1 /* $NetBSD: vfs_getcwd.c,v 1.27 2005/06/05 23:47:48 thorpej 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 1.27 2005/06/05 23:47:48 thorpej 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 <ufs/ufs/dir.h> /* XXX only for DIRBLKSIZ */ 56 57 #include <sys/sa.h> 58 #include <sys/syscallargs.h> 59 60 #define DIRENT_MINSIZE (sizeof(struct dirent) - (MAXNAMLEN + 1) + 4) 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 proc *p) 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 struct componentname cn; 114 int len, reclen; 115 tries = 0; 116 117 /* 118 * If we want the filename, get some info we need while the 119 * current directory is still locked. 120 */ 121 if (bufp != NULL) { 122 error = VOP_GETATTR(lvp, &va, p->p_ucred, p); 123 if (error) { 124 vput(lvp); 125 *lvpp = NULL; 126 *uvpp = NULL; 127 return error; 128 } 129 } 130 131 /* 132 * Ok, we have to do it the hard way.. 133 * Next, get parent vnode using lookup of .. 134 */ 135 cn.cn_nameiop = LOOKUP; 136 cn.cn_flags = ISLASTCN | ISDOTDOT | RDONLY; 137 cn.cn_proc = p; 138 cn.cn_cred = p->p_ucred; 139 cn.cn_pnbuf = NULL; 140 cn.cn_nameptr = ".."; 141 cn.cn_namelen = 2; 142 cn.cn_hash = 0; 143 cn.cn_consume = 0; 144 145 /* 146 * At this point, lvp is locked and will be unlocked by the lookup. 147 * On successful return, *uvpp will be locked 148 */ 149 error = VOP_LOOKUP(lvp, uvpp, &cn); 150 if (error) { 151 vput(lvp); 152 *lvpp = NULL; 153 *uvpp = NULL; 154 return error; 155 } 156 uvp = *uvpp; 157 158 /* If we don't care about the pathname, we're done */ 159 if (bufp == NULL) { 160 vrele(lvp); 161 *lvpp = NULL; 162 return 0; 163 } 164 165 fileno = va.va_fileid; 166 167 dirbuflen = DIRBLKSIZ; 168 if (dirbuflen < va.va_blocksize) 169 dirbuflen = va.va_blocksize; 170 dirbuf = (char *)malloc(dirbuflen, M_TEMP, M_WAITOK); 171 172 #if 0 173 unionread: 174 #endif 175 off = 0; 176 do { 177 /* call VOP_READDIR of parent */ 178 iov.iov_base = dirbuf; 179 iov.iov_len = dirbuflen; 180 181 uio.uio_iov = &iov; 182 uio.uio_iovcnt = 1; 183 uio.uio_offset = off; 184 uio.uio_resid = dirbuflen; 185 uio.uio_segflg = UIO_SYSSPACE; 186 uio.uio_rw = UIO_READ; 187 uio.uio_procp = NULL; 188 189 eofflag = 0; 190 191 error = VOP_READDIR(uvp, &uio, p->p_ucred, &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) { 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 proc *p) 359 { 360 struct cwdinfo *cwdi = p->p_cwdi; 361 struct vnode *uvp = NULL; 362 char *bp = NULL; 363 int error; 364 int perms = VEXEC; 365 366 if (rvp == NULL) { 367 rvp = cwdi->cwdi_rdir; 368 if (rvp == NULL) 369 rvp = rootvnode; 370 } 371 372 VREF(rvp); 373 VREF(lvp); 374 375 /* 376 * Error handling invariant: 377 * Before a `goto out': 378 * lvp is either NULL, or locked and held. 379 * uvp is either NULL, or locked and held. 380 */ 381 382 error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY); 383 if (error) { 384 vrele(lvp); 385 lvp = NULL; 386 goto out; 387 } 388 if (bufp) 389 bp = *bpp; 390 /* 391 * this loop will terminate when one of the following happens: 392 * - we hit the root 393 * - getdirentries or lookup fails 394 * - we run out of space in the buffer. 395 */ 396 if (lvp == rvp) { 397 if (bp) 398 *(--bp) = '/'; 399 goto out; 400 } 401 do { 402 if (lvp->v_type != VDIR) { 403 error = ENOTDIR; 404 goto out; 405 } 406 407 /* 408 * access check here is optional, depending on 409 * whether or not caller cares. 410 */ 411 if (flags & GETCWD_CHECK_ACCESS) { 412 error = VOP_ACCESS(lvp, perms, p->p_ucred, p); 413 if (error) 414 goto out; 415 perms = VEXEC|VREAD; 416 } 417 418 /* 419 * step up if we're a covered vnode.. 420 */ 421 while (lvp->v_flag & VROOT) { 422 struct vnode *tvp; 423 424 if (lvp == rvp) 425 goto out; 426 427 tvp = lvp; 428 lvp = lvp->v_mount->mnt_vnodecovered; 429 vput(tvp); 430 /* 431 * hodie natus est radici frater 432 */ 433 if (lvp == NULL) { 434 error = ENOENT; 435 goto out; 436 } 437 VREF(lvp); 438 error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY); 439 if (error != 0) { 440 vrele(lvp); 441 lvp = NULL; 442 goto out; 443 } 444 } 445 /* 446 * Look in the name cache; if that fails, look in the 447 * directory.. 448 */ 449 error = getcwd_getcache(&lvp, &uvp, &bp, bufp); 450 if (error == -1) 451 error = getcwd_scandir(&lvp, &uvp, &bp, bufp, p); 452 if (error) 453 goto out; 454 #if DIAGNOSTIC 455 if (lvp != NULL) 456 panic("getcwd: oops, forgot to null lvp"); 457 if (bufp && (bp <= bufp)) { 458 panic("getcwd: oops, went back too far"); 459 } 460 #endif 461 if (bp) 462 *(--bp) = '/'; 463 lvp = uvp; 464 uvp = NULL; 465 limit--; 466 } while ((lvp != rvp) && (limit > 0)); 467 468 out: 469 if (bpp) 470 *bpp = bp; 471 if (uvp) 472 vput(uvp); 473 if (lvp) 474 vput(lvp); 475 vrele(rvp); 476 return error; 477 } 478 479 /* 480 * Check if one directory can be found inside another in the directory 481 * hierarchy. 482 * 483 * Intended to be used in chroot, chdir, fchdir, etc., to ensure that 484 * chroot() actually means something. 485 */ 486 int 487 vn_isunder(struct vnode *lvp, struct vnode *rvp, struct proc *p) 488 { 489 int error; 490 491 error = getcwd_common(lvp, rvp, NULL, NULL, MAXPATHLEN / 2, 0, p); 492 493 if (!error) 494 return 1; 495 else 496 return 0; 497 } 498 499 /* 500 * Returns true if proc p1's root directory equal to or under p2's 501 * root directory. 502 * 503 * Intended to be used from ptrace/procfs sorts of things. 504 */ 505 506 int 507 proc_isunder(struct proc *p1, struct proc *p2) 508 { 509 struct vnode *r1 = p1->p_cwdi->cwdi_rdir; 510 struct vnode *r2 = p2->p_cwdi->cwdi_rdir; 511 512 if (r1 == NULL) 513 return (r2 == NULL); 514 else if (r2 == NULL) 515 return 1; 516 else 517 return vn_isunder(r1, r2, p2); 518 } 519 520 /* 521 * Find pathname of process's current directory. 522 * 523 * Use vfs vnode-to-name reverse cache; if that fails, fall back 524 * to reading directory contents. 525 */ 526 527 int 528 sys___getcwd(struct lwp *l, void *v, register_t *retval) 529 { 530 struct sys___getcwd_args /* { 531 syscallarg(char *) bufp; 532 syscallarg(size_t) length; 533 } */ *uap = v; 534 535 int error; 536 char *path; 537 char *bp, *bend; 538 int len = SCARG(uap, length); 539 int lenused; 540 541 if (len > MAXPATHLEN * 4) 542 len = MAXPATHLEN * 4; 543 else if (len < 2) 544 return ERANGE; 545 546 path = (char *)malloc(len, M_TEMP, M_WAITOK); 547 if (!path) 548 return ENOMEM; 549 550 bp = &path[len]; 551 bend = bp; 552 *(--bp) = '\0'; 553 554 /* 555 * 5th argument here is "max number of vnodes to traverse". 556 * Since each entry takes up at least 2 bytes in the output buffer, 557 * limit it to N/2 vnodes for an N byte buffer. 558 */ 559 error = getcwd_common(l->l_proc->p_cwdi->cwdi_cdir, NULL, &bp, path, 560 len / 2, GETCWD_CHECK_ACCESS, l->l_proc); 561 562 if (error) 563 goto out; 564 lenused = bend - bp; 565 *retval = lenused; 566 /* put the result into user buffer */ 567 error = copyout(bp, SCARG(uap, bufp), lenused); 568 569 out: 570 free(path, M_TEMP); 571 return error; 572 } 573