CVE-2026-80929

In the Linux kernel, the following vulnerability has been resolved:

sysctl: move the "cad pid" entry from pid table[] to kern reboot table[]

cad pid is global, and kill cad pid() is only used in the root namespace.

However, due to pid table root permissions(), a non-root user can unshare pid/user namespaces and modify it from the child namespace. This makes no sense and is simply wrong.

Move it to kern reboot table[] where it logically belongs; this ensures that only GLOBAL ROOT UID can read/modify this sysctl.

Note that this patch doesn't preserve "#ifdef CONFIG PROC SYSCTL" around the "cad pid"; CONFIG PROC SYSCTL selects CONFIG SYSCTL, so it is always set when kern reboot table[] is compiled.