<linearGradient id="grad" x1="0" x2="0" y1="0" y2="1">
y2
заменить значение с 1
на 100%
:<linearGradient id="grad" x1="0" x2="0" y1="0" y2="100%">
gradientUnits
со значением userSpaceOnUse
:<linearGradient id="grad" x1="0" x2="0" y1="0" y2="100%" gradientUnits="userSpaceOnUse">
gradientUnits
.