Claude spots a real stack buffer overflow in OpenBLAS while casually explaining kernel code
Aizkmusic · x · 2026-11-06
A user pasted OpenBLAS kernel code into Claude just to learn about it — and Claude insisted there was a bug. After 15 minutes of analysis and testing it confirmed one: the dgemmkernel16x2skylakex.S kernel copies the B panel into fixed 8,192-byte stack buffers holding only 341 k values, while K-chunks reach 384 (SkylakeX) or 512 (Zen 4/5), causing silent wrong results then crashes on Clang/Windows AVX-512 builds. Filed as OpenBLAS issue #6232, with the technical write-up written by Claude and reproduced by the human.
Related event: Claude Finds Real OpenBLAS Bug While Explaining the Code(3 posts)→
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