Preferred subj= with multiple LSMs

[Casey Schaufler]

On 7/22/2019 1:50 PM, James Morris wrote:
> On Fri, 19 Jul 2019, Paul Moore wrote:
>
>>> We've never had to think about having general rules on
>>> what security modules do before, because with only one
>>> active each could do whatever it wanted without fear of
>>> conflict. If there is already a character that none of
>>> the existing modules use, how would it be wrong to
>>> reserve it?
>> "We've never had to think about having general rules on what security
>> modules do before..."
>>
>> We famously haven't imposed restrictions on the label format before
>> now, and this seems like a pretty poor reason to start.
> Agreed.

In a follow on thread

https://www.spinics.net/lists/linux-security-module/msg29996.html

we've been discussing the needs of dbus-daemon in a multiple LSM
environment. I suggest that if supporting dbus well is assisted by
making reasonable restrictions on what constitutes a valid LSM
"context" that we have a good reason. While there are ways to
present groups of arbitrary hunks of data, why would we want to?