Heap OOB access in unicode ops

@@ -533,6 +533,17 @@ class UnicodeEncodeOp : public OpKernel {
     const Tensor& input_splits = context->input(1);
     const auto input_splits_flat = input_splits.flat<SPLITS_TYPE>();
 
+    // Operation will treat first argument in input_splits as if it were zero
+    // regardless of its actual value since splits should begin with zero and
+    // end with the length of the input values vector.
+    OP_REQUIRES(
+        context, input_splits_flat(0) == 0,
+        errors::InvalidArgument("First value in input_splits must be zero."));
+    OP_REQUIRES(context,
+                input_splits_flat(input_splits_flat.size() - 1) ==
+                    input_tensor_flat.size(),
+                errors::InvalidArgument("Last value in input_splits must be "
+                                        "equal to length of input_tensor."));
     // Since we limit to a 2-D input (flat_values of rank 1 and a single splits
     // tensor), our output dimension will be 1 with it's size equal to the
     // number of splits (outer dimension or ragged tensor).
@@ -548,6 +559,14 @@ class UnicodeEncodeOp : public OpKernel {
     for (int i = 1; i < input_splits_flat.size(); ++i) {
       icu::UnicodeString unicode_string;
       icu::UnicodeStringAppendable appendable_unicode_string(unicode_string);
+      OP_REQUIRES(
+          context, input_splits_flat(i - 1) <= input_splits_flat(i),
+          errors::InvalidArgument(
+              "Values in input_splits must be equal or in ascending order."));
+      OP_REQUIRES(
+          context, input_splits_flat(i) <= input_tensor_flat.size(),
+          errors::InvalidArgument("Values in input_splits must be less than or "
+                                  "equal to input_tensor length."));
       for (; idx < input_splits_flat(i); ++idx) {
         int32 code_point = input_tensor_flat(idx);
         // Check for invalid code point