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glibc/sysdeps/unix/sysv/linux/readonly-area.c
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/* Copyright (C) 2004-2016 Free Software Foundation, Inc. | |
This file is part of the GNU C Library. | |
The GNU C Library is free software; you can redistribute it and/or | |
modify it under the terms of the GNU Lesser General Public | |
License as published by the Free Software Foundation; either | |
version 2.1 of the License, or (at your option) any later version. | |
The GNU C Library is distributed in the hope that it will be useful, | |
but WITHOUT ANY WARRANTY; without even the implied warranty of | |
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
Lesser General Public License for more details. | |
You should have received a copy of the GNU Lesser General Public | |
License along with the GNU C Library; if not, see | |
<http://www.gnu.org/licenses/>. */ | |
#include <errno.h> | |
#include <stdint.h> | |
#include <stdio.h> | |
#include <stdio_ext.h> | |
#include <stdlib.h> | |
#include <string.h> | |
#include "libio/libioP.h" | |
/* Return 1 if the whole area PTR .. PTR+SIZE is not writable. | |
Return -1 if it is writable. */ | |
int | |
__readonly_area (const char *ptr, size_t size) | |
{ | |
const void *ptr_end = ptr + size; | |
FILE *fp = fopen ("/proc/self/maps", "rce"); | |
if (fp == NULL) | |
{ | |
/* It is the system administrator's choice to not have /proc | |
available to this process (e.g., because it runs in a chroot | |
environment. Don't fail in this case. */ | |
if (errno == ENOENT | |
/* The kernel has a bug in that a process is denied access | |
to the /proc filesystem if it is set[ug]id. There has | |
been no willingness to change this in the kernel so | |
far. */ | |
|| errno == EACCES) | |
return 1; | |
return -1; | |
} | |
/* We need no locking. */ | |
__fsetlocking (fp, FSETLOCKING_BYCALLER); | |
char *line = NULL; | |
size_t linelen = 0; | |
while (! feof_unlocked (fp)) | |
{ | |
if (_IO_getdelim (&line, &linelen, '\n', fp) <= 0) | |
break; | |
char *p; | |
uintptr_t from = strtoul (line, &p, 16); | |
if (p == line || *p++ != '-') | |
break; | |
char *q; | |
uintptr_t to = strtoul (p, &q, 16); | |
if (q == p || *q++ != ' ') | |
break; | |
if (from < (uintptr_t) ptr_end && to > (uintptr_t) ptr) | |
{ | |
/* Found an entry that at least partially covers the area. */ | |
if (*q++ != 'r' || *q++ != '-') | |
break; | |
if (from <= (uintptr_t) ptr && to >= (uintptr_t) ptr_end) | |
{ | |
size = 0; | |
break; | |
} | |
else if (from <= (uintptr_t) ptr) | |
size -= to - (uintptr_t) ptr; | |
else if (to >= (uintptr_t) ptr_end) | |
size -= (uintptr_t) ptr_end - from; | |
else | |
size -= to - from; | |
if (!size) | |
break; | |
} | |
} | |
fclose (fp); | |
free (line); | |
/* If the whole area between ptr and ptr_end is covered by read-only | |
VMAs, return 1. Otherwise return -1. */ | |
return size == 0 ? 1 : -1; | |
} |