Division by 0 in `QuantizedAdd`

### Impact An attacker can cause a runtime division by zero error and denial of service in `tf.raw_ops.QuantizedAdd`: ```python import tensorflow as tf x = tf.constant([68, 228], shape=[2, 1], dtype=tf.quint8) y = tf.constant([], shape=[2, 0], dtype=tf.quint8) min_x = tf.constant(10.723421015884028) max_x = tf.constant(15.19578006631113) min_y = tf.constant(-5.539003866682977) max_y = tf.constant(42.18819949559947) tf.raw_ops.QuantizedAdd(x=x, y=y, min_x=min_x, max_x=max_x, min_y=min_y, max_y=max_y) ``` This is because the [implementation](https://github.com/tensorflow/tensorflow/blob/6f26b3f3418201479c264f2a02000880d8df151c/tensorflow/core/kernels/quantized_add_op.cc#L289-L295) computes a modulo operation without validating that the divisor is not zero. ```cc void VectorTensorAddition(const T* vector_data, float min_vector, float max_vector, int64 vector_num_elements, const T* tensor_data, float min_tensor, float max_tensor, int64 tensor_num_elements, float output_min, float output_max, Toutput* output) { for (int i = 0; i < tensor_num_elements; ++i) { const int64 vector_i = i % vector_num_elements; ... } } ``` Since `vector_num_elements` is [determined based on input shapes](https://github.com/tensorflow/tensorflow/blob/6f26b3f3418201479c264f2a02000880d8df151c/tensorflow/core/kernels/quantized_add_op.cc#L522-L544), a user can trigger scenarios where this quantity is 0. ### Patches We have patched the issue in GitHub commit [744009c9e5cc5d0447f0dc39d055f917e1fd9e16](https://github.com/tensorflow/tensorflow/commit/744009c9e5cc5d0447f0dc39d055f917e1fd9e16). 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.

CVSS 3.1

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

Severity from

GitHub (reviewed advisory)

Weakness

CWE-369

Also known as

BIT-tensorflow-2021-29549, CVE-2021-29549, PYSEC-2021-186, PYSEC-2021-477, PYSEC-2021-675

• github.com/tensorflow/tensorflow/security/advisories/GHSA-x83m-p7pv-ch8v
• nvd.nist.gov/vuln/detail/CVE-2021-29549
• github.com/tensorflow/tensorflow/commit/744009c9e5cc5d0447f0dc39d055f917e1fd9e16
• github.com/pypa/advisory-database/tree/main/vulns/tensorflow-cpu/PYSEC-2021-477.yaml
• github.com/pypa/advisory-database/tree/main/vulns/tensorflow-gpu/PYSEC-2021-675.yaml
• github.com/pypa/advisory-database/tree/main/vulns/tensorflow/PYSEC-2021-186.yaml
• github.com/tensorflow/tensorflow