heap-buffer-overflow on Display removal

[uli42]

Runnin nxagent :55 -ac on a dual monitor setup the nxagent window was located on the first screen. I unplugged the HDMI cable of the second display and got this from the nxagent:

==31263==ERROR: AddressSanitizer: heap-use-after-free on address 0x617000002728 at pc 0x55ccbd9a94d9 bp 0x7ffc6eb194d0 sp 0x7ffc6eb194c8
READ of size 4 at 0x617000002728 thread T0
    #0 0x55ccbd9a94d8 in nxagentDropOutput /home/uli/work/nx/ArcticaProject/nx-libs/pr/windowfixes/nx-X11/programs/Xserver/hw/nxagent/Screen.c:3787
    #1 0x55ccbd9aa5ef in nxagentAdjustRandRXinerama /home/uli/work/nx/ArcticaProject/nx-libs/pr/windowfixes/nx-X11/programs/Xserver/hw/nxagent/Screen.c:3950
    #2 0x55ccbd9a93a6 in nxagentChangeScreenConfig /home/uli/work/nx/ArcticaProject/nx-libs/pr/windowfixes/nx-X11/programs/Xserver/hw/nxagent/Screen.c:3759
    #3 0x55ccbd952c75 in nxagentHandleConfigureNotify /home/uli/work/nx/ArcticaProject/nx-libs/pr/windowfixes/nx-X11/programs/Xserver/hw/nxagent/Events.c:3466
    #4 0x55ccbd94a7e3 in nxagentDispatchEvents /home/uli/work/nx/ArcticaProject/nx-libs/pr/windowfixes/nx-X11/programs/Xserver/hw/nxagent/Events.c:1976
    #5 0x55ccbd9830f8 in nxagentWakeupHandler /home/uli/work/nx/ArcticaProject/nx-libs/pr/windowfixes/nx-X11/programs/Xserver/hw/nxagent/Handlers.c:606
    #6 0x55ccbd8b217a in WakeupHandler /home/uli/work/nx/ArcticaProject/nx-libs/pr/windowfixes/nx-X11/programs/Xserver/dix/dixutils.c:433
    #7 0x55ccbd8e2147 in WaitForSomething /home/uli/work/nx/ArcticaProject/nx-libs/pr/windowfixes/nx-X11/programs/Xserver/os/WaitFor.c:354
    #8 0x55ccbd83b3d8 in Dispatch /home/uli/work/nx/ArcticaProject/nx-libs/pr/windowfixes/nx-X11/programs/Xserver/hw/nxagent/NXdispatch.c:365
    #9 0x55ccbd8c2fd8 in main /home/uli/work/nx/ArcticaProject/nx-libs/pr/windowfixes/nx-X11/programs/Xserver/dix/main.c:350
    #10 0x7f070f4e109a in __libc_start_main ../csu/libc-start.c:308
    #11 0x55ccbd7c32e9 in _start (/home/uli/work/nx/ArcticaProject/nx-libs/pr/windowfixes/nx-X11/programs/Xserver/nxagent+0xd02e9)

0x617000002728 is located 40 bytes inside of 728-byte region [0x617000002700,0x6170000029d8)
freed by thread T0 here:
    #0 0x7f0710ee7fb0 in __interceptor_free (/lib/x86_64-linux-gnu/libasan.so.5+0xe8fb0)
    #1 0x55ccbe4d1346 in RRCrtcDestroyResource /home/uli/work/nx/ArcticaProject/nx-libs/pr/windowfixes/nx-X11/programs/Xserver/randr/rrcrtc.c:773
    #2 0x55ccbd86d57c in FreeResource /home/uli/work/nx/ArcticaProject/nx-libs/pr/windowfixes/nx-X11/programs/Xserver/hw/nxagent/NXresource.c:306
    #3 0x55ccbe4d0fd9 in RRCrtcDestroy /home/uli/work/nx/ArcticaProject/nx-libs/pr/windowfixes/nx-X11/programs/Xserver/randr/rrcrtc.c:742
    #4 0x55ccbd9aa07d in nxagentAdjustRandRXinerama /home/uli/work/nx/ArcticaProject/nx-libs/pr/windowfixes/nx-X11/programs/Xserver/hw/nxagent/Screen.c:3914
    #5 0x55ccbd9a93a6 in nxagentChangeScreenConfig /home/uli/work/nx/ArcticaProject/nx-libs/pr/windowfixes/nx-X11/programs/Xserver/hw/nxagent/Screen.c:3759
    #6 0x55ccbd952c75 in nxagentHandleConfigureNotify /home/uli/work/nx/ArcticaProject/nx-libs/pr/windowfixes/nx-X11/programs/Xserver/hw/nxagent/Events.c:3466
    #7 0x55ccbd94a7e3 in nxagentDispatchEvents /home/uli/work/nx/ArcticaProject/nx-libs/pr/windowfixes/nx-X11/programs/Xserver/hw/nxagent/Events.c:1976
    #8 0x55ccbd9830f8 in nxagentWakeupHandler /home/uli/work/nx/ArcticaProject/nx-libs/pr/windowfixes/nx-X11/programs/Xserver/hw/nxagent/Handlers.c:606
    #9 0x55ccbd8b217a in WakeupHandler /home/uli/work/nx/ArcticaProject/nx-libs/pr/windowfixes/nx-X11/programs/Xserver/dix/dixutils.c:433
    #10 0x55ccbd8e2147 in WaitForSomething /home/uli/work/nx/ArcticaProject/nx-libs/pr/windowfixes/nx-X11/programs/Xserver/os/WaitFor.c:354
    #11 0x55ccbd83b3d8 in Dispatch /home/uli/work/nx/ArcticaProject/nx-libs/pr/windowfixes/nx-X11/programs/Xserver/hw/nxagent/NXdispatch.c:365
    #12 0x55ccbd8c2fd8 in main /home/uli/work/nx/ArcticaProject/nx-libs/pr/windowfixes/nx-X11/programs/Xserver/dix/main.c:350
    #13 0x7f070f4e109a in __libc_start_main ../csu/libc-start.c:308

previously allocated by thread T0 here:
    #0 0x7f0710ee8518 in calloc (/lib/x86_64-linux-gnu/libasan.so.5+0xe9518)
    #1 0x55ccbe4cd8bc in RRCrtcCreate /home/uli/work/nx/ArcticaProject/nx-libs/pr/windowfixes/nx-X11/programs/Xserver/randr/rrcrtc.c:98
    #2 0x55ccbd9aa093 in nxagentAdjustRandRXinerama /home/uli/work/nx/ArcticaProject/nx-libs/pr/windowfixes/nx-X11/programs/Xserver/hw/nxagent/Screen.c:3921
    #3 0x55ccbd9a93a6 in nxagentChangeScreenConfig /home/uli/work/nx/ArcticaProject/nx-libs/pr/windowfixes/nx-X11/programs/Xserver/hw/nxagent/Screen.c:3759
    #4 0x55ccbd95284b in nxagentHandleConfigureNotify /home/uli/work/nx/ArcticaProject/nx-libs/pr/windowfixes/nx-X11/programs/Xserver/hw/nxagent/Events.c:3445
    #5 0x55ccbd94a7e3 in nxagentDispatchEvents /home/uli/work/nx/ArcticaProject/nx-libs/pr/windowfixes/nx-X11/programs/Xserver/hw/nxagent/Events.c:1976
    #6 0x55ccbd9830f8 in nxagentWakeupHandler /home/uli/work/nx/ArcticaProject/nx-libs/pr/windowfixes/nx-X11/programs/Xserver/hw/nxagent/Handlers.c:606
    #7 0x55ccbd8b217a in WakeupHandler /home/uli/work/nx/ArcticaProject/nx-libs/pr/windowfixes/nx-X11/programs/Xserver/dix/dixutils.c:433
    #8 0x55ccbd8e2147 in WaitForSomething /home/uli/work/nx/ArcticaProject/nx-libs/pr/windowfixes/nx-X11/programs/Xserver/os/WaitFor.c:354
    #9 0x55ccbd83b3d8 in Dispatch /home/uli/work/nx/ArcticaProject/nx-libs/pr/windowfixes/nx-X11/programs/Xserver/hw/nxagent/NXdispatch.c:365
    #10 0x55ccbd8c2fd8 in main /home/uli/work/nx/ArcticaProject/nx-libs/pr/windowfixes/nx-X11/programs/Xserver/dix/main.c:350
    #11 0x7f070f4e109a in __libc_start_main ../csu/libc-start.c:308

SUMMARY: AddressSanitizer: heap-use-after-free /home/uli/work/nx/ArcticaProject/nx-libs/pr/windowfixes/nx-X11/programs/Xserver/hw/nxagent/Screen.c:3787 in nxagentDropOutput
Shadow bytes around the buggy address:
  0x0c2e7fff8490: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c2e7fff84a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c2e7fff84b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c2e7fff84c0: 00 00 00 00 00 00 00 00 00 00 00 fa fa fa fa fa
  0x0c2e7fff84d0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
=>0x0c2e7fff84e0: fd fd fd fd fd[fd]fd fd fd fd fd fd fd fd fd fd
  0x0c2e7fff84f0: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c2e7fff8500: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c2e7fff8510: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c2e7fff8520: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c2e7fff8530: fd fd fd fd fd fd fd fd fd fd fd fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07 
  Heap left redzone:       fa
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
==31263==ABORTING