Segfault and heap buffer overflow in `{Experimental,}DatasetToTFRecord`

### Impact The implementation for `tf.raw_ops.ExperimentalDatasetToTFRecord` and `tf.raw_ops.DatasetToTFRecord` can trigger heap buffer overflow and segmentation fault: ```python import tensorflow as tf dataset = tf.data.Dataset.range(3) dataset = tf.data.experimental.to_variant(dataset) tf.raw_ops.ExperimentalDatasetToTFRecord( input_dataset=dataset, filename='/tmp/output', compression_type='') ``` The [implementation](https://github.com/tensorflow/tensorflow/blob/f24faa153ad31a4b51578f8181d3aaab77a1ddeb/tensorflow/core/kernels/data/experimental/to_tf_record_op.cc#L93-L102) assumes that all records in the dataset are of string type. However, there is no check for that, and the example given above uses numeric types. ### Patches We have patched the issue in GitHub commit [e0b6e58c328059829c3eb968136f17aa72b6c876](https://github.com/tensorflow/tensorflow/commit/e0b6e58c328059829c3eb968136f17aa72b6c876). The fix will be included in TensorFlow 2.6.0. We will also cherrypick this commit on TensorFlow 2.5.1, TensorFlow 2.4.3, and TensorFlow 2.3.4, 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 members of the Aivul Team from Qihoo 360.

CVSS 3.1

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Severity from

GitHub (reviewed advisory)

Weakness

CWE-120, CWE-787

Also known as

BIT-tensorflow-2021-37650, CVE-2021-37650, PYSEC-2021-272, PYSEC-2021-563, PYSEC-2021-761

• github.com/tensorflow/tensorflow/security/advisories/GHSA-f8h4-7rgh-q2gm
• nvd.nist.gov/vuln/detail/CVE-2021-37650
• github.com/tensorflow/tensorflow/commit/e0b6e58c328059829c3eb968136f17aa72b6c876
• github.com/pypa/advisory-database/tree/main/vulns/tensorflow-cpu/PYSEC-2021-563.yaml
• github.com/pypa/advisory-database/tree/main/vulns/tensorflow-gpu/PYSEC-2021-761.yaml
• github.com/pypa/advisory-database/tree/main/vulns/tensorflow/PYSEC-2021-272.yaml
• github.com/tensorflow/tensorflow