Fix GH-19739: imagefilledellipse/imageellipse overflow

Author: devnexen

ext/gd/libgd/gd.c

@@ -1730,6 +1730,9 @@ void gdImageEllipse(gdImagePtr im, int mx, int my, int w, int h, int c)
 	bq = b * b;
 	dx = aq << 1;
 	dy = bq << 1;
+	if (bq > 0 && a > INT64_MAX / bq) {
+		return;
+	}
 	r  = a * bq;
 	rx = r << 1;
 	ry = 0;
@@ -1774,6 +1777,9 @@ void gdImageFilledEllipse (gdImagePtr im, int mx, int my, int w, int h, int c)
 	bq = b * b;
 	dx = aq << 1;
 	dy = bq << 1;
+	if (bq > 0 && a > INT64_MAX / bq) {
+		return;
+	}
 	r  = a * bq;
 	rx = r << 1;
 	ry = 0;