linux-kernel - Re: [PATCH v5 9/9] devcg: propagate local changes down the hierarchy

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Date:	Mon, 4 Feb 2013 10:09:30 -0500
From:	Aristeu Rozanski <aris@...hat.com>
To:	"Serge E. Hallyn" <serge@...lyn.com>
Cc:	linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
	Tejun Heo <tj@...nel.org>,
	Serge Hallyn <serge.hallyn@...onical.com>
Subject: Re: [PATCH v5 9/9] devcg: propagate local changes down the hierarchy

On Sat, Feb 02, 2013 at 04:20:52PM +0000, Serge E. Hallyn wrote:
> Quoting Aristeu Rozanski (aris@...hat.com):
> > +static int propagate_exception(struct dev_cgroup *devcg_root)
> > +{
> > +	struct cgroup *root = devcg_root->css.cgroup;
> > +	struct dev_cgroup *devcg, *parent, *tmp;
> > +	int rc = 0;
> > +	LIST_HEAD(pending);
> > +
> > +	get_online_devcg(root, &pending);
> > +
> > +	list_for_each_entry_safe(devcg, tmp, &pending, propagate_pending) {
> > +		parent = cgroup_to_devcgroup(devcg->css.cgroup->parent);
> > +
> > +		dev_exception_clean(&devcg->exceptions);
> > +		if (devcg->behavior == parent->behavior) {
> > +			rc = dev_exceptions_copy(&devcg->exceptions, &parent->exceptions);
> 
> Let's say parent A and child B both have DEFAULT_DENY, with a set of let's
> say 5 whitelist exceptions.  Now the parent adds two more whitelist
> exceptions.  As you say, we don't propagate those.
> 
> Now the parent removes one of it's whitelist exceptions.
> devcgroup_update_access() calls dev_exception_rm() followed by
> propagate_exception(), which comes here and copies the parent's
> whitelist - including the two new whitelist rules - to the
> child.

ugh, I see your point. This gonna be trickier to fix.

-- 
Aristeu

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