Good article. This is how buffer overflow is exploited. But I
guess, kernel provides some random stack alignment to prevent this.
I think you mean ASLR. On Linux, this can be turned off by running
echo 0 > /proc/sys/kernel/randomize_va_space. On
Windows, DEP can be turned off at Control Panel →
System → Advanced →
Performance → Settings, if I remember
echo 0 > /proc/sys/kernel/randomize_va_space