It's a great question! Thinking back...

At the time this bug was introduced it would probably have been cost prohibitive to create a test case. We were proud of 100mbit networks, had flaky nics the vendors didn't help maintain much of the time (and which were often broken in hardware) and the filesystem max file size was something like 2tb, and most drives wee're in the handful of gbs. Conceiving of testing for something like this would have been expensive. And none of the big system vendors took Linux seriously then.

Though perhaps flooding zeros across a TCP socket could work, I really think that a kernel hacker would have found a lot of other hardware and driver issues before ever being able to trigger this.