--- Andi Kleen <[email protected]> wrote:
> Casey Schaufler <[email protected]> writes:
>
> > Smack is the Simplified Mandatory Access Control Kernel.
>
> I like the simplified part.
>
> > +static int smk_get_access(smack_t sub, smack_t obj)
> > +{
> > + struct smk_list_entry *sp = smack_list;
> > +
> > + for (; sp != NULL; sp = sp->smk_next)
> > + if (sp->smk_rule.smk_subject == sub &&
> > + sp->smk_rule.smk_object == obj)
> > + return sp->smk_rule.smk_access;
>
> Do I miss something, or is there really no locking for the reader side
> of the list? That looks dangerous. Of course a global lock for readers
> would be likely a scaling disaster. You could use RCU.
Entries are never deleted, although they can be modified.
> Or if you assume rules are changed only very infrequently it might
> be more cache friendly to compile all the rules into a linear buffer
> and then just replace the whole buffer atomically with a RCU
> grace period on cahnges.
Individual entries can be modified without changing the whole
thing, but they shouldn't change often.
> It doesn't look like it would scale to larger numbers of rules though.
> Is that intended? Would caching of decisions fit into the design?
I put some thought into clever schemes for supporting large rule sets
well but decided to go ahead with the simplest possible mechanism
because I expect that in real deployments the number of rules will
be small. In fact, experiance says that virtually all access choices
will be covered either by the subject==object case or the subject can
read floor case. Cacheing, hashing, and 2D structures are all
possibilties that I would be happy to entertain as enhancements.
> Also in general code style would need some improvements;
> e.g. no externs in .c; no ../.. include hacks etc.
> You also seem weak on the Documentation front.
Yes, it is pretty sparse.
> Other than that it looks reasonably clean (haven't read all of it)
Thank you for your comments. I think the next version will be improved.
Casey Schaufler
[email protected]
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