selinux - 为什么 stuff_u 和 sysadm_r 不能运行 postsuper？

Question

我正在尝试了解 selinux 限制用户的实际工作方式，但有些行为我仍无法理解。根据红帽

SELinux 用户功能

stuff_u 用户应该能够运行 sudo，但不能运行 su。因此我创建了用户某些用户并将其映射到 staff_u

[someuser@testserver ~]$ id -Z
staff_u:staff_r:staff_t:s0-s0:c0.c1023

现在，如果我使用 sudo 添加完全权限，但不在 sudoers 上设置角色/类型，我将无法做很多事情（正如预期的那样）。

[someuser@testserver ~]$ sudo -l
Matching Defaults entries for someuser on testserver:
    !visiblepw, always_set_home, match_group_by_gid, always_query_group_plugin, env_reset, env_keep="COLORS DISPLAY HOSTNAME HISTSIZE KDEDIR LS_COLORS", env_keep+="MAIL PS1 PS2 QTDIR USERNAME LANG LC_ADDRESS LC_CTYPE",
    env_keep+="LC_COLLATE LC_IDENTIFICATION LC_MEASUREMENT LC_MESSAGES", env_keep+="LC_MONETARY LC_NAME LC_NUMERIC LC_PAPER LC_TELEPHONE", env_keep+="LC_TIME LC_ALL LANGUAGE LINGUAS _XKB_CHARSET XAUTHORITY",
    secure_path=/sbin\:/bin\:/usr/sbin\:/usr/bin

User someuser may run the following commands on testserver:
    (ALL) NOPASSWD: ALL

[someuser@testserver ~]$ sudo ls -la /var/log/audit/audit.log 
ls: cannot access '/var/log/audit/audit.log': Permission denied

[someuser@testserver ~]$ sudo ausearch -m avc -ts recent
Error opening config file (Permission denied)
NOTE - using built-in logs: /var/log/audit/audit.log
Error opening /var/log/audit/audit.log (Permission denied)
[someuser@testserver ~]$ 

如果我更改 sudoers 以转换到 sysadm_r 和 sysadm_t，我期望获得执行任何操作的基本权限，但这并不是我所得到的。

我可以做很多事情：

[someuser@testserver ~]$ sudo -l
Matching Defaults entries for someuser on testserver:
    !visiblepw, always_set_home, match_group_by_gid, always_query_group_plugin, env_reset, env_keep="COLORS DISPLAY HOSTNAME HISTSIZE KDEDIR LS_COLORS", env_keep+="MAIL PS1 PS2 QTDIR USERNAME LANG LC_ADDRESS LC_CTYPE",
    env_keep+="LC_COLLATE LC_IDENTIFICATION LC_MEASUREMENT LC_MESSAGES", env_keep+="LC_MONETARY LC_NAME LC_NUMERIC LC_PAPER LC_TELEPHONE", env_keep+="LC_TIME LC_ALL LANGUAGE LINGUAS _XKB_CHARSET XAUTHORITY",
    secure_path=/sbin\:/bin\:/usr/sbin\:/usr/bin

User someuser may run the following commands on testserver:
    (ALL) ROLE=sysadm_r TYPE=sysadm_t NOPASSWD: ALL
[someuser@testserver ~]$ sudo ausearch -m avc -ts recent | wc -l
66
[someuser@testserver ~]$ sudo ls -la /var/log/audit/audit.log 
-rw-------. 1 root root 1996980 Jul 30 12:55 /var/log/audit/audit.log
[someuser@testserver ~]$ sudo cat /var/log/audit/audit.log  | wc -l
8172
[someuser@testserver ~]$ 

但有些命令仍然被阻止，例如 postfix 包中的 postsuper。

[someuser@testserver ~]$ sudo postsuper
sesh: unable to execute /sbin/postsuper: Permission denied
[someuser@testserver ~]$ file /sbin/postsuper
/sbin/postsuper: cannot open `/sbin/postsuper' (Permission denied)
[someuser@testserver ~]$ sudo file /sbin/postsuper
/sbin/postsuper: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 3.2.0, BuildID[sha1]=aa0157870508c475195fe5fb1dafe5a9b3898a61, stripped
[someuser@testserver ~]$ 

有人能解释一下原因吗？最奇怪的是，我没有在 /var/log/audit/audit.log 上看到任何关于 postsuper 命令的拒绝。但这一定与 SELINUX 有关，因为如果我将用户改回 unconfined_u，一切正常。