Re: sleep in selinux_audit_rule_init

[Janne Karhunen <janne.karhunen@gmail.com>]

On Thu, May 30, 2019 at 3:08 PM Stephen Smalley <sds@tycho.nsa.gov> wrote:

> > @@ -269,11 +269,23 @@ static void ima_lsm_update_rules(void)
> >                                                             Audit_equal,
> >                                                             entry->lsm[i].args_p,
> >                                                             &entry->lsm[i].rule);
> > -                       BUG_ON(!entry->lsm[i].rule);
> > +                       if (result == -EINVAL)
> > +                               pr_warn("ima: rule for LSM \'%d\' is invalid\n",
> > +                                       entry->lsm[i].type);
>
> I could be wrong, but I think there is still a problem here in that you
> are modifying entry->lsm[i].rule in-place, but it is protected under RCU
> and therefore needs to be duplicated and then modified?  Also you are
> leaking the old rule?

Right. Bit too fast tapping the keyboard without thinking, will fix
and post in the proper form. But I guess the original point was to
verify if that 'notifier_block' is indeed the right way to get the
update notification?


>  Both of those issues also exist prior to your
> patch but you aren't fixing them here. And lastly, it looks like lsm
> notifiers are atomic notifiers (not clear to me why) so you can't block
> in the callback, thereby requiring scheduling the work as is done in
> infiniband.

Great catch, thank you. That's an easy fix if no-one objects pushing
these through the system-wq for example.


--
Janne