Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753308Ab2K2T7s (ORCPT ); Thu, 29 Nov 2012 14:59:48 -0500 Received: from mx1.redhat.com ([209.132.183.28]:6166 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752306Ab2K2T7r (ORCPT ); Thu, 29 Nov 2012 14:59:47 -0500 Date: Thu, 29 Nov 2012 14:59:42 -0500 From: Aristeu Rozanski To: "Serge E. Hallyn" Cc: linux-kernel@vger.kernel.org, Tejun Heo , Serge Hallyn , cgroups@vger.kernel.org Subject: Re: [PATCH 3/5] device_cgroup: keep track of local group settings Message-ID: <20121129195942.GW32112@redhat.com> References: <20121127193501.255267751@napanee.usersys.redhat.com> <20121127193502.482004744@napanee.usersys.redhat.com> <20121129192945.GD26104@mail.hallyn.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20121129192945.GD26104@mail.hallyn.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2557 Lines: 67 On Thu, Nov 29, 2012 at 07:29:45PM +0000, Serge E. Hallyn wrote: > Quoting Aristeu Rozanski (aris@redhat.com): > > In preparation for better hierarchy support, it's needed to retain the local > > settings in order to try to reapply them after a propagated change if they're > > still valid. > > > > Cc: Tejun Heo > > Cc: Serge Hallyn > > Signed-off-by: Aristeu Rozanski > > > > --- > > security/device_cgroup.c | 108 ++++++++++++++++++++++++++++++++++------------- > > 1 file changed, 80 insertions(+), 28 deletions(-) > > Hi, > > thanks for doing this. I've got one concern though. I don't see > any place where devcgroup_create() was updated to create the > local exceptions list. I think we need a guarantee that at the local exceptions list is part of the dev_cgroup structure and it's initialized on the patch 'device_cgroup: keep track of local group setting': @@ -190,6 +238,8 @@ if (!dev_cgroup) return ERR_PTR(-ENOMEM); INIT_LIST_HEAD(&dev_cgroup->exceptions); + INIT_LIST_HEAD(&dev_cgroup->local.exceptions); + dev_cgroup->local.behavior = DEVCG_DEFAULT_NONE; parent_cgroup = cgroup->parent; if (parent_cgroup == NULL) > any time the local exceptions list will contain all the entries > contained in the cgroup->exceptions list. Otherwise you cannot hm, no. the local exceptions are meant to be used for stuff written locally. the devcgroup->exceptions list is the list in effect. > use the exception_add() the way you do (or you can't use RCU), > since there could be a window between the successful addition > of a rule to cgroup->local.exceptions and the failed addition to > cgroup->exceptions, during which a task (since it won't need > the mutex for devcg_allow()) could exceed allowed permissions. > > It's possible I'm misunderstanding. If you think that's the case > just kick me and I'll take a fresh look. I see your point. it's indeed a problem. in dev_exception_add(), it needs to check for permissions before actually adding to devcgroup->exceptions. > (Btw is there a git tree or gitweb view I could look at alongside > the patchset?) I'll rebase the patchset along with a fix for this and resubmit with a link to the git repo. -- Aristeu -- 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/