Commit message: Validate inputs of `FractionalAvgPoolGrad`.

PiperOrigin-RevId: 372420640
Change-Id: Icc583928e6cdc3062e12498e4d2337a8fe3da016
CVE: CVE-2021-29578
CWE: CWE-369
Vulnerability description: TensorFlow is an end-to-end open source platform for machine learning. The implementation of `tf.raw_ops.FractionalAvgPoolGrad` is vulnerable to a heap buffer overflow. The implementation(https://github.com/tensorflow/tensorflow/blob/dcba796a28364d6d7f003f6fe733d82726dda713/tensorflow/core/kernels/fractional_avg_pool_op.cc#L216) fails to validate that the pooling sequence arguments have enough elements as required by the `out_backprop` tensor shape. 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.

Project: tensorflow
File: fractional_avg_pool_op.cc

  void Compute(OpKernelContext* context) override {
    // Here's the basic idea:
    // Batch and depth dimension are independent from row and col dimension. And
    // because FractionalAvgPool currently only support pooling along row and
    // col, we can basically think of this 4D tensor backpropagation as
    // operation of a series of 2D planes.
    //
    // For each element of a 'slice' (2D plane) of output_backprop, we need to
    // figure out its contributors when doing FractionalAvgPool operation. This
    // can be done based on row_pooling_sequence, col_pooling_seq and
    // overlapping.
    // Once we figure out the original contributors, we just need to evenly
    // divide the value of this element among these contributors.
    //
    // Internally, we divide the out_backprop tensor and store it in a temporary
    // tensor of double type. And cast it to the corresponding type.
    typedef Eigen::Map<const Eigen::Matrix<T, Eigen::Dynamic, Eigen::Dynamic>>
        ConstEigenMatrixMap;
    typedef Eigen::Map<Eigen::Matrix<double, Eigen::Dynamic, Eigen::Dynamic>>
        EigenDoubleMatrixMap;

    // Grab the inputs.
    const Tensor& orig_input_tensor_shape = context->input(0);
    OP_REQUIRES(context,
                orig_input_tensor_shape.dims() == 1 &&
                    orig_input_tensor_shape.NumElements() == 4,
                errors::InvalidArgument("original input tensor shape must be"
                                        "1-dimensional and 4 elements"));
    const Tensor& out_backprop = context->input(1);
    const Tensor& row_seq_tensor = context->input(2);
    const Tensor& col_seq_tensor = context->input(3);

    const int64 out_batch = out_backprop.dim_size(0);
    const int64 out_rows = out_backprop.dim_size(1);
    const int64 out_cols = out_backprop.dim_size(2);
    const int64 out_depth = out_backprop.dim_size(3);

    auto row_seq_tensor_flat = row_seq_tensor.flat<int64>();
    auto col_seq_tensor_flat = col_seq_tensor.flat<int64>();
    auto orig_input_tensor_shape_flat = orig_input_tensor_shape.flat<int64>();

    const int64 in_batch = orig_input_tensor_shape_flat(0);
    const int64 in_rows = orig_input_tensor_shape_flat(1);
    const int64 in_cols = orig_input_tensor_shape_flat(2);
    const int64 in_depth = orig_input_tensor_shape_flat(3);

    constexpr int tensor_in_and_out_dims = 4;
    // Transform orig_input_tensor_shape into TensorShape
    TensorShape in_shape;
    for (auto i = 0; i < tensor_in_and_out_dims; ++i) {
      in_shape.AddDim(orig_input_tensor_shape_flat(i));
    }

    // Create intermediate in_backprop.
    Tensor in_backprop_tensor_temp;
    OP_REQUIRES_OK(context, context->forward_input_or_allocate_temp(
                                {0}, DataTypeToEnum<double>::v(), in_shape,
                                &in_backprop_tensor_temp));
    in_backprop_tensor_temp.flat<double>().setZero();
    // Transform 4D tensor to 2D matrix.
    EigenDoubleMatrixMap in_backprop_tensor_temp_mat(
        in_backprop_tensor_temp.flat<double>().data(), in_depth,
        in_cols * in_rows * in_batch);
    ConstEigenMatrixMap out_backprop_mat(out_backprop.flat<T>().data(),
                                         out_depth,
                                         out_cols * out_rows * out_batch);
    // Loop through each element of out_backprop and evenly distribute the
    // element to the corresponding pooling cell.
    const int64 in_max_row_index = in_rows - 1;
    const int64 in_max_col_index = in_cols - 1;
    for (int64 b = 0; b < out_batch; ++b) {
      for (int64 r = 0; r < out_rows; ++r) {
        const int64 in_row_start = row_seq_tensor_flat(r);
        int64 in_row_end = overlapping_ ? row_seq_tensor_flat(r + 1)
                                        : row_seq_tensor_flat(r + 1) - 1;
        in_row_end = std::min(in_row_end, in_max_row_index);
        for (int64 c = 0; c < out_cols; ++c) {
          const int64 in_col_start = col_seq_tensor_flat(c);
          int64 in_col_end = overlapping_ ? col_seq_tensor_flat(c + 1)
                                          : col_seq_tensor_flat(c + 1) - 1;
          in_col_end = std::min(in_col_end, in_max_col_index);

          const int64 num_elements_in_pooling_cell =
              (in_row_end - in_row_start + 1) * (in_col_end - in_col_start + 1);
          const int64 out_index = (b * out_rows + r) * out_cols + c;
          // Now we can evenly distribute out_backprop(b, h, w, *) to
          // in_backprop(b, hs:he, ws:we, *).
          for (int64 in_r = in_row_start; in_r <= in_row_end; ++in_r) {
            for (int64 in_c = in_col_start; in_c <= in_col_end; ++in_c) {
              const int64 in_index = (b * in_rows + in_r) * in_cols + in_c;
              // Walk through each channel (depth).
              for (int64 d = 0; d < out_depth; ++d) {
                const double out_backprop_element = static_cast<double>(
                    out_backprop_mat.coeffRef(d, out_index));
                double& in_backprop_ref =
                    in_backprop_tensor_temp_mat.coeffRef(d, in_index);
                in_backprop_ref +=
                    out_backprop_element / num_elements_in_pooling_cell;
              }
            }
          }
        }
      }
    }

    // Depending on the type, cast double to type T.
    Tensor* in_backprop_tensor = nullptr;
    OP_REQUIRES_OK(context, context->forward_input_or_allocate_output(
                                {0}, 0, in_shape, &in_backprop_tensor));
    auto in_backprop_tensor_flat = in_backprop_tensor->flat<T>();
    auto in_backprop_tensor_temp_flat = in_backprop_tensor_temp.flat<double>();
    for (int64 i = 0; i < in_backprop_tensor_flat.size(); ++i) {
      in_backprop_tensor_flat(i) =
          static_cast<T>(in_backprop_tensor_temp_flat(i));
    }
  }