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@guan404ming guan404ming commented Jan 1, 2026

Why

size() and stride() methods could access memory out of bounds when given invalid indices

How

  • Add bounds checking after adjusting negative indices
  • Throw IndexError with descriptive message when index is out of bounds
  • Add tests for both Tensor and TensorView classes

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Summary of Changes

Hello @guan404ming, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly improves the safety and reliability of tensor dimension access by introducing explicit index bounds checking to the size and stride methods within the Tensor and TensorView classes. These changes ensure that attempts to access dimensions with invalid indices will now correctly raise an IndexError, preventing potential runtime issues. Complementary C++ unit tests have been added to validate this new error-handling behavior. Additionally, minor type hinting updates were applied to Python test files for better code maintainability.

Highlights

  • Enhanced Index Safety: Implemented robust index bounds checking for size and stride methods in both Tensor and TensorView classes, preventing out-of-bounds access.
  • Improved Error Handling: Modified size and stride methods to throw tvm::ffi::IndexError when an invalid index is provided, improving error detection and handling.
  • Comprehensive Testing: Added new C++ unit tests (TEST(Tensor, SizeStrideOutOfBounds)) to explicitly verify that out-of-bounds index access correctly triggers tvm::ffi::Error for these methods.
  • Python Type Hinting: Updated Python test files to use numpy.typing and npt.NDArray[Any] for improved type clarity and static analysis.

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Code Review

This pull request adds bounds checking to the size() and stride() methods of tvm::ffi::Tensor and tvm::ffi::TensorView to prevent out-of-bounds memory access, along with corresponding C++ tests. It also improves Python type hints in the test suite.

The changes are a good improvement for robustness. However, there's a significant discrepancy between the pull request title/description and the actual code changes. The title ("fix: integer overflow in GetDataSize") and description state that this PR fixes an integer overflow in GetDataSize, but the provided patches only contain bounds checking logic for size() and stride() methods. Please consider updating the title and description to accurately reflect the changes made in this PR.

I've left one comment regarding code duplication that could be addressed to improve maintainability.

Comment on lines 326 to 334
int64_t size(int64_t idx) const {
const TensorObj* ptr = get();
return ptr->shape[idx >= 0 ? idx : (ptr->ndim + idx)];
int64_t adjusted_idx = idx >= 0 ? idx : (ptr->ndim + idx);
if (adjusted_idx < 0 || adjusted_idx >= ptr->ndim) {
TVM_FFI_THROW(IndexError) << "Index " << idx << " out of bounds for tensor with " << ptr->ndim
<< " dimensions";
}
return ptr->shape[adjusted_idx];
}
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medium

The index adjustment and bounds checking logic is duplicated in Tensor::size, Tensor::stride, TensorView::size, and TensorView::stride. To improve maintainability and reduce code duplication, consider extracting this logic into a common helper function.

For example, you could add a free helper function in a details namespace:

namespace tvm {
namespace ffi {
namespace details {
inline int64_t CheckAndAdjustTensorIndex(int64_t idx, int32_t ndim) {
    int64_t adjusted_idx = idx >= 0 ? idx : (ndim + idx);
    if (adjusted_idx < 0 || adjusted_idx >= ndim) {
      TVM_FFI_THROW(IndexError) << "Index " << idx << " out of bounds for tensor with " << ndim
                                << " dimensions";
    }
    return adjusted_idx;
}
} // namespace details
} // namespace ffi
} // namespace tvm

Then Tensor::size and TensorView::size could be simplified to:

// Tensor::size
int64_t size(int64_t idx) const {
  const TensorObj* ptr = get();
  return ptr->shape[details::CheckAndAdjustTensorIndex(idx, ptr->ndim)];
}

// TensorView::size
int64_t size(int64_t idx) const {
  return tensor_.shape[details::CheckAndAdjustTensorIndex(idx, tensor_.ndim)];
}

A similar simplification would apply to the stride methods.

@guan404ming guan404ming changed the title fix: integer overflow in GetDataSize fix: add bounds checking for size() and stride() methods Jan 1, 2026
@guan404ming guan404ming marked this pull request as ready for review January 1, 2026 15:49
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Looks good to me!

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Given that we already have conditionals in size(), I'd say it won't add to too much overhead and happy to get it in

@junrushao junrushao merged commit e54d15d into apache:main Jan 1, 2026
7 checks passed
@guan404ming guan404ming deleted the fix/tensor-negative-index-bounds branch January 2, 2026 06:59
@guan404ming
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Thanks!

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2 participants