Pull up following revision(s) (requested by christos in ticket #336):
sys/uvm/uvm_mmap.c: revision 1.167
[syzkaller] Fix for PR #52658 as suggested by riastradh@
The bug was found by Dmitry Vyukov (dvyukov%google.com@localhost)
using syzkaller and was tested by me on a VM running
8.99.5

(snj)