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 * Copyright (c) 1982, 1986, 1989, 1993 3 * The Regents of the University of California. All rights reserved. 4 * (c) UNIX System Laboratories, Inc. 5 * All or some portions of this file are derived from material licensed 6 * to the University of California by American Telephone and Telegraph 7 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 8 * the permission of UNIX System Laboratories, Inc. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 4. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 * 34 * @(#)vfs_lookup.c 8.4 (Berkeley) 2/16/94 35 */ 36 37 #include <sys/cdefs.h> 38 __FBSDID("$FreeBSD: releng/11.2/sys/kern/vfs_lookup.c 331722 2018-03-29 02:50:57Z eadler $"); 39 40 #include "opt_capsicum.h" 41 #include "opt_ktrace.h" 42 43 #include <sys/param.h> 44 #include <sys/systm.h> 45 #include <sys/kernel.h> 46 #include <sys/capsicum.h> 47 #include <sys/fcntl.h> 48 #include <sys/jail.h> 49 #include <sys/lock.h> 50 #include <sys/mutex.h> 51 #include <sys/namei.h> 52 #include <sys/vnode.h> 53 #include <sys/mount.h> 54 #include <sys/filedesc.h> 55 #include <sys/proc.h> 56 #include <sys/sdt.h> 57 #include <sys/syscallsubr.h> 58 #include <sys/sysctl.h> 59 #ifdef KTRACE 60 #include <sys/ktrace.h> 61 #endif 62 63 #include <security/audit/audit.h> 64 #include <security/mac/mac_framework.h> 65 66 #include <vm/uma.h> 67 68 #define NAMEI_DIAGNOSTIC 1 69 #undef NAMEI_DIAGNOSTIC 70 71 SDT_PROVIDER_DECLARE(vfs); 72 SDT_PROBE_DEFINE3(vfs, namei, lookup, entry, "struct vnode *", "char *", 73 "unsigned long"); 74 SDT_PROBE_DEFINE2(vfs, namei, lookup, return, "int", "struct vnode *"); 75 76 /* Allocation zone for namei. */ 77 uma_zone_t namei_zone; 78 79 /* Placeholder vnode for mp traversal. */ 80 static struct vnode *vp_crossmp; 81 82 static int 83 crossmp_vop_islocked(struct vop_islocked_args *ap) 84 { 85 86 return (LK_SHARED); 87 } 88 89 static int 90 crossmp_vop_lock1(struct vop_lock1_args *ap) 91 { 92 struct vnode *vp; 93 struct lock *lk; 94 const char *file; 95 int flags, line; 96 97 vp = ap->a_vp; 98 lk = vp->v_vnlock; 99 flags = ap->a_flags; 100 file = ap->a_file; 101 line = ap->a_line; 102 103 if ((flags & LK_SHARED) == 0) 104 panic("invalid lock request for crossmp"); 105 106 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER, file, line, 107 flags & LK_INTERLOCK ? &VI_MTX(vp)->lock_object : NULL); 108 WITNESS_LOCK(&lk->lock_object, 0, file, line); 109 if ((flags & LK_INTERLOCK) != 0) 110 VI_UNLOCK(vp); 111 LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, ap->a_file, line); 112 return (0); 113 } 114 115 static int 116 crossmp_vop_unlock(struct vop_unlock_args *ap) 117 { 118 struct vnode *vp; 119 struct lock *lk; 120 int flags; 121 122 vp = ap->a_vp; 123 lk = vp->v_vnlock; 124 flags = ap->a_flags; 125 126 if ((flags & LK_INTERLOCK) != 0) 127 VI_UNLOCK(vp); 128 WITNESS_UNLOCK(&lk->lock_object, 0, LOCK_FILE, LOCK_LINE); 129 LOCK_LOG_LOCK("SUNLOCK", &lk->lock_object, 0, 0, LOCK_FILE, 130 LOCK_LINE); 131 return (0); 132 } 133 134 static struct vop_vector crossmp_vnodeops = { 135 .vop_default = &default_vnodeops, 136 .vop_islocked = crossmp_vop_islocked, 137 .vop_lock1 = crossmp_vop_lock1, 138 .vop_unlock = crossmp_vop_unlock, 139 }; 140 141 struct nameicap_tracker { 142 struct vnode *dp; 143 TAILQ_ENTRY(nameicap_tracker) nm_link; 144 }; 145 146 /* Zone for cap mode tracker elements used for dotdot capability checks. */ 147 static uma_zone_t nt_zone; 148 149 static void 150 nameiinit(void *dummy __unused) 151 { 152 153 namei_zone = uma_zcreate("NAMEI", MAXPATHLEN, NULL, NULL, NULL, NULL, 154 UMA_ALIGN_PTR, 0); 155 nt_zone = uma_zcreate("rentr", sizeof(struct nameicap_tracker), 156 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0); 157 getnewvnode("crossmp", NULL, &crossmp_vnodeops, &vp_crossmp); 158 } 159 SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_SECOND, nameiinit, NULL); 160 161 static int lookup_shared = 1; 162 SYSCTL_INT(_vfs, OID_AUTO, lookup_shared, CTLFLAG_RWTUN, &lookup_shared, 0, 163 "enables shared locks for path name translation"); 164 165 static int lookup_cap_dotdot = 1; 166 SYSCTL_INT(_vfs, OID_AUTO, lookup_cap_dotdot, CTLFLAG_RWTUN, 167 &lookup_cap_dotdot, 0, 168 "enables \"..\" components in path lookup in capability mode"); 169 static int lookup_cap_dotdot_nonlocal = 1; 170 SYSCTL_INT(_vfs, OID_AUTO, lookup_cap_dotdot_nonlocal, CTLFLAG_RWTUN, 171 &lookup_cap_dotdot_nonlocal, 0, 172 "enables \"..\" components in path lookup in capability mode " 173 "on non-local mount"); 174 175 static void 176 nameicap_tracker_add(struct nameidata *ndp, struct vnode *dp) 177 { 178 struct nameicap_tracker *nt; 179 180 if ((ndp->ni_lcf & NI_LCF_CAP_DOTDOT) == 0 || dp->v_type != VDIR) 181 return; 182 nt = uma_zalloc(nt_zone, M_WAITOK); 183 vhold(dp); 184 nt->dp = dp; 185 TAILQ_INSERT_TAIL(&ndp->ni_cap_tracker, nt, nm_link); 186 } 187 188 static void 189 nameicap_cleanup(struct nameidata *ndp) 190 { 191 struct nameicap_tracker *nt, *nt1; 192 193 KASSERT(TAILQ_EMPTY(&ndp->ni_cap_tracker) || 194 (ndp->ni_lcf & NI_LCF_CAP_DOTDOT) != 0, ("not strictrelative")); 195 TAILQ_FOREACH_SAFE(nt, &ndp->ni_cap_tracker, nm_link, nt1) { 196 TAILQ_REMOVE(&ndp->ni_cap_tracker, nt, nm_link); 197 vdrop(nt->dp); 198 uma_zfree(nt_zone, nt); 199 } 200 } 201 202 /* 203 * For dotdot lookups in capability mode, only allow the component 204 * lookup to succeed if the resulting directory was already traversed 205 * during the operation. Also fail dotdot lookups for non-local 206 * filesystems, where external agents might assist local lookups to 207 * escape the compartment. 208 */ 209 static int 210 nameicap_check_dotdot(struct nameidata *ndp, struct vnode *dp) 211 { 212 struct nameicap_tracker *nt; 213 struct mount *mp; 214 215 if ((ndp->ni_lcf & NI_LCF_CAP_DOTDOT) == 0 || dp == NULL || 216 dp->v_type != VDIR) 217 return (0); 218 mp = dp->v_mount; 219 if (lookup_cap_dotdot_nonlocal == 0 && mp != NULL && 220 (mp->mnt_flag & MNT_LOCAL) == 0) 221 return (ENOTCAPABLE); 222 TAILQ_FOREACH_REVERSE(nt, &ndp->ni_cap_tracker, nameicap_tracker_head, 223 nm_link) { 224 if (dp == nt->dp) 225 return (0); 226 } 227 return (ENOTCAPABLE); 228 } 229 230 static void 231 namei_cleanup_cnp(struct componentname *cnp) 232 { 233 234 uma_zfree(namei_zone, cnp->cn_pnbuf); 235 #ifdef DIAGNOSTIC 236 cnp->cn_pnbuf = NULL; 237 cnp->cn_nameptr = NULL; 238 #endif 239 } 240 241 static int 242 namei_handle_root(struct nameidata *ndp, struct vnode **dpp) 243 { 244 struct componentname *cnp; 245 246 cnp = &ndp->ni_cnd; 247 if ((ndp->ni_lcf & NI_LCF_STRICTRELATIVE) != 0) { 248 #ifdef KTRACE 249 if (KTRPOINT(curthread, KTR_CAPFAIL)) 250 ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL); 251 #endif 252 return (ENOTCAPABLE); 253 } 254 while (*(cnp->cn_nameptr) == '/') { 255 cnp->cn_nameptr++; 256 ndp->ni_pathlen--; 257 } 258 *dpp = ndp->ni_rootdir; 259 vrefact(*dpp); 260 return (0); 261 } 262 263 /* 264 * Convert a pathname into a pointer to a locked vnode. 265 * 266 * The FOLLOW flag is set when symbolic links are to be followed 267 * when they occur at the end of the name translation process. 268 * Symbolic links are always followed for all other pathname 269 * components other than the last. 270 * 271 * The segflg defines whether the name is to be copied from user 272 * space or kernel space. 273 * 274 * Overall outline of namei: 275 * 276 * copy in name 277 * get starting directory 278 * while (!done && !error) { 279 * call lookup to search path. 280 * if symbolic link, massage name in buffer and continue 281 * } 282 */ 283 int 284 namei(struct nameidata *ndp) 285 { 286 struct filedesc *fdp; /* pointer to file descriptor state */ 287 char *cp; /* pointer into pathname argument */ 288 struct vnode *dp; /* the directory we are searching */ 289 struct iovec aiov; /* uio for reading symbolic links */ 290 struct componentname *cnp; 291 struct thread *td; 292 struct proc *p; 293 cap_rights_t rights; 294 struct uio auio; 295 int error, linklen, startdir_used; 296 297 cnp = &ndp->ni_cnd; 298 td = cnp->cn_thread; 299 p = td->td_proc; 300 ndp->ni_cnd.cn_cred = ndp->ni_cnd.cn_thread->td_ucred; 301 KASSERT(cnp->cn_cred && p, ("namei: bad cred/proc")); 302 KASSERT((cnp->cn_nameiop & (~OPMASK)) == 0, 303 ("namei: nameiop contaminated with flags")); 304 KASSERT((cnp->cn_flags & OPMASK) == 0, 305 ("namei: flags contaminated with nameiops")); 306 MPASS(ndp->ni_startdir == NULL || ndp->ni_startdir->v_type == VDIR || 307 ndp->ni_startdir->v_type == VBAD); 308 if (!lookup_shared) 309 cnp->cn_flags &= ~LOCKSHARED; 310 fdp = p->p_fd; 311 TAILQ_INIT(&ndp->ni_cap_tracker); 312 ndp->ni_lcf = 0; 313 314 /* We will set this ourselves if we need it. */ 315 cnp->cn_flags &= ~TRAILINGSLASH; 316 317 /* 318 * Get a buffer for the name to be translated, and copy the 319 * name into the buffer. 320 */ 321 if ((cnp->cn_flags & HASBUF) == 0) 322 cnp->cn_pnbuf = uma_zalloc(namei_zone, M_WAITOK); 323 if (ndp->ni_segflg == UIO_SYSSPACE) 324 error = copystr(ndp->ni_dirp, cnp->cn_pnbuf, MAXPATHLEN, 325 &ndp->ni_pathlen); 326 else 327 error = copyinstr(ndp->ni_dirp, cnp->cn_pnbuf, MAXPATHLEN, 328 &ndp->ni_pathlen); 329 330 /* 331 * Don't allow empty pathnames. 332 */ 333 if (error == 0 && *cnp->cn_pnbuf == '\0') 334 error = ENOENT; 335 336 #ifdef CAPABILITY_MODE 337 /* 338 * In capability mode, lookups must be restricted to happen in 339 * the subtree with the root specified by the file descriptor: 340 * - The root must be real file descriptor, not the pseudo-descriptor 341 * AT_FDCWD. 342 * - The passed path must be relative and not absolute. 343 * - If lookup_cap_dotdot is disabled, path must not contain the 344 * '..' components. 345 * - If lookup_cap_dotdot is enabled, we verify that all '..' 346 * components lookups result in the directories which were 347 * previously walked by us, which prevents an escape from 348 * the relative root. 349 */ 350 if (error == 0 && IN_CAPABILITY_MODE(td) && 351 (cnp->cn_flags & NOCAPCHECK) == 0) { 352 ndp->ni_lcf |= NI_LCF_STRICTRELATIVE; 353 if (ndp->ni_dirfd == AT_FDCWD) { 354 #ifdef KTRACE 355 if (KTRPOINT(td, KTR_CAPFAIL)) 356 ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL); 357 #endif 358 error = ECAPMODE; 359 } 360 } 361 #endif 362 if (error != 0) { 363 namei_cleanup_cnp(cnp); 364 ndp->ni_vp = NULL; 365 return (error); 366 } 367 ndp->ni_loopcnt = 0; 368 #ifdef KTRACE 369 if (KTRPOINT(td, KTR_NAMEI)) { 370 KASSERT(cnp->cn_thread == curthread, 371 ("namei not using curthread")); 372 ktrnamei(cnp->cn_pnbuf); 373 } 374 #endif 375 /* 376 * Get starting point for the translation. 377 */ 378 FILEDESC_SLOCK(fdp); 379 ndp->ni_rootdir = fdp->fd_rdir; 380 vrefact(ndp->ni_rootdir); 381 ndp->ni_topdir = fdp->fd_jdir; 382 383 /* 384 * If we are auditing the kernel pathname, save the user pathname. 385 */ 386 if (cnp->cn_flags & AUDITVNODE1) 387 AUDIT_ARG_UPATH1(td, ndp->ni_dirfd, cnp->cn_pnbuf); 388 if (cnp->cn_flags & AUDITVNODE2) 389 AUDIT_ARG_UPATH2(td, ndp->ni_dirfd, cnp->cn_pnbuf); 390 391 startdir_used = 0; 392 dp = NULL; 393 cnp->cn_nameptr = cnp->cn_pnbuf; 394 if (cnp->cn_pnbuf[0] == '/') { 395 error = namei_handle_root(ndp, &dp); 396 } else { 397 if (ndp->ni_startdir != NULL) { 398 dp = ndp->ni_startdir; 399 startdir_used = 1; 400 } else if (ndp->ni_dirfd == AT_FDCWD) { 401 dp = fdp->fd_cdir; 402 vrefact(dp); 403 } else { 404 rights = ndp->ni_rightsneeded; 405 cap_rights_set(&rights, CAP_LOOKUP); 406 407 if (cnp->cn_flags & AUDITVNODE1) 408 AUDIT_ARG_ATFD1(ndp->ni_dirfd); 409 if (cnp->cn_flags & AUDITVNODE2) 410 AUDIT_ARG_ATFD2(ndp->ni_dirfd); 411 error = fgetvp_rights(td, ndp->ni_dirfd, 412 &rights, &ndp->ni_filecaps, &dp); 413 if (error == EINVAL) 414 error = ENOTDIR; 415 #ifdef CAPABILITIES 416 /* 417 * If file descriptor doesn't have all rights, 418 * all lookups relative to it must also be 419 * strictly relative. 420 */ 421 CAP_ALL(&rights); 422 if (!cap_rights_contains(&ndp->ni_filecaps.fc_rights, 423 &rights) || 424 ndp->ni_filecaps.fc_fcntls != CAP_FCNTL_ALL || 425 ndp->ni_filecaps.fc_nioctls != -1) { 426 ndp->ni_lcf |= NI_LCF_STRICTRELATIVE; 427 } 428 #endif 429 } 430 if (error == 0 && dp->v_type != VDIR) 431 error = ENOTDIR; 432 } 433 FILEDESC_SUNLOCK(fdp); 434 if (ndp->ni_startdir != NULL && !startdir_used) 435 vrele(ndp->ni_startdir); 436 if (error != 0) { 437 if (dp != NULL) 438 vrele(dp); 439 goto out; 440 } 441 if ((ndp->ni_lcf & NI_LCF_STRICTRELATIVE) != 0 && 442 lookup_cap_dotdot != 0) 443 ndp->ni_lcf |= NI_LCF_CAP_DOTDOT; 444 SDT_PROBE3(vfs, namei, lookup, entry, dp, cnp->cn_pnbuf, 445 cnp->cn_flags); 446 for (;;) { 447 ndp->ni_startdir = dp; 448 error = lookup(ndp); 449 if (error != 0) 450 goto out; 451 /* 452 * If not a symbolic link, we're done. 453 */ 454 if ((cnp->cn_flags & ISSYMLINK) == 0) { 455 vrele(ndp->ni_rootdir); 456 if ((cnp->cn_flags & (SAVENAME | SAVESTART)) == 0) { 457 namei_cleanup_cnp(cnp); 458 } else 459 cnp->cn_flags |= HASBUF; 460 nameicap_cleanup(ndp); 461 SDT_PROBE2(vfs, namei, lookup, return, 0, ndp->ni_vp); 462 return (0); 463 } 464 if (ndp->ni_loopcnt++ >= MAXSYMLINKS) { 465 error = ELOOP; 466 break; 467 } 468 #ifdef MAC 469 if ((cnp->cn_flags & NOMACCHECK) == 0) { 470 error = mac_vnode_check_readlink(td->td_ucred, 471 ndp->ni_vp); 472 if (error != 0) 473 break; 474 } 475 #endif 476 if (ndp->ni_pathlen > 1) 477 cp = uma_zalloc(namei_zone, M_WAITOK); 478 else 479 cp = cnp->cn_pnbuf; 480 aiov.iov_base = cp; 481 aiov.iov_len = MAXPATHLEN; 482 auio.uio_iov = &aiov; 483 auio.uio_iovcnt = 1; 484 auio.uio_offset = 0; 485 auio.uio_rw = UIO_READ; 486 auio.uio_segflg = UIO_SYSSPACE; 487 auio.uio_td = td; 488 auio.uio_resid = MAXPATHLEN; 489 error = VOP_READLINK(ndp->ni_vp, &auio, cnp->cn_cred); 490 if (error != 0) { 491 if (ndp->ni_pathlen > 1) 492 uma_zfree(namei_zone, cp); 493 break; 494 } 495 linklen = MAXPATHLEN - auio.uio_resid; 496 if (linklen == 0) { 497 if (ndp->ni_pathlen > 1) 498 uma_zfree(namei_zone, cp); 499 error = ENOENT; 500 break; 501 } 502 if (linklen + ndp->ni_pathlen >= MAXPATHLEN) { 503 if (ndp->ni_pathlen > 1) 504 uma_zfree(namei_zone, cp); 505 error = ENAMETOOLONG; 506 break; 507 } 508 if (ndp->ni_pathlen > 1) { 509 bcopy(ndp->ni_next, cp + linklen, ndp->ni_pathlen); 510 uma_zfree(namei_zone, cnp->cn_pnbuf); 511 cnp->cn_pnbuf = cp; 512 } else 513 cnp->cn_pnbuf[linklen] = '\0'; 514 ndp->ni_pathlen += linklen; 515 vput(ndp->ni_vp); 516 dp = ndp->ni_dvp; 517 /* 518 * Check if root directory should replace current directory. 519 */ 520 cnp->cn_nameptr = cnp->cn_pnbuf; 521 if (*(cnp->cn_nameptr) == '/') { 522 vrele(dp); 523 error = namei_handle_root(ndp, &dp); 524 if (error != 0) 525 goto out; 526 } 527 } 528 vput(ndp->ni_vp); 529 ndp->ni_vp = NULL; 530 vrele(ndp->ni_dvp); 531 out: 532 vrele(ndp->ni_rootdir); 533 namei_cleanup_cnp(cnp); 534 nameicap_cleanup(ndp); 535 SDT_PROBE2(vfs, namei, lookup, return, error, NULL); 536 return (error); 537 } 538 539 static int 540 compute_cn_lkflags(struct mount *mp, int lkflags, int cnflags) 541 { 542 543 if (mp == NULL || ((lkflags & LK_SHARED) && 544 (!(mp->mnt_kern_flag & MNTK_LOOKUP_SHARED) || 545 ((cnflags & ISDOTDOT) && 546 (mp->mnt_kern_flag & MNTK_LOOKUP_EXCL_DOTDOT))))) { 547 lkflags &= ~LK_SHARED; 548 lkflags |= LK_EXCLUSIVE; 549 } 550 lkflags |= LK_NODDLKTREAT; 551 return (lkflags); 552 } 553 554 static __inline int 555 needs_exclusive_leaf(struct mount *mp, int flags) 556 { 557 558 /* 559 * Intermediate nodes can use shared locks, we only need to 560 * force an exclusive lock for leaf nodes. 561 */ 562 if ((flags & (ISLASTCN | LOCKLEAF)) != (ISLASTCN | LOCKLEAF)) 563 return (0); 564 565 /* Always use exclusive locks if LOCKSHARED isn't set. */ 566 if (!(flags & LOCKSHARED)) 567 return (1); 568 569 /* 570 * For lookups during open(), if the mount point supports 571 * extended shared operations, then use a shared lock for the 572 * leaf node, otherwise use an exclusive lock. 573 */ 574 if ((flags & ISOPEN) != 0) 575 return (!MNT_EXTENDED_SHARED(mp)); 576 577 /* 578 * Lookup requests outside of open() that specify LOCKSHARED 579 * only need a shared lock on the leaf vnode. 580 */ 581 return (0); 582 } 583 584 /* 585 * Search a pathname. 586 * This is a very central and rather complicated routine. 587 * 588 * The pathname is pointed to by ni_ptr and is of length ni_pathlen. 589 * The starting directory is taken from ni_startdir. The pathname is 590 * descended until done, or a symbolic link is encountered. The variable 591 * ni_more is clear if the path is completed; it is set to one if a 592 * symbolic link needing interpretation is encountered. 593 * 594 * The flag argument is LOOKUP, CREATE, RENAME, or DELETE depending on 595 * whether the name is to be looked up, created, renamed, or deleted. 596 * When CREATE, RENAME, or DELETE is specified, information usable in 597 * creating, renaming, or deleting a directory entry may be calculated. 598 * If flag has LOCKPARENT or'ed into it, the parent directory is returned 599 * locked. If flag has WANTPARENT or'ed into it, the parent directory is 600 * returned unlocked. Otherwise the parent directory is not returned. If 601 * the target of the pathname exists and LOCKLEAF is or'ed into the flag 602 * the target is returned locked, otherwise it is returned unlocked. 603 * When creating or renaming and LOCKPARENT is specified, the target may not 604 * be ".". When deleting and LOCKPARENT is specified, the target may be ".". 605 * 606 * Overall outline of lookup: 607 * 608 * dirloop: 609 * identify next component of name at ndp->ni_ptr 610 * handle degenerate case where name is null string 611 * if .. and crossing mount points and on mounted filesys, find parent 612 * call VOP_LOOKUP routine for next component name 613 * directory vnode returned in ni_dvp, unlocked unless LOCKPARENT set 614 * component vnode returned in ni_vp (if it exists), locked. 615 * if result vnode is mounted on and crossing mount points, 616 * find mounted on vnode 617 * if more components of name, do next level at dirloop 618 * return the answer in ni_vp, locked if LOCKLEAF set 619 * if LOCKPARENT set, return locked parent in ni_dvp 620 * if WANTPARENT set, return unlocked parent in ni_dvp 621 */ 622 int 623 lookup(struct nameidata *ndp) 624 { 625 char *cp; /* pointer into pathname argument */ 626 char *prev_ni_next; /* saved ndp->ni_next */ 627 struct vnode *dp = NULL; /* the directory we are searching */ 628 struct vnode *tdp; /* saved dp */ 629 struct mount *mp; /* mount table entry */ 630 struct prison *pr; 631 size_t prev_ni_pathlen; /* saved ndp->ni_pathlen */ 632 int docache; /* == 0 do not cache last component */ 633 int wantparent; /* 1 => wantparent or lockparent flag */ 634 int rdonly; /* lookup read-only flag bit */ 635 int error = 0; 636 int dpunlocked = 0; /* dp has already been unlocked */ 637 int relookup = 0; /* do not consume the path component */ 638 struct componentname *cnp = &ndp->ni_cnd; 639 int lkflags_save; 640 int ni_dvp_unlocked; 641 642 /* 643 * Setup: break out flag bits into variables. 644 */ 645 ni_dvp_unlocked = 0; 646 wantparent = cnp->cn_flags & (LOCKPARENT | WANTPARENT); 647 KASSERT(cnp->cn_nameiop == LOOKUP || wantparent, 648 ("CREATE, DELETE, RENAME require LOCKPARENT or WANTPARENT.")); 649 docache = (cnp->cn_flags & NOCACHE) ^ NOCACHE; 650 if (cnp->cn_nameiop == DELETE || 651 (wantparent && cnp->cn_nameiop != CREATE && 652 cnp->cn_nameiop != LOOKUP)) 653 docache = 0; 654 rdonly = cnp->cn_flags & RDONLY; 655 cnp->cn_flags &= ~ISSYMLINK; 656 ndp->ni_dvp = NULL; 657 /* 658 * We use shared locks until we hit the parent of the last cn then 659 * we adjust based on the requesting flags. 660 */ 661 if (lookup_shared) 662 cnp->cn_lkflags = LK_SHARED; 663 else 664 cnp->cn_lkflags = LK_EXCLUSIVE; 665 dp = ndp->ni_startdir; 666 ndp->ni_startdir = NULLVP; 667 vn_lock(dp, 668 compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags | LK_RETRY, 669 cnp->cn_flags)); 670 671 dirloop: 672 /* 673 * Search a new directory. 674 * 675 * The last component of the filename is left accessible via 676 * cnp->cn_nameptr for callers that need the name. Callers needing 677 * the name set the SAVENAME flag. When done, they assume 678 * responsibility for freeing the pathname buffer. 679 */ 680 for (cp = cnp->cn_nameptr; *cp != 0 && *cp != '/'; cp++) 681 continue; 682 cnp->cn_namelen = cp - cnp->cn_nameptr; 683 if (cnp->cn_namelen > NAME_MAX) { 684 error = ENAMETOOLONG; 685 goto bad; 686 } 687 #ifdef NAMEI_DIAGNOSTIC 688 { char c = *cp; 689 *cp = '\0'; 690 printf("{%s}: ", cnp->cn_nameptr); 691 *cp = c; } 692 #endif 693 prev_ni_pathlen = ndp->ni_pathlen; 694 ndp->ni_pathlen -= cnp->cn_namelen; 695 KASSERT(ndp->ni_pathlen <= PATH_MAX, 696 ("%s: ni_pathlen underflow to %zd\n", __func__, ndp->ni_pathlen)); 697 prev_ni_next = ndp->ni_next; 698 ndp->ni_next = cp; 699 700 /* 701 * Replace multiple slashes by a single slash and trailing slashes 702 * by a null. This must be done before VOP_LOOKUP() because some 703 * fs's don't know about trailing slashes. Remember if there were 704 * trailing slashes to handle symlinks, existing non-directories 705 * and non-existing files that won't be directories specially later. 706 */ 707 while (*cp == '/' && (cp[1] == '/' || cp[1] == '\0')) { 708 cp++; 709 ndp->ni_pathlen--; 710 if (*cp == '\0') { 711 *ndp->ni_next = '\0'; 712 cnp->cn_flags |= TRAILINGSLASH; 713 } 714 } 715 ndp->ni_next = cp; 716 717 cnp->cn_flags |= MAKEENTRY; 718 if (*cp == '\0' && docache == 0) 719 cnp->cn_flags &= ~MAKEENTRY; 720 if (cnp->cn_namelen == 2 && 721 cnp->cn_nameptr[1] == '.' && cnp->cn_nameptr[0] == '.') 722 cnp->cn_flags |= ISDOTDOT; 723 else 724 cnp->cn_flags &= ~ISDOTDOT; 725 if (*ndp->ni_next == 0) 726 cnp->cn_flags |= ISLASTCN; 727 else 728 cnp->cn_flags &= ~ISLASTCN; 729 730 if ((cnp->cn_flags & ISLASTCN) != 0 && 731 cnp->cn_namelen == 1 && cnp->cn_nameptr[0] == '.' && 732 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) { 733 error = EINVAL; 734 goto bad; 735 } 736 737 nameicap_tracker_add(ndp, dp); 738 739 /* 740 * Check for degenerate name (e.g. / or "") 741 * which is a way of talking about a directory, 742 * e.g. like "/." or ".". 743 */ 744 if (cnp->cn_nameptr[0] == '\0') { 745 if (dp->v_type != VDIR) { 746 error = ENOTDIR; 747 goto bad; 748 } 749 if (cnp->cn_nameiop != LOOKUP) { 750 error = EISDIR; 751 goto bad; 752 } 753 if (wantparent) { 754 ndp->ni_dvp = dp; 755 VREF(dp); 756 } 757 ndp->ni_vp = dp; 758 759 if (cnp->cn_flags & AUDITVNODE1) 760 AUDIT_ARG_VNODE1(dp); 761 else if (cnp->cn_flags & AUDITVNODE2) 762 AUDIT_ARG_VNODE2(dp); 763 764 if (!(cnp->cn_flags & (LOCKPARENT | LOCKLEAF))) 765 VOP_UNLOCK(dp, 0); 766 /* XXX This should probably move to the top of function. */ 767 if (cnp->cn_flags & SAVESTART) 768 panic("lookup: SAVESTART"); 769 goto success; 770 } 771 772 /* 773 * Handle "..": five special cases. 774 * 0. If doing a capability lookup and lookup_cap_dotdot is 775 * disabled, return ENOTCAPABLE. 776 * 1. Return an error if this is the last component of 777 * the name and the operation is DELETE or RENAME. 778 * 2. If at root directory (e.g. after chroot) 779 * or at absolute root directory 780 * then ignore it so can't get out. 781 * 3. If this vnode is the root of a mounted 782 * filesystem, then replace it with the 783 * vnode which was mounted on so we take the 784 * .. in the other filesystem. 785 * 4. If the vnode is the top directory of 786 * the jail or chroot, don't let them out. 787 * 5. If doing a capability lookup and lookup_cap_dotdot is 788 * enabled, return ENOTCAPABLE if the lookup would escape 789 * from the initial file descriptor directory. Checks are 790 * done by ensuring that namei() already traversed the 791 * result of dotdot lookup. 792 */ 793 if (cnp->cn_flags & ISDOTDOT) { 794 if ((ndp->ni_lcf & (NI_LCF_STRICTRELATIVE | NI_LCF_CAP_DOTDOT)) 795 == NI_LCF_STRICTRELATIVE) { 796 #ifdef KTRACE 797 if (KTRPOINT(curthread, KTR_CAPFAIL)) 798 ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL); 799 #endif 800 error = ENOTCAPABLE; 801 goto bad; 802 } 803 if ((cnp->cn_flags & ISLASTCN) != 0 && 804 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) { 805 error = EINVAL; 806 goto bad; 807 } 808 for (;;) { 809 for (pr = cnp->cn_cred->cr_prison; pr != NULL; 810 pr = pr->pr_parent) 811 if (dp == pr->pr_root) 812 break; 813 if (dp == ndp->ni_rootdir || 814 dp == ndp->ni_topdir || 815 dp == rootvnode || 816 pr != NULL || 817 ((dp->v_vflag & VV_ROOT) != 0 && 818 (cnp->cn_flags & NOCROSSMOUNT) != 0)) { 819 ndp->ni_dvp = dp; 820 ndp->ni_vp = dp; 821 VREF(dp); 822 goto nextname; 823 } 824 if ((dp->v_vflag & VV_ROOT) == 0) 825 break; 826 if (dp->v_iflag & VI_DOOMED) { /* forced unmount */ 827 error = ENOENT; 828 goto bad; 829 } 830 tdp = dp; 831 dp = dp->v_mount->mnt_vnodecovered; 832 VREF(dp); 833 vput(tdp); 834 vn_lock(dp, 835 compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags | 836 LK_RETRY, ISDOTDOT)); 837 error = nameicap_check_dotdot(ndp, dp); 838 if (error != 0) { 839 #ifdef KTRACE 840 if (KTRPOINT(curthread, KTR_CAPFAIL)) 841 ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL); 842 #endif 843 goto bad; 844 } 845 } 846 } 847 848 /* 849 * We now have a segment name to search for, and a directory to search. 850 */ 851 unionlookup: 852 #ifdef MAC 853 if ((cnp->cn_flags & NOMACCHECK) == 0) { 854 error = mac_vnode_check_lookup(cnp->cn_thread->td_ucred, dp, 855 cnp); 856 if (error) 857 goto bad; 858 } 859 #endif 860 ndp->ni_dvp = dp; 861 ndp->ni_vp = NULL; 862 ASSERT_VOP_LOCKED(dp, "lookup"); 863 /* 864 * If we have a shared lock we may need to upgrade the lock for the 865 * last operation. 866 */ 867 if ((cnp->cn_flags & LOCKPARENT) && (cnp->cn_flags & ISLASTCN) && 868 dp != vp_crossmp && VOP_ISLOCKED(dp) == LK_SHARED) 869 vn_lock(dp, LK_UPGRADE|LK_RETRY); 870 if ((dp->v_iflag & VI_DOOMED) != 0) { 871 error = ENOENT; 872 goto bad; 873 } 874 /* 875 * If we're looking up the last component and we need an exclusive 876 * lock, adjust our lkflags. 877 */ 878 if (needs_exclusive_leaf(dp->v_mount, cnp->cn_flags)) 879 cnp->cn_lkflags = LK_EXCLUSIVE; 880 #ifdef NAMEI_DIAGNOSTIC 881 vn_printf(dp, "lookup in "); 882 #endif 883 lkflags_save = cnp->cn_lkflags; 884 cnp->cn_lkflags = compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags, 885 cnp->cn_flags); 886 error = VOP_LOOKUP(dp, &ndp->ni_vp, cnp); 887 cnp->cn_lkflags = lkflags_save; 888 if (error != 0) { 889 KASSERT(ndp->ni_vp == NULL, ("leaf should be empty")); 890 #ifdef NAMEI_DIAGNOSTIC 891 printf("not found\n"); 892 #endif 893 if ((error == ENOENT) && 894 (dp->v_vflag & VV_ROOT) && (dp->v_mount != NULL) && 895 (dp->v_mount->mnt_flag & MNT_UNION)) { 896 tdp = dp; 897 dp = dp->v_mount->mnt_vnodecovered; 898 VREF(dp); 899 vput(tdp); 900 vn_lock(dp, 901 compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags | 902 LK_RETRY, cnp->cn_flags)); 903 nameicap_tracker_add(ndp, dp); 904 goto unionlookup; 905 } 906 907 if (error == ERELOOKUP) { 908 vref(dp); 909 ndp->ni_vp = dp; 910 error = 0; 911 relookup = 1; 912 goto good; 913 } 914 915 if (error != EJUSTRETURN) 916 goto bad; 917 /* 918 * At this point, we know we're at the end of the 919 * pathname. If creating / renaming, we can consider 920 * allowing the file or directory to be created / renamed, 921 * provided we're not on a read-only filesystem. 922 */ 923 if (rdonly) { 924 error = EROFS; 925 goto bad; 926 } 927 /* trailing slash only allowed for directories */ 928 if ((cnp->cn_flags & TRAILINGSLASH) && 929 !(cnp->cn_flags & WILLBEDIR)) { 930 error = ENOENT; 931 goto bad; 932 } 933 if ((cnp->cn_flags & LOCKPARENT) == 0) 934 VOP_UNLOCK(dp, 0); 935 /* 936 * We return with ni_vp NULL to indicate that the entry 937 * doesn't currently exist, leaving a pointer to the 938 * (possibly locked) directory vnode in ndp->ni_dvp. 939 */ 940 if (cnp->cn_flags & SAVESTART) { 941 ndp->ni_startdir = ndp->ni_dvp; 942 VREF(ndp->ni_startdir); 943 } 944 goto success; 945 } 946 947 good: 948 #ifdef NAMEI_DIAGNOSTIC 949 printf("found\n"); 950 #endif 951 dp = ndp->ni_vp; 952 953 /* 954 * Check to see if the vnode has been mounted on; 955 * if so find the root of the mounted filesystem. 956 */ 957 while (dp->v_type == VDIR && (mp = dp->v_mountedhere) && 958 (cnp->cn_flags & NOCROSSMOUNT) == 0) { 959 if (vfs_busy(mp, 0)) 960 continue; 961 vput(dp); 962 if (dp != ndp->ni_dvp) 963 vput(ndp->ni_dvp); 964 else 965 vrele(ndp->ni_dvp); 966 vrefact(vp_crossmp); 967 ndp->ni_dvp = vp_crossmp; 968 error = VFS_ROOT(mp, compute_cn_lkflags(mp, cnp->cn_lkflags, 969 cnp->cn_flags), &tdp); 970 vfs_unbusy(mp); 971 if (vn_lock(vp_crossmp, LK_SHARED | LK_NOWAIT)) 972 panic("vp_crossmp exclusively locked or reclaimed"); 973 if (error) { 974 dpunlocked = 1; 975 goto bad2; 976 } 977 ndp->ni_vp = dp = tdp; 978 } 979 980 /* 981 * Check for symbolic link 982 */ 983 if ((dp->v_type == VLNK) && 984 ((cnp->cn_flags & FOLLOW) || (cnp->cn_flags & TRAILINGSLASH) || 985 *ndp->ni_next == '/')) { 986 cnp->cn_flags |= ISSYMLINK; 987 if (dp->v_iflag & VI_DOOMED) { 988 /* 989 * We can't know whether the directory was mounted with 990 * NOSYMFOLLOW, so we can't follow safely. 991 */ 992 error = ENOENT; 993 goto bad2; 994 } 995 if (dp->v_mount->mnt_flag & MNT_NOSYMFOLLOW) { 996 error = EACCES; 997 goto bad2; 998 } 999 /* 1000 * Symlink code always expects an unlocked dvp. 1001 */ 1002 if (ndp->ni_dvp != ndp->ni_vp) { 1003 VOP_UNLOCK(ndp->ni_dvp, 0); 1004 ni_dvp_unlocked = 1; 1005 } 1006 goto success; 1007 } 1008 1009 nextname: 1010 /* 1011 * Not a symbolic link that we will follow. Continue with the 1012 * next component if there is any; otherwise, we're done. 1013 */ 1014 KASSERT((cnp->cn_flags & ISLASTCN) || *ndp->ni_next == '/', 1015 ("lookup: invalid path state.")); 1016 if (relookup) { 1017 relookup = 0; 1018 ndp->ni_pathlen = prev_ni_pathlen; 1019 ndp->ni_next = prev_ni_next; 1020 if (ndp->ni_dvp != dp) 1021 vput(ndp->ni_dvp); 1022 else 1023 vrele(ndp->ni_dvp); 1024 goto dirloop; 1025 } 1026 if (cnp->cn_flags & ISDOTDOT) { 1027 error = nameicap_check_dotdot(ndp, ndp->ni_vp); 1028 if (error != 0) { 1029 #ifdef KTRACE 1030 if (KTRPOINT(curthread, KTR_CAPFAIL)) 1031 ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL); 1032 #endif 1033 goto bad2; 1034 } 1035 } 1036 if (*ndp->ni_next == '/') { 1037 cnp->cn_nameptr = ndp->ni_next; 1038 while (*cnp->cn_nameptr == '/') { 1039 cnp->cn_nameptr++; 1040 ndp->ni_pathlen--; 1041 } 1042 if (ndp->ni_dvp != dp) 1043 vput(ndp->ni_dvp); 1044 else 1045 vrele(ndp->ni_dvp); 1046 goto dirloop; 1047 } 1048 /* 1049 * If we're processing a path with a trailing slash, 1050 * check that the end result is a directory. 1051 */ 1052 if ((cnp->cn_flags & TRAILINGSLASH) && dp->v_type != VDIR) { 1053 error = ENOTDIR; 1054 goto bad2; 1055 } 1056 /* 1057 * Disallow directory write attempts on read-only filesystems. 1058 */ 1059 if (rdonly && 1060 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) { 1061 error = EROFS; 1062 goto bad2; 1063 } 1064 if (cnp->cn_flags & SAVESTART) { 1065 ndp->ni_startdir = ndp->ni_dvp; 1066 VREF(ndp->ni_startdir); 1067 } 1068 if (!wantparent) { 1069 ni_dvp_unlocked = 2; 1070 if (ndp->ni_dvp != dp) 1071 vput(ndp->ni_dvp); 1072 else 1073 vrele(ndp->ni_dvp); 1074 } else if ((cnp->cn_flags & LOCKPARENT) == 0 && ndp->ni_dvp != dp) { 1075 VOP_UNLOCK(ndp->ni_dvp, 0); 1076 ni_dvp_unlocked = 1; 1077 } 1078 1079 if (cnp->cn_flags & AUDITVNODE1) 1080 AUDIT_ARG_VNODE1(dp); 1081 else if (cnp->cn_flags & AUDITVNODE2) 1082 AUDIT_ARG_VNODE2(dp); 1083 1084 if ((cnp->cn_flags & LOCKLEAF) == 0) 1085 VOP_UNLOCK(dp, 0); 1086 success: 1087 /* 1088 * Because of lookup_shared we may have the vnode shared locked, but 1089 * the caller may want it to be exclusively locked. 1090 */ 1091 if (needs_exclusive_leaf(dp->v_mount, cnp->cn_flags) && 1092 VOP_ISLOCKED(dp) != LK_EXCLUSIVE) { 1093 vn_lock(dp, LK_UPGRADE | LK_RETRY); 1094 if (dp->v_iflag & VI_DOOMED) { 1095 error = ENOENT; 1096 goto bad2; 1097 } 1098 } 1099 return (0); 1100 1101 bad2: 1102 if (ni_dvp_unlocked != 2) { 1103 if (dp != ndp->ni_dvp && !ni_dvp_unlocked) 1104 vput(ndp->ni_dvp); 1105 else 1106 vrele(ndp->ni_dvp); 1107 } 1108 bad: 1109 if (!dpunlocked) 1110 vput(dp); 1111 ndp->ni_vp = NULL; 1112 return (error); 1113 } 1114 1115 /* 1116 * relookup - lookup a path name component 1117 * Used by lookup to re-acquire things. 1118 */ 1119 int 1120 relookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp) 1121 { 1122 struct vnode *dp = NULL; /* the directory we are searching */ 1123 int wantparent; /* 1 => wantparent or lockparent flag */ 1124 int rdonly; /* lookup read-only flag bit */ 1125 int error = 0; 1126 1127 KASSERT(cnp->cn_flags & ISLASTCN, 1128 ("relookup: Not given last component.")); 1129 /* 1130 * Setup: break out flag bits into variables. 1131 */ 1132 wantparent = cnp->cn_flags & (LOCKPARENT|WANTPARENT); 1133 KASSERT(wantparent, ("relookup: parent not wanted.")); 1134 rdonly = cnp->cn_flags & RDONLY; 1135 cnp->cn_flags &= ~ISSYMLINK; 1136 dp = dvp; 1137 cnp->cn_lkflags = LK_EXCLUSIVE; 1138 vn_lock(dp, LK_EXCLUSIVE | LK_RETRY); 1139 1140 /* 1141 * Search a new directory. 1142 * 1143 * The last component of the filename is left accessible via 1144 * cnp->cn_nameptr for callers that need the name. Callers needing 1145 * the name set the SAVENAME flag. When done, they assume 1146 * responsibility for freeing the pathname buffer. 1147 */ 1148 #ifdef NAMEI_DIAGNOSTIC 1149 printf("{%s}: ", cnp->cn_nameptr); 1150 #endif 1151 1152 /* 1153 * Check for "" which represents the root directory after slash 1154 * removal. 1155 */ 1156 if (cnp->cn_nameptr[0] == '\0') { 1157 /* 1158 * Support only LOOKUP for "/" because lookup() 1159 * can't succeed for CREATE, DELETE and RENAME. 1160 */ 1161 KASSERT(cnp->cn_nameiop == LOOKUP, ("nameiop must be LOOKUP")); 1162 KASSERT(dp->v_type == VDIR, ("dp is not a directory")); 1163 1164 if (!(cnp->cn_flags & LOCKLEAF)) 1165 VOP_UNLOCK(dp, 0); 1166 *vpp = dp; 1167 /* XXX This should probably move to the top of function. */ 1168 if (cnp->cn_flags & SAVESTART) 1169 panic("lookup: SAVESTART"); 1170 return (0); 1171 } 1172 1173 if (cnp->cn_flags & ISDOTDOT) 1174 panic ("relookup: lookup on dot-dot"); 1175 1176 /* 1177 * We now have a segment name to search for, and a directory to search. 1178 */ 1179 #ifdef NAMEI_DIAGNOSTIC 1180 vn_printf(dp, "search in "); 1181 #endif 1182 if ((error = VOP_LOOKUP(dp, vpp, cnp)) != 0) { 1183 KASSERT(*vpp == NULL, ("leaf should be empty")); 1184 if (error != EJUSTRETURN) 1185 goto bad; 1186 /* 1187 * If creating and at end of pathname, then can consider 1188 * allowing file to be created. 1189 */ 1190 if (rdonly) { 1191 error = EROFS; 1192 goto bad; 1193 } 1194 /* ASSERT(dvp == ndp->ni_startdir) */ 1195 if (cnp->cn_flags & SAVESTART) 1196 VREF(dvp); 1197 if ((cnp->cn_flags & LOCKPARENT) == 0) 1198 VOP_UNLOCK(dp, 0); 1199 /* 1200 * We return with ni_vp NULL to indicate that the entry 1201 * doesn't currently exist, leaving a pointer to the 1202 * (possibly locked) directory vnode in ndp->ni_dvp. 1203 */ 1204 return (0); 1205 } 1206 1207 dp = *vpp; 1208 1209 /* 1210 * Disallow directory write attempts on read-only filesystems. 1211 */ 1212 if (rdonly && 1213 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) { 1214 if (dvp == dp) 1215 vrele(dvp); 1216 else 1217 vput(dvp); 1218 error = EROFS; 1219 goto bad; 1220 } 1221 /* 1222 * Set the parent lock/ref state to the requested state. 1223 */ 1224 if ((cnp->cn_flags & LOCKPARENT) == 0 && dvp != dp) { 1225 if (wantparent) 1226 VOP_UNLOCK(dvp, 0); 1227 else 1228 vput(dvp); 1229 } else if (!wantparent) 1230 vrele(dvp); 1231 /* 1232 * Check for symbolic link 1233 */ 1234 KASSERT(dp->v_type != VLNK || !(cnp->cn_flags & FOLLOW), 1235 ("relookup: symlink found.\n")); 1236 1237 /* ASSERT(dvp == ndp->ni_startdir) */ 1238 if (cnp->cn_flags & SAVESTART) 1239 VREF(dvp); 1240 1241 if ((cnp->cn_flags & LOCKLEAF) == 0) 1242 VOP_UNLOCK(dp, 0); 1243 return (0); 1244 bad: 1245 vput(dp); 1246 *vpp = NULL; 1247 return (error); 1248 } 1249 1250 void 1251 NDINIT_ALL(struct nameidata *ndp, u_long op, u_long flags, enum uio_seg segflg, 1252 const char *namep, int dirfd, struct vnode *startdir, cap_rights_t *rightsp, 1253 struct thread *td) 1254 { 1255 1256 ndp->ni_cnd.cn_nameiop = op; 1257 ndp->ni_cnd.cn_flags = flags; 1258 ndp->ni_segflg = segflg; 1259 ndp->ni_dirp = namep; 1260 ndp->ni_dirfd = dirfd; 1261 ndp->ni_startdir = startdir; 1262 if (rightsp != NULL) 1263 ndp->ni_rightsneeded = *rightsp; 1264 else 1265 cap_rights_init(&ndp->ni_rightsneeded); 1266 filecaps_init(&ndp->ni_filecaps); 1267 ndp->ni_cnd.cn_thread = td; 1268 } 1269 1270 /* 1271 * Free data allocated by namei(); see namei(9) for details. 1272 */ 1273 void 1274 NDFREE(struct nameidata *ndp, const u_int flags) 1275 { 1276 int unlock_dvp; 1277 int unlock_vp; 1278 1279 unlock_dvp = 0; 1280 unlock_vp = 0; 1281 1282 if (!(flags & NDF_NO_FREE_PNBUF) && 1283 (ndp->ni_cnd.cn_flags & HASBUF)) { 1284 uma_zfree(namei_zone, ndp->ni_cnd.cn_pnbuf); 1285 ndp->ni_cnd.cn_flags &= ~HASBUF; 1286 } 1287 if (!(flags & NDF_NO_VP_UNLOCK) && 1288 (ndp->ni_cnd.cn_flags & LOCKLEAF) && ndp->ni_vp) 1289 unlock_vp = 1; 1290 if (!(flags & NDF_NO_VP_RELE) && ndp->ni_vp) { 1291 if (unlock_vp) { 1292 vput(ndp->ni_vp); 1293 unlock_vp = 0; 1294 } else 1295 vrele(ndp->ni_vp); 1296 ndp->ni_vp = NULL; 1297 } 1298 if (unlock_vp) 1299 VOP_UNLOCK(ndp->ni_vp, 0); 1300 if (!(flags & NDF_NO_DVP_UNLOCK) && 1301 (ndp->ni_cnd.cn_flags & LOCKPARENT) && 1302 ndp->ni_dvp != ndp->ni_vp) 1303 unlock_dvp = 1; 1304 if (!(flags & NDF_NO_DVP_RELE) && 1305 (ndp->ni_cnd.cn_flags & (LOCKPARENT|WANTPARENT))) { 1306 if (unlock_dvp) { 1307 vput(ndp->ni_dvp); 1308 unlock_dvp = 0; 1309 } else 1310 vrele(ndp->ni_dvp); 1311 ndp->ni_dvp = NULL; 1312 } 1313 if (unlock_dvp) 1314 VOP_UNLOCK(ndp->ni_dvp, 0); 1315 if (!(flags & NDF_NO_STARTDIR_RELE) && 1316 (ndp->ni_cnd.cn_flags & SAVESTART)) { 1317 vrele(ndp->ni_startdir); 1318 ndp->ni_startdir = NULL; 1319 } 1320 } 1321 1322 /* 1323 * Determine if there is a suitable alternate filename under the specified 1324 * prefix for the specified path. If the create flag is set, then the 1325 * alternate prefix will be used so long as the parent directory exists. 1326 * This is used by the various compatibility ABIs so that Linux binaries prefer 1327 * files under /compat/linux for example. The chosen path (whether under 1328 * the prefix or under /) is returned in a kernel malloc'd buffer pointed 1329 * to by pathbuf. The caller is responsible for free'ing the buffer from 1330 * the M_TEMP bucket if one is returned. 1331 */ 1332 int 1333 kern_alternate_path(struct thread *td, const char *prefix, const char *path, 1334 enum uio_seg pathseg, char **pathbuf, int create, int dirfd) 1335 { 1336 struct nameidata nd, ndroot; 1337 char *ptr, *buf, *cp; 1338 size_t len, sz; 1339 int error; 1340 1341 buf = (char *) malloc(MAXPATHLEN, M_TEMP, M_WAITOK); 1342 *pathbuf = buf; 1343 1344 /* Copy the prefix into the new pathname as a starting point. */ 1345 len = strlcpy(buf, prefix, MAXPATHLEN); 1346 if (len >= MAXPATHLEN) { 1347 *pathbuf = NULL; 1348 free(buf, M_TEMP); 1349 return (EINVAL); 1350 } 1351 sz = MAXPATHLEN - len; 1352 ptr = buf + len; 1353 1354 /* Append the filename to the prefix. */ 1355 if (pathseg == UIO_SYSSPACE) 1356 error = copystr(path, ptr, sz, &len); 1357 else 1358 error = copyinstr(path, ptr, sz, &len); 1359 1360 if (error) { 1361 *pathbuf = NULL; 1362 free(buf, M_TEMP); 1363 return (error); 1364 } 1365 1366 /* Only use a prefix with absolute pathnames. */ 1367 if (*ptr != '/') { 1368 error = EINVAL; 1369 goto keeporig; 1370 } 1371 1372 if (dirfd != AT_FDCWD) { 1373 /* 1374 * We want the original because the "prefix" is 1375 * included in the already opened dirfd. 1376 */ 1377 bcopy(ptr, buf, len); 1378 return (0); 1379 } 1380 1381 /* 1382 * We know that there is a / somewhere in this pathname. 1383 * Search backwards for it, to find the file's parent dir 1384 * to see if it exists in the alternate tree. If it does, 1385 * and we want to create a file (cflag is set). We don't 1386 * need to worry about the root comparison in this case. 1387 */ 1388 1389 if (create) { 1390 for (cp = &ptr[len] - 1; *cp != '/'; cp--); 1391 *cp = '\0'; 1392 1393 NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_SYSSPACE, buf, td); 1394 error = namei(&nd); 1395 *cp = '/'; 1396 if (error != 0) 1397 goto keeporig; 1398 } else { 1399 NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_SYSSPACE, buf, td); 1400 1401 error = namei(&nd); 1402 if (error != 0) 1403 goto keeporig; 1404 1405 /* 1406 * We now compare the vnode of the prefix to the one 1407 * vnode asked. If they resolve to be the same, then we 1408 * ignore the match so that the real root gets used. 1409 * This avoids the problem of traversing "../.." to find the 1410 * root directory and never finding it, because "/" resolves 1411 * to the emulation root directory. This is expensive :-( 1412 */ 1413 NDINIT(&ndroot, LOOKUP, FOLLOW, UIO_SYSSPACE, prefix, 1414 td); 1415 1416 /* We shouldn't ever get an error from this namei(). */ 1417 error = namei(&ndroot); 1418 if (error == 0) { 1419 if (nd.ni_vp == ndroot.ni_vp) 1420 error = ENOENT; 1421 1422 NDFREE(&ndroot, NDF_ONLY_PNBUF); 1423 vrele(ndroot.ni_vp); 1424 } 1425 } 1426 1427 NDFREE(&nd, NDF_ONLY_PNBUF); 1428 vrele(nd.ni_vp); 1429 1430 keeporig: 1431 /* If there was an error, use the original path name. */ 1432 if (error) 1433 bcopy(ptr, buf, len); 1434 return (error); 1435 }
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