Division by zero in TFLite's implementation of `EmbeddingLookup`

The implementation of the EmbeddingLookup TFLite operator is [vulnerable to a division by zero error](https://github.com/tensorflow/tensorflow/blob/e4b29809543b250bc9b19678ec4776299dd569ba/tensorflow/lite/kernels/embedding_lookup.cc#L73-L74):

```cc

const int row_size = SizeOfDimension(value, 0);

const int row_bytes = value->bytes / row_size;

`

An attacker can craft a model such that the first dimension of the value input is 0.

Patches

We have patched the issue in GitHub commit [f61c57bd425878be108ec787f4d96390579fb83e](https://github.com/tensorflow/tensorflow/commit/f61c57bd425878be108ec787f4d96390579fb83e).

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.