Integer underflow in the xTrapezoidValid macro in render/picture.h in X.Org
allows context-dependent attackers to cause a denial of service (crash) via
a negative bottom value.
Signed-off-by: Baogen Shang <baogen.shang@windriver.com> Signed-off-by: Kai Kang <kai.kang@windriver.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>