Hunting a 34 year old pointer bug in EtherSlip
Summary
This article provides a detailed retrospective on debugging a 34-year-old NULL-pointer data corruption bug in the EtherSlip SLIP packet driver for DOS. It explains how a mix-up of DS and ES during a REP MOVSB corrupted memory, how tracing revealed the root cause, and the fixes and lessons for memory safety in legacy networking code.