Re: [RFC] Virtualization steps

[ebiederm@xmission.com (Eric W. Biederman)]

Sam Vilain <sam@vilain.net> writes:

>
> We could even end up making security modules to implement standard unix
> security. ie, which processes can send any signal to other processes.
> Why hardcode the (!sender.user_id || (sender.user_id == target.user_id)
> ) rule at all? That rule should be the default rule in a security module
> chain.
>
> I just think that doing it this way is the wrong way around, but I guess
> I'm hardly qualified to speak on this. Aren't security modules supposed
> to be for custom security policy, not standard system semantics ?

It is simply my contention that you into at least a semi custom
configuration when you have multiple users with the same uid.
Especially when that uid == 0.

For guests you have to change the rule about what permissions
a setuid root executable gets or else it will have CAP_SYS_MKNOD,
and CAP_RAW_IO.  (Unless I didn't read that code right).

Plus all of the /proc and sysfs issues.

Now perhaps we can sit down and figure out how to get completely
isolated and only allow a new uid namespace when that is
the case, but that doesn't sound to interesting.

So at least until I can imagine what the semantics of a new uid
namespace are when we don't have perfect isolation that feels
like a job for a security module.

Eric
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