e62246641b
CreateGC() allocates a new GC and then checks the resource access rights with XaceHook(). If the call to XaceHook() fails (i.e. GC creation is not granted to the client), CreateGC() exits early and calls FreeGC() to avoid leaking the newly allocated GC. If that happens, the screen's own CreateGC() has not yet been invoked, and as a result the GC functions (GCfuncs) have not been set yet. FreeGC() will invoke the funcs->DestroyClip() and the funcs->DestroyGC() functions, but since those haven't been set, the Xserver will segfault trying to call a NULL function. To prevent that issue, make sure the GC's functions are initialized prior to call them in FreeGC(). Closes: https://gitlab.freedesktop.org/xorg/xserver/-/issues/1625 Reviewed-by: Olivier Fourdan <ofourdan@redhat.com>
X Server
The X server accepts requests from client applications to create windows, which are (normally rectangular) "virtual screens" that the client program can draw into.
Windows are then composed on the actual screen by the X server (or by a separate composite manager) as directed by the window manager, which usually communicates with the user via graphical controls such as buttons and draggable titlebars and borders.
For a comprehensive overview of X Server and X Window System, consult the following article: https://en.wikipedia.org/wiki/X_server
All questions regarding this software should be directed at the Xorg mailing list:
https://lists.freedesktop.org/mailman/listinfo/xorg
The primary development code repository can be found at:
https://gitlab.freedesktop.org/xorg/xserver
For patch submission instructions, see:
https://www.x.org/wiki/Development/Documentation/SubmittingPatches
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