LibGfx: Protect against over-large bitmaps

Libraries/LibGfx/Bitmap.cpp

@@ -44,11 +44,16 @@
 
 namespace Gfx {
 
-static bool size_would_overflow(BitmapFormat format, const IntSize& size)
+static bool size_would_overflow(BitmapFormat, const IntSize& size)
 {
  if (size.width() < 0 || size.height() < 0)
  return true;
- return Checked<size_t>::multiplication_would_overflow(size.width(), size.height(), Bitmap::bpp_for_format(format));
+ // This check is a bit arbitrary, but should protect us from most shenanigans:
+ if (size.width() >= 32768 || size.height() >= 32768)
+ return true;
+ // This check is absolutely necessary. Note that Bitmap::Bitmap always stores
+ // data as RGBA32 internally, so currently we ignore the indicated format.
+ return Checked<size_t>::multiplication_would_overflow(size.width(), size.height(), sizeof(RGBA32));
 }
 
 RefPtr<Bitmap> Bitmap::create(BitmapFormat format, const IntSize& size)