1/*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1983, 1993
5 *	The Regents of the University of California.  All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 * 3. Neither the name of the University nor the names of its contributors
16 *    may be used to endorse or promote products derived from this software
17 *    without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 */
31
32#include "namespace.h"
33#include <sys/param.h>
34
35#include <dirent.h>
36#include <errno.h>
37#include <fcntl.h>
38#include <stdlib.h>
39#include <string.h>
40#include <unistd.h>
41#include "un-namespace.h"
42
43#include "gen-private.h"
44#include "telldir.h"
45
46static DIR * __opendir_common(int, int, bool);
47
48/*
49 * Open a directory.
50 */
51DIR *
52opendir(const char *name)
53{
54
55	return (__opendir2(name, DTF_HIDEW|DTF_NODUP));
56}
57
58/*
59 * Open a directory with existing file descriptor.
60 */
61DIR *
62fdopendir(int fd)
63{
64
65	if (_fcntl(fd, F_SETFD, FD_CLOEXEC) == -1)
66		return (NULL);
67	return (__opendir_common(fd, DTF_HIDEW|DTF_NODUP, true));
68}
69
70DIR *
71__opendir2(const char *name, int flags)
72{
73	int fd;
74	DIR *dir;
75	int saved_errno;
76
77	if ((flags & (__DTF_READALL | __DTF_SKIPREAD)) != 0)
78		return (NULL);
79	if ((fd = _open(name,
80	    O_RDONLY | O_NONBLOCK | O_DIRECTORY | O_CLOEXEC)) == -1)
81		return (NULL);
82
83	dir = __opendir_common(fd, flags, false);
84	if (dir == NULL) {
85		saved_errno = errno;
86		_close(fd);
87		errno = saved_errno;
88	}
89	return (dir);
90}
91
92static int
93opendir_compar(const void *p1, const void *p2)
94{
95
96	return (strcmp((*(const struct dirent * const *)p1)->d_name,
97	    (*(const struct dirent * const *)p2)->d_name));
98}
99
100/*
101 * For a directory at the top of a unionfs stack, the entire directory's
102 * contents are read and cached locally until the next call to rewinddir().
103 * For the fdopendir() case, the initial seek position must be preserved.
104 * For rewinddir(), the full directory should always be re-read from the
105 * beginning.
106 *
107 * If an error occurs, the existing buffer and state of 'dirp' is left
108 * unchanged.
109 */
110bool
111_filldir(DIR *dirp, bool use_current_pos)
112{
113	struct dirent **dpv;
114	char *buf, *ddptr, *ddeptr;
115	off_t pos;
116	int fd2, incr, len, n, saved_errno, space;
117
118	len = 0;
119	space = 0;
120	buf = NULL;
121	ddptr = NULL;
122
123	/*
124	 * Use the system page size if that is a multiple of DIRBLKSIZ.
125	 * Hopefully this can be a big win someday by allowing page
126	 * trades to user space to be done by _getdirentries().
127	 */
128	incr = getpagesize();
129	if ((incr % DIRBLKSIZ) != 0)
130		incr = DIRBLKSIZ;
131
132	/*
133	 * The strategy here is to read all the directory
134	 * entries into a buffer, sort the buffer, and
135	 * remove duplicate entries by setting the inode
136	 * number to zero.
137	 *
138	 * We reopen the directory because _getdirentries()
139	 * on a MNT_UNION mount modifies the open directory,
140	 * making it refer to the lower directory after the
141	 * upper directory's entries are exhausted.
142	 * This would otherwise break software that uses
143	 * the directory descriptor for fchdir or *at
144	 * functions, such as fts.c.
145	 */
146	if ((fd2 = _openat(dirp->dd_fd, ".", O_RDONLY | O_CLOEXEC)) == -1)
147		return (false);
148
149	if (use_current_pos) {
150		pos = lseek(dirp->dd_fd, 0, SEEK_CUR);
151		if (pos == -1 || lseek(fd2, pos, SEEK_SET) == -1) {
152			saved_errno = errno;
153			_close(fd2);
154			errno = saved_errno;
155			return (false);
156		}
157	}
158
159	do {
160		/*
161		 * Always make at least DIRBLKSIZ bytes
162		 * available to _getdirentries
163		 */
164		if (space < DIRBLKSIZ) {
165			space += incr;
166			len += incr;
167			buf = reallocf(buf, len);
168			if (buf == NULL) {
169				saved_errno = errno;
170				_close(fd2);
171				errno = saved_errno;
172				return (false);
173			}
174			ddptr = buf + (len - space);
175		}
176
177		n = _getdirentries(fd2, ddptr, space, &dirp->dd_seek);
178		if (n > 0) {
179			ddptr += n;
180			space -= n;
181		}
182		if (n < 0) {
183			saved_errno = errno;
184			_close(fd2);
185			errno = saved_errno;
186			return (false);
187		}
188	} while (n > 0);
189	_close(fd2);
190
191	ddeptr = ddptr;
192
193	/*
194	 * There is now a buffer full of (possibly) duplicate
195	 * names.
196	 */
197	dirp->dd_buf = buf;
198
199	/*
200	 * Go round this loop twice...
201	 *
202	 * Scan through the buffer, counting entries.
203	 * On the second pass, save pointers to each one.
204	 * Then sort the pointers and remove duplicate names.
205	 */
206	for (dpv = NULL;;) {
207		n = 0;
208		ddptr = buf;
209		while (ddptr < ddeptr) {
210			struct dirent *dp;
211
212			dp = (struct dirent *) ddptr;
213			if ((long)dp & 03L)
214				break;
215			if ((dp->d_reclen <= 0) ||
216			    (dp->d_reclen > (ddeptr + 1 - ddptr)))
217				break;
218			ddptr += dp->d_reclen;
219			if (dp->d_fileno) {
220				if (dpv)
221					dpv[n] = dp;
222				n++;
223			}
224		}
225
226		if (dpv) {
227			struct dirent *xp;
228
229			/*
230			 * This sort must be stable.
231			 */
232			mergesort(dpv, n, sizeof(*dpv), opendir_compar);
233
234			dpv[n] = NULL;
235			xp = NULL;
236
237			/*
238			 * Scan through the buffer in sort order,
239			 * zapping the inode number of any
240			 * duplicate names.
241			 */
242			for (n = 0; dpv[n]; n++) {
243				struct dirent *dp = dpv[n];
244
245				if ((xp == NULL) ||
246				    strcmp(dp->d_name, xp->d_name)) {
247					xp = dp;
248				} else {
249					dp->d_fileno = 0;
250				}
251				if (dp->d_type == DT_WHT &&
252				    (dirp->dd_flags & DTF_HIDEW))
253					dp->d_fileno = 0;
254			}
255
256			free(dpv);
257			break;
258		} else {
259			dpv = malloc((n+1) * sizeof(struct dirent *));
260			if (dpv == NULL)
261				break;
262		}
263	}
264
265	dirp->dd_len = len;
266	dirp->dd_size = ddptr - dirp->dd_buf;
267	return (true);
268}
269
270static bool
271is_unionstack(int fd)
272{
273	int unionstack;
274
275	unionstack = _fcntl(fd, F_ISUNIONSTACK, 0);
276	if (unionstack != -1)
277		return (unionstack);
278
279	/*
280	 * Should not happen unless running on a kernel without the op,
281	 * but no use rendering the system useless in such a case.
282	 */
283	return (0);
284}
285
286/*
287 * Common routine for opendir(3), __opendir2(3) and fdopendir(3).
288 */
289static DIR *
290__opendir_common(int fd, int flags, bool use_current_pos)
291{
292	DIR *dirp;
293	int incr;
294	int saved_errno;
295	bool unionstack;
296
297	if ((dirp = malloc(sizeof(DIR) + sizeof(struct _telldir))) == NULL)
298		return (NULL);
299
300	dirp->dd_buf = NULL;
301	dirp->dd_fd = fd;
302	dirp->dd_flags = flags;
303	dirp->dd_loc = 0;
304	dirp->dd_lock = NULL;
305	dirp->dd_td = (struct _telldir *)((char *)dirp + sizeof(DIR));
306	LIST_INIT(&dirp->dd_td->td_locq);
307	dirp->dd_td->td_loccnt = 0;
308	dirp->dd_compat_de = NULL;
309
310	/*
311	 * Use the system page size if that is a multiple of DIRBLKSIZ.
312	 * Hopefully this can be a big win someday by allowing page
313	 * trades to user space to be done by _getdirentries().
314	 */
315	incr = getpagesize();
316	if ((incr % DIRBLKSIZ) != 0)
317		incr = DIRBLKSIZ;
318
319	/*
320	 * Determine whether this directory is the top of a union stack.
321	 */
322	unionstack = false;
323	if (flags & DTF_NODUP) {
324		unionstack = is_unionstack(fd);
325	}
326
327	if (unionstack) {
328		if (!_filldir(dirp, use_current_pos))
329			goto fail;
330		dirp->dd_flags |= __DTF_READALL;
331	} else {
332		dirp->dd_len = incr;
333		dirp->dd_buf = malloc(dirp->dd_len);
334		if (dirp->dd_buf == NULL)
335			goto fail;
336		if (use_current_pos) {
337			/*
338			 * Read the first batch of directory entries
339			 * to prime dd_seek.  This also checks if the
340			 * fd passed to fdopendir() is a directory.
341			 */
342			dirp->dd_size = _getdirentries(dirp->dd_fd,
343			    dirp->dd_buf, dirp->dd_len, &dirp->dd_seek);
344			if (dirp->dd_size < 0) {
345				if (errno == EINVAL)
346					errno = ENOTDIR;
347				goto fail;
348			}
349			dirp->dd_flags |= __DTF_SKIPREAD;
350		} else {
351			dirp->dd_size = 0;
352			dirp->dd_seek = 0;
353		}
354	}
355
356	return (dirp);
357
358fail:
359	saved_errno = errno;
360	free(dirp->dd_buf);
361	free(dirp);
362	errno = saved_errno;
363	return (NULL);
364}
365