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74627d13c7
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>
The X server uses this directory to store the compiled version of the
current keymap and/or any scratch keymaps used by clients. The X server
or some other tool might destroy or replace the files in this directory,
so it is not a safe place to store compiled keymaps for long periods of
time. The default keymap for any server is usually stored in:
X<num>-default.xkm
where <num> is the display number of the server in question, which makes
it possible for several servers *on the same host* to share the same
directory.
Unless the X server is modified, sharing this directory between servers on
different hosts could cause problems.