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From: Paul Moore <paul@paul-moore.com>
To: Richard Guy Briggs <rgb@redhat.com>
Cc: nhorman@tuxdriver.com, linux-api@vger.kernel.org,
	containers@lists.linux-foundation.org,
	LKML <linux-kernel@vger.kernel.org>,
	dhowells@redhat.com,
	Linux-Audit Mailing List <linux-audit@redhat.com>,
	netfilter-devel@vger.kernel.org, ebiederm@xmission.com,
	simo@redhat.com, netdev@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, Eric Paris <eparis@parisplace.org>,
	mpatel@redhat.com, Serge Hallyn <serge@hallyn.com>
Subject: Re: [PATCH ghak90 V9 02/13] audit: add container id
Date: Fri, 21 Aug 2020 15:36:49 -0400
Message-ID: <CAHC9VhQTiu+yY6cY8tvBf-1ZtZrre3Ljs+Zd6Jf9ZM766bhUYQ@mail.gmail.com> (raw)
In-Reply-To: <20200729200545.5apwc7fashwsnglj@madcap2.tricolour.ca>

On Wed, Jul 29, 2020 at 4:06 PM Richard Guy Briggs <rgb@redhat.com> wrote:
> On 2020-07-05 11:09, Paul Moore wrote:
> > On Sat, Jun 27, 2020 at 9:22 AM Richard Guy Briggs <rgb@redhat.com> wrote:

...

> > > @@ -212,6 +219,33 @@ void __init audit_task_init(void)
> > >                                              0, SLAB_PANIC, NULL);
> > >  }
> > >
> > > +/* rcu_read_lock must be held by caller unless new */
> > > +static struct audit_contobj *_audit_contobj_hold(struct audit_contobj *cont)
> > > +{
> > > +       if (cont)
> > > +               refcount_inc(&cont->refcount);
> > > +       return cont;
> > > +}
> > > +
> > > +static struct audit_contobj *_audit_contobj_get(struct task_struct *tsk)
> > > +{
> > > +       if (!tsk->audit)
> > > +               return NULL;
> > > +       return _audit_contobj_hold(tsk->audit->cont);
> > > +}
> > > +
> > > +/* rcu_read_lock must be held by caller */
> > > +static void _audit_contobj_put(struct audit_contobj *cont)
> > > +{
> > > +       if (!cont)
> > > +               return;
> > > +       if (refcount_dec_and_test(&cont->refcount)) {
> > > +               put_task_struct(cont->owner);
> > > +               list_del_rcu(&cont->list);
> >
> > You should check your locking; I'm used to seeing exclusive locks
> > (e.g. the spinlock) around list adds/removes, it just reads/traversals
> > that can be done with just the RCU lock held.
>
> Ok, I've redone the locking yet again.  I knew this on one level but
> that didn't translate consistently to code...
>
> > > +               kfree_rcu(cont, rcu);
> > > +       }
> > > +}
> >
> > Another nitpick, but it might be nice to have similar arguments to the
> > _get() and _put() functions, e.g. struct audit_contobj, but that is
> > some serious bikeshedding (basically rename _hold() to _get() and
> > rename _hold to audit_task_contid_hold() or similar).
>
> I have some idea what you are trying to say, but I think you misspoke.
> Did you mean rename _hold to _get, rename _get to
> audit_task_contobj_hold()?

It reads okay to me, but I know what I'm intending here :)  I agree it
could be a bit confusing.  Let me try to put my suggestion into some
quick pseudo-code function prototypes to make things a bit more
concrete.

The _audit_contobj_hold() function would become:
   struct audit_contobj *_audit_contobj_hold(struct task_struct *tsk);

The _audit_contobj_get() function would become:
   struct audit_contobj *_audit_contobj_get(struct audit_contobj *cont);

The _audit_contobj_put() function would become:
   void _audit_contobj_put(struct audit_contobj *cont);

Basically swap the _get() and _hold() function names so that the
arguments are the same for both the _get() and _set() functions.  Does
this make more sense?

> > >  /**
> > >   * audit_alloc - allocate an audit info block for a task
> > >   * @tsk: task
> > > @@ -232,6 +266,9 @@ int audit_alloc(struct task_struct *tsk)
> > >         }
> > >         info->loginuid = audit_get_loginuid(current);
> > >         info->sessionid = audit_get_sessionid(current);
> > > +       rcu_read_lock();
> > > +       info->cont = _audit_contobj_get(current);
> > > +       rcu_read_unlock();
> >
> > The RCU locks aren't strictly necessary here, are they?  In fact I
> > suppose we could probably just replace the _get() call with a
> > refcount_set(1) just as we do in audit_set_contid(), yes?
>
> I don't understand what you are getting at here.  It needs a *contobj,
> along with bumping up the refcount of the existing contobj.

Sorry, you can disregard.  My mental definition for audit_alloc() is
permanently messed up; I usually double check myself before commenting
on related code, but I must have forgotten here.

-- 
paul moore
www.paul-moore.com

--
Linux-audit mailing list
Linux-audit@redhat.com
https://www.redhat.com/mailman/listinfo/linux-audit


  reply index

Thread overview: 51+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-27 13:20 [PATCH ghak90 V9 00/13] audit: implement container identifier Richard Guy Briggs
2020-06-27 13:20 ` [PATCH ghak90 V9 01/13] audit: collect audit task parameters Richard Guy Briggs
2020-07-05 15:09   ` Paul Moore
2020-07-07  2:50     ` Richard Guy Briggs
2020-07-08  1:42       ` Paul Moore
2020-07-13 20:29         ` Richard Guy Briggs
2020-07-14  0:44           ` Paul Moore
2020-06-27 13:20 ` [PATCH ghak90 V9 02/13] audit: add container id Richard Guy Briggs
2020-07-04 13:29   ` Paul Moore
2020-07-04 13:30     ` Paul Moore
2020-07-05 15:09   ` Paul Moore
2020-07-29 20:05     ` Richard Guy Briggs
2020-08-21 19:36       ` Paul Moore [this message]
2020-06-27 13:20 ` [PATCH ghak90 V9 03/13] audit: read container ID of a process Richard Guy Briggs
2020-06-27 13:20 ` [PATCH ghak90 V9 04/13] audit: log drop of contid on exit of last task Richard Guy Briggs
2020-07-05 15:10   ` Paul Moore
2020-06-27 13:20 ` [PATCH ghak90 V9 05/13] audit: log container info of syscalls Richard Guy Briggs
2020-07-05 15:10   ` Paul Moore
2020-07-29 19:40     ` Richard Guy Briggs
2020-08-21 19:15       ` Paul Moore
2020-10-02 19:52         ` Richard Guy Briggs
2020-10-21 16:39           ` Richard Guy Briggs
2020-10-21 16:49             ` Steve Grubb
2020-10-21 17:53               ` Richard Guy Briggs
2020-10-23  1:21             ` Paul Moore
2020-10-23 20:40               ` Richard Guy Briggs
2020-10-28  1:35                 ` Paul Moore
2020-06-27 13:20 ` [PATCH ghak90 V9 06/13] audit: add contid support for signalling the audit daemon Richard Guy Briggs
2020-07-05 15:10   ` Paul Moore
2020-07-29 19:00     ` Richard Guy Briggs
2020-08-21 18:48       ` Paul Moore
2020-10-02 19:25         ` Richard Guy Briggs
2020-06-27 13:20 ` [PATCH ghak90 V9 07/13] audit: add support for non-syscall auxiliary records Richard Guy Briggs
2020-07-05 15:11   ` Paul Moore
2020-06-27 13:20 ` [PATCH ghak90 V9 08/13] audit: add containerid support for user records Richard Guy Briggs
2020-07-05 15:11   ` Paul Moore
2020-07-18  0:43     ` Richard Guy Briggs
2020-08-21 18:34       ` Paul Moore
2020-06-27 13:20 ` [PATCH ghak90 V9 09/13] audit: add containerid filtering Richard Guy Briggs
2020-06-27 13:20 ` [PATCH ghak90 V9 10/13] audit: add support for containerid to network namespaces Richard Guy Briggs
2020-07-05 15:11   ` Paul Moore
2020-07-21 22:05     ` Richard Guy Briggs
2020-06-27 13:20 ` [PATCH ghak90 V9 11/13] audit: contid check descendancy and nesting Richard Guy Briggs
2020-07-05 15:11   ` Paul Moore
2020-08-07 17:10     ` Richard Guy Briggs
2020-08-21 20:13       ` Paul Moore
2020-10-06 20:03         ` Richard Guy Briggs
2020-06-27 13:20 ` [PATCH ghak90 V9 12/13] audit: track container nesting Richard Guy Briggs
2020-07-05 15:11   ` Paul Moore
2020-06-27 13:20 ` [PATCH ghak90 V9 13/13] audit: add capcontid to set contid outside init_user_ns Richard Guy Briggs
2020-07-05 15:11   ` Paul Moore

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