[RFC PATCH] security: add an interface to lookup the lockdown reason

[Stephen Smalley]

On 12/10/19 10:58 AM, Paul Moore wrote:
> On Tue, Dec 10, 2019 at 10:45 AM Stephen Smalley <sds at tycho.nsa.gov> wrote:
>> On 12/10/19 10:04 AM, Paul Moore wrote:
>>> On Tue, Dec 10, 2019 at 9:59 AM Stephen Smalley <sds at tycho.nsa.gov> wrote:
>>>> On 12/9/19 9:28 PM, Paul Moore wrote:
>>>>> With CONFIG_AUDIT enabled but CONFIG_SECURITY disabled we run into
>>>>> a problem where the lockdown reason table is missing.  This patch
>>>>> attempts to fix this by hiding the table behind a lookup function.
>>>>
>>>> Shouldn't lsm_audit.c be conditional on both CONFIG_AUDIT and
>>>> CONFIG_SECURITY?  When/why would we want it built without
>>>> CONFIG_SECURITY enabled?
>>>
>>> My first thought of a fix was just that, but I remembered that the
>>> capabilities code is built regardless of the CONFIG_SECURITY setting
>>> and I thought there might be some value in allowing for lsm_audit to
>>> be used in commoncap (although in full disclosure commoncap doesn't
>>> currently make use of lsm_audit).
>>
>> Seems contrary to normal practice, i.e. if/when commoncap grows a
>> dependency, it can be changed then.
> 
> Okay, want to submit a tested patch?  I really would like to get this
> fixed before today's linux-next run.

In looking at it, I'm wondering if we could just change the Makefile to 
use obj-$(CONFIG_SECURITY) instead of obj-$(CONFIG_AUDIT) for 
lsm_audit.c.  I think it might build just fine without CONFIG_AUDIT 
since audit.h provides static inlines that boil away to nothing for 
audit_log*() in that case. Offhand I don't see any support/examples of 
specifying two different config options for an obj list in a Makefile.

The other option would be to introduce its own CONFIG_LSM_AUDIT option 
and select that option automatically for the modules that use it, which 
would currently be selinux, apparmor, and smack.  Then if you aren't 
using any of those modules you can omit it from your kernel.