blob: 780d9f136cbcfc6cf30f35408c29b3d5451d3223 [file] [log] [blame]
/*
* Copyright (C) 2016 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 <ctype.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <cutils/android_get_control_file.h>
#include "android_get_control_env.h"
#ifndef TEMP_FAILURE_RETRY
#define TEMP_FAILURE_RETRY(exp) (exp) // KISS implementation
#endif
LIBCUTILS_HIDDEN int __android_get_control_from_env(const char* prefix,
const char* name) {
if (!prefix || !name) return -1;
char *key = NULL;
if (asprintf(&key, "%s%s", prefix, name) < 0) return -1;
if (!key) return -1;
char *cp = key;
while (*cp) {
if (!isalnum(*cp)) *cp = '_';
++cp;
}
const char* val = getenv(key);
free(key);
if (!val) return -1;
errno = 0;
long fd = strtol(val, NULL, 10);
if (errno) return -1;
// validity checking
if ((fd < 0) || (fd > INT_MAX)) return -1;
// Since we are inheriting an fd, it could legitimately exceed _SC_OPEN_MAX
// Still open?
#if defined(F_GETFD) // Lowest overhead
if (TEMP_FAILURE_RETRY(fcntl(fd, F_GETFD)) < 0) return -1;
#elif defined(F_GETFL) // Alternate lowest overhead
if (TEMP_FAILURE_RETRY(fcntl(fd, F_GETFL)) < 0) return -1;
#else // Hail Mary pass
struct stat s;
if (TEMP_FAILURE_RETRY(fstat(fd, &s)) < 0) return -1;
#endif
return static_cast<int>(fd);
}
int android_get_control_file(const char* path) {
int fd = __android_get_control_from_env(ANDROID_FILE_ENV_PREFIX, path);
#if defined(__linux__)
// Find file path from /proc and make sure it is correct
char *proc = NULL;
if (asprintf(&proc, "/proc/self/fd/%d", fd) < 0) return -1;
if (!proc) return -1;
size_t len = strlen(path);
// readlink() does not guarantee a nul byte, len+2 so we catch truncation.
char *buf = static_cast<char *>(calloc(1, len + 2));
if (!buf) {
free(proc);
return -1;
}
ssize_t ret = TEMP_FAILURE_RETRY(readlink(proc, buf, len + 1));
free(proc);
int cmp = (len != static_cast<size_t>(ret)) || strcmp(buf, path);
free(buf);
if (ret < 0) return -1;
if (cmp != 0) return -1;
// It is what we think it is
#endif
return fd;
}