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
35 #include "private/ScopedFd.h"
36
37 extern "C" int __fchmodat(int, const char*, mode_t);
38
fchmodat(int dirfd,const char * pathname,mode_t mode,int flags)39 int fchmodat(int dirfd, const char* pathname, mode_t mode, int flags) {
40 if ((flags & ~AT_SYMLINK_NOFOLLOW) != 0) {
41 errno = EINVAL;
42 return -1;
43 }
44
45 if (flags & AT_SYMLINK_NOFOLLOW) {
46 // Emulate AT_SYMLINK_NOFOLLOW using the mechanism described
47 // at https://sourceware.org/bugzilla/show_bug.cgi?id=14578
48 // comment #10
49
50 ScopedFd fd(openat(dirfd, pathname, O_PATH | O_NOFOLLOW | O_CLOEXEC));
51 if (fd.get() == -1) return -1;
52
53 // POSIX requires that ENOTSUP be returned when the system
54 // doesn't support setting the mode of a symbolic link.
55 // This is true for all Linux kernels.
56 // We rely on the O_PATH compatibility layer added in the
57 // fchmod() function to get errno correct.
58 return fchmod(fd.get(), mode);
59 }
60
61 return __fchmodat(dirfd, pathname, mode);
62 }
63