Division by zero in TFLite's implementation of `DepthToSpace`
### Impact
The implementation of the `DepthToSpace` TFLite operator is vulnerable to a division by zero error
https://github.com/tensorflow/tensorflow/blob/0d45ea1ca641b21b73bcf9c00e0179cda284e7e7/tensorflow/lite/kernels/depth_to_space.cc#L63-L69:
```cc
const int block_size = params->block_size;
...
const int input_channels = input->dims->data[3];
...
int output_channels = input_channels / block_size / block_size;
```
An attacker can craft a model such that `params->block_size` is 0.
### Patches
We have patched the issue in GitHub commit 106d8f4fb89335a2c52d7c895b7a7485465ca8d9
https://github.com/tensorflow/tensorflow/commit/106d8f4fb89335a2c52d7c895b7a7485465ca8d9.
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 members of the Aivul Team from Qihoo 360.