linux-kernel - Re: [PATCH ghak90 V9 05/13] audit: log container info of syscalls

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Message-ID: <CAHC9VhRUwCKBjffA_XNSjUwvUn8e6zfmy8WD203dK7R2KD0__g@mail.gmail.com>
Date:   Fri, 21 Aug 2020 15:15:17 -0400
From:   Paul Moore <paul@...l-moore.com>
To:     Richard Guy Briggs <rgb@...hat.com>
Cc:     containers@...ts.linux-foundation.org, linux-api@...r.kernel.org,
        Linux-Audit Mailing List <linux-audit@...hat.com>,
        linux-fsdevel@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        netdev@...r.kernel.org, netfilter-devel@...r.kernel.org,
        sgrubb@...hat.com, Ondrej Mosnacek <omosnace@...hat.com>,
        dhowells@...hat.com, simo@...hat.com,
        Eric Paris <eparis@...isplace.org>,
        Serge Hallyn <serge@...lyn.com>, ebiederm@...ssion.com,
        nhorman@...driver.com, Dan Walsh <dwalsh@...hat.com>,
        mpatel@...hat.com
Subject: Re: [PATCH ghak90 V9 05/13] audit: log container info of syscalls

On Wed, Jul 29, 2020 at 3:41 PM Richard Guy Briggs <rgb@...hat.com> wrote:
> On 2020-07-05 11:10, Paul Moore wrote:
> > On Sat, Jun 27, 2020 at 9:22 AM Richard Guy Briggs <rgb@...hat.com> wrote:

...

> > > diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> > > index f03d3eb0752c..9e79645e5c0e 100644
> > > --- a/kernel/auditsc.c
> > > +++ b/kernel/auditsc.c
> > > @@ -1458,6 +1466,7 @@ static void audit_log_exit(void)
> > >         struct audit_buffer *ab;
> > >         struct audit_aux_data *aux;
> > >         struct audit_names *n;
> > > +       struct audit_contobj *cont;
> > >
> > >         context->personality = current->personality;
> > >
> > > @@ -1541,7 +1550,7 @@ static void audit_log_exit(void)
> > >         for (aux = context->aux_pids; aux; aux = aux->next) {
> > >                 struct audit_aux_data_pids *axs = (void *)aux;
> > >
> > > -               for (i = 0; i < axs->pid_count; i++)
> > > +               for (i = 0; i < axs->pid_count; i++) {
> > >                         if (audit_log_pid_context(context, axs->target_pid[i],
> > >                                                   axs->target_auid[i],
> > >                                                   axs->target_uid[i],
> > > @@ -1549,14 +1558,20 @@ static void audit_log_exit(void)
> > >                                                   axs->target_sid[i],
> > >                                                   axs->target_comm[i]))
> > >                                 call_panic = 1;
> > > +                       audit_log_container_id(context, axs->target_cid[i]);
> > > +               }
> >
> > It might be nice to see an audit event example including the
> > ptrace/signal information.  I'm concerned there may be some confusion
> > about associating the different audit container IDs with the correct
> > information in the event.
>
> This is the subject of ghat81, which is a test for ptrace and signal
> records.
>
> This was the reason I had advocated for an op= field since there is a
> possibility of multiple contid records per event.

I think an "op=" field is the wrong way to link audit container ID to
a particular record.  It may be convenient, but I fear that it would
be overloading the field too much.

Like I said above, I think it would be good to see an audit event
example including the ptrace/signal information.  This way we can talk
about it on-list and hash out the various solutions if it proves to be
a problem.

> > > @@ -1575,6 +1590,14 @@ static void audit_log_exit(void)
> > >
> > >         audit_log_proctitle();
> > >
> > > +       rcu_read_lock();
> > > +       cont = _audit_contobj_get(current);
> > > +       rcu_read_unlock();
> > > +       audit_log_container_id(context, cont);
> > > +       rcu_read_lock();
> > > +       _audit_contobj_put(cont);
> > > +       rcu_read_unlock();
> >
> > Do we need to grab an additional reference for the audit container
> > object here?  We don't create any additional references here that
> > persist beyond the lifetime of this function, right?
>
> Why do we need another reference?  There's one for each pointer pointing
> to it and so far we have just one from this task.  Or are you thinking
> of the contid hash list, which is only added to when a task points to it
> and gets removed from that list when the last task stops pointing to it.
> Later that gets more complicated with network namespaces and nested
> container objects.  For now we just needed it while generating the
> record, then it gets freed.

I don't think we need to grab an additional reference here, that is
why I asked the question.  The code above grabs a reference for the
audit container ID object associated with the current task and then
drops it before returning; if the current task, and it's associated
audit container ID object, disappears in the middle of the function
we've got much bigger worries :)

-- 
paul moore
www.paul-moore.com