1 /*-
2 * Copyright (c) 1990, 1993
3 * The Regents of the University of California. All rights reserved.
4 *
5 * This code is derived from software contributed to Berkeley by
6 * Chris Torek.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. Neither the name of the University nor the names of its contributors
17 * may be used to endorse or promote products derived from this software
18 * without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 */
32
33 #include <errno.h>
34 #include <signal.h>
35 #include <stdio.h>
36 #include <stdlib.h>
37 #include <sys/stat.h>
38 #include <sys/types.h>
39 #include <unistd.h>
40
41 #include "private/ErrnoRestorer.h"
42 #include "private/ScopedSignalBlocker.h"
43
__tmpfile_dir(const char * tmp_dir)44 static FILE* __tmpfile_dir(const char* tmp_dir) {
45 char* path = nullptr;
46 if (asprintf(&path, "%s/tmp.XXXXXXXXXX", tmp_dir) == -1) {
47 return nullptr;
48 }
49
50 int fd;
51 {
52 ScopedSignalBlocker ssb;
53 fd = mkstemp(path);
54 if (fd == -1) {
55 free(path);
56 return nullptr;
57 }
58
59 // Unlink the file now so that it's removed when closed.
60 unlink(path);
61 free(path);
62
63 // Can we still use the file now it's unlinked?
64 // File systems without hard link support won't have the usual Unix semantics.
65 struct stat sb;
66 int rc = fstat(fd, &sb);
67 if (rc == -1) {
68 ErrnoRestorer errno_restorer;
69 close(fd);
70 return nullptr;
71 }
72 }
73
74 // Turn the file descriptor into a FILE*.
75 FILE* fp = fdopen(fd, "w+");
76 if (fp != nullptr) {
77 return fp;
78 }
79
80 // Failure. Clean up. We already unlinked, so we just need to close.
81 ErrnoRestorer errno_restorer;
82 close(fd);
83 return nullptr;
84 }
85
tmpfile()86 FILE* tmpfile() {
87 // TODO: get this app's temporary directory from the framework ("/data/data/app/cache").
88
89 // $EXTERNAL_STORAGE turns out not to be very useful because it doesn't support hard links.
90 // This means we can't do the usual trick of calling unlink before handing the file back.
91
92 FILE* fp = __tmpfile_dir("/data/local/tmp");
93 if (fp == nullptr) {
94 // P_tmpdir is "/tmp/", but POSIX explicitly says that tmpdir(3) should try P_tmpdir before
95 // giving up. This is potentially useful for bionic on the host anyway.
96 fp = __tmpfile_dir(P_tmpdir);
97 }
98 return fp;
99 }
100 __strong_alias(tmpfile64, tmpfile);
101