Calling strlen on char[4] that does not need to contain '\0' is wrong and X
server may end up running into uninitialized memory.
In addition GCC 8 is clever enough that it knows that strlen on char[4] can
return 0, 1, 2, 3 or cause undefined behavior. With this knowledge it can
optimize away the min(..., 4). In reality it can cause the memcpy to be called
with bigger size than 4 and overflow the destination buffer.
Fixes: 83913de25d (xkb: Silence some compiler warnings)
Closes: https://gitlab.freedesktop.org/xorg/xserver/-/issues/288
Signed-off-by: Matt Turner <mattst88@gmail.com>
(cherry picked from commit 74627d13c7)
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.
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