On Thu, Nov 29, 2012 at 07:29:45PM +0000, Serge E. Hallyn wrote:
> Quoting Aristeu Rozanski (aris@xxxxxxxxxx):
> > 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@xxxxxxxxxx>
> > Cc: Serge Hallyn <serge.hallyn@xxxxxxxxxxxxx>
> > Signed-off-by: Aristeu Rozanski <aris@xxxxxxxxxx>
> >
> > ---
> > 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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