chore: import upstream snapshot with attribution

tensorflow/security/advisory/tfsa-2021-102.md

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+## TFSA-2021-102: Interpreter crash from `tf.io.decode_raw`
+
+### CVE Number
+CVE-2021-29614
+
+### Impact
+The implementation of `tf.io.decode_raw` produces incorrect results and crashes
+the Python interpreter when combining `fixed_length` and wider datatypes.
+
+```python
+import tensorflow as tf
+
+tf.io.decode_raw(tf.constant(["1","2","3","4"]), tf.uint16, fixed_length=4)
+```
+
+The [implementation of the padded
+version](https://github.com/tensorflow/tensorflow/blob/1d8903e5b167ed0432077a3db6e462daf781d1fe/tensorflow/core/kernels/decode_padded_raw_op.cc)
+is buggy due to a confusion about pointer arithmetic rules.
+
+First, the code
+[computes](https://github.com/tensorflow/tensorflow/blob/1d8903e5b167ed0432077a3db6e462daf781d1fe/tensorflow/core/kernels/decode_padded_raw_op.cc#L61)
+the width of each output element by dividing the `fixed_length` value to the
+size of the type argument:
+
+```cc
+int width = fixed_length / sizeof(T);
+```
+
+The `fixed_length` argument is also used to determine the [size needed for the
+output
+tensor](https://github.com/tensorflow/tensorflow/blob/1d8903e5b167ed0432077a3db6e462daf781d1fe/tensorflow/core/kernels/decode_padded_raw_op.cc#L63-L79):
+
+```cc
+TensorShape out_shape = input.shape();
+out_shape.AddDim(width);
+Tensor* output_tensor = nullptr;
+OP_REQUIRES_OK(context, context->allocate_output("output", out_shape, &output_tensor));
+
+auto out = output_tensor->flat_inner_dims<T>();
+T* out_data = out.data();
+memset(out_data, 0, fixed_length * flat_in.size());
+```
+
+This is followed by [reencoding
+code](https://github.com/tensorflow/tensorflow/blob/1d8903e5b167ed0432077a3db6e462daf781d1fe/tensorflow/core/kernels/decode_padded_raw_op.cc#L85-L94):
+
+```cc
+for (int64 i = 0; i < flat_in.size(); ++i) {
+  const T* in_data = reinterpret_cast<const T*>(flat_in(i).data());
+
+  if (flat_in(i).size() > fixed_length) {
+    memcpy(out_data, in_data, fixed_length);
+  } else {
+    memcpy(out_data, in_data, flat_in(i).size());
+  }
+  out_data += fixed_length;
+}
+```
+
+The erroneous code is the last line above: it is moving the `out_data` pointer
+by `fixed_length * sizeof(T)` bytes whereas it only copied at most
+`fixed_length` bytes from the input. This results in parts of the input not
+being decoded into the output.
+
+Furthermore, because the pointer advance is far wider than desired, this quickly
+leads to writing to outside the bounds of the backing data. This OOB write leads
+to interpreter crash in the reproducer mentioned here, but more severe attacks
+can be mounted too, given that this gadget allows writing to periodically placed
+locations in memory.
+
+### Patches
+We have patched the issue in GitHub commit
+[698e01511f62a3c185754db78ebce0eee1f0184d](https://github.com/tensorflow/tensorflow/commit/698e01511f62a3c185754db78ebce0eee1f0184d).
+
+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.