Validate `data_splits` for `tf.StringNGrams`.

Without validation, we can cause a heap buffer overflow which results in data leakage and/or segfaults.

PiperOrigin-RevId: 332543478
Change-Id: Iee5bda24497a195d09d122355502480830b1b317

tensorflow/core/kernels/string_ngrams_op.cc

@@ -19,6 +19,7 @@ limitations under the License.
 #include "absl/strings/ascii.h"
 #include "absl/strings/str_cat.h"
 #include "tensorflow/core/framework/op_kernel.h"
+#include "tensorflow/core/platform/errors.h"
 
 namespace tensorflow {
 namespace text {
@@ -60,6 +61,18 @@ class StringNGramsOp : public tensorflow::OpKernel {
     OP_REQUIRES_OK(context, context->input("data_splits", &splits));
     const auto& splits_vec = splits->flat<SPLITS_TYPE>();
 
+    // Validate that the splits are valid indices into data
+    const int input_data_size = data->flat<tstring>().size();
+    const int splits_vec_size = splits_vec.size();
+    for (int i = 0; i < splits_vec_size; ++i) {
+      bool valid_splits = splits_vec(i) >= 0;
+      valid_splits = valid_splits && (splits_vec(i) <= input_data_size);
+      OP_REQUIRES(
+          context, valid_splits,
+          errors::InvalidArgument("Invalid split value ", splits_vec(i),
+                                  ", must be in [0,", input_data_size, "]"));
+    }
+
     // If there is no data or size, return an empty RT.
     if (data->flat<tstring>().size() == 0 || splits_vec.size() == 0) {
       tensorflow::Tensor* empty;

tensorflow/python/ops/raw_ops_test.py

@@ -18,16 +18,21 @@ from __future__ import absolute_import
 from __future__ import division
 from __future__ import print_function
 
+from absl.testing import parameterized
+
 from tensorflow.python.eager import context
 from tensorflow.python.framework import constant_op
+from tensorflow.python.framework import errors
 from tensorflow.python.framework import ops
 from tensorflow.python.framework import test_util
 from tensorflow.python.ops import gen_math_ops
+from tensorflow.python.ops import gen_string_ops
 from tensorflow.python.platform import test
 
 
 @test_util.run_all_in_graph_and_eager_modes
-class RawOpsTest(test.TestCase):
+@test_util.disable_tfrt
+class RawOpsTest(test.TestCase, parameterized.TestCase):
 
   def testSimple(self):
     x = constant_op.constant(1)
@@ -58,6 +63,22 @@ class RawOpsTest(test.TestCase):
         gen_math_ops.Any(input=x, axis=0),
         gen_math_ops.Any(input=x, axis=0, keep_dims=False))
 
+  @parameterized.parameters([[0, 8]], [[-1, 6]])
+  def testStringNGramsBadDataSplits(self, splits):
+    data = ["aa", "bb", "cc", "dd", "ee", "ff"]
+    with self.assertRaisesRegex(errors.InvalidArgumentError,
+                                "Invalid split value"):
+      self.evaluate(
+          gen_string_ops.string_n_grams(
+              data=data,
+              data_splits=splits,
+              separator="",
+              ngram_widths=[2],
+              left_pad="",
+              right_pad="",
+              pad_width=0,
+              preserve_short_sequences=False))
+
 
 if __name__ == "__main__":
   ops.enable_eager_execution()