CVE-2021-29550 (published 2021-05-14T20:15Z)

TensorFlow is an end-to-end open source platform for machine learning. An attacker can cause a runtime division by zero error and denial of service in `tf.raw_ops.FractionalAvgPool`. This is because the implementation(https://github.com/tensorflow/tensorflow/blob/acc8ee69f5f46f92a3f1f11230f49c6ac266f10c/tensorflow/core/kernels/fractional_avg_pool_op.cc#L85-L89) computes a divisor quantity by dividing two user controlled values. The user controls the values of `input_size[i]` and `pooling_ratio_[i]` (via the `value.shape()` and `pooling_ratio` arguments). If the value in `input_size[i]` is smaller than the `pooling_ratio_[i]`, then the floor operation results in `output_size[i]` being 0. The `DCHECK_GT` line is a no-op outside of debug mode, so in released versions of TF this does not trigger. Later, these computed values are used as arguments(https://github.com/tensorflow/tensorflow/blob/acc8ee69f5f46f92a3f1f11230f49c6ac266f10c/tensorflow/core/kernels/fractional_avg_pool_op.cc#L96-L99) to `GeneratePoolingSequence`(https://github.com/tensorflow/tensorflow/blob/acc8ee69f5f46f92a3f1f11230f49c6ac266f10c/tensorflow/core/kernels/fractional_pool_common.cc#L100-L108). There, the first computation is a division in a modulo operation. Since `output_length` can be 0, this results in runtime crashing. 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.

Severity: LOW
CVSS v2 base score: 2.1 (AV:L/AC:L/Au:N/C:N/I:N/A:P)
CVSS v3 base score: 5.5, MEDIUM (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H)

Weakness information:
cwe_id: CWE-369
cwe_name: Divide By Zero
description: The product divides a value by zero.
extended_description: This weakness typically occurs when an unexpected value is provided to the product, or if an error occurs that is not properly detected. It frequently occurs in calculations involving physical dimensions such as size, length, width, and height.
         

Fix information:
repo_url: https://github.com/tensorflow/tensorflow
commit_details: repo_url: https://github.com/tensorflow/tensorflow
author: Laura Pak
author_date: 2021-04-29 08:38:16-07:00
msg: Fix divide by zero error in `fractional_pool_common.cc`.

PiperOrigin-RevId: 371126221
Change-Id: Iea4b2f363aaeb116ab460e3bc592c687484af344
repository: repo_url: https://github.com/tensorflow/tensorflow
repo_name: tensorflow/tensorflow
description: An Open Source Machine Learning Framework for Everyone
repo_language: C++
owner: tensorflow
file_changes: filename: fractional_avg_pool_op.cc
change_type: ModificationType.MODIFY
diff: @@ -80,6 +80,10 @@ class FractionalAvgPoolOp : public OpKernel {
     std::vector<int> output_size(tensor_in_and_out_dims);
     for (int i = 0; i < tensor_in_and_out_dims; ++i) {
       input_size[i] = tensor_in.dim_size(i);
+      OP_REQUIRES(
+          context, pooling_ratio_[i] <= input_size[i],
+          errors::InvalidArgument(
+              "Pooling ratio cannot be bigger than input tensor dim size."));
     }
     // Output size.
     for (int i = 0; i < tensor_in_and_out_dims; ++i) {

programming_language: C++