xcursor: Fix heap overflows when parsing malicious files
xcursor: Fix heap overflows when parsing malicious files

It is possible to trigger heap overflows due to an integer overflow
while parsing images.

The integer overflow occurs because the chosen limit 0x10000 for
dimensions is too large for 32 bit systems, because each pixel takes
4 bytes. Properly chosen values allow an overflow which in turn will
lead to less allocated memory than needed for subsequent reads.

See also:
https://cgit.freedesktop.org/xorg/lib/libXcursor/commit/?id=4794b5dd34688158fb51a2943032569d3780c4b8
https://gitlab.freedesktop.org/wayland/wayland/commit/5d201df72f3d4f4cb8b8f75f980169b03507da38

swaywm/wlroots,swaywm/wlroots,ascent12/wlroots,ascent12/wlroots,SirCmpwn/wlroots