fixes for stack clash vulnerability

[Mark Millard]

Jov amutu at amutu.com wrote on Wed Jun 28 14:40:16 UTC 2017

> There is a commit fix this: https://svnweb.freebsd.org/changeset/base/320317


Unfortunately the change broke other behavior resulting
in some failing stack allocations for new threads and
so there is also now:

https://lists.freebsd.org/pipermail/svn-src-head/2017-June/102259.html

and its:

https://svnweb.freebsd.org/changeset/base/320430

to keep the overall system behavior correct.

(At least that is my understanding of the relationship
between those two commits.)

===
Mark Millard
markmi at dsl-only.net