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 *
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 __FBSDID("$FreeBSD: releng/10.0/sys/compat/linux/linux_getcwd.c 204523 2010-03-01 17:20:04Z joel $");
34
35 #include "opt_compat.h"
36
37 #include <sys/param.h>
38 #include <sys/systm.h>
39 #include <sys/namei.h>
40 #include <sys/filedesc.h>
41 #include <sys/kernel.h>
42 #include <sys/file.h>
43 #include <sys/stat.h>
44 #include <sys/syscallsubr.h>
45 #include <sys/vnode.h>
46 #include <sys/mount.h>
47 #include <sys/proc.h>
48 #include <sys/uio.h>
49 #include <sys/malloc.h>
50 #include <sys/dirent.h>
51 #include <ufs/ufs/dir.h> /* XXX only for DIRBLKSIZ */
52
53 #ifdef COMPAT_LINUX32
54 #include <machine/../linux32/linux.h>
55 #include <machine/../linux32/linux32_proto.h>
56 #else
57 #include <machine/../linux/linux.h>
58 #include <machine/../linux/linux_proto.h>
59 #endif
60 #include <compat/linux/linux_util.h>
61
62 #include <security/mac/mac_framework.h>
63
64 static int
65 linux_getcwd_scandir(struct vnode **, struct vnode **,
66 char **, char *, struct thread *);
67 static int
68 linux_getcwd_common(struct vnode *, struct vnode *,
69 char **, char *, int, int, struct thread *);
70
71 #define DIRENT_MINSIZE (sizeof(struct dirent) - (MAXNAMLEN+1) + 4)
72
73 /*
74 * Vnode variable naming conventions in this file:
75 *
76 * rvp: the current root we're aiming towards.
77 * lvp, *lvpp: the "lower" vnode
78 * uvp, *uvpp: the "upper" vnode.
79 *
80 * Since all the vnodes we're dealing with are directories, and the
81 * lookups are going *up* in the filesystem rather than *down*, the
82 * usual "pvp" (parent) or "dvp" (directory) naming conventions are
83 * too confusing.
84 */
85
86 /*
87 * XXX Will infinite loop in certain cases if a directory read reliably
88 * returns EINVAL on last block.
89 * XXX is EINVAL the right thing to return if a directory is malformed?
90 */
91
92 /*
93 * XXX Untested vs. mount -o union; probably does the wrong thing.
94 */
95
96 /*
97 * Find parent vnode of *lvpp, return in *uvpp
98 *
99 * If we care about the name, scan it looking for name of directory
100 * entry pointing at lvp.
101 *
102 * Place the name in the buffer which starts at bufp, immediately
103 * before *bpp, and move bpp backwards to point at the start of it.
104 *
105 * On entry, *lvpp is a locked vnode reference; on exit, it is vput and NULL'ed
106 * On exit, *uvpp is either NULL or is a locked vnode reference.
107 */
108 static int
109 linux_getcwd_scandir(lvpp, uvpp, bpp, bufp, td)
110 struct vnode **lvpp;
111 struct vnode **uvpp;
112 char **bpp;
113 char *bufp;
114 struct thread *td;
115 {
116 int error = 0;
117 int eofflag;
118 off_t off;
119 int tries;
120 struct uio uio;
121 struct iovec iov;
122 char *dirbuf = NULL;
123 int dirbuflen;
124 ino_t fileno;
125 struct vattr va;
126 struct vnode *uvp = NULL;
127 struct vnode *lvp = *lvpp;
128 struct componentname cn;
129 int len, reclen;
130 tries = 0;
131
132 /*
133 * If we want the filename, get some info we need while the
134 * current directory is still locked.
135 */
136 if (bufp != NULL) {
137 error = VOP_GETATTR(lvp, &va, td->td_ucred);
138 if (error) {
139 vput(lvp);
140 *lvpp = NULL;
141 *uvpp = NULL;
142 return error;
143 }
144 }
145
146 /*
147 * Ok, we have to do it the hard way..
148 * Next, get parent vnode using lookup of ..
149 */
150 cn.cn_nameiop = LOOKUP;
151 cn.cn_flags = ISLASTCN | ISDOTDOT | RDONLY;
152 cn.cn_thread = td;
153 cn.cn_cred = td->td_ucred;
154 cn.cn_pnbuf = NULL;
155 cn.cn_nameptr = "..";
156 cn.cn_namelen = 2;
157 cn.cn_consume = 0;
158 cn.cn_lkflags = LK_SHARED;
159
160 /*
161 * At this point, lvp is locked and will be unlocked by the lookup.
162 * On successful return, *uvpp will be locked
163 */
164 #ifdef MAC
165 error = mac_vnode_check_lookup(td->td_ucred, lvp, &cn);
166 if (error == 0)
167 #endif
168 error = VOP_LOOKUP(lvp, uvpp, &cn);
169 if (error) {
170 vput(lvp);
171 *lvpp = NULL;
172 *uvpp = NULL;
173 return error;
174 }
175 uvp = *uvpp;
176
177 /* If we don't care about the pathname, we're done */
178 if (bufp == NULL) {
179 vput(lvp);
180 *lvpp = NULL;
181 return 0;
182 }
183
184 fileno = va.va_fileid;
185
186 dirbuflen = DIRBLKSIZ;
187 if (dirbuflen < va.va_blocksize)
188 dirbuflen = va.va_blocksize;
189 dirbuf = (char *)malloc(dirbuflen, M_TEMP, M_WAITOK);
190
191 #if 0
192 unionread:
193 #endif
194 off = 0;
195 do {
196 /* call VOP_READDIR of parent */
197 iov.iov_base = dirbuf;
198 iov.iov_len = dirbuflen;
199
200 uio.uio_iov = &iov;
201 uio.uio_iovcnt = 1;
202 uio.uio_offset = off;
203 uio.uio_resid = dirbuflen;
204 uio.uio_segflg = UIO_SYSSPACE;
205 uio.uio_rw = UIO_READ;
206 uio.uio_td = td;
207
208 eofflag = 0;
209
210 #ifdef MAC
211 error = mac_vnode_check_readdir(td->td_ucred, uvp);
212 if (error == 0)
213 #endif /* MAC */
214 error = VOP_READDIR(uvp, &uio, td->td_ucred, &eofflag,
215 0, 0);
216
217 off = uio.uio_offset;
218
219 /*
220 * Try again if NFS tosses its cookies.
221 * XXX this can still loop forever if the directory is busted
222 * such that the second or subsequent page of it always
223 * returns EINVAL
224 */
225 if ((error == EINVAL) && (tries < 3)) {
226 off = 0;
227 tries++;
228 continue; /* once more, with feeling */
229 }
230
231 if (!error) {
232 char *cpos;
233 struct dirent *dp;
234
235 cpos = dirbuf;
236 tries = 0;
237
238 /* scan directory page looking for matching vnode */
239 for (len = (dirbuflen - uio.uio_resid); len > 0; len -= reclen) {
240 dp = (struct dirent *) cpos;
241 reclen = dp->d_reclen;
242
243 /* check for malformed directory.. */
244 if (reclen < DIRENT_MINSIZE) {
245 error = EINVAL;
246 goto out;
247 }
248 /*
249 * XXX should perhaps do VOP_LOOKUP to
250 * check that we got back to the right place,
251 * but getting the locking games for that
252 * right would be heinous.
253 */
254 if ((dp->d_type != DT_WHT) &&
255 (dp->d_fileno == fileno)) {
256 char *bp = *bpp;
257 bp -= dp->d_namlen;
258
259 if (bp <= bufp) {
260 error = ERANGE;
261 goto out;
262 }
263 bcopy(dp->d_name, bp, dp->d_namlen);
264 error = 0;
265 *bpp = bp;
266 goto out;
267 }
268 cpos += reclen;
269 }
270 }
271 } while (!eofflag);
272 error = ENOENT;
273
274 out:
275 vput(lvp);
276 *lvpp = NULL;
277 free(dirbuf, M_TEMP);
278 return error;
279 }
280
281
282 /*
283 * common routine shared by sys___getcwd() and linux_vn_isunder()
284 */
285
286 #define GETCWD_CHECK_ACCESS 0x0001
287
288 static int
289 linux_getcwd_common (lvp, rvp, bpp, bufp, limit, flags, td)
290 struct vnode *lvp;
291 struct vnode *rvp;
292 char **bpp;
293 char *bufp;
294 int limit;
295 int flags;
296 struct thread *td;
297 {
298 struct filedesc *fdp = td->td_proc->p_fd;
299 struct vnode *uvp = NULL;
300 char *bp = NULL;
301 int error;
302 accmode_t accmode = VEXEC;
303
304 if (rvp == NULL) {
305 rvp = fdp->fd_rdir;
306 if (rvp == NULL)
307 rvp = rootvnode;
308 }
309
310 VREF(rvp);
311 VREF(lvp);
312
313 /*
314 * Error handling invariant:
315 * Before a `goto out':
316 * lvp is either NULL, or locked and held.
317 * uvp is either NULL, or locked and held.
318 */
319
320 error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY);
321 if (error != 0)
322 panic("vn_lock LK_RETRY returned error %d", error);
323 if (bufp)
324 bp = *bpp;
325 /*
326 * this loop will terminate when one of the following happens:
327 * - we hit the root
328 * - getdirentries or lookup fails
329 * - we run out of space in the buffer.
330 */
331 if (lvp == rvp) {
332 if (bp)
333 *(--bp) = '/';
334 goto out;
335 }
336 do {
337 if (lvp->v_type != VDIR) {
338 error = ENOTDIR;
339 goto out;
340 }
341
342 /*
343 * access check here is optional, depending on
344 * whether or not caller cares.
345 */
346 if (flags & GETCWD_CHECK_ACCESS) {
347 error = VOP_ACCESS(lvp, accmode, td->td_ucred, td);
348 if (error)
349 goto out;
350 accmode = VEXEC|VREAD;
351 }
352
353 /*
354 * step up if we're a covered vnode..
355 */
356 while (lvp->v_vflag & VV_ROOT) {
357 struct vnode *tvp;
358
359 if (lvp == rvp)
360 goto out;
361
362 tvp = lvp;
363 lvp = lvp->v_mount->mnt_vnodecovered;
364 vput(tvp);
365 /*
366 * hodie natus est radici frater
367 */
368 if (lvp == NULL) {
369 error = ENOENT;
370 goto out;
371 }
372 VREF(lvp);
373 error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY);
374 if (error != 0)
375 panic("vn_lock LK_RETRY returned %d", error);
376 }
377 error = linux_getcwd_scandir(&lvp, &uvp, &bp, bufp, td);
378 if (error)
379 goto out;
380 #ifdef DIAGNOSTIC
381 if (lvp != NULL)
382 panic("getcwd: oops, forgot to null lvp");
383 if (bufp && (bp <= bufp)) {
384 panic("getcwd: oops, went back too far");
385 }
386 #endif
387 if (bp)
388 *(--bp) = '/';
389 lvp = uvp;
390 uvp = NULL;
391 limit--;
392 } while ((lvp != rvp) && (limit > 0));
393
394 out:
395 if (bpp)
396 *bpp = bp;
397 if (uvp)
398 vput(uvp);
399 if (lvp)
400 vput(lvp);
401 vrele(rvp);
402 return error;
403 }
404
405
406 /*
407 * Find pathname of process's current directory.
408 *
409 * Use vfs vnode-to-name reverse cache; if that fails, fall back
410 * to reading directory contents.
411 */
412
413 int
414 linux_getcwd(struct thread *td, struct linux_getcwd_args *args)
415 {
416 caddr_t bp, bend, path;
417 int error, len, lenused;
418
419 #ifdef DEBUG
420 if (ldebug(getcwd))
421 printf(ARGS(getcwd, "%p, %ld"), args->buf, (long)args->bufsize);
422 #endif
423
424 len = args->bufsize;
425
426 if (len > MAXPATHLEN*4)
427 len = MAXPATHLEN*4;
428 else if (len < 2)
429 return ERANGE;
430
431 path = (char *)malloc(len, M_TEMP, M_WAITOK);
432
433 error = kern___getcwd(td, path, UIO_SYSSPACE, len);
434 if (!error) {
435 lenused = strlen(path) + 1;
436 if (lenused <= args->bufsize) {
437 td->td_retval[0] = lenused;
438 error = copyout(path, args->buf, lenused);
439 }
440 else
441 error = ERANGE;
442 } else {
443 bp = &path[len];
444 bend = bp;
445 *(--bp) = '\0';
446
447 /*
448 * 5th argument here is "max number of vnodes to traverse".
449 * Since each entry takes up at least 2 bytes in the output buffer,
450 * limit it to N/2 vnodes for an N byte buffer.
451 */
452
453 mtx_lock(&Giant);
454 error = linux_getcwd_common (td->td_proc->p_fd->fd_cdir, NULL,
455 &bp, path, len/2, GETCWD_CHECK_ACCESS, td);
456 mtx_unlock(&Giant);
457
458 if (error)
459 goto out;
460 lenused = bend - bp;
461 td->td_retval[0] = lenused;
462 /* put the result into user buffer */
463 error = copyout(bp, args->buf, lenused);
464 }
465 out:
466 free(path, M_TEMP);
467 return (error);
468 }
469
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