Created attachment 840439 [details] A config that leads to the error This pops up in some (but not all) configurations with CONFIG_WERROR=y and CONFIG_NF_CONNTRACK_MARK=n. Looks like it's caused by something Gentoo backported from mainline, where it has also been reported: https://lore.kernel.org/lkml/CAGjnhw_2oSWfMjNPZMneJXxdvT+qoqhKV8787NYuHnOauhSVyw@mail.gmail.com/ Worked around, of course, by changing either of the above options.
Created attachment 840441 [details] Build log
Thanks for your detailed report and attachments. It made my job easier. The upstream patch will be included in gentoo-sources-6.0.12 and other kernels which include genpatches
This is released in gentoo-sources-6.0.12 and other kernels that include genpatches-6.0-11