有没有 SELinux 高手直白地说一下，它究竟能在传统的基于用户权限的安全策略基础上增加多少安全性？为此而维护一套庞大的规则是否值得？

Fedora 26 原始发行版本，启动后就发现一堆安全策略没有定义，比如：

[    4.795945] SELinux:  Class sctp_socket not defined in policy.
[    4.796810] SELinux:  Class icmp_socket not defined in policy.
[    4.797669] SELinux:  Class ax25_socket not defined in policy.
[    4.798520] SELinux:  Class ipx_socket not defined in policy.
[    4.799365] SELinux:  Class netrom_socket not defined in policy.
[    4.800222] SELinux:  Class atmpvc_socket not defined in policy.
[    4.801076] SELinux:  Class x25_socket not defined in policy.
[    4.801933] SELinux:  Class rose_socket not defined in policy.
[    4.802792] SELinux:  Class decnet_socket not defined in policy.
[    4.803651] SELinux:  Class atmsvc_socket not defined in policy.
[    4.804511] SELinux:  Class rds_socket not defined in policy.
[    4.805382] SELinux:  Class irda_socket not defined in policy.
[    4.806251] SELinux:  Class pppox_socket not defined in policy.
[    4.807121] SELinux:  Class llc_socket not defined in policy.
[    4.807991] SELinux:  Class can_socket not defined in policy.
[    4.808845] SELinux:  Class tipc_socket not defined in policy.
[    4.809692] SELinux:  Class bluetooth_socket not defined in policy.
[    4.810549] SELinux:  Class iucv_socket not defined in policy.
[    4.811411] SELinux:  Class rxrpc_socket not defined in policy.
[    4.812281] SELinux:  Class isdn_socket not defined in policy.
[    4.813149] SELinux:  Class phonet_socket not defined in policy.
[    4.814022] SELinux:  Class ieee802154_socket not defined in policy.
[    4.814899] SELinux:  Class caif_socket not defined in policy.
[    4.815777] SELinux:  Class alg_socket not defined in policy.
[    4.816660] SELinux:  Class nfc_socket not defined in policy.
[    4.817536] SELinux:  Class vsock_socket not defined in policy.
[    4.818402] SELinux:  Class kcm_socket not defined in policy.
[    4.819260] SELinux:  Class qipcrtr_socket not defined in policy.
[    4.820109] SELinux:  Class smc_socket not defined in policy.
[    4.820948] SELinux:  Class infiniband_pkey not defined in policy.
[    4.821789] SELinux:  Class infiniband_endport not defined in policy.
[    4.822630] SELinux: the above unknown classes and permissions will be allowed

更新到最新的 selinux-policy-targeted-3.13.1-260.13.fc26，不仅没有解决，反而未定义的更多了，这个包相当大，安装后有 20 多 MB，我觉得，rh 的开发人员定义这么庞大的规则确实不容易，普通用户根本不想触碰它们，但费这么大力气，究竟能带来多大的安全提升呢？貌似就只有 RH 系的发行版默认启用 SELinux。