On Wed, May 15, 2019 at 06:18:30 -0500,
  Bruno Wolff III <bruno@wolff.to> wrote:
>Now I'm looking at: f6ad55a6a184ebdf3d98a90eab0895f73ce9797e Merge 
>branch 'nla_nest_start', which looks like it might also cause a 
>problem.

Changing nla_nest_start to nla_nest_start_noflag didn't seem to help.

In case anyone else is working on getting wireguard to work with 5.2, 
I'm attaching my latest test diff.