CVE request: screen stack overflow (deep recursion)

[Florian Weimer <fw () deneb enyo de>]

Upstream bug report by Kuang-che Wu:

“
How to reproduce:
Run this command inside screen
$ printf '\x1b[10000000T'

screen will recursively call MScrollV to depth n/256. This is time consuming and will overflow stack if n is huge.
”

<https://savannah.gnu.org/bugs/?45713>

Upstream fix:

http://git.savannah.gnu.org/cgit/screen.git/commit/?id=b7484c224738247b510ed0d268cd577076958f1b

Debian bug:

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=797624

MScrollV creates a very large stack frame, so it could theoreticall
jump over the guard page at the top of the stack, and it might be
feasible to exploit this for something else besides denial-of-service.