Here is a more detail article about what actually happened

https://www.xda-developers.com/linus-torvalds-fixed-a-linux-bug-using-ai-highlighting-both-the-strengths-and-weaknesses-of-the-new-tech/

It sounds like AI helped find the issue and write NOTES about it, but Linus explains he basically had to force the AI assistant because it kept on giving up. Linus wrote the fix himself.

I’d like to call it my tireless helper, but the AI several times stated flat out that this was impossible and unsolvable and that we should just write a report about it. I suspect those things have been trained by people who may not be quite as stubborn as I am.