GH-50063: [C++] Validate buffer size for row-major tensors

[metsw24-max]

Rationale for this change

ValidateTensorParameters in cpp/src/arrow/tensor.cc only runs the CheckTensorStridesValidity buffer-overrun guard when strides are passed explicitly. With implicit (row-major) strides it computes strides for overflow but never checks the data buffer is large enough for the shape, so a tensor whose shape exceeds its buffer is accepted and later read out of bounds. This is reachable from IPC ReadTensor, where the shape comes from the flatbuffer and the body size is independent of it.

What changes are included in this PR?

Run CheckTensorStridesValidity on the computed row-major strides too.

Are these changes tested?

Added a case to TestTensor.MakeFailureCases.

Are there any user-facing changes?

No.

This PR contains a "Critical Fix". Crafted IPC tensor metadata (or any caller building a row-major tensor over an undersized buffer) bypassed the bounds check, enabling an out-of-bounds read.

• GitHub Issue: [C++] Tensor::Make skips buffer-size check for row-major (implicit strides) tensors #50063

[github-actions]

⚠️ GitHub issue #50063 has been automatically assigned in GitHub to PR creator.

[github-actions]

⚠️ GitHub issue #50063 has no components, please add labels for components.

[rok]

Yes, we should do this.

[Copilot]

Pull request overview

This PR fixes a safety gap in C++ tensor validation where row-major tensors created with implicit strides could bypass the existing buffer-overrun guard, allowing tensors whose shape exceeds the backing buffer to be constructed (notably reachable via IPC ReadTensor where shape comes from metadata).

Changes:

• Run CheckTensorStridesValidity even when strides are implicit (row-major), using the computed row-major strides.
• Add a regression test ensuring Tensor::Make rejects row-major tensors whose shape requires more bytes than the buffer provides.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
cpp/src/arrow/tensor.cc	Ensures implicit row-major strides also trigger the buffer-size / overrun validation.
cpp/src/arrow/tensor_test.cc	Adds a failure-case regression test for undersized buffers with implicit row-major strides.

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[rok]

Thanks contributing @metsw24-max

[conbench-apache-arrow]

After merging your PR, Conbench analyzed the 4 benchmarking runs that have been run so far on merge-commit ca8a194.

There were no benchmark performance regressions. 🎉

The full Conbench report has more details. It also includes information about 8 possible false positives for unstable benchmarks that are known to sometimes produce them.