In recent years, the kernel has (finally) upped its game when it comes to
hardening. It is rather harder to compromise a running kernel than it used
to be. But “rather harder” is relative: attackers still manage to find
ways to exploit kernel bugs. One piece of information that can be helpful
to attackers is the location of the kernel stack; this
patch set from Kees Cook and Elena Reshetova may soon make that
information harder to come by and nearly useless in any case.

Source: LWN.net – [$] Per-system-call kernel-stack offset randomization