[RFC PATCH] lsm: add the inode_free_security_rcu() LSM implementation hook

[Paul Moore]

On Wed, Jul 10, 2024 at 12:41 PM Casey Schaufler <casey at schaufler-ca.com> wrote:
> On 7/10/2024 9:20 AM, Paul Moore wrote:

...

> > However, I have always thought we should add some better
> > structure/typing to these opaque LSM blobs both to get away from the
> > raw pointer math and add a marginal layer of safety.  I've envisioned
> > doing something like this:
> >
> >   struct lsm_blob_inode {
> >     struct selinux_blob_inode selinux;
> >     struct smack_blob_inode smack;
> >     struct aa_blob_inode apparmor;
> >     ...
> >     struct rcu_head rcu;
> >   }
>
> I have considered doing this as part of the stacking effort for quite
> some time. I've already done it for the lsmblob structure that will replace
> most uses of the u32 secid in the LSM APIs. I am concerned that there would
> be considerable gnashing of teeth over the potential increase in the blob
> sizes for kernels compiled with LSMs that aren't active.

Yes, that's a fair point and something that needs to be considered.

> I have been frantically
> avoiding anything that might slow the stacking effort further. If this would
> help moving this along I'll include it in v40.

No, don't worry about this as part of improving the multi-LSM support,
this is something that can be done independently, if at all.

-- 
paul-moore.com