linux_getcwd.c revision 321009 
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: stable/10/sys/compat/linux/linux_getcwd.c 321009 2017-07-15 14:48:31Z dchagin $");
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_misc.h>
61#include <compat/linux/linux_util.h>
62
63#include <security/mac/mac_framework.h>
64
65static int
66linux_getcwd_scandir(struct vnode **, struct vnode **,
67    char **, char *, struct thread *);
68static int
69linux_getcwd_common(struct vnode *, struct vnode *,
70		   char **, char *, int, int, struct thread *);
71
72#define DIRENT_MINSIZE (sizeof(struct dirent) - (MAXNAMLEN+1) + 4)
73
74/*
75 * Vnode variable naming conventions in this file:
76 *
77 * rvp: the current root we're aiming towards.
78 * lvp, *lvpp: the "lower" vnode
79 * uvp, *uvpp: the "upper" vnode.
80 *
81 * Since all the vnodes we're dealing with are directories, and the
82 * lookups are going *up* in the filesystem rather than *down*, the
83 * usual "pvp" (parent) or "dvp" (directory) naming conventions are
84 * too confusing.
85 */
86
87/*
88 * XXX Will infinite loop in certain cases if a directory read reliably
89 *	returns EINVAL on last block.
90 * XXX is EINVAL the right thing to return if a directory is malformed?
91 */
92
93/*
94 * XXX Untested vs. mount -o union; probably does the wrong thing.
95 */
96
97/*
98 * Find parent vnode of *lvpp, return in *uvpp
99 *
100 * If we care about the name, scan it looking for name of directory
101 * entry pointing at lvp.
102 *
103 * Place the name in the buffer which starts at bufp, immediately
104 * before *bpp, and move bpp backwards to point at the start of it.
105 *
106 * On entry, *lvpp is a locked vnode reference; on exit, it is vput and NULL'ed
107 * On exit, *uvpp is either NULL or is a locked vnode reference.
108 */
109static int
110linux_getcwd_scandir(lvpp, uvpp, bpp, bufp, td)
111	struct vnode **lvpp;
112	struct vnode **uvpp;
113	char **bpp;
114	char *bufp;
115	struct thread *td;
116{
117	int     error = 0;
118	int     eofflag;
119	off_t   off;
120	int     tries;
121	struct uio uio;
122	struct iovec iov;
123	char   *dirbuf = NULL;
124	int	dirbuflen;
125	ino_t   fileno;
126	struct vattr va;
127	struct vnode *uvp = NULL;
128	struct vnode *lvp = *lvpp;
129	struct componentname cn;
130	int len, reclen;
131	tries = 0;
132
133	/*
134	 * If we want the filename, get some info we need while the
135	 * current directory is still locked.
136	 */
137	if (bufp != NULL) {
138		error = VOP_GETATTR(lvp, &va, td->td_ucred);
139		if (error) {
140			vput(lvp);
141			*lvpp = NULL;
142			*uvpp = NULL;
143			return error;
144		}
145	}
146
147	/*
148	 * Ok, we have to do it the hard way..
149	 * Next, get parent vnode using lookup of ..
150	 */
151	cn.cn_nameiop = LOOKUP;
152	cn.cn_flags = ISLASTCN | ISDOTDOT | RDONLY;
153	cn.cn_thread = td;
154	cn.cn_cred = td->td_ucred;
155	cn.cn_pnbuf = NULL;
156	cn.cn_nameptr = "..";
157	cn.cn_namelen = 2;
158	cn.cn_consume = 0;
159	cn.cn_lkflags = LK_SHARED;
160
161	/*
162	 * At this point, lvp is locked and will be unlocked by the lookup.
163	 * On successful return, *uvpp will be locked
164	 */
165#ifdef MAC
166	error = mac_vnode_check_lookup(td->td_ucred, lvp, &cn);
167	if (error == 0)
168#endif
169		error = VOP_LOOKUP(lvp, uvpp, &cn);
170	if (error) {
171		vput(lvp);
172		*lvpp = NULL;
173		*uvpp = NULL;
174		return error;
175	}
176	uvp = *uvpp;
177
178	/* If we don't care about the pathname, we're done */
179	if (bufp == NULL) {
180		vput(lvp);
181		*lvpp = NULL;
182		return 0;
183	}
184
185	fileno = va.va_fileid;
186
187	dirbuflen = DIRBLKSIZ;
188	if (dirbuflen < va.va_blocksize)
189		dirbuflen = va.va_blocksize;
190	dirbuf = malloc(dirbuflen, M_LINUX, M_WAITOK);
191
192#if 0
193unionread:
194#endif
195	off = 0;
196	do {
197		/* call VOP_READDIR of parent */
198		iov.iov_base = dirbuf;
199		iov.iov_len = dirbuflen;
200
201		uio.uio_iov = &iov;
202		uio.uio_iovcnt = 1;
203		uio.uio_offset = off;
204		uio.uio_resid = dirbuflen;
205		uio.uio_segflg = UIO_SYSSPACE;
206		uio.uio_rw = UIO_READ;
207		uio.uio_td = td;
208
209		eofflag = 0;
210
211#ifdef MAC
212		error = mac_vnode_check_readdir(td->td_ucred, uvp);
213		if (error == 0)
214#endif /* MAC */
215			error = VOP_READDIR(uvp, &uio, td->td_ucred, &eofflag,
216			    0, 0);
217
218		off = uio.uio_offset;
219
220		/*
221		 * Try again if NFS tosses its cookies.
222		 * XXX this can still loop forever if the directory is busted
223		 * such that the second or subsequent page of it always
224		 * returns EINVAL
225		 */
226		if ((error == EINVAL) && (tries < 3)) {
227			off = 0;
228			tries++;
229			continue;	/* once more, with feeling */
230		}
231
232		if (!error) {
233			char   *cpos;
234			struct dirent *dp;
235
236			cpos = dirbuf;
237			tries = 0;
238
239			/* scan directory page looking for matching vnode */
240			for (len = (dirbuflen - uio.uio_resid); len > 0; len -= reclen) {
241				dp = (struct dirent *) cpos;
242				reclen = dp->d_reclen;
243
244				/* check for malformed directory.. */
245				if (reclen < DIRENT_MINSIZE) {
246					error = EINVAL;
247					goto out;
248				}
249				/*
250				 * XXX should perhaps do VOP_LOOKUP to
251				 * check that we got back to the right place,
252				 * but getting the locking games for that
253				 * right would be heinous.
254				 */
255				if ((dp->d_type != DT_WHT) &&
256				    (dp->d_fileno == fileno)) {
257					char *bp = *bpp;
258					bp -= dp->d_namlen;
259
260					if (bp <= bufp) {
261						error = ERANGE;
262						goto out;
263					}
264					bcopy(dp->d_name, bp, dp->d_namlen);
265					error = 0;
266					*bpp = bp;
267					goto out;
268				}
269				cpos += reclen;
270			}
271		}
272	} while (!eofflag);
273	error = ENOENT;
274
275out:
276	vput(lvp);
277	*lvpp = NULL;
278	free(dirbuf, M_LINUX);
279	return error;
280}
281
282
283/*
284 * common routine shared by sys___getcwd() and linux_vn_isunder()
285 */
286
287#define GETCWD_CHECK_ACCESS 0x0001
288
289static int
290linux_getcwd_common (lvp, rvp, bpp, bufp, limit, flags, td)
291	struct vnode *lvp;
292	struct vnode *rvp;
293	char **bpp;
294	char *bufp;
295	int limit;
296	int flags;
297	struct thread *td;
298{
299	struct filedesc *fdp = td->td_proc->p_fd;
300	struct vnode *uvp = NULL;
301	char *bp = NULL;
302	int error;
303	accmode_t accmode = VEXEC;
304
305	if (rvp == NULL) {
306		rvp = fdp->fd_rdir;
307		if (rvp == NULL)
308			rvp = rootvnode;
309	}
310
311	VREF(rvp);
312	VREF(lvp);
313
314	/*
315	 * Error handling invariant:
316	 * Before a `goto out':
317	 *	lvp is either NULL, or locked and held.
318	 *	uvp is either NULL, or locked and held.
319	 */
320
321	error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY);
322	if (error != 0)
323		panic("vn_lock LK_RETRY returned error %d", error);
324	if (bufp)
325		bp = *bpp;
326	/*
327	 * this loop will terminate when one of the following happens:
328	 *	- we hit the root
329	 *	- getdirentries or lookup fails
330	 *	- we run out of space in the buffer.
331	 */
332	if (lvp == rvp) {
333		if (bp)
334			*(--bp) = '/';
335		goto out;
336	}
337	do {
338		if (lvp->v_type != VDIR) {
339			error = ENOTDIR;
340			goto out;
341		}
342
343		/*
344		 * access check here is optional, depending on
345		 * whether or not caller cares.
346		 */
347		if (flags & GETCWD_CHECK_ACCESS) {
348			error = VOP_ACCESS(lvp, accmode, td->td_ucred, td);
349			if (error)
350				goto out;
351			accmode = VEXEC|VREAD;
352		}
353
354		/*
355		 * step up if we're a covered vnode..
356		 */
357		while (lvp->v_vflag & VV_ROOT) {
358			struct vnode *tvp;
359
360			if (lvp == rvp)
361				goto out;
362
363			tvp = lvp;
364			lvp = lvp->v_mount->mnt_vnodecovered;
365			vput(tvp);
366			/*
367			 * hodie natus est radici frater
368			 */
369			if (lvp == NULL) {
370				error = ENOENT;
371				goto out;
372			}
373			VREF(lvp);
374			error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY);
375			if (error != 0)
376				panic("vn_lock LK_RETRY returned %d", error);
377		}
378		error = linux_getcwd_scandir(&lvp, &uvp, &bp, bufp, td);
379		if (error)
380			goto out;
381#ifdef DIAGNOSTIC
382		if (lvp != NULL)
383			panic("getcwd: oops, forgot to null lvp");
384		if (bufp && (bp <= bufp)) {
385			panic("getcwd: oops, went back too far");
386		}
387#endif
388		if (bp)
389			*(--bp) = '/';
390		lvp = uvp;
391		uvp = NULL;
392		limit--;
393	} while ((lvp != rvp) && (limit > 0));
394
395out:
396	if (bpp)
397		*bpp = bp;
398	if (uvp)
399		vput(uvp);
400	if (lvp)
401		vput(lvp);
402	vrele(rvp);
403	return error;
404}
405
406
407/*
408 * Find pathname of process's current directory.
409 *
410 * Use vfs vnode-to-name reverse cache; if that fails, fall back
411 * to reading directory contents.
412 */
413
414int
415linux_getcwd(struct thread *td, struct linux_getcwd_args *args)
416{
417	char *bp, *bend, *path;
418	int error, len, lenused;
419
420#ifdef DEBUG
421	if (ldebug(getcwd))
422		printf(ARGS(getcwd, "%p, %ld"), args->buf, (long)args->bufsize);
423#endif
424
425	len = args->bufsize;
426
427	if (len > LINUX_PATH_MAX)
428		len = LINUX_PATH_MAX;
429	else if (len < 2)
430		return ERANGE;
431
432	path = malloc(len, M_TEMP, M_WAITOK);
433
434	error = kern___getcwd(td, path, UIO_SYSSPACE, len, LINUX_PATH_MAX);
435	if (!error) {
436		lenused = strlen(path) + 1;
437		if (lenused <= args->bufsize) {
438			td->td_retval[0] = lenused;
439			error = copyout(path, args->buf, lenused);
440		}
441		else
442			error = ERANGE;
443	} else {
444		bp = &path[len];
445		bend = bp;
446		*(--bp) = '\0';
447
448		/*
449		 * 5th argument here is "max number of vnodes to traverse".
450		 * Since each entry takes up at least 2 bytes in the output buffer,
451		 * limit it to N/2 vnodes for an N byte buffer.
452		 */
453
454		error = linux_getcwd_common (td->td_proc->p_fd->fd_cdir, NULL,
455		    &bp, path, len/2, GETCWD_CHECK_ACCESS, td);
456		if (error)
457			goto out;
458		lenused = bend - bp;
459		td->td_retval[0] = lenused;
460		/* put the result into user buffer */
461		error = copyout(bp, args->buf, lenused);
462	}
463out:
464	free(path, M_TEMP);
465	return (error);
466}
467
468