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 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
