twm deadlocks the server

[Antoine Martin]

Hi,

I've just come across this easy DoS with twm and
X.Org X Server 1.19.3 from Fedora 26.

Steps:
/usr/libexec/Xorg -noreset -novtswitch -config /etc/xpra/xorg.conf :10&
#verify we can access the display:
DISPLAY=:10 xprop -root
#start xterm so we have a window, then twm:
DISPLAY=:10 xterm&
DISPLAY=:10 twm&
#now click on the title bar of the xterm:
DISPLAY=:10 xdotool mousemove 90 10 mousedown 1
#and now the X11 server is inaccessible:
DISPLAY=:10 xprop -root

Cheers
Antoine

PS: the xorg.conf to use for the dummy driver can be found here:
http://xpra.org/trac/browser/xpra/tags/v2.0.x/src/etc/xpra/xorg.conf