Crash in `tf.strings.substr` due to `CHECK`-fail

@@ -51,6 +51,11 @@ class SubstrOp : public OpKernel {
     const Tensor& len_tensor = context->input(2);
     const TensorShape& input_shape = input_tensor.shape();
     const TensorShape& pos_shape = pos_tensor.shape();
+    const TensorShape& len_shape = len_tensor.shape();
+    OP_REQUIRES(context, (pos_shape == len_shape),
+                errors::InvalidArgument(
+                    "pos and len should have the same shape, got: ",
+                    pos_shape.DebugString(), " vs. ", len_shape.DebugString()));
 
     bool is_scalar = TensorShapeUtils::IsScalar(pos_shape);
 

@@ -492,6 +492,16 @@ def testInvalidUnit(self):
       with self.assertRaises(ValueError):
         string_ops.substr(b"test", 3, 1, unit="UTF8")
 
+  def testInvalidPos(self):
+    # Test case for GitHub issue 46900.
+    with self.assertRaises((ValueError, errors_impl.InvalidArgumentError)):
+      x = string_ops.substr(b"abc", len=1, pos=[1, -1])
+      self.evaluate(x)
+
+    with self.assertRaises((ValueError, errors_impl.InvalidArgumentError)):
+      x = string_ops.substr(b"abc", len=1, pos=[1, 2])
+      self.evaluate(x)
+
 
 if __name__ == "__main__":
   test.main()