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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 <unistd.h>
#include <errno.h>
extern "C" int __faccessat(int, const char*, int);
int faccessat(int dirfd, const char* pathname, int mode, int flags) {
// "The mode specifies the accessibility check(s) to be performed,
// and is either the value F_OK, or a mask consisting of the
// bitwise OR of one or more of R_OK, W_OK, and X_OK."
if ((mode != F_OK) && ((mode & ~(R_OK | W_OK | X_OK)) != 0) &&
((mode & (R_OK | W_OK | X_OK)) == 0)) {
errno = EINVAL;
return -1;
}
if (flags != 0) {
// We deliberately don't support AT_SYMLINK_NOFOLLOW, a glibc
// only feature which is error prone and dangerous.
// More details at http://permalink.gmane.org/gmane.linux.lib.musl.general/6952
//
// AT_EACCESS isn't supported either. Android doesn't have setuid
// programs, and never runs code with euid!=uid.
//
// We could use faccessat2(2) from Linux 5.8, but since we don't want the
// first feature and don't need the second, we just reject such requests.
errno = EINVAL;
return -1;
}
return __faccessat(dirfd, pathname, mode);
}
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