From: Neil Brown <neilb@suse.de>
To: "Akinobu Mita" <akinobu.mita@gmail.com>
Date: Tue, 31 Oct 2006 15:13:02 +1100
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Message-ID: <17734.52558.476874.72042@cse.unsw.edu.au>
Cc: "Trond Myklebust" <Trond.Myklebust@netapp.com>,
       linux-kernel@vger.kernel.org, "Andy Adamson" <andros@citi.umich.edu>,
       "J. Bruce Fields" <bfields@citi.umich.edu>,
       "Olaf Kirch" <okir@monad.swb.de>
Subject: Re: [PATCH 2/2] auth_gss: unregister gss_domain when unloading module
In-Reply-To: message from Akinobu Mita on Tuesday October 31
References: <20061028185554.GM9973@localhost>
	<20061029133551.GA10072@localhost>
	<20061029133700.GA10295@localhost>
	<20061029133816.GB10295@localhost>
	<1162152960.5545.57.camel@lade.trondhjem.org>
	<20061030145404.GA7258@localhost>
	<1162221449.5517.70.camel@lade.trondhjem.org>
	<961aa3350610301915i5a954dbemd5420a350fd0c625@mail.gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1231
Lines: 34

On Tuesday October 31, akinobu.mita@gmail.com wrote:
> 
> But I noticed that even if we have this kind of smp-safe code, there
> is no guarantee that 2nd auth_domain_put() in
> svcauth_gss_unregister_pseudoflavor() is the last reference of
> this gss_domain.
> 
> So it is possible to happen invalid dereference by real last user of
> this gss_domain after unloading module. If this is not wrong,
> Is it neccesary to have try_get_module()/put_module() somewhere to
> prevent this?

After a quick look, it seems to me that one reasonable option would
be:

  svcauth_gss_register_pseudoflavor
     returns a void* which is 'new', and possible calls try_get_module(),
     failing if that fails. and
  svcauth_gss_unregister_pseudoflavor
     takes the void* (not a name) and calls auth_domain_put on it, and
     then calls put_module().

  'struct pf_desc' would have to gain a
        void * handle;
  to hold the returned value.

Would that solve the problem as you see it?

NeilBrown
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/