fb51d5dd53
ZDI-CAN-19866/CVE-2023-1393
If a client explicitly destroys the compositor overlay window (aka COW),
we would leave a dangling pointer to that window in the CompScreen
structure, which will trigger a use-after-free later.
Make sure to clear the CompScreen pointer to the COW when the latter gets
destroyed explicitly by the client.
This vulnerability was discovered by:
Jan-Niklas Sohn working with Trend Micro Zero Day Initiative
Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>
(cherry picked from commit 26ef545b35)
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
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