1 /* $NetBSD: vfs_getcwd.c,v 1.50 2014/02/07 15:29:22 hannken 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 1.50 2014/02/07 15:29:22 hannken 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 /* At this point, lvp is locked */ 136 error = VOP_LOOKUP(lvp, uvpp, &cn); 137 vput(lvp); 138 if (error) { 139 *lvpp = NULL; 140 *uvpp = NULL; 141 return error; 142 } 143 uvp = *uvpp; 144 /* Now lvp is unlocked, try to lock uvp */ 145 error = vn_lock(uvp, LK_EXCLUSIVE); 146 if (error) { 147 *lvpp = NULL; 148 *uvpp = NULL; 149 return error; 150 } 151 152 /* If we don't care about the pathname, we're done */ 153 if (bufp == NULL) { 154 *lvpp = NULL; 155 return 0; 156 } 157 158 fileno = va.va_fileid; 159 160 /* I guess UFS_DIRBLKSIZ is a good guess at a good size to use? */ 161 dirbuflen = UFS_DIRBLKSIZ; 162 if (dirbuflen < va.va_blocksize) 163 dirbuflen = va.va_blocksize; 164 dirbuf = kmem_alloc(dirbuflen, KM_SLEEP); 165 166 #if 0 167 unionread: 168 #endif 169 off = 0; 170 do { 171 /* call VOP_READDIR of parent */ 172 iov.iov_base = dirbuf; 173 iov.iov_len = dirbuflen; 174 175 uio.uio_iov = &iov; 176 uio.uio_iovcnt = 1; 177 uio.uio_offset = off; 178 uio.uio_resid = dirbuflen; 179 uio.uio_rw = UIO_READ; 180 UIO_SETUP_SYSSPACE(&uio); 181 182 eofflag = 0; 183 184 error = VOP_READDIR(uvp, &uio, cred, &eofflag, 0, 0); 185 186 off = uio.uio_offset; 187 188 /* 189 * Try again if NFS tosses its cookies. 190 * XXX this can still loop forever if the directory is busted 191 * such that the second or subsequent page of it always 192 * returns EINVAL 193 */ 194 if ((error == EINVAL) && (tries < 3)) { 195 off = 0; 196 tries++; 197 continue; /* once more, with feeling */ 198 } 199 200 if (!error) { 201 char *cpos; 202 struct dirent *dp; 203 204 cpos = dirbuf; 205 tries = 0; 206 207 /* scan directory page looking for matching vnode */ 208 for (len = (dirbuflen - uio.uio_resid); len > 0; 209 len -= reclen) { 210 dp = (struct dirent *) cpos; 211 reclen = dp->d_reclen; 212 213 /* check for malformed directory.. */ 214 if (reclen < _DIRENT_MINSIZE(dp)) { 215 error = EINVAL; 216 goto out; 217 } 218 /* 219 * XXX should perhaps do VOP_LOOKUP to 220 * check that we got back to the right place, 221 * but getting the locking games for that 222 * right would be heinous. 223 */ 224 if ((dp->d_type != DT_WHT) && 225 (dp->d_fileno == fileno)) { 226 char *bp = *bpp; 227 228 bp -= dp->d_namlen; 229 if (bp <= bufp) { 230 error = ERANGE; 231 goto out; 232 } 233 memcpy(bp, dp->d_name, dp->d_namlen); 234 error = 0; 235 *bpp = bp; 236 goto out; 237 } 238 cpos += reclen; 239 } 240 } else 241 goto out; 242 } while (!eofflag); 243 #if 0 244 /* 245 * Deal with mount -o union, which unions only the 246 * root directory of the mount. 247 */ 248 if ((uvp->v_vflag & VV_ROOT) && 249 (uvp->v_mount->mnt_flag & MNT_UNION)) { 250 struct vnode *tvp = uvp; 251 252 uvp = uvp->v_mount->mnt_vnodecovered; 253 vput(tvp); 254 vref(uvp); 255 *uvpp = uvp; 256 vn_lock(uvp, LK_EXCLUSIVE | LK_RETRY); 257 goto unionread; 258 } 259 #endif 260 error = ENOENT; 261 262 out: 263 *lvpp = NULL; 264 kmem_free(dirbuf, dirbuflen); 265 return error; 266 } 267 268 /* 269 * Look in the vnode-to-name reverse cache to see if 270 * we can find things the easy way. 271 * 272 * XXX vget failure path is untested. 273 * 274 * On entry, *lvpp is a locked vnode reference. 275 * On exit, one of the following is the case: 276 * 0) Both *lvpp and *uvpp are NULL and failure is returned. 277 * 1) *uvpp is NULL, *lvpp remains locked and -1 is returned (cache miss) 278 * 2) *uvpp is a locked vnode reference, *lvpp is vput and NULL'ed 279 * and 0 is returned (cache hit) 280 */ 281 282 static int 283 getcwd_getcache(struct vnode **lvpp, struct vnode **uvpp, char **bpp, 284 char *bufp) 285 { 286 struct vnode *lvp, *uvp = NULL; 287 int error; 288 289 lvp = *lvpp; 290 291 /* 292 * This returns 0 on a cache hit, -1 on a clean cache miss, 293 * or an errno on other failure. 294 */ 295 error = cache_revlookup(lvp, uvpp, bpp, bufp); 296 if (error) { 297 if (error != -1) { 298 vput(lvp); 299 *lvpp = NULL; 300 *uvpp = NULL; 301 } 302 return error; 303 } 304 uvp = *uvpp; 305 306 /* 307 * Since we're going up, we have to release the current lock 308 * before we take the parent lock. 309 */ 310 311 VOP_UNLOCK(lvp); 312 vn_lock(uvp, LK_EXCLUSIVE | LK_RETRY); 313 vrele(lvp); 314 *lvpp = NULL; 315 316 return error; 317 } 318 319 /* 320 * common routine shared by sys___getcwd() and vn_isunder() 321 */ 322 323 int 324 getcwd_common(struct vnode *lvp, struct vnode *rvp, char **bpp, char *bufp, 325 int limit, int flags, struct lwp *l) 326 { 327 struct cwdinfo *cwdi = l->l_proc->p_cwdi; 328 kauth_cred_t cred = l->l_cred; 329 struct vnode *uvp = NULL; 330 char *bp = NULL; 331 int error; 332 int perms = VEXEC; 333 334 error = 0; 335 if (rvp == NULL) { 336 rvp = cwdi->cwdi_rdir; 337 if (rvp == NULL) 338 rvp = rootvnode; 339 } 340 341 vref(rvp); 342 vref(lvp); 343 344 /* 345 * Error handling invariant: 346 * Before a `goto out': 347 * lvp is either NULL, or locked and held. 348 * uvp is either NULL, or locked and held. 349 */ 350 351 vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY); 352 if (bufp) 353 bp = *bpp; 354 355 /* 356 * this loop will terminate when one of the following happens: 357 * - we hit the root 358 * - getdirentries or lookup fails 359 * - we run out of space in the buffer. 360 */ 361 if (lvp == rvp) { 362 if (bp) 363 *(--bp) = '/'; 364 goto out; 365 } 366 do { 367 /* 368 * access check here is optional, depending on 369 * whether or not caller cares. 370 */ 371 if (flags & GETCWD_CHECK_ACCESS) { 372 error = VOP_ACCESS(lvp, perms, cred); 373 if (error) 374 goto out; 375 perms = VEXEC|VREAD; 376 } 377 378 /* 379 * step up if we're a covered vnode.. 380 */ 381 while (lvp->v_vflag & VV_ROOT) { 382 struct vnode *tvp; 383 384 if (lvp == rvp) 385 goto out; 386 387 tvp = lvp; 388 lvp = lvp->v_mount->mnt_vnodecovered; 389 vput(tvp); 390 /* 391 * hodie natus est radici frater 392 */ 393 if (lvp == NULL) { 394 error = ENOENT; 395 goto out; 396 } 397 vref(lvp); 398 error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY); 399 if (error != 0) { 400 vrele(lvp); 401 lvp = NULL; 402 goto out; 403 } 404 } 405 /* 406 * Look in the name cache; if that fails, look in the 407 * directory.. 408 */ 409 error = getcwd_getcache(&lvp, &uvp, &bp, bufp); 410 if (error == -1) { 411 if (lvp->v_type != VDIR) { 412 error = ENOTDIR; 413 goto out; 414 } 415 error = getcwd_scandir(&lvp, &uvp, &bp, bufp, l); 416 } 417 if (error) 418 goto out; 419 #if DIAGNOSTIC 420 if (lvp != NULL) 421 panic("getcwd: oops, forgot to null lvp"); 422 if (bufp && (bp <= bufp)) { 423 panic("getcwd: oops, went back too far"); 424 } 425 #endif 426 if (bp) 427 *(--bp) = '/'; 428 lvp = uvp; 429 uvp = NULL; 430 limit--; 431 } while ((lvp != rvp) && (limit > 0)); 432 433 out: 434 if (bpp) 435 *bpp = bp; 436 if (uvp) 437 vput(uvp); 438 if (lvp) 439 vput(lvp); 440 vrele(rvp); 441 return error; 442 } 443 444 /* 445 * Check if one directory can be found inside another in the directory 446 * hierarchy. 447 * 448 * Intended to be used in chroot, chdir, fchdir, etc., to ensure that 449 * chroot() actually means something. 450 */ 451 int 452 vn_isunder(struct vnode *lvp, struct vnode *rvp, struct lwp *l) 453 { 454 int error; 455 456 error = getcwd_common(lvp, rvp, NULL, NULL, MAXPATHLEN / 2, 0, l); 457 458 if (!error) 459 return 1; 460 else 461 return 0; 462 } 463 464 /* 465 * Returns true if proc p1's root directory equal to or under p2's 466 * root directory. 467 * 468 * Intended to be used from ptrace/procfs sorts of things. 469 */ 470 471 int 472 proc_isunder(struct proc *p1, struct lwp *l2) 473 { 474 struct vnode *r1 = p1->p_cwdi->cwdi_rdir; 475 struct vnode *r2 = l2->l_proc->p_cwdi->cwdi_rdir; 476 477 if (r1 == NULL) 478 return (r2 == NULL); 479 else if (r2 == NULL) 480 return 1; 481 else 482 return vn_isunder(r1, r2, l2); 483 } 484 485 /* 486 * Find pathname of process's current directory. 487 * 488 * Use vfs vnode-to-name reverse cache; if that fails, fall back 489 * to reading directory contents. 490 */ 491 492 int 493 sys___getcwd(struct lwp *l, const struct sys___getcwd_args *uap, register_t *retval) 494 { 495 /* { 496 syscallarg(char *) bufp; 497 syscallarg(size_t) length; 498 } */ 499 500 int error; 501 char *path; 502 char *bp, *bend; 503 int len = SCARG(uap, length); 504 int lenused; 505 struct cwdinfo *cwdi; 506 507 if (len > MAXPATHLEN * 4) 508 len = MAXPATHLEN * 4; 509 else if (len < 2) 510 return ERANGE; 511 512 path = kmem_alloc(len, KM_SLEEP); 513 if (!path) 514 return ENOMEM; 515 516 bp = &path[len]; 517 bend = bp; 518 *(--bp) = '\0'; 519 520 /* 521 * 5th argument here is "max number of vnodes to traverse". 522 * Since each entry takes up at least 2 bytes in the output buffer, 523 * limit it to N/2 vnodes for an N byte buffer. 524 */ 525 cwdi = l->l_proc->p_cwdi; 526 rw_enter(&cwdi->cwdi_lock, RW_READER); 527 error = getcwd_common(cwdi->cwdi_cdir, NULL, &bp, path, 528 len/2, GETCWD_CHECK_ACCESS, l); 529 rw_exit(&cwdi->cwdi_lock); 530 531 if (error) 532 goto out; 533 lenused = bend - bp; 534 *retval = lenused; 535 /* put the result into user buffer */ 536 error = copyout(bp, SCARG(uap, bufp), lenused); 537 538 out: 539 kmem_free(path, len); 540 return error; 541 } 542 543 /* 544 * Try to find a pathname for a vnode. Since there is no mapping 545 * vnode -> parent directory, this needs the NAMECACHE_ENTER_REVERSE 546 * option to work (to make cache_revlookup succeed). Caller holds a 547 * reference to the vnode. 548 */ 549 int 550 vnode_to_path(char *path, size_t len, struct vnode *vp, struct lwp *curl, 551 struct proc *p) 552 { 553 struct proc *curp = curl->l_proc; 554 int error, lenused, elen; 555 char *bp, *bend; 556 struct vnode *dvp; 557 558 KASSERT(vp->v_usecount > 0); 559 560 bp = bend = &path[len]; 561 *(--bp) = '\0'; 562 563 error = vn_lock(vp, LK_EXCLUSIVE | LK_RETRY); 564 if (error != 0) 565 return error; 566 error = cache_revlookup(vp, &dvp, &bp, path); 567 VOP_UNLOCK(vp); 568 if (error != 0) 569 return (error == -1 ? ENOENT : error); 570 571 *(--bp) = '/'; 572 error = getcwd_common(dvp, NULL, &bp, path, len / 2, 573 GETCWD_CHECK_ACCESS, curl); 574 vrele(dvp); 575 576 /* 577 * Strip off emulation path for emulated processes looking at 578 * the maps file of a process of the same emulation. (Won't 579 * work if /emul/xxx is a symlink..) 580 */ 581 if (curp->p_emul == p->p_emul && curp->p_emul->e_path != NULL) { 582 elen = strlen(curp->p_emul->e_path); 583 if (!strncmp(bp, curp->p_emul->e_path, elen)) 584 bp = &bp[elen]; 585 } 586 587 lenused = bend - bp; 588 589 memcpy(path, bp, lenused); 590 path[lenused] = 0; 591 592 return 0; 593 } 594