1 /* $NetBSD: vfs_getcwd.c,v 1.31 2006/05/14 21:15:12 elad 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 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the NetBSD 21 * Foundation, Inc. and its contributors. 22 * 4. Neither the name of The NetBSD Foundation nor the names of its 23 * contributors may be used to endorse or promote products derived 24 * from this software without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 27 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 28 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 29 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 30 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 31 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 32 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 33 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 34 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 35 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 36 * POSSIBILITY OF SUCH DAMAGE. 37 */ 38 39 #include <sys/cdefs.h> 40 __KERNEL_RCSID(0, "$NetBSD: vfs_getcwd.c,v 1.31 2006/05/14 21:15:12 elad Exp $"); 41 42 #include <sys/param.h> 43 #include <sys/systm.h> 44 #include <sys/namei.h> 45 #include <sys/filedesc.h> 46 #include <sys/kernel.h> 47 #include <sys/file.h> 48 #include <sys/stat.h> 49 #include <sys/vnode.h> 50 #include <sys/mount.h> 51 #include <sys/proc.h> 52 #include <sys/uio.h> 53 #include <sys/malloc.h> 54 #include <sys/dirent.h> 55 #include <sys/kauth.h> 56 57 #include <ufs/ufs/dir.h> /* XXX only for DIRBLKSIZ */ 58 59 #include <sys/sa.h> 60 #include <sys/syscallargs.h> 61 62 /* 63 * Vnode variable naming conventions in this file: 64 * 65 * rvp: the current root we're aiming towards. 66 * lvp, *lvpp: the "lower" vnode 67 * uvp, *uvpp: the "upper" vnode. 68 * 69 * Since all the vnodes we're dealing with are directories, and the 70 * lookups are going *up* in the filesystem rather than *down*, the 71 * usual "pvp" (parent) or "dvp" (directory) naming conventions are 72 * too confusing. 73 */ 74 75 /* 76 * XXX Will infinite loop in certain cases if a directory read reliably 77 * returns EINVAL on last block. 78 * XXX is EINVAL the right thing to return if a directory is malformed? 79 */ 80 81 /* 82 * XXX Untested vs. mount -o union; probably does the wrong thing. 83 */ 84 85 /* 86 * Find parent vnode of *lvpp, return in *uvpp 87 * 88 * If we care about the name, scan it looking for name of directory 89 * entry pointing at lvp. 90 * 91 * Place the name in the buffer which starts at bufp, immediately 92 * before *bpp, and move bpp backwards to point at the start of it. 93 * 94 * On entry, *lvpp is a locked vnode reference; on exit, it is vput and NULL'ed 95 * On exit, *uvpp is either NULL or is a locked vnode reference. 96 */ 97 static int 98 getcwd_scandir(struct vnode **lvpp, struct vnode **uvpp, char **bpp, 99 char *bufp, struct lwp *l) 100 { 101 int error = 0; 102 int eofflag; 103 off_t off; 104 int tries; 105 struct uio uio; 106 struct iovec iov; 107 char *dirbuf = NULL; 108 int dirbuflen; 109 ino_t fileno; 110 struct vattr va; 111 struct vnode *uvp = NULL; 112 struct vnode *lvp = *lvpp; 113 kauth_cred_t cred = l->l_proc->p_cred; 114 struct componentname cn; 115 int len, reclen; 116 tries = 0; 117 118 /* 119 * If we want the filename, get some info we need while the 120 * current directory is still locked. 121 */ 122 if (bufp != NULL) { 123 error = VOP_GETATTR(lvp, &va, cred, l); 124 if (error) { 125 vput(lvp); 126 *lvpp = NULL; 127 *uvpp = NULL; 128 return error; 129 } 130 } 131 132 /* 133 * Ok, we have to do it the hard way.. 134 * Next, get parent vnode using lookup of .. 135 */ 136 cn.cn_nameiop = LOOKUP; 137 cn.cn_flags = ISLASTCN | ISDOTDOT | RDONLY; 138 cn.cn_lwp = l; 139 cn.cn_cred = cred; 140 cn.cn_pnbuf = NULL; 141 cn.cn_nameptr = ".."; 142 cn.cn_namelen = 2; 143 cn.cn_hash = 0; 144 cn.cn_consume = 0; 145 146 /* 147 * At this point, lvp is locked and will be unlocked by the lookup. 148 * On successful return, *uvpp will be locked 149 */ 150 error = VOP_LOOKUP(lvp, uvpp, &cn); 151 if (error) { 152 vput(lvp); 153 *lvpp = NULL; 154 *uvpp = NULL; 155 return error; 156 } 157 uvp = *uvpp; 158 159 /* If we don't care about the pathname, we're done */ 160 if (bufp == NULL) { 161 vrele(lvp); 162 *lvpp = NULL; 163 return 0; 164 } 165 166 fileno = va.va_fileid; 167 168 dirbuflen = DIRBLKSIZ; 169 if (dirbuflen < va.va_blocksize) 170 dirbuflen = va.va_blocksize; 171 dirbuf = (char *)malloc(dirbuflen, M_TEMP, M_WAITOK); 172 173 #if 0 174 unionread: 175 #endif 176 off = 0; 177 do { 178 /* call VOP_READDIR of parent */ 179 iov.iov_base = dirbuf; 180 iov.iov_len = dirbuflen; 181 182 uio.uio_iov = &iov; 183 uio.uio_iovcnt = 1; 184 uio.uio_offset = off; 185 uio.uio_resid = dirbuflen; 186 uio.uio_rw = UIO_READ; 187 UIO_SETUP_SYSSPACE(&uio); 188 189 eofflag = 0; 190 191 error = VOP_READDIR(uvp, &uio, cred, &eofflag, 0, 0); 192 193 off = uio.uio_offset; 194 195 /* 196 * Try again if NFS tosses its cookies. 197 * XXX this can still loop forever if the directory is busted 198 * such that the second or subsequent page of it always 199 * returns EINVAL 200 */ 201 if ((error == EINVAL) && (tries < 3)) { 202 off = 0; 203 tries++; 204 continue; /* once more, with feeling */ 205 } 206 207 if (!error) { 208 char *cpos; 209 struct dirent *dp; 210 211 cpos = dirbuf; 212 tries = 0; 213 214 /* scan directory page looking for matching vnode */ 215 for (len = (dirbuflen - uio.uio_resid); len > 0; 216 len -= reclen) { 217 dp = (struct dirent *) cpos; 218 reclen = dp->d_reclen; 219 220 /* check for malformed directory.. */ 221 if (reclen < _DIRENT_MINSIZE(dp)) { 222 error = EINVAL; 223 goto out; 224 } 225 /* 226 * XXX should perhaps do VOP_LOOKUP to 227 * check that we got back to the right place, 228 * but getting the locking games for that 229 * right would be heinous. 230 */ 231 if ((dp->d_type != DT_WHT) && 232 (dp->d_fileno == fileno)) { 233 char *bp = *bpp; 234 235 bp -= dp->d_namlen; 236 if (bp <= bufp) { 237 error = ERANGE; 238 goto out; 239 } 240 memcpy(bp, dp->d_name, dp->d_namlen); 241 error = 0; 242 *bpp = bp; 243 goto out; 244 } 245 cpos += reclen; 246 } 247 } else 248 goto out; 249 } while (!eofflag); 250 #if 0 251 /* 252 * Deal with mount -o union, which unions only the 253 * root directory of the mount. 254 */ 255 if ((uvp->v_flag & VROOT) && 256 (uvp->v_mount->mnt_flag & MNT_UNION)) { 257 struct vnode *tvp = uvp; 258 259 uvp = uvp->v_mount->mnt_vnodecovered; 260 vput(tvp); 261 VREF(uvp); 262 *uvpp = uvp; 263 error = vn_lock(uvp, LK_EXCLUSIVE | LK_RETRY); 264 if (error != 0) { 265 vrele(uvp); 266 *uvpp = uvp = NULL; 267 goto out; 268 } 269 goto unionread; 270 } 271 #endif 272 error = ENOENT; 273 274 out: 275 vrele(lvp); 276 *lvpp = NULL; 277 free(dirbuf, M_TEMP); 278 return error; 279 } 280 281 /* 282 * Look in the vnode-to-name reverse cache to see if 283 * we can find things the easy way. 284 * 285 * XXX vget failure path is untested. 286 * 287 * On entry, *lvpp is a locked vnode reference. 288 * On exit, one of the following is the case: 289 * 0) Both *lvpp and *uvpp are NULL and failure is returned. 290 * 1) *uvpp is NULL, *lvpp remains locked and -1 is returned (cache miss) 291 * 2) *uvpp is a locked vnode reference, *lvpp is vput and NULL'ed 292 * and 0 is returned (cache hit) 293 */ 294 295 static int 296 getcwd_getcache(struct vnode **lvpp, struct vnode **uvpp, char **bpp, 297 char *bufp) 298 { 299 struct vnode *lvp, *uvp = NULL; 300 char *obp = *bpp; 301 int error; 302 303 lvp = *lvpp; 304 305 /* 306 * This returns 0 on a cache hit, -1 on a clean cache miss, 307 * or an errno on other failure. 308 */ 309 error = cache_revlookup(lvp, uvpp, bpp, bufp); 310 if (error) { 311 if (error != -1) { 312 vput(lvp); 313 *lvpp = NULL; 314 *uvpp = NULL; 315 } 316 return error; 317 } 318 uvp = *uvpp; 319 320 /* 321 * Since we're going up, we have to release the current lock 322 * before we take the parent lock. 323 */ 324 325 VOP_UNLOCK(lvp, 0); 326 327 error = vget(uvp, LK_EXCLUSIVE | LK_RETRY); 328 /* 329 * Verify that vget succeeded while we were waiting for the 330 * lock. 331 */ 332 if (error) { 333 /* 334 * Oops, we missed. If the vget failed try to get our 335 * lock back; if that works, rewind the `bp' and tell 336 * caller to try things the hard way, otherwise give 337 * up. 338 */ 339 *uvpp = NULL; 340 error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY); 341 if (error == 0) { 342 *bpp = obp; 343 return -1; 344 } 345 } 346 vrele(lvp); 347 *lvpp = NULL; 348 349 return error; 350 } 351 352 /* 353 * common routine shared by sys___getcwd() and vn_isunder() 354 */ 355 356 int 357 getcwd_common(struct vnode *lvp, struct vnode *rvp, char **bpp, char *bufp, 358 int limit, int flags, struct lwp *l) 359 { 360 struct cwdinfo *cwdi = l->l_proc->p_cwdi; 361 kauth_cred_t cred = l->l_proc->p_cred; 362 struct vnode *uvp = NULL; 363 char *bp = NULL; 364 int error; 365 int perms = VEXEC; 366 367 if (rvp == NULL) { 368 rvp = cwdi->cwdi_rdir; 369 if (rvp == NULL) 370 rvp = rootvnode; 371 } 372 373 VREF(rvp); 374 VREF(lvp); 375 376 /* 377 * Error handling invariant: 378 * Before a `goto out': 379 * lvp is either NULL, or locked and held. 380 * uvp is either NULL, or locked and held. 381 */ 382 383 error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY); 384 if (error) { 385 vrele(lvp); 386 lvp = NULL; 387 goto out; 388 } 389 if (bufp) 390 bp = *bpp; 391 /* 392 * this loop will terminate when one of the following happens: 393 * - we hit the root 394 * - getdirentries or lookup fails 395 * - we run out of space in the buffer. 396 */ 397 if (lvp == rvp) { 398 if (bp) 399 *(--bp) = '/'; 400 goto out; 401 } 402 do { 403 if (lvp->v_type != VDIR) { 404 error = ENOTDIR; 405 goto out; 406 } 407 408 /* 409 * access check here is optional, depending on 410 * whether or not caller cares. 411 */ 412 if (flags & GETCWD_CHECK_ACCESS) { 413 error = VOP_ACCESS(lvp, perms, cred, l); 414 if (error) 415 goto out; 416 perms = VEXEC|VREAD; 417 } 418 419 /* 420 * step up if we're a covered vnode.. 421 */ 422 while (lvp->v_flag & VROOT) { 423 struct vnode *tvp; 424 425 if (lvp == rvp) 426 goto out; 427 428 tvp = lvp; 429 lvp = lvp->v_mount->mnt_vnodecovered; 430 vput(tvp); 431 /* 432 * hodie natus est radici frater 433 */ 434 if (lvp == NULL) { 435 error = ENOENT; 436 goto out; 437 } 438 VREF(lvp); 439 error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY); 440 if (error != 0) { 441 vrele(lvp); 442 lvp = NULL; 443 goto out; 444 } 445 } 446 /* 447 * Look in the name cache; if that fails, look in the 448 * directory.. 449 */ 450 error = getcwd_getcache(&lvp, &uvp, &bp, bufp); 451 if (error == -1) 452 error = getcwd_scandir(&lvp, &uvp, &bp, bufp, l); 453 if (error) 454 goto out; 455 #if DIAGNOSTIC 456 if (lvp != NULL) 457 panic("getcwd: oops, forgot to null lvp"); 458 if (bufp && (bp <= bufp)) { 459 panic("getcwd: oops, went back too far"); 460 } 461 #endif 462 if (bp) 463 *(--bp) = '/'; 464 lvp = uvp; 465 uvp = NULL; 466 limit--; 467 } while ((lvp != rvp) && (limit > 0)); 468 469 out: 470 if (bpp) 471 *bpp = bp; 472 if (uvp) 473 vput(uvp); 474 if (lvp) 475 vput(lvp); 476 vrele(rvp); 477 return error; 478 } 479 480 /* 481 * Check if one directory can be found inside another in the directory 482 * hierarchy. 483 * 484 * Intended to be used in chroot, chdir, fchdir, etc., to ensure that 485 * chroot() actually means something. 486 */ 487 int 488 vn_isunder(struct vnode *lvp, struct vnode *rvp, struct lwp *l) 489 { 490 int error; 491 492 error = getcwd_common(lvp, rvp, NULL, NULL, MAXPATHLEN / 2, 0, l); 493 494 if (!error) 495 return 1; 496 else 497 return 0; 498 } 499 500 /* 501 * Returns true if proc p1's root directory equal to or under p2's 502 * root directory. 503 * 504 * Intended to be used from ptrace/procfs sorts of things. 505 */ 506 507 int 508 proc_isunder(struct proc *p1, struct lwp *l2) 509 { 510 struct vnode *r1 = p1->p_cwdi->cwdi_rdir; 511 struct vnode *r2 = l2->l_proc->p_cwdi->cwdi_rdir; 512 513 if (r1 == NULL) 514 return (r2 == NULL); 515 else if (r2 == NULL) 516 return 1; 517 else 518 return vn_isunder(r1, r2, l2); 519 } 520 521 /* 522 * Find pathname of process's current directory. 523 * 524 * Use vfs vnode-to-name reverse cache; if that fails, fall back 525 * to reading directory contents. 526 */ 527 528 int 529 sys___getcwd(struct lwp *l, void *v, register_t *retval) 530 { 531 struct sys___getcwd_args /* { 532 syscallarg(char *) bufp; 533 syscallarg(size_t) length; 534 } */ *uap = v; 535 536 int error; 537 char *path; 538 char *bp, *bend; 539 int len = SCARG(uap, length); 540 int lenused; 541 542 if (len > MAXPATHLEN * 4) 543 len = MAXPATHLEN * 4; 544 else if (len < 2) 545 return ERANGE; 546 547 path = (char *)malloc(len, M_TEMP, M_WAITOK); 548 if (!path) 549 return ENOMEM; 550 551 bp = &path[len]; 552 bend = bp; 553 *(--bp) = '\0'; 554 555 /* 556 * 5th argument here is "max number of vnodes to traverse". 557 * Since each entry takes up at least 2 bytes in the output buffer, 558 * limit it to N/2 vnodes for an N byte buffer. 559 */ 560 error = getcwd_common(l->l_proc->p_cwdi->cwdi_cdir, NULL, &bp, path, 561 len/2, GETCWD_CHECK_ACCESS, l); 562 563 if (error) 564 goto out; 565 lenused = bend - bp; 566 *retval = lenused; 567 /* put the result into user buffer */ 568 error = copyout(bp, SCARG(uap, bufp), lenused); 569 570 out: 571 free(path, M_TEMP); 572 return error; 573 } 574