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
46 static DIR * __opendir_common(int, int, bool);
47
48 /*
49 * Open a directory.
50 */
51 DIR *
opendir(const char * name)52 opendir(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 */
61 DIR *
fdopendir(int fd)62 fdopendir(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
70 DIR *
__opendir2(const char * name,int flags)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
92 static int
opendir_compar(const void * p1,const void * p2)93 opendir_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 */
110 bool
_filldir(DIR * dirp,bool use_current_pos)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
270 static bool
is_unionstack(int fd)271 is_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 */
289 static DIR *
__opendir_common(int fd,int flags,bool use_current_pos)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
358 fail:
359 saved_errno = errno;
360 free(dirp->dd_buf);
361 free(dirp);
362 errno = saved_errno;
363 return (NULL);
364 }
365