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/*
* Copyright (C) 2015 The Android Open Source Project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <errno.h>
#include <unistd.h>
#include <stdio.h>
extern "C" int ___fchmod(int, mode_t);
int fchmod(int fd, mode_t mode) {
int saved_errno = errno;
int result = ___fchmod(fd, mode);
if ((result == 0) || (errno != EBADF)) {
return result;
}
// fd could be an O_PATH file descriptor, and the kernel
// may not directly support fchmod() on such a file descriptor.
// Use /proc/self/fd instead to emulate this support.
// https://sourceware.org/bugzilla/show_bug.cgi?id=14578
//
// As of February 2015, there are no kernels which support fchmod
// on an O_PATH file descriptor, and "man open" documents fchmod
// on O_PATH file descriptors as returning EBADF.
int fd_flag = fcntl(fd, F_GETFL);
if ((fd_flag == -1) || ((fd_flag & O_PATH) == 0)) {
errno = EBADF;
return -1;
}
char buf[40];
snprintf(buf, sizeof(buf), "/proc/self/fd/%d", fd);
errno = saved_errno;
result = chmod(buf, mode);
if ((result == -1) && (errno == ELOOP)) {
// Linux does not support changing the mode of a symlink.
// For fchmodat(AT_SYMLINK_NOFOLLOW), POSIX requires a return
// value of ENOTSUP. Assume that's true here too.
errno = ENOTSUP;
}
return result;
}
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