2.2.6 [SVG11] Section 13.3, Patterns
The specification states:
SVG's user agent style sheet sets the 'overflow' property for 'pattern' elements to hidden, which causes a rectangular clipping path to be created at the bounds of the pattern tile. Unless the 'overflow' property is overridden, any graphics within the pattern which goes outside of the pattern rectangle will be clipped. Example pattern01 below shows the effect of clipping to the pattern tile.
IE9 Mode, IE10 Mode, and IE11 Mode (All Versions)
The overflow property on pattern elements is always treated as if the value
hidden is assigned to it; it cannot be overridden.