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

On Tue, Dec 10, 2019 at 11:20 AM Stephen Smalley [off-list ref] wrote:

On 12/10/19 10:58 AM, Paul Moore wrote:

quoted

On Tue, Dec 10, 2019 at 10:45 AM Stephen Smalley [off-list ref] wrote:

quoted

On 12/10/19 10:04 AM, Paul Moore wrote:

quoted

On Tue, Dec 10, 2019 at 9:59 AM Stephen Smalley [off-list ref] wrote:

quoted

On 12/9/19 9:28 PM, Paul Moore wrote:

quoted

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.

That should work too I think.

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.

This seems to be both the right thing to do, as well as overly complicated :)

I'm not sure I have a strong preference at this point, other than
getting it fixed.

-- 
paul moore
www.paul-moore.com