1 /*
2 * Copyright (C) 2015 The Android Open Source Project
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * * Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * * Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in
12 * the documentation and/or other materials provided with the
13 * distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29 #include <fcntl.h>
30 #include <sys/stat.h>
31 #include <sys/types.h>
32 #include <errno.h>
33 #include <unistd.h>
34 #include <stdio.h>
35
36 #include "private/FdPath.h"
37
38 extern "C" int __fchmod(int, mode_t);
39
fchmod(int fd,mode_t mode)40 int fchmod(int fd, mode_t mode) {
41 int saved_errno = errno;
42 int result = __fchmod(fd, mode);
43 if (result == 0 || errno != EBADF) {
44 return result;
45 }
46
47 // fd could be an O_PATH file descriptor, and the kernel
48 // may not directly support fchmod() on such a file descriptor.
49 // Use /proc/self/fd instead to emulate this support.
50 // https://sourceware.org/bugzilla/show_bug.cgi?id=14578
51 //
52 // As of February 2015, there are no kernels which support fchmod
53 // on an O_PATH file descriptor, and "man open" documents fchmod
54 // on O_PATH file descriptors as returning EBADF.
55 int fd_flag = fcntl(fd, F_GETFL);
56 if (fd_flag == -1 || (fd_flag & O_PATH) == 0) {
57 errno = EBADF;
58 return -1;
59 }
60
61 errno = saved_errno;
62 result = chmod(FdPath(fd).c_str(), mode);
63 if (result == -1 && errno == ELOOP) {
64 // Linux does not support changing the mode of a symlink.
65 // For fchmodat(AT_SYMLINK_NOFOLLOW), POSIX requires a return
66 // value of ENOTSUP. Assume that's true here too.
67 errno = ENOTSUP;
68 }
69
70 return result;
71 }
72