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