1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1990, 1993
5 * The Regents of the University of California. All rights reserved.
6 *
7 * This code is derived from software contributed to Berkeley by
8 * Chris Torek.
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. Neither the name of the University nor the names of its contributors
19 * may be used to endorse or promote products derived from this software
20 * without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34
35 #include "namespace.h"
36 #include <sys/types.h>
37 #include <sys/stat.h>
38 #include <fcntl.h>
39 #include <errno.h>
40 #include <limits.h>
41 #include <unistd.h>
42 #include <stdio.h>
43 #include <stdlib.h>
44 #include "un-namespace.h"
45 #include "libc_private.h"
46 #include "local.h"
47
48 /*
49 * Re-direct an existing, open (probably) file to some other file.
50 * ANSI is written such that the original file gets closed if at
51 * all possible, no matter what.
52 */
53 FILE *
freopen(const char * __restrict file,const char * __restrict mode,FILE * __restrict fp)54 freopen(const char * __restrict file, const char * __restrict mode,
55 FILE * __restrict fp)
56 {
57 int f;
58 int dflags, fdflags, flags, isopen, oflags, sverrno, wantfd;
59
60 if ((flags = __sflags(mode, &oflags)) == 0) {
61 sverrno = errno;
62 (void) fclose(fp);
63 errno = sverrno;
64 return (NULL);
65 }
66
67 FLOCKFILE_CANCELSAFE(fp);
68
69 if (!__sdidinit)
70 __sinit();
71
72 /*
73 * If the filename is a NULL pointer, the caller is asking us to
74 * re-open the same file with a different mode. We allow this only
75 * if the modes are compatible.
76 */
77 if (file == NULL) {
78 /* See comment below regarding freopen() of closed files. */
79 if (fp->_flags == 0) {
80 errno = EINVAL;
81 fp = NULL;
82 goto end;
83 }
84 if ((dflags = _fcntl(fp->_file, F_GETFL)) < 0) {
85 sverrno = errno;
86 fclose(fp);
87 errno = sverrno;
88 fp = NULL;
89 goto end;
90 }
91 /* Work around incorrect O_ACCMODE. */
92 if ((dflags & O_ACCMODE) != O_RDWR &&
93 (dflags & (O_ACCMODE | O_EXEC)) != (oflags & O_ACCMODE)) {
94 fclose(fp);
95 errno = EBADF;
96 fp = NULL;
97 goto end;
98 }
99 if (fp->_flags & __SWR)
100 (void) __sflush(fp);
101 if ((oflags ^ dflags) & O_APPEND) {
102 dflags &= ~O_APPEND;
103 dflags |= oflags & O_APPEND;
104 if (_fcntl(fp->_file, F_SETFL, dflags) < 0) {
105 sverrno = errno;
106 fclose(fp);
107 errno = sverrno;
108 fp = NULL;
109 goto end;
110 }
111 }
112 if (oflags & O_TRUNC)
113 (void) ftruncate(fp->_file, (off_t)0);
114 if (!(oflags & O_APPEND))
115 (void) _sseek(fp, (fpos_t)0, SEEK_SET);
116 if ((oflags & O_CLOEXEC) != 0) {
117 fdflags = _fcntl(fp->_file, F_GETFD, 0);
118 if (fdflags != -1 && (fdflags & FD_CLOEXEC) == 0)
119 (void) _fcntl(fp->_file, F_SETFD,
120 fdflags | FD_CLOEXEC);
121 }
122 f = fp->_file;
123 isopen = 0;
124 wantfd = -1;
125 goto finish;
126 }
127
128 /*
129 * There are actually programs that depend on being able to "freopen"
130 * descriptors that weren't originally open. Keep this from breaking.
131 * Remember whether the stream was open to begin with, and which file
132 * descriptor (if any) was associated with it. If it was attached to
133 * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin)
134 * should work. This is unnecessary if it was not a Unix file.
135 */
136 if (fp->_flags == 0) {
137 fp->_flags = __SEOF; /* hold on to it */
138 isopen = 0;
139 wantfd = -1;
140 } else {
141 /* flush the stream; ANSI doesn't require this. */
142 if (fp->_flags & __SWR)
143 (void) __sflush(fp);
144 /* if close is NULL, closing is a no-op, hence pointless */
145 isopen = fp->_close != NULL;
146 if ((wantfd = fp->_file) < 0 && isopen) {
147 (void) (*fp->_close)(fp->_cookie);
148 isopen = 0;
149 }
150 }
151
152 /* Get a new descriptor to refer to the new file. */
153 f = _open(file, oflags, DEFFILEMODE);
154 /* If out of fd's close the old one and try again. */
155 if (f < 0 && isopen && wantfd > STDERR_FILENO &&
156 (errno == ENFILE || errno == EMFILE)) {
157 (void) (*fp->_close)(fp->_cookie);
158 isopen = 0;
159 wantfd = -1;
160 f = _open(file, oflags, DEFFILEMODE);
161 }
162 sverrno = errno;
163
164 finish:
165 /*
166 * Finish closing fp. Even if the open succeeded above, we cannot
167 * keep fp->_base: it may be the wrong size. This loses the effect
168 * of any setbuffer calls, but stdio has always done this before.
169 *
170 * Leave the existing file descriptor open until dup2() is called
171 * below to avoid races where a concurrent open() in another thread
172 * could claim the existing descriptor.
173 */
174 if (fp->_flags & __SMBF)
175 free((char *)fp->_bf._base);
176 fp->_w = 0;
177 fp->_r = 0;
178 fp->_p = NULL;
179 fp->_bf._base = NULL;
180 fp->_bf._size = 0;
181 fp->_lbfsize = 0;
182 if (HASUB(fp))
183 FREEUB(fp);
184 fp->_ub._size = 0;
185 if (HASLB(fp))
186 FREELB(fp);
187 fp->_lb._size = 0;
188 fp->_orientation = 0;
189 memset(&fp->_mbstate, 0, sizeof(mbstate_t));
190 fp->_flags2 = 0;
191
192 if (f < 0) { /* did not get it after all */
193 if (isopen)
194 (void) (*fp->_close)(fp->_cookie);
195 fp->_flags = 0; /* set it free */
196 errno = sverrno; /* restore in case _close clobbered */
197 fp = NULL;
198 goto end;
199 }
200
201 /*
202 * If reopening something that was open before on a real file, try
203 * to maintain the descriptor. Various C library routines (perror)
204 * assume stderr is always fd STDERR_FILENO, even if being freopen'd.
205 */
206 if (wantfd >= 0) {
207 if ((oflags & O_CLOEXEC ? _fcntl(f, F_DUP2FD_CLOEXEC, wantfd) :
208 _dup2(f, wantfd)) >= 0) {
209 (void)_close(f);
210 f = wantfd;
211 } else
212 (void)_close(fp->_file);
213 }
214
215 /*
216 * File descriptors are a full int, but _file is only a short.
217 * If we get a valid file descriptor that is greater than
218 * SHRT_MAX, then the fd will get sign-extended into an
219 * invalid file descriptor. Handle this case by failing the
220 * open.
221 */
222 if (f > SHRT_MAX) {
223 fp->_flags = 0; /* set it free */
224 errno = EMFILE;
225 fp = NULL;
226 goto end;
227 }
228
229 fp->_flags = flags;
230 fp->_file = f;
231 fp->_cookie = fp;
232 fp->_read = __sread;
233 fp->_write = __swrite;
234 fp->_seek = __sseek;
235 fp->_close = __sclose;
236 /*
237 * When opening in append mode, even though we use O_APPEND,
238 * we need to seek to the end so that ftell() gets the right
239 * answer. If the user then alters the seek pointer, or
240 * the file extends, this will fail, but there is not much
241 * we can do about this. (We could set __SAPP and check in
242 * fseek and ftell.)
243 */
244 if (oflags & O_APPEND) {
245 fp->_flags2 |= __S2OAP;
246 (void) _sseek(fp, (fpos_t)0, SEEK_END);
247 }
248 end:
249 FUNLOCKFILE_CANCELSAFE();
250 return (fp);
251 }
252