Loadable modules aren't part of the C spec. Whatever the meaning of &func in 2 different modules potentially compiled by 2 different compilers is is specified by the ABI.
CFI is a breaking change to the contract the Linux kernel makes with kernel modules, but it doesn't have anything in particular to do with C the language.
CFI is a breaking change to the contract the Linux kernel makes with kernel modules, but it doesn't have anything in particular to do with C the language.