linux-4.1.42 has just been released, which includes a backport of the Stack Clash mitigation. Hopefully the corresponding linux-libre release will be out in the next day or so.
If you're impatient, you could cherry-pick the following two commits: https://git.kernel.org/pub/scm/linux/kernel/git/sashal/linux-stable.git/commit/?h=linux-4.1.y&id=8b18c6b2a0dde5186ed83a60c4915c0909cbeb0a https://git.kernel.org/pub/scm/linux/kernel/git/sashal/linux-stable.git/commit/?h=linux-4.1.y&id=dcda279dede75d5cb4e6af18ba90eb4ca1e813ee It would be similar to commit 91c623aae0f10992aa46957b9072679534e4cd28, but applied only to linux-libre-4.1. Mark
