I think there are some static analysis tool. At first it was some proprietary tools ran by who knows who, but this was obviously an enormous problem in the context of Linux dev, so IIRC somebody wrote something (that might be quite primitive but that is better than nothing) to detect potential cases. Anyway, a compiler plugin is a neat idea. It won't detect everything but at least it can detect (and fix!) local cases. Not sure if the open source analyzers (if any) can detect less local cases, though -- but then with this pattern most cases should be quite local, so I might actually be the best to have something simple.

The article describes grsecurity's 'respectre' compiler plugin [1].

[1] https://grsecurity.net/respectre_announce.php

While they say that Respectre would have caught it, the actual discovery was apparently made this way:

"We independently backported the fix on July 9th 2019 and on noticing the warning, fixed it correctly. When the upstream kernels later backported their bad fix, it created a conflict in our git repo that led to us immediately spotting their flaw (and keeping our existing fixes)."