1 /* $NetBSD: vfs_getcwd.c,v 1.48 2012/11/05 17:24:11 dholland Exp $ */ 2 3 /*- 4 * Copyright (c) 1999 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by Bill Sommerfeld. 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 * 19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 29 * POSSIBILITY OF SUCH DAMAGE. 30 */ 31 32 #include <sys/cdefs.h> 33 __KERNEL_RCSID(0, "$NetBSD: vfs_getcwd.c,v 1.48 2012/11/05 17:24:11 dholland Exp $"); 34 35 #include <sys/param.h> 36 #include <sys/systm.h> 37 #include <sys/namei.h> 38 #include <sys/filedesc.h> 39 #include <sys/kernel.h> 40 #include <sys/file.h> 41 #include <sys/stat.h> 42 #include <sys/vnode.h> 43 #include <sys/mount.h> 44 #include <sys/proc.h> 45 #include <sys/uio.h> 46 #include <sys/kmem.h> 47 #include <sys/dirent.h> 48 #include <sys/kauth.h> 49 50 #include <ufs/ufs/dir.h> /* XXX only for DIRBLKSIZ */ 51 52 #include <sys/syscallargs.h> 53 54 /* 55 * Vnode variable naming conventions in this file: 56 * 57 * rvp: the current root we're aiming towards. 58 * lvp, *lvpp: the "lower" vnode 59 * uvp, *uvpp: the "upper" vnode. 60 * 61 * Since all the vnodes we're dealing with are directories, and the 62 * lookups are going *up* in the filesystem rather than *down*, the 63 * usual "pvp" (parent) or "dvp" (directory) naming conventions are 64 * too confusing. 65 */ 66 67 /* 68 * XXX Will infinite loop in certain cases if a directory read reliably 69 * returns EINVAL on last block. 70 * XXX is EINVAL the right thing to return if a directory is malformed? 71 */ 72 73 /* 74 * XXX Untested vs. mount -o union; probably does the wrong thing. 75 */ 76 77 /* 78 * Find parent vnode of *lvpp, return in *uvpp 79 * 80 * If we care about the name, scan it looking for name of directory 81 * entry pointing at lvp. 82 * 83 * Place the name in the buffer which starts at bufp, immediately 84 * before *bpp, and move bpp backwards to point at the start of it. 85 * 86 * On entry, *lvpp is a locked vnode reference; on exit, it is vput and NULL'ed 87 * On exit, *uvpp is either NULL or is a locked vnode reference. 88 */ 89 static int 90 getcwd_scandir(struct vnode **lvpp, struct vnode **uvpp, char **bpp, 91 char *bufp, struct lwp *l) 92 { 93 int error = 0; 94 int eofflag; 95 off_t off; 96 int tries; 97 struct uio uio; 98 struct iovec iov; 99 char *dirbuf = NULL; 100 int dirbuflen; 101 ino_t fileno; 102 struct vattr va; 103 struct vnode *uvp = NULL; 104 struct vnode *lvp = *lvpp; 105 kauth_cred_t cred = l->l_cred; 106 struct componentname cn; 107 int len, reclen; 108 tries = 0; 109 110 /* 111 * If we want the filename, get some info we need while the 112 * current directory is still locked. 113 */ 114 if (bufp != NULL) { 115 error = VOP_GETATTR(lvp, &va, cred); 116 if (error) { 117 vput(lvp); 118 *lvpp = NULL; 119 *uvpp = NULL; 120 return error; 121 } 122 } 123 124 /* 125 * Ok, we have to do it the hard way.. 126 * Next, get parent vnode using lookup of .. 127 */ 128 cn.cn_nameiop = LOOKUP; 129 cn.cn_flags = ISLASTCN | ISDOTDOT | RDONLY; 130 cn.cn_cred = cred; 131 cn.cn_nameptr = ".."; 132 cn.cn_namelen = 2; 133 cn.cn_consume = 0; 134 135 /* 136 * At this point, lvp is locked. 137 * On successful return, *uvpp will be locked 138 */ 139 error = VOP_LOOKUP(lvp, uvpp, &cn); 140 vput(lvp); 141 if (error) { 142 *lvpp = NULL; 143 *uvpp = NULL; 144 return error; 145 } 146 uvp = *uvpp; 147 148 /* If we don't care about the pathname, we're done */ 149 if (bufp == NULL) { 150 *lvpp = NULL; 151 return 0; 152 } 153 154 fileno = va.va_fileid; 155 156 dirbuflen = DIRBLKSIZ; 157 if (dirbuflen < va.va_blocksize) 158 dirbuflen = va.va_blocksize; 159 dirbuf = kmem_alloc(dirbuflen, KM_SLEEP); 160 161 #if 0 162 unionread: 163 #endif 164 off = 0; 165 do { 166 /* call VOP_READDIR of parent */ 167 iov.iov_base = dirbuf; 168 iov.iov_len = dirbuflen; 169 170 uio.uio_iov = &iov; 171 uio.uio_iovcnt = 1; 172 uio.uio_offset = off; 173 uio.uio_resid = dirbuflen; 174 uio.uio_rw = UIO_READ; 175 UIO_SETUP_SYSSPACE(&uio); 176 177 eofflag = 0; 178 179 error = VOP_READDIR(uvp, &uio, cred, &eofflag, 0, 0); 180 181 off = uio.uio_offset; 182 183 /* 184 * Try again if NFS tosses its cookies. 185 * XXX this can still loop forever if the directory is busted 186 * such that the second or subsequent page of it always 187 * returns EINVAL 188 */ 189 if ((error == EINVAL) && (tries < 3)) { 190 off = 0; 191 tries++; 192 continue; /* once more, with feeling */ 193 } 194 195 if (!error) { 196 char *cpos; 197 struct dirent *dp; 198 199 cpos = dirbuf; 200 tries = 0; 201 202 /* scan directory page looking for matching vnode */ 203 for (len = (dirbuflen - uio.uio_resid); len > 0; 204 len -= reclen) { 205 dp = (struct dirent *) cpos; 206 reclen = dp->d_reclen; 207 208 /* check for malformed directory.. */ 209 if (reclen < _DIRENT_MINSIZE(dp)) { 210 error = EINVAL; 211 goto out; 212 } 213 /* 214 * XXX should perhaps do VOP_LOOKUP to 215 * check that we got back to the right place, 216 * but getting the locking games for that 217 * right would be heinous. 218 */ 219 if ((dp->d_type != DT_WHT) && 220 (dp->d_fileno == fileno)) { 221 char *bp = *bpp; 222 223 bp -= dp->d_namlen; 224 if (bp <= bufp) { 225 error = ERANGE; 226 goto out; 227 } 228 memcpy(bp, dp->d_name, dp->d_namlen); 229 error = 0; 230 *bpp = bp; 231 goto out; 232 } 233 cpos += reclen; 234 } 235 } else 236 goto out; 237 } while (!eofflag); 238 #if 0 239 /* 240 * Deal with mount -o union, which unions only the 241 * root directory of the mount. 242 */ 243 if ((uvp->v_vflag & VV_ROOT) && 244 (uvp->v_mount->mnt_flag & MNT_UNION)) { 245 struct vnode *tvp = uvp; 246 247 uvp = uvp->v_mount->mnt_vnodecovered; 248 vput(tvp); 249 vref(uvp); 250 *uvpp = uvp; 251 vn_lock(uvp, LK_EXCLUSIVE | LK_RETRY); 252 goto unionread; 253 } 254 #endif 255 error = ENOENT; 256 257 out: 258 *lvpp = NULL; 259 kmem_free(dirbuf, dirbuflen); 260 return error; 261 } 262 263 /* 264 * Look in the vnode-to-name reverse cache to see if 265 * we can find things the easy way. 266 * 267 * XXX vget failure path is untested. 268 * 269 * On entry, *lvpp is a locked vnode reference. 270 * On exit, one of the following is the case: 271 * 0) Both *lvpp and *uvpp are NULL and failure is returned. 272 * 1) *uvpp is NULL, *lvpp remains locked and -1 is returned (cache miss) 273 * 2) *uvpp is a locked vnode reference, *lvpp is vput and NULL'ed 274 * and 0 is returned (cache hit) 275 */ 276 277 static int 278 getcwd_getcache(struct vnode **lvpp, struct vnode **uvpp, char **bpp, 279 char *bufp) 280 { 281 struct vnode *lvp, *uvp = NULL; 282 int error; 283 284 lvp = *lvpp; 285 286 /* 287 * This returns 0 on a cache hit, -1 on a clean cache miss, 288 * or an errno on other failure. 289 */ 290 error = cache_revlookup(lvp, uvpp, bpp, bufp); 291 if (error) { 292 if (error != -1) { 293 vput(lvp); 294 *lvpp = NULL; 295 *uvpp = NULL; 296 } 297 return error; 298 } 299 uvp = *uvpp; 300 301 /* 302 * Since we're going up, we have to release the current lock 303 * before we take the parent lock. 304 */ 305 306 VOP_UNLOCK(lvp); 307 vn_lock(uvp, LK_EXCLUSIVE | LK_RETRY); 308 vrele(lvp); 309 *lvpp = NULL; 310 311 return error; 312 } 313 314 /* 315 * common routine shared by sys___getcwd() and vn_isunder() 316 */ 317 318 int 319 getcwd_common(struct vnode *lvp, struct vnode *rvp, char **bpp, char *bufp, 320 int limit, int flags, struct lwp *l) 321 { 322 struct cwdinfo *cwdi = l->l_proc->p_cwdi; 323 kauth_cred_t cred = l->l_cred; 324 struct vnode *uvp = NULL; 325 char *bp = NULL; 326 int error; 327 int perms = VEXEC; 328 329 error = 0; 330 if (rvp == NULL) { 331 rvp = cwdi->cwdi_rdir; 332 if (rvp == NULL) 333 rvp = rootvnode; 334 } 335 336 vref(rvp); 337 vref(lvp); 338 339 /* 340 * Error handling invariant: 341 * Before a `goto out': 342 * lvp is either NULL, or locked and held. 343 * uvp is either NULL, or locked and held. 344 */ 345 346 vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY); 347 if (bufp) 348 bp = *bpp; 349 350 /* 351 * this loop will terminate when one of the following happens: 352 * - we hit the root 353 * - getdirentries or lookup fails 354 * - we run out of space in the buffer. 355 */ 356 if (lvp == rvp) { 357 if (bp) 358 *(--bp) = '/'; 359 goto out; 360 } 361 do { 362 /* 363 * access check here is optional, depending on 364 * whether or not caller cares. 365 */ 366 if (flags & GETCWD_CHECK_ACCESS) { 367 error = VOP_ACCESS(lvp, perms, cred); 368 if (error) 369 goto out; 370 perms = VEXEC|VREAD; 371 } 372 373 /* 374 * step up if we're a covered vnode.. 375 */ 376 while (lvp->v_vflag & VV_ROOT) { 377 struct vnode *tvp; 378 379 if (lvp == rvp) 380 goto out; 381 382 tvp = lvp; 383 lvp = lvp->v_mount->mnt_vnodecovered; 384 vput(tvp); 385 /* 386 * hodie natus est radici frater 387 */ 388 if (lvp == NULL) { 389 error = ENOENT; 390 goto out; 391 } 392 vref(lvp); 393 error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY); 394 if (error != 0) { 395 vrele(lvp); 396 lvp = NULL; 397 goto out; 398 } 399 } 400 /* 401 * Look in the name cache; if that fails, look in the 402 * directory.. 403 */ 404 error = getcwd_getcache(&lvp, &uvp, &bp, bufp); 405 if (error == -1) { 406 if (lvp->v_type != VDIR) { 407 error = ENOTDIR; 408 goto out; 409 } 410 error = getcwd_scandir(&lvp, &uvp, &bp, bufp, l); 411 } 412 if (error) 413 goto out; 414 #if DIAGNOSTIC 415 if (lvp != NULL) 416 panic("getcwd: oops, forgot to null lvp"); 417 if (bufp && (bp <= bufp)) { 418 panic("getcwd: oops, went back too far"); 419 } 420 #endif 421 if (bp) 422 *(--bp) = '/'; 423 lvp = uvp; 424 uvp = NULL; 425 limit--; 426 } while ((lvp != rvp) && (limit > 0)); 427 428 out: 429 if (bpp) 430 *bpp = bp; 431 if (uvp) 432 vput(uvp); 433 if (lvp) 434 vput(lvp); 435 vrele(rvp); 436 return error; 437 } 438 439 /* 440 * Check if one directory can be found inside another in the directory 441 * hierarchy. 442 * 443 * Intended to be used in chroot, chdir, fchdir, etc., to ensure that 444 * chroot() actually means something. 445 */ 446 int 447 vn_isunder(struct vnode *lvp, struct vnode *rvp, struct lwp *l) 448 { 449 int error; 450 451 error = getcwd_common(lvp, rvp, NULL, NULL, MAXPATHLEN / 2, 0, l); 452 453 if (!error) 454 return 1; 455 else 456 return 0; 457 } 458 459 /* 460 * Returns true if proc p1's root directory equal to or under p2's 461 * root directory. 462 * 463 * Intended to be used from ptrace/procfs sorts of things. 464 */ 465 466 int 467 proc_isunder(struct proc *p1, struct lwp *l2) 468 { 469 struct vnode *r1 = p1->p_cwdi->cwdi_rdir; 470 struct vnode *r2 = l2->l_proc->p_cwdi->cwdi_rdir; 471 472 if (r1 == NULL) 473 return (r2 == NULL); 474 else if (r2 == NULL) 475 return 1; 476 else 477 return vn_isunder(r1, r2, l2); 478 } 479 480 /* 481 * Find pathname of process's current directory. 482 * 483 * Use vfs vnode-to-name reverse cache; if that fails, fall back 484 * to reading directory contents. 485 */ 486 487 int 488 sys___getcwd(struct lwp *l, const struct sys___getcwd_args *uap, register_t *retval) 489 { 490 /* { 491 syscallarg(char *) bufp; 492 syscallarg(size_t) length; 493 } */ 494 495 int error; 496 char *path; 497 char *bp, *bend; 498 int len = SCARG(uap, length); 499 int lenused; 500 struct cwdinfo *cwdi; 501 502 if (len > MAXPATHLEN * 4) 503 len = MAXPATHLEN * 4; 504 else if (len < 2) 505 return ERANGE; 506 507 path = kmem_alloc(len, KM_SLEEP); 508 if (!path) 509 return ENOMEM; 510 511 bp = &path[len]; 512 bend = bp; 513 *(--bp) = '\0'; 514 515 /* 516 * 5th argument here is "max number of vnodes to traverse". 517 * Since each entry takes up at least 2 bytes in the output buffer, 518 * limit it to N/2 vnodes for an N byte buffer. 519 */ 520 cwdi = l->l_proc->p_cwdi; 521 rw_enter(&cwdi->cwdi_lock, RW_READER); 522 error = getcwd_common(cwdi->cwdi_cdir, NULL, &bp, path, 523 len/2, GETCWD_CHECK_ACCESS, l); 524 rw_exit(&cwdi->cwdi_lock); 525 526 if (error) 527 goto out; 528 lenused = bend - bp; 529 *retval = lenused; 530 /* put the result into user buffer */ 531 error = copyout(bp, SCARG(uap, bufp), lenused); 532 533 out: 534 kmem_free(path, len); 535 return error; 536 } 537 538 /* 539 * Try to find a pathname for a vnode. Since there is no mapping 540 * vnode -> parent directory, this needs the NAMECACHE_ENTER_REVERSE 541 * option to work (to make cache_revlookup succeed). Caller holds a 542 * reference to the vnode. 543 */ 544 int 545 vnode_to_path(char *path, size_t len, struct vnode *vp, struct lwp *curl, 546 struct proc *p) 547 { 548 struct proc *curp = curl->l_proc; 549 int error, lenused, elen; 550 char *bp, *bend; 551 struct vnode *dvp; 552 553 KASSERT(vp->v_usecount > 0); 554 555 bp = bend = &path[len]; 556 *(--bp) = '\0'; 557 558 error = vn_lock(vp, LK_EXCLUSIVE | LK_RETRY); 559 if (error != 0) 560 return error; 561 error = cache_revlookup(vp, &dvp, &bp, path); 562 VOP_UNLOCK(vp); 563 if (error != 0) 564 return (error == -1 ? ENOENT : error); 565 566 *(--bp) = '/'; 567 error = getcwd_common(dvp, NULL, &bp, path, len / 2, 568 GETCWD_CHECK_ACCESS, curl); 569 vrele(dvp); 570 571 /* 572 * Strip off emulation path for emulated processes looking at 573 * the maps file of a process of the same emulation. (Won't 574 * work if /emul/xxx is a symlink..) 575 */ 576 if (curp->p_emul == p->p_emul && curp->p_emul->e_path != NULL) { 577 elen = strlen(curp->p_emul->e_path); 578 if (!strncmp(bp, curp->p_emul->e_path, elen)) 579 bp = &bp[elen]; 580 } 581 582 lenused = bend - bp; 583 584 memcpy(path, bp, lenused); 585 path[lenused] = 0; 586 587 return 0; 588 } 589