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

[Richard Guy Briggs <rgb@redhat.com>]

On 2020-08-21 15:15, Paul Moore wrote:
> On Wed, Jul 29, 2020 at 3:41 PM Richard Guy Briggs <rgb@redhat.com> wrote:
> > On 2020-07-05 11:10, Paul Moore wrote:
> > > On Sat, Jun 27, 2020 at 9:22 AM Richard Guy Briggs <rgb@redhat.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.

Ok, after looking at the field dictionary how about item, rel, ref or rec?
Item perhaps could be added to the OBJ_PID records, but that might be
overloading a field that is already used in PATH records.  "rel" for
relates-to, "ref" for reference to, "rec" for record...  Perhaps pid=
would be enough to tie this record to the OBJ_PID record or the SYSCALL
record, but in the case of network events, the pid may refer to a kernel
thread.

> 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.

See the list posting from 2020-09-29 "auditing signals" pointing to
ghat81 test case about testing ptrace and signals from 18 months ago.

I think I have a way to generate a signal to multiple targets in one
syscall...  The added challenge is to also give those targets different
audit container identifiers.

> > > > @@ -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 :)

I misunderstood your question previously thinking you wanted yet another
reference taken in this case, when in fact it was the opposite and you
thought the one taken here was superfluous.

I don't *need* to grab the additional references here, but those are the
accessor functions that exist, so I either create sub-accessor functions
without the refcount manipulations that called from the primary accessor
functions or open code a reduncancy...  The locking has been updated to
protect the _put by a spin-lock.  Now that I look at it, the 4th to 7th
lines could be bypassed by a cont == NULL check.

It is somewhat hidden now since this sequence of 7 commands has been
abstracted into another function that is called from a second location.

> paul moore

- RGB

--
Richard Guy Briggs <rgb@redhat.com>
Sr. S/W Engineer, Kernel Security, Base Operating Systems
Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
Voice: +1.647.777.2635, Internal: (81) 32635

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