Release arrow-rs / parquet Patch version `56.2.1` (May 2026)

[alamb]

• Part of [EPIC] A collection of release tickets #7392
• Follow on to Release arrow-rs / parquet Minor version 56.2.0 (September 2025) #7836

There have been several overflow fixes recently that I think are important enough to warrant a minor patch release to increase the security posture of arrow-rs. The most recent 56 line release was Sep 2025, 6 months ago, so I believe it would be good to release a minor release with overflow protection for those users still upgrading.

We will target this branch:

• https://github.com/apache/arrow-rs/tree/56_maintenance

Release Checklist:

• Release notes and bump version: Prepare 56.2.1 release #9942
• Release Candidate + Vote thread: https://lists.apache.org/thread/y84xgk6pjjrntvxzlpknk6box8pv6y9f
• Release to crates.io / approval:

Required items for release

• [56_maintenance] Fix cargo_audit: Pin cargo-msrv and Cargo.lock in CI #9902
• [arrow-array] Integer overflow in FixedSizeBinaryArray::value leads to undefined behavior #9898. Original PR: Prevent FixedSizeBinaryArray i32 offset overflows (try 2) #9872. Branch PR: [56_maintenance] Prevent FixedSizeBinaryArray i32 offset overflows (#9872) #9917
• [arrow-data] Integer overflow in ArrayData::slice leads to undefined behavior #9899. Original PR: Prevent ArrayData::slice length overflow #9813. Branch PR: [56_maintenance] Prevent ArrayData::slice length overflow (#9813) #9916
• [arrow-buffer] Integer overflow in BufferBuilder::reserve leads to undefined behavior #9897. Original PR: Prevent buffer builder length overflow in MutableBuffer::extend_zeros #9820. Branch PR: [56_maintenance] Prevent buffer builder length overflow in MutableBuffer::extend_zeros (#9820) #9915
• [arrow-data] Integer overflow in ArrayData validation leads to undefined behavior #9900. Original PR: Prevent ArrayData validation length overflow #9816. Branch PR: [56_maintenance] Prevent ArrayData validation length overflow (#9816) #9914
• [arrow-row] Integer overflow in Rows::row index handling leads to undefined behavior #9901. Original PR: Prevent Rows row index overflow #9817. Branch PR: [56_maintenance] Prevent Rows row index overflow (#9817) #9913
• [arrow-buffer] Integer overflow in BitChunks::new leads to undefined behavior #9903. Original PR: Prevent BitChunks length overflow #9818. Branch PR: [56_maintenance] Prevent BitChunks length overflow (#9818) #9896

Items not needed

• [arrow-buffer] Integer overflow in repeat_slice_n_times leads to undefined behavior #9904. Original PR: Prevent repeat slice length overflow #9819. (repeat_n_times is not present on 56.x releases). Rejected PR: [56_maintenance] Prevent repeat slice length overflow (#9819) #9912

[alamb]

Ok, I now have the the content of the release ready in PRs (linked above) Once this one is merged

• [56_maintenance] Fix cargo_audit: Pin cargo-msrv and Cargo.lock in CI #9902

Then I will get the other ready for review