fix CVE-2019-20808
This makes sure reads are confined to vga video memory.
v3: use uint32_t, fix cut+paste bug.
v2: fix ati_cursor_draw_line too.
Reported-by: xu hang <flier_m@outlook.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: BALATON Zoltan <balaton@eik.bme.hu>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20190917111441.27405-3-kraxel@redhat.com
cherry-pick from aab0e2a661b2b6bf7915c0aefe807fb60d6d9d13
Signed-off-by: Jiajie Li <lijiajie11@huawei.com>
