1 /* $OpenBSD: linux_getcwd.c,v 1.2 2001/05/16 12:50:21 ho Exp $ */
2 /* $NetBSD: vfs_getcwd.c,v 1.3.2.3 1999/07/11 10:24:09 sommerfeld Exp $ */
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 __FBSDID("$FreeBSD: src/sys/compat/linux/linux_getcwd.c,v 1.31 2008/10/28 13:44:11 trasz Exp $");
41
42 #include "opt_compat.h"
43 #include "opt_mac.h"
44
45 #include <sys/param.h>
46 #include <sys/systm.h>
47 #include <sys/namei.h>
48 #include <sys/filedesc.h>
49 #include <sys/kernel.h>
50 #include <sys/file.h>
51 #include <sys/stat.h>
52 #include <sys/syscallsubr.h>
53 #include <sys/vnode.h>
54 #include <sys/mount.h>
55 #include <sys/proc.h>
56 #include <sys/uio.h>
57 #include <sys/malloc.h>
58 #include <sys/dirent.h>
59 #include <ufs/ufs/dir.h> /* XXX only for DIRBLKSIZ */
60
61 #ifdef COMPAT_LINUX32
62 #include <machine/../linux32/linux.h>
63 #include <machine/../linux32/linux32_proto.h>
64 #else
65 #include <machine/../linux/linux.h>
66 #include <machine/../linux/linux_proto.h>
67 #endif
68 #include <compat/linux/linux_util.h>
69
70 #include <security/mac/mac_framework.h>
71
72 static int
73 linux_getcwd_scandir(struct vnode **, struct vnode **,
74 char **, char *, struct thread *);
75 static int
76 linux_getcwd_common(struct vnode *, struct vnode *,
77 char **, char *, int, int, struct thread *);
78
79 #define DIRENT_MINSIZE (sizeof(struct dirent) - (MAXNAMLEN+1) + 4)
80
81 /*
82 * Vnode variable naming conventions in this file:
83 *
84 * rvp: the current root we're aiming towards.
85 * lvp, *lvpp: the "lower" vnode
86 * uvp, *uvpp: the "upper" vnode.
87 *
88 * Since all the vnodes we're dealing with are directories, and the
89 * lookups are going *up* in the filesystem rather than *down*, the
90 * usual "pvp" (parent) or "dvp" (directory) naming conventions are
91 * too confusing.
92 */
93
94 /*
95 * XXX Will infinite loop in certain cases if a directory read reliably
96 * returns EINVAL on last block.
97 * XXX is EINVAL the right thing to return if a directory is malformed?
98 */
99
100 /*
101 * XXX Untested vs. mount -o union; probably does the wrong thing.
102 */
103
104 /*
105 * Find parent vnode of *lvpp, return in *uvpp
106 *
107 * If we care about the name, scan it looking for name of directory
108 * entry pointing at lvp.
109 *
110 * Place the name in the buffer which starts at bufp, immediately
111 * before *bpp, and move bpp backwards to point at the start of it.
112 *
113 * On entry, *lvpp is a locked vnode reference; on exit, it is vput and NULL'ed
114 * On exit, *uvpp is either NULL or is a locked vnode reference.
115 */
116 static int
117 linux_getcwd_scandir(lvpp, uvpp, bpp, bufp, td)
118 struct vnode **lvpp;
119 struct vnode **uvpp;
120 char **bpp;
121 char *bufp;
122 struct thread *td;
123 {
124 int error = 0;
125 int eofflag;
126 off_t off;
127 int tries;
128 struct uio uio;
129 struct iovec iov;
130 char *dirbuf = NULL;
131 int dirbuflen;
132 ino_t fileno;
133 struct vattr va;
134 struct vnode *uvp = NULL;
135 struct vnode *lvp = *lvpp;
136 struct componentname cn;
137 int len, reclen;
138 tries = 0;
139
140 /*
141 * If we want the filename, get some info we need while the
142 * current directory is still locked.
143 */
144 if (bufp != NULL) {
145 error = VOP_GETATTR(lvp, &va, td->td_ucred);
146 if (error) {
147 vput(lvp);
148 *lvpp = NULL;
149 *uvpp = NULL;
150 return error;
151 }
152 }
153
154 /*
155 * Ok, we have to do it the hard way..
156 * Next, get parent vnode using lookup of ..
157 */
158 cn.cn_nameiop = LOOKUP;
159 cn.cn_flags = ISLASTCN | ISDOTDOT | RDONLY;
160 cn.cn_thread = td;
161 cn.cn_cred = td->td_ucred;
162 cn.cn_pnbuf = NULL;
163 cn.cn_nameptr = "..";
164 cn.cn_namelen = 2;
165 cn.cn_consume = 0;
166 cn.cn_lkflags = LK_EXCLUSIVE;
167
168 /*
169 * At this point, lvp is locked and will be unlocked by the lookup.
170 * On successful return, *uvpp will be locked
171 */
172 #ifdef MAC
173 error = mac_vnode_check_lookup(td->td_ucred, lvp, &cn);
174 if (error == 0)
175 #endif
176 error = VOP_LOOKUP(lvp, uvpp, &cn);
177 if (error) {
178 vput(lvp);
179 *lvpp = NULL;
180 *uvpp = NULL;
181 return error;
182 }
183 uvp = *uvpp;
184
185 /* If we don't care about the pathname, we're done */
186 if (bufp == NULL) {
187 vput(lvp);
188 *lvpp = NULL;
189 return 0;
190 }
191
192 fileno = va.va_fileid;
193
194 dirbuflen = DIRBLKSIZ;
195 if (dirbuflen < va.va_blocksize)
196 dirbuflen = va.va_blocksize;
197 dirbuf = (char *)malloc(dirbuflen, M_TEMP, M_WAITOK);
198
199 #if 0
200 unionread:
201 #endif
202 off = 0;
203 do {
204 /* call VOP_READDIR of parent */
205 iov.iov_base = dirbuf;
206 iov.iov_len = dirbuflen;
207
208 uio.uio_iov = &iov;
209 uio.uio_iovcnt = 1;
210 uio.uio_offset = off;
211 uio.uio_resid = dirbuflen;
212 uio.uio_segflg = UIO_SYSSPACE;
213 uio.uio_rw = UIO_READ;
214 uio.uio_td = td;
215
216 eofflag = 0;
217
218 #ifdef MAC
219 error = mac_vnode_check_readdir(td->td_ucred, uvp);
220 if (error == 0)
221 #endif /* MAC */
222 error = VOP_READDIR(uvp, &uio, td->td_ucred, &eofflag,
223 0, 0);
224
225 off = uio.uio_offset;
226
227 /*
228 * Try again if NFS tosses its cookies.
229 * XXX this can still loop forever if the directory is busted
230 * such that the second or subsequent page of it always
231 * returns EINVAL
232 */
233 if ((error == EINVAL) && (tries < 3)) {
234 off = 0;
235 tries++;
236 continue; /* once more, with feeling */
237 }
238
239 if (!error) {
240 char *cpos;
241 struct dirent *dp;
242
243 cpos = dirbuf;
244 tries = 0;
245
246 /* scan directory page looking for matching vnode */
247 for (len = (dirbuflen - uio.uio_resid); len > 0; len -= reclen) {
248 dp = (struct dirent *) cpos;
249 reclen = dp->d_reclen;
250
251 /* check for malformed directory.. */
252 if (reclen < DIRENT_MINSIZE) {
253 error = EINVAL;
254 goto out;
255 }
256 /*
257 * XXX should perhaps do VOP_LOOKUP to
258 * check that we got back to the right place,
259 * but getting the locking games for that
260 * right would be heinous.
261 */
262 if ((dp->d_type != DT_WHT) &&
263 (dp->d_fileno == fileno)) {
264 char *bp = *bpp;
265 bp -= dp->d_namlen;
266
267 if (bp <= bufp) {
268 error = ERANGE;
269 goto out;
270 }
271 bcopy(dp->d_name, bp, dp->d_namlen);
272 error = 0;
273 *bpp = bp;
274 goto out;
275 }
276 cpos += reclen;
277 }
278 }
279 } while (!eofflag);
280 error = ENOENT;
281
282 out:
283 vput(lvp);
284 *lvpp = NULL;
285 free(dirbuf, M_TEMP);
286 return error;
287 }
288
289
290 /*
291 * common routine shared by sys___getcwd() and linux_vn_isunder()
292 */
293
294 #define GETCWD_CHECK_ACCESS 0x0001
295
296 static int
297 linux_getcwd_common (lvp, rvp, bpp, bufp, limit, flags, td)
298 struct vnode *lvp;
299 struct vnode *rvp;
300 char **bpp;
301 char *bufp;
302 int limit;
303 int flags;
304 struct thread *td;
305 {
306 struct filedesc *fdp = td->td_proc->p_fd;
307 struct vnode *uvp = NULL;
308 char *bp = NULL;
309 int error;
310 accmode_t accmode = VEXEC;
311
312 if (rvp == NULL) {
313 rvp = fdp->fd_rdir;
314 if (rvp == NULL)
315 rvp = rootvnode;
316 }
317
318 VREF(rvp);
319 VREF(lvp);
320
321 /*
322 * Error handling invariant:
323 * Before a `goto out':
324 * lvp is either NULL, or locked and held.
325 * uvp is either NULL, or locked and held.
326 */
327
328 error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY);
329 if (error != 0)
330 panic("vn_lock LK_RETRY returned error %d", error);
331 if (bufp)
332 bp = *bpp;
333 /*
334 * this loop will terminate when one of the following happens:
335 * - we hit the root
336 * - getdirentries or lookup fails
337 * - we run out of space in the buffer.
338 */
339 if (lvp == rvp) {
340 if (bp)
341 *(--bp) = '/';
342 goto out;
343 }
344 do {
345 if (lvp->v_type != VDIR) {
346 error = ENOTDIR;
347 goto out;
348 }
349
350 /*
351 * access check here is optional, depending on
352 * whether or not caller cares.
353 */
354 if (flags & GETCWD_CHECK_ACCESS) {
355 error = VOP_ACCESS(lvp, accmode, td->td_ucred, td);
356 if (error)
357 goto out;
358 accmode = VEXEC|VREAD;
359 }
360
361 /*
362 * step up if we're a covered vnode..
363 */
364 while (lvp->v_vflag & VV_ROOT) {
365 struct vnode *tvp;
366
367 if (lvp == rvp)
368 goto out;
369
370 tvp = lvp;
371 lvp = lvp->v_mount->mnt_vnodecovered;
372 vput(tvp);
373 /*
374 * hodie natus est radici frater
375 */
376 if (lvp == NULL) {
377 error = ENOENT;
378 goto out;
379 }
380 VREF(lvp);
381 error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY);
382 if (error != 0)
383 panic("vn_lock LK_RETRY returned %d", error);
384 }
385 error = linux_getcwd_scandir(&lvp, &uvp, &bp, bufp, td);
386 if (error)
387 goto out;
388 #ifdef DIAGNOSTIC
389 if (lvp != NULL)
390 panic("getcwd: oops, forgot to null lvp");
391 if (bufp && (bp <= bufp)) {
392 panic("getcwd: oops, went back too far");
393 }
394 #endif
395 if (bp)
396 *(--bp) = '/';
397 lvp = uvp;
398 uvp = NULL;
399 limit--;
400 } while ((lvp != rvp) && (limit > 0));
401
402 out:
403 if (bpp)
404 *bpp = bp;
405 if (uvp)
406 vput(uvp);
407 if (lvp)
408 vput(lvp);
409 vrele(rvp);
410 return error;
411 }
412
413
414 /*
415 * Find pathname of process's current directory.
416 *
417 * Use vfs vnode-to-name reverse cache; if that fails, fall back
418 * to reading directory contents.
419 */
420
421 int
422 linux_getcwd(struct thread *td, struct linux_getcwd_args *args)
423 {
424 caddr_t bp, bend, path;
425 int error, len, lenused;
426
427 #ifdef DEBUG
428 if (ldebug(getcwd))
429 printf(ARGS(getcwd, "%p, %ld"), args->buf, (long)args->bufsize);
430 #endif
431
432 len = args->bufsize;
433
434 if (len > MAXPATHLEN*4)
435 len = MAXPATHLEN*4;
436 else if (len < 2)
437 return ERANGE;
438
439 path = (char *)malloc(len, M_TEMP, M_WAITOK);
440
441 error = kern___getcwd(td, path, UIO_SYSSPACE, len);
442 if (!error) {
443 lenused = strlen(path) + 1;
444 if (lenused <= args->bufsize) {
445 td->td_retval[0] = lenused;
446 error = copyout(path, args->buf, lenused);
447 }
448 else
449 error = ERANGE;
450 } else {
451 bp = &path[len];
452 bend = bp;
453 *(--bp) = '\0';
454
455 /*
456 * 5th argument here is "max number of vnodes to traverse".
457 * Since each entry takes up at least 2 bytes in the output buffer,
458 * limit it to N/2 vnodes for an N byte buffer.
459 */
460
461 mtx_lock(&Giant);
462 error = linux_getcwd_common (td->td_proc->p_fd->fd_cdir, NULL,
463 &bp, path, len/2, GETCWD_CHECK_ACCESS, td);
464 mtx_unlock(&Giant);
465
466 if (error)
467 goto out;
468 lenused = bend - bp;
469 td->td_retval[0] = lenused;
470 /* put the result into user buffer */
471 error = copyout(bp, args->buf, lenused);
472 }
473 out:
474 free(path, M_TEMP);
475 return (error);
476 }
477
478 Cache object: 9dc1021dea71be7ad9bf0132534a427d
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