Messages in this thread Patch in this message | | | Date | Thu, 29 Nov 2012 14:59:42 -0500 | From | Aristeu Rozanski <> | Subject | Re: [PATCH 3/5] device_cgroup: keep track of local group settings |
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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
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