Check SetMap request length carefully.

Avoid out of bounds memory accesses on too short request.

ZDI-CAN 11572 /  CVE-2020-14360

This vulnerability was discovered by:
Jan-Niklas Sohn working with Trend Micro Zero Day Initiative

Signed-off-by: Matthieu Herrb <matthieu@herrb.eu>
(cherry picked from commit 446ff2d3)
3 jobs for backport-562 in 3 minutes and 38 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Docker Image
passed #5896847
debian-testing

00:00:11

 
  Build And Test
passed #5896848
autotools-build-and-test

00:03:27

passed #5896849
meson-build-and-test

00:01:08