CVE-2021-29541 — Null pointer dereference in `StringNGrams`

Affected: tensorflow

TensorFlow is an end-to-end open source platform for machine learning. An attacker can trigger a dereference of a null pointer in `tf.raw_ops.StringNGrams`. This is because the implementation(https://github.com/tensorflow/tensorflow/blob/1cdd4da14282210cc759e468d9781741ac7d01bf/tensorflow/core/kernels/string_ngrams_op.cc#L67-L74) does not fully validate the `data_splits` argument. This would result in `ngrams_data`(https://github.com/tensorflow/tensorflow/blob/1cdd4da14282210cc759e468d9781741ac7d01bf/tensorflow/core/kernels/string_ngrams_op.cc#L106-L110) to be a null pointer when the output would be computed to have 0 or negative size. Later writes to the output tensor would then cause a null pointer dereference. 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.

GHSA-xqfj-35wv-m3cr — Null pointer dereference in `StringNGrams`

Affected: PyPI: tensorflow, PyPI: tensorflow-cpu, PyPI: tensorflow-gpu

### Impact An attacker can trigger a dereference of a null pointer in `tf.raw_ops.StringNGrams`:

```python import tensorflow as tf

data=tf.constant([''] * 11, shape=[11], dtype=tf.string)

splits = [0]*115 splits.append(3) data_splits=tf.constant(splits, shape=[116], dtype=tf.int64)

tf.raw_ops.StringNGrams(data=data, data_splits=data_splits, separator=b'Ss', ngram_widths=[7,6,11], left_pad='ABCDE', right_pad=b'ZYXWVU', pad_width=50, preserve_short_sequences=True) ```

This is because the [implementation](https://github.com/tensorflow/tensorflow/blob/1cdd4da14282210cc759e468d9781741ac7d01bf/tensorflow/core/kernels/string_ngrams_op.cc#L67-L74) does not fully validate the `data_splits` argument. This would result in [`ngrams_data`](https://github.com/tensorflow/tensorflow/blob/1cdd4da14282210cc759e468d9781741ac7d01bf/tensorflow/core/kernels/string_ngrams_op.cc#L106-L110) to be a null pointer when the output would be computed to have 0 or negative size.

Later writes to the output tensor would then cause a null pointer dereference.

### Patches We have patched the issue in GitHub commit [ba424dd8f16f7110eea526a8086f1a155f14f22b](https://github.com/tensorflow/tensorflow/commit/ba424dd8f16f7110eea526a8086f1a155f14f22b). 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 affecte…

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CVE-2021-29541 — Null pointer dereference in `StringNGrams`

GHSA-xqfj-35wv-m3cr — Null pointer dereference in `StringNGrams`