Prevent degenerate linear gradient instantiation

If the point distance exceeds SkScalar, nasty things tend to happen.

R=reed@google.com
BUG=636194
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2234663002

Review-Url: https://codereview.chromium.org/2234663002

2 files changed, 18 insertions, 1 deletions

diff --git a/src/effects/gradients/SkGradientShader.cpp b/src/effects/gradients/SkGradientShader.cpp
index 710bde826e..820c5b225d 100644
--- a/src/effects/gradients/SkGradientShader.cpp
+++ b/src/effects/gradients/SkGradientShader.cpp
@@ -790,7 +790,7 @@ sk_sp<SkShader> SkGradientShader::MakeLinear(const SkPoint pts[2],
                                          SkShader::TileMode mode,
                                          uint32_t flags,
                                          const SkMatrix* localMatrix) {
-    if (!pts) {
+    if (!pts || !SkScalarIsFinite((pts[1] - pts[0]).length())) {
         return nullptr;
     }
     if (!valid_grad(colors, pos, colorCount, mode)) {
diff --git a/tests/GradientTest.cpp b/tests/GradientTest.cpp
index 7add42d875..3ed2f518cc 100644
--- a/tests/GradientTest.cpp
+++ b/tests/GradientTest.cpp
@@ -253,6 +253,22 @@ static void test_clamping_overflow(skiatest::Reporter*) {
     // Passes if we don't trigger asserts.
 }
 
+// http://crbug.com/636194
+static void text_degenerate_linear(skiatest::Reporter*) {
+    SkPaint p;
+    const SkColor colors[] = { SK_ColorRED, SK_ColorGREEN };
+    const SkPoint pts[] = {
+        SkPoint::Make(-46058024627067344430605278824628224.0f, 0),
+        SkPoint::Make(SK_ScalarMax, 0)
+    };
+
+    p.setShader(SkGradientShader::MakeLinear(pts, colors, nullptr, 2, SkShader::kClamp_TileMode));
+    sk_sp<SkSurface> surface(SkSurface::MakeRasterN32Premul(50, 50));
+    surface->getCanvas()->drawPaint(p);
+
+    // Passes if we don't trigger asserts.
+}
+
 DEF_TEST(Gradient, reporter) {
     TestGradientShaders(reporter);
     TestConstantGradient(reporter);
@@ -261,4 +277,5 @@ DEF_TEST(Gradient, reporter) {
     test_linear_fuzz(reporter);
     test_two_point_conical_zero_radius(reporter);
     test_clamping_overflow(reporter);
+    text_degenerate_linear(reporter);
 }