From: Aristeu Rozanski <aris@redhat.com>
To: "Serge E. Hallyn" <serge@hallyn.com>
Cc: linux-kernel@vger.kernel.org, Tejun Heo <tj@kernel.org>,
Serge Hallyn <serge.hallyn@canonical.com>,
cgroups@vger.kernel.org
Subject: Re: [PATCH 3/5] device_cgroup: keep track of local group settings
Date: Thu, 29 Nov 2012 14:59:42 -0500 [thread overview]
Message-ID: <20121129195942.GW32112@redhat.com> (raw)
In-Reply-To: <20121129192945.GD26104@mail.hallyn.com>
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 <tj@kernel.org>
> > Cc: Serge Hallyn <serge.hallyn@canonical.com>
> > Signed-off-by: Aristeu Rozanski <aris@redhat.com>
> >
> > ---
> > 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
next prev parent reply other threads:[~2012-11-29 19:59 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-27 19:35 [PATCH 0/5] devcg: introduce proper hierarchy support Aristeu Rozanski
2012-11-27 19:35 ` [PATCH 1/5] device_cgroup: fix locking in devcgroup_destroy() Aristeu Rozanski
2012-11-29 19:06 ` Serge E. Hallyn
2012-12-03 17:29 ` Tejun Heo
2012-11-27 19:35 ` [PATCH 2/5] device_cgroup: prepare exception list handling functions for two lists Aristeu Rozanski
2012-11-29 19:07 ` Serge E. Hallyn
2012-12-03 17:31 ` Tejun Heo
2012-11-27 19:35 ` [PATCH 3/5] device_cgroup: keep track of local group settings Aristeu Rozanski
2012-11-29 19:29 ` Serge E. Hallyn
2012-11-29 19:59 ` Aristeu Rozanski [this message]
2012-11-29 20:26 ` Serge E. Hallyn
2012-11-29 22:31 ` Aristeu Rozanski
2012-12-03 18:01 ` Serge E. Hallyn
2012-12-03 19:06 ` Aristeu Rozanski
2012-12-06 4:31 ` Serge E. Hallyn
2012-11-29 20:11 ` Aristeu Rozanski
2012-11-27 19:35 ` [PATCH 4/5] device_cgroup: make may_access() stronger Aristeu Rozanski
2012-12-03 17:44 ` Tejun Heo
2012-12-03 19:01 ` Aristeu Rozanski
2012-11-27 19:35 ` [PATCH 5/5] device_cgroup: propagate local changes down the hierarchy Aristeu Rozanski
2012-12-03 18:01 ` Tejun Heo
2012-12-03 19:14 ` Aristeu Rozanski
2012-12-03 21:36 ` Tejun Heo
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20121129195942.GW32112@redhat.com \
--to=aris@redhat.com \
--cc=cgroups@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=serge.hallyn@canonical.com \
--cc=serge@hallyn.com \
--cc=tj@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).