) { 1451 MPASS((ndp->ni_cnd.cn_flags & (SAVENAME | SAVESTART)) != 0); 1452 uma_zfree(namei_zone, ndp->ni_cnd.cn_pnbuf); 1453 ndp->ni_cnd.cn_flags &= ~HASBUF; 1454 } 1455 } 1456 1457 /* 1458 * NDFREE_PNBUF replacement for callers that know there is no buffer. 1459 * 1460 * This is a hack. Preferably the VFS layer would not produce anything more 1461 * than it was asked to do. Unfortunately several non-LOOKUP cases can add the 1462 * HASBUF flag to the result. Even then an interface could be implemented where 1463 * the caller specifies what they expected to see in the result and what they 1464 * are going to take care of. 1465 * 1466 * In the meantime provide this kludge as a trivial replacement for NDFREE_PNBUF 1467 * calls scattered throughout the kernel where we know for a fact the flag must not 1468 * be seen. 1469 */ 1470 #ifdef INVARIANTS 1471 void 1472 NDFREE_NOTHING(struct nameidata *ndp) 1473 { 1474 struct componentname *cnp; 1475 1476 cnp = &ndp->ni_cnd; 1477 KASSERT(cnp->cn_nameiop == LOOKUP, ("%s: got non-LOOKUP op %d\n", 1478 __func__, cnp->cn_nameiop)); 1479 KASSERT((cnp->cn_flags & (SAVENAME | HASBUF)) == 0, 1480 ("%s: bad flags \%" PRIx64 "\n", __func__, cnp->cn_flags)); 1481 } 1482 #endif 1483 1484 void 1485 (NDFREE)(struct nameidata *ndp, const u_int flags) 1486 { 1487 int unlock_dvp; 1488 int unlock_vp; 1489 1490 unlock_dvp = 0; 1491 unlock_vp = 0; 1492 1493 if (!(flags & NDF_NO_FREE_PNBUF)) { 1494 NDFREE_PNBUF(ndp); 1495 } 1496 if (!(flags & NDF_NO_VP_UNLOCK) && 1497 (ndp->ni_cnd.cn_flags & LOCKLEAF) && ndp->ni_vp) 1498 unlock_vp = 1; 1499 if (!(flags & NDF_NO_DVP_UNLOCK) && 1500 (ndp->ni_cnd.cn_flags & LOCKPARENT) && 1501 ndp->ni_dvp != ndp->ni_vp) 1502 unlock_dvp = 1; 1503 if (!(flags & NDF_NO_VP_RELE) && ndp->ni_vp) { 1504 if (unlock_vp) { 1505 vput(ndp->ni_vp); 1506 unlock_vp = 0; 1507 } else 1508 vrele(ndp->ni_vp); 1509 ndp->ni_vp = NULL; 1510 } 1511 if (unlock_vp) 1512 VOP_UNLOCK(ndp->ni_vp); 1513 if (!(flags & NDF_NO_DVP_RELE) && 1514 (ndp->ni_cnd.cn_flags & (LOCKPARENT|WANTPARENT))) { 1515 if (unlock_dvp) { 1516 vput(ndp->ni_dvp); 1517 unlock_dvp = 0; 1518 } else 1519 vrele(ndp->ni_dvp); 1520 ndp->ni_dvp = NULL; 1521 } 1522 if (unlock_dvp) 1523 VOP_UNLOCK(ndp->ni_dvp); 1524 if (!(flags & NDF_NO_STARTDIR_RELE) && 1525 (ndp->ni_cnd.cn_flags & SAVESTART)) { 1526 vrele(ndp->ni_startdir); 1527 ndp->ni_startdir = NULL; 1528 } 1529 } 1530 1531 #ifdef INVARIANTS 1532 /* 1533 * Validate the final state of ndp after the lookup. 1534 * 1535 * Historically filesystems were allowed to modify cn_flags. Most notably they 1536 * can add SAVENAME to the request, resulting in HASBUF and pushing subsequent 1537 * clean up to the consumer. In practice this seems to only concern != LOOKUP 1538 * operations. 1539 * 1540 * As a step towards stricter API contract this routine validates the state to 1541 * clean up. Note validation is a work in progress with the intent of becoming 1542 * stricter over time. 1543 */ 1544 #define NDMODIFYINGFLAGS (LOCKLEAF | LOCKPARENT | WANTPARENT | SAVENAME | SAVESTART | HASBUF) 1545 void 1546 NDVALIDATE(struct nameidata *ndp) 1547 { 1548 struct componentname *cnp; 1549 u_int64_t used, orig; 1550 1551 cnp = &ndp->ni_cnd; 1552 orig = cnp->cn_origflags; 1553 used = cnp->cn_flags; 1554 switch (cnp->cn_nameiop) { 1555 case LOOKUP: 1556 /* 1557 * For plain lookup we require strict conformance -- nothing 1558 * to clean up if it was not requested by the caller. 1559 */ 1560 orig &= NDMODIFYINGFLAGS; 1561 used &= NDMODIFYINGFLAGS; 1562 if ((orig & (SAVENAME | SAVESTART)) != 0) 1563 orig |= HASBUF; 1564 if (orig != used) { 1565 goto out_mismatch; 1566 } 1567 break; 1568 case CREATE: 1569 case DELETE: 1570 case RENAME: 1571 /* 1572 * Some filesystems set SAVENAME to provoke HASBUF, accomodate 1573 * for it until it gets fixed. 1574 */ 1575 orig &= NDMODIFYINGFLAGS; 1576 orig |= (SAVENAME | HASBUF); 1577 used &= NDMODIFYINGFLAGS; 1578 used |= (SAVENAME | HASBUF); 1579 if (orig != used) { 1580 goto out_mismatch; 1581 } 1582 break; 1583 } 1584 return; 1585 out_mismatch: 1586 panic("%s: mismatched flags for op %d: added %" PRIx64 ", " 1587 "removed %" PRIx64" (%" PRIx64" != %" PRIx64"; stored %" PRIx64" != %" PRIx64")", 1588 __func__, cnp->cn_nameiop, used & ~orig, orig &~ used, 1589 orig, used, cnp->cn_origflags, cnp->cn_flags); 1590 } 1591 #endif 1592 1593 /* 1594 * Determine if there is a suitable alternate filename under the specified 1595 * prefix for the specified path. If the create flag is set, then the 1596 * alternate prefix will be used so long as the parent directory exists. 1597 * This is used by the various compatibility ABIs so that Linux binaries prefer 1598 * files under /compat/linux for example. The chosen path (whether under 1599 * the prefix or under /) is returned in a kernel malloc'd buffer pointed 1600 * to by pathbuf. The caller is responsible for free'ing the buffer from 1601 * the M_TEMP bucket if one is returned. 1602 */ 1603 int 1604 kern_alternate_path(struct thread *td, const char *prefix, const char *path, 1605 enum uio_seg pathseg, char **pathbuf, int create, int dirfd) 1606 { 1607 struct nameidata nd, ndroot; 1608 char *ptr, *buf, *cp; 1609 size_t len, sz; 1610 int error; 1611 1612 buf = (char *) malloc(MAXPATHLEN, M_TEMP, M_WAITOK); 1613 *pathbuf = buf; 1614 1615 /* Copy the prefix into the new pathname as a starting point. */ 1616 len = strlcpy(buf, prefix, MAXPATHLEN); 1617 if (len >= MAXPATHLEN) { 1618 *pathbuf = NULL; 1619 free(buf, M_TEMP); 1620 return (EINVAL); 1621 } 1622 sz = MAXPATHLEN - len; 1623 ptr = buf + len; 1624 1625 /* Append the filename to the prefix. */ 1626 if (pathseg == UIO_SYSSPACE) 1627 error = copystr(path, ptr, sz, &len); 1628 else 1629 error = copyinstr(path, ptr, sz, &len); 1630 1631 if (error) { 1632 *pathbuf = NULL; 1633 free(buf, M_TEMP); 1634 return (error); 1635 } 1636 1637 /* Only use a prefix with absolute pathnames. */ 1638 if (*ptr != '/') { 1639 error = EINVAL; 1640 goto keeporig; 1641 } 1642 1643 if (dirfd != AT_FDCWD) { 1644 /* 1645 * We want the original because the "prefix" is 1646 * included in the already opened dirfd. 1647 */ 1648 bcopy(ptr, buf, len); 1649 return (0); 1650 } 1651 1652 /* 1653 * We know that there is a / somewhere in this pathname. 1654 * Search backwards for it, to find the file's parent dir 1655 * to see if it exists in the alternate tree. If it does, 1656 * and we want to create a file (cflag is set). We don't 1657 * need to worry about the root comparison in this case. 1658 */ 1659 1660 if (create) { 1661 for (cp = &ptr[len] - 1; *cp != '/'; cp--); 1662 *cp = '\0'; 1663 1664 NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_SYSSPACE, buf, td); 1665 error = namei(&nd); 1666 *cp = '/'; 1667 if (error != 0) 1668 goto keeporig; 1669 } else { 1670 NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_SYSSPACE, buf, td); 1671 1672 error = namei(&nd); 1673 if (error != 0) 1674 goto keeporig; 1675 1676 /* 1677 * We now compare the vnode of the prefix to the one 1678 * vnode asked. If they resolve to be the same, then we 1679 * ignore the match so that the real root gets used. 1680 * This avoids the problem of traversing "../.." to find the 1681 * root directory and never finding it, because "/" resolves 1682 * to the emulation root directory. This is expensive :-( 1683 */ 1684 NDINIT(&ndroot, LOOKUP, FOLLOW, UIO_SYSSPACE, prefix, 1685 td); 1686 1687 /* We shouldn't ever get an error from this namei(). */ 1688 error = namei(&ndroot); 1689 if (error == 0) { 1690 if (nd.ni_vp == ndroot.ni_vp) 1691 error = ENOENT; 1692 1693 NDFREE(&ndroot, NDF_ONLY_PNBUF); 1694 vrele(ndroot.ni_vp); 1695 } 1696 } 1697 1698 NDFREE(&nd, NDF_ONLY_PNBUF); 1699 vrele(nd.ni_vp); 1700 1701 keeporig: 1702 /* If there was an error, use the original path name. */ 1703 if (error) 1704 bcopy(ptr, buf, len); 1705 return (error); 1706 }
Cache object: eaa6225a17a541f84b42acc5d47e7e40
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