X11 Segfault in Fullscreen mode manipulating root window

[jamie@…]

Attempts to manipulate the root window apparently can cause segfaults in X11.bin when in fullscreen mode. Steps to replicate:

• Start X11, with Full Screen mode disabled in Preferences.
• Enter Preferences, enable Full Screen Mode.
• Press Ctrl-Option-A to enter Full Screen mode.
• In xterm type "xsetroot -solid Red"

Crashreport:
Thread 2 Crashed:
0   libpixman-1.0.dylib           	0x003d0a51 pixman_fill + 170
1   X11.bin                       	0x0008fd20 fbFillRegionSolid + 182
2   X11.bin                       	0x00090072 fbPaintWindow + 263
3   X11.bin                       	0x000d2602 damagePaintWindow + 129
4   X11.bin                       	0x0001fbcb RootlessPaintWindowBackground + 136
5   X11.bin                       	0x0003ec0c miClearToBackground + 362
6   X11.bin                       	0x0005c4fd ProcClearToBackground + 164
7   X11.bin                       	0x0006078d Dispatch + 828
8   X11.bin                       	0x0006efac dix_main + 1333
9   X11.bin                       	0x00013c84 server_thread + 53
10  libSystem.B.dylib             	0x96941095 _pthread_start + 321
11  libSystem.B.dylib             	0x96940f52 thread_start + 34

[jeremyhu@…]

From my testing, this was happening before I fixed the white-rectangle issue... can you please confirm when you first noticed this (and when you know it wasn't crashing)?

[jeremyhu@…]

I notice that this doesn't happen if you enter-fullscreen, leave-fullscreen, then enter it again, then do the setroot...

I wonder if this is a buffer-overrun that is associated with the menubar-height region at the bottom that is not covered by the root window...

[jeremyhu@…]

Fixed in git (will be in 2.3.2):

​http://cgit.freedesktop.org/xorg/xserver/commit/?id=508aa95bc2cd3fdc3dff448ec090919bf807d153