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/* Copyright (C) 2004-2020 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
<https://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;
}
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