[entrope]

It got arm-waved to a race condition in munmap(). Claude (or a distill of Claude) didn't identify a race, it just convinced itself that was the cause.

[cyberax]

Andy Lutomirski seems to think that it is a bug: https://lore.kernel.org/all/CALCETrXbj__SFQMzPZhES5y6-sh4np-...

I looked at the explanation, and it seems to be at very least plausible. The kernel version bisection also lines up. We'll see if the proposed patch fixes this.