chore: import upstream snapshot with attribution

tensorflow/security/advisory/tfsa-2021-113.md

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+## TFSA-2021-113: Null pointer dereference and heap OOB read in operations restoring tensors
+
+### CVE Number
+CVE-2021-37639
+
+### Impact
+When restoring tensors via raw APIs, if the tensor name is not provided,
+TensorFlow can be tricked into dereferencing a null pointer:
+
+```python
+import tensorflow as tf
+
+tf.raw_ops.Restore(
+  file_pattern=['/tmp'],
+  tensor_name=[],
+  default_value=21,
+  dt=tf.int,
+  preferred_shard=1)
+```
+
+The same undefined behavior can be triggered by `tf.raw_ops.RestoreSlice`:
+
+```python
+import tensorflow as tf
+
+tf.raw_ops.RestoreSlice(
+  file_pattern=['/tmp'],
+  tensor_name=[],
+  shape_and_slice='2',
+  dt=inp.array([tf.int]),
+  preferred_shard=1)
+```
+
+Alternatively, attackers can read memory outside the bounds of heap allocated
+data by providing some tensor names but not enough for a successful restoration:
+
+```python
+import tensorflow as tf
+
+tf.raw_ops.Restore(
+  file_pattern=['/tmp'],
+  tensor_name=['x'],
+  default_value=21,
+  dt=tf.int,
+  preferred_shard=42)
+```
+
+The
+[implementation](https://github.com/tensorflow/tensorflow/blob/47a06f40411a69c99f381495f490536972152ac0/tensorflow/core/kernels/save_restore_tensor.cc#L158-L159)
+retrieves the tensor list corresponding to the `tensor_name` user controlled
+input and immediately retrieves the tensor at the restoration index (controlled
+via `preferred_shard` argument). This occurs without validating that the
+provided list has enough values.
+
+If the list is empty this results in dereferencing a null pointer (undefined
+behavior). If, however, the list has some elements, if the restoration index is
+outside the bounds this results in heap OOB read.
+
+### Patches
+We have patched the issue in GitHub commit
+[9e82dce6e6bd1f36a57e08fa85af213e2b2f2622](https://github.com/tensorflow/tensorflow/commit/9e82dce6e6bd1f36a57e08fa85af213e2b2f2622).
+
+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](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.