Avoid divide-by-zero in shadow code

Bug: oss-fuzz:6728
Change-Id: Id87140c8ee3b4e438c0c1e7d9b108a40e2a65fbe
Reviewed-on: https://skia-review.googlesource.com/131145
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/src/utils/SkShadowTessellator.cpp b/src/utils/SkShadowTessellator.cpp
index c377579de2..c07311c43d 100755
--- a/src/utils/SkShadowTessellator.cpp
+++ b/src/utils/SkShadowTessellator.cpp
@@ -1587,7 +1587,8 @@ sk_sp<SkVertices> SkShadowTessellator::MakeSpot(const SkPath& path, const SkMatr
                                                 const SkPoint3& zPlane, const SkPoint3& lightPos,
                                                 SkScalar lightRadius,  bool transparent) {
     if (!ctm.mapRect(path.getBounds()).isFinite() || !zPlane.isFinite() ||
-        !lightPos.isFinite() || !SkScalarIsFinite(lightRadius) || !(lightRadius > 0)) {
+        !lightPos.isFinite() || !(lightPos.fZ >= SK_ScalarNearlyZero) ||
+        !SkScalarIsFinite(lightRadius) || !(lightRadius >= SK_ScalarNearlyZero)) {
         return nullptr;
     }
     SkSpotShadowTessellator spotTess(path, ctm, zPlane, lightPos, lightRadius, transparent);