`SparseFillEmptyRows` heap OOB
### Impact
The implementation
https://github.com/tensorflow/tensorflow/blob/e71b86d47f8bc1816bf54d7bddc4170e47670b97/tensorflow/core/kernels/sparse_fill_empty_rows_op.cc#L194-L241 of `SparseFillEmptyRows` can be made to trigger a heap OOB access:
```python
import tensorflow as tf
data=tf.raw_ops.SparseFillEmptyRows(
indices=[[0,0],[0,0],[0,0]],
values=['sssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssss'],
dense_shape=[5,3],
default_value='o')
```
This occurs whenever the size of `indices` does not match the size of `values`.
### Patches
We have patched the issue in GitHub commit 67bfd9feeecfb3c61d80f0e46d89c170fbee682b
https://github.com/tensorflow/tensorflow/commit/67bfd9feeecfb3c61d80f0e46d89c170fbee682b.
The fix will be included in TensorFlow 2.7.0. We will also cherrypick this commit on TensorFlow 2.6.1, TensorFlow 2.5.2, and TensorFlow 2.4.4, 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.