CVE-2021-37654: Heap OOB and CHECK fail in `ResourceGather` in TensorFlow

First published: Thu Aug 12 2021(Updated: )

### Impact An attacker can trigger a crash via a `CHECK`-fail in debug builds of TensorFlow using `tf.raw_ops.ResourceGather` or a read from outside the bounds of heap allocated data in the same API in a release build: ```python import tensorflow as tf tensor = tf.constant(value=[[1,2],[3,4],[5,6]],shape=(3,2),dtype=tf.uint32) v = tf.Variable(tensor) tf.raw_ops.ResourceGather( resource=v.handle, indices=[0], dtype=tf.uint32, batch_dims=10, validate_indices=False) ``` The [implementation](https://github.com/tensorflow/tensorflow/blob/f24faa153ad31a4b51578f8181d3aaab77a1ddeb/tensorflow/core/kernels/resource_variable_ops.cc#L660-L668) does not check that the `batch_dims` value that the user supplies is less than the rank of the input tensor. Since the implementation uses several for loops over the dimensions of `tensor`, this results in reading data from outside the bounds of heap allocated buffer backing the tensor: ```cc // batch_dims_ = > params.dims() (10 > 2) for (int i = 0; i < batch_dims_; ++i) { result_shape.AddDim(params.dim_size(i)); } for (int i = batch_dims_; i < indices.dims(); ++i) { result_shape.AddDim(indices.dim_size(i)); } for (int i = batch_dims_ + 1; i < params.dims(); ++i) { result_shape.AddDim(params.dim_size(i)); } ``` In debug mode, `.dim_size(i)` validates that the argument is less than `.dims()` using a `DCHECK`. But the `DCHECK` is a no-op in release builds. ### Patches We have patched the issue in GitHub commit [bc9c546ce7015c57c2f15c168b3d9201de679a1d](https://github.com/tensorflow/tensorflow/commit/bc9c546ce7015c57c2f15c168b3d9201de679a1d). 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.

Credit: security-advisories@github.com security-advisories@github.com

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