Commit message: Fix FPE issue in external Eigen source code issue with `tf.raw_ops.SparseMatMul`.

PiperOrigin-RevId: 370992919
Change-Id: Icfb276fef5fb40928b27c3e44608d2aca72c9fd7
CVE: CVE-2021-29557
CWE: CWE-369
Vulnerability description: TensorFlow is an end-to-end open source platform for machine learning. An attacker can cause a denial of service via a FPE runtime error in `tf.raw_ops.SparseMatMul`. The division by 0 occurs deep in Eigen code because the `b` tensor is empty. 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: sparse_matmul_op.cc

  void Compute(OpKernelContext* ctx) override {
    const Tensor& a = ctx->input(0);
    const Tensor& b = ctx->input(1);
    OP_REQUIRES(ctx, TensorShapeUtils::IsMatrix(a.shape()),
                errors::InvalidArgument("a is not a matrix"));
    OP_REQUIRES(ctx, TensorShapeUtils::IsMatrix(b.shape()),
                errors::InvalidArgument("b is not a matrix"));

    const int m = transpose_a_ ? a.dim_size(1) : a.dim_size(0);
    const int k = transpose_a_ ? a.dim_size(0) : a.dim_size(1);
    const int n = transpose_b_ ? b.dim_size(0) : b.dim_size(1);
    const int k2 = transpose_b_ ? b.dim_size(1) : b.dim_size(0);

    OP_REQUIRES(ctx, k == k2,
                errors::InvalidArgument(
                    "Matrix size incompatible: a: ", a.shape().DebugString(),
                    ", b: ", b.shape().DebugString()));
    Tensor* output = nullptr;
    OP_REQUIRES_OK(ctx, ctx->allocate_output(0, TensorShape({m, n}), &output));

    if (k == 0) {
      // If the inner dimension k in the matrix multiplication is zero, we fill
      // the output with zeros.
      functor::SetZeroFunctor<CPUDevice, float> f;
      f(ctx->eigen_device<CPUDevice>(), output->flat<float>());
      return;
    }

    auto out = output->matrix<float>();

    std::unique_ptr<Tensor> a_float;
    std::unique_ptr<Tensor> b_float;
    if (!a_is_sparse_ && !b_is_sparse_) {
      auto left = &a;
      auto right = &b;
      // TODO(agarwal): multi-thread the conversions from bfloat16 to float.
      if (std::is_same<TL, bfloat16>::value) {
        a_float.reset(new Tensor(DT_FLOAT, a.shape()));
        BFloat16ToFloat(a.flat<bfloat16>().data(),
                        a_float->flat<float>().data(), a.NumElements());
        left = a_float.get();
      }
      if (std::is_same<TR, bfloat16>::value) {
        b_float.reset(new Tensor(DT_FLOAT, b.shape()));
        BFloat16ToFloat(b.flat<bfloat16>().data(),
                        b_float->flat<float>().data(), b.NumElements());
        right = b_float.get();
      }
      Eigen::array<Eigen::IndexPair<Eigen::DenseIndex>, 1> dim_pair;
      dim_pair[0].first = transpose_a_ ? 0 : 1;
      dim_pair[0].second = transpose_b_ ? 1 : 0;

      out.device(ctx->template eigen_device<CPUDevice>()) =
          left->matrix<float>().contract(right->matrix<float>(), dim_pair);
      return;
    }

    auto left = &a;
    auto right = &b;
    bool transpose_output = false;
    bool transpose_a = transpose_a_;
    bool transpose_b = transpose_b_;
    if (!a_is_sparse_) {
      // Swap the order of multiplications using the identity:
      // A * B = (B' *  A')'.
      std::swap(left, right);
      std::swap(transpose_a, transpose_b);
      transpose_a = !transpose_a;
      transpose_b = !transpose_b;
      transpose_output = !transpose_output;
    }

    std::unique_ptr<Tensor> right_tr;
    if (transpose_b) {
      // TODO(agarwal): avoid transposing the matrix here and directly handle
      // transpose in CreateDenseSlices.
      right_tr.reset(
          new Tensor(right->dtype(),
                     TensorShape({right->dim_size(1), right->dim_size(0)})));

      const auto perm = dsizes_10();
      if (transpose_output) {
        right_tr->matrix<TL>().device(ctx->template eigen_device<CPUDevice>()) =
            right->matrix<TL>().shuffle(perm);
      } else {
        right_tr->matrix<TR>().device(ctx->template eigen_device<CPUDevice>()) =
            right->matrix<TR>().shuffle(perm);
      }
      right = right_tr.get();
    }

    if (transpose_output) {
      DoMatMul<TR, TL>::Compute(&this->cache_tr_, left->matrix<TR>(),
                                right->matrix<TL>(), transpose_a,
                                ctx->device()->tensorflow_cpu_worker_threads(),
                                transpose_output, &out);
    } else {
      DoMatMul<TL, TR>::Compute(&this->cache_nt_, left->matrix<TL>(),
                                right->matrix<TR>(), transpose_a,
                                ctx->device()->tensorflow_cpu_worker_threads(),
                                transpose_output, &out);
    }
  }