From: Aristeu Rozanski <aris@redhat.com>
To: "Serge E. Hallyn" <serge@hallyn.com>
Cc: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org,
Tejun Heo <tj@kernel.org>,
Serge Hallyn <serge.hallyn@canonical.com>
Subject: Re: [PATCH v4 9/9] devcg: propagate local changes down the hierarchy
Date: Thu, 31 Jan 2013 17:00:37 -0500 [thread overview]
Message-ID: <20130131220036.GN17632@redhat.com> (raw)
In-Reply-To: <20130131041932.GB14576@mail.hallyn.com>
On Thu, Jan 31, 2013 at 04:19:32AM +0000, Serge E. Hallyn wrote:
> Quoting aris@redhat.com (aris@redhat.com):
> > +/**
> > + * propagate_behavior - propagates a change in the behavior down in hierarchy
> > + * @devcg_root: device cgroup that changed behavior
> > + *
> > + * returns: 0 in case of success, != 0 in case of error
> > + *
> > + * This is one of the two key functions for hierarchy implementation.
> > + * All cgroup's children recursively will have the behavior changed and
> > + * exceptions copied from the parent then its local behavior and exceptions
> > + * re-evaluated and applied if they're still allowed. Refer to
> > + * Documentation/cgroups/devices.txt for more details.
> > + */
> > +static int propagate_behavior(struct dev_cgroup *devcg_root)
> > +{
> > + struct cgroup *root = devcg_root->css.cgroup;
> > + struct dev_cgroup *parent, *devcg, *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);
> > +
> > + /* first copy parent's state */
> > + devcg->behavior = parent->behavior;
> > + dev_exception_clean(&devcg->exceptions);
> > + rc = dev_exceptions_copy(&devcg->exceptions, &parent->exceptions);
> > + if (rc) {
> > + devcg->behavior = DEVCG_DEFAULT_DENY;
> > + break;
> > + }
> > +
> > + if (devcg->local.behavior == DEVCG_DEFAULT_DENY &&
> > + devcg->behavior == DEVCG_DEFAULT_ALLOW) {
> > + devcg->behavior = DEVCG_DEFAULT_DENY;
> > + }
>
> I think you might need another special case here. If A and it's
> child B are both ALLOW, and A switches to DENY, then if I read this
> right B will be switched to DENY, but its local->exceptions will
> not be cleared. They won't be immediately applied, so at first it's
> ok. But if B then adds an exception, what happens? It'll call
> revalidate_exceptions on the full old list plus new exception. If
> any exceptions aren't allowed by the parent then it won't be applied,
> but it's possible that it is allowed in the parent but (its sense
> now being inverted from blacklist to whitelist) not intended to be
> allowed in the child. But there will be nothing to stop it.
>
> So do you need
>
> if (devcg->local.behavior == DEVCG_DEFAULT_ALLOW &&
> devcg->behavior == DEVCG_DEFAULT_DENY) {
> dev_exception_clean(&devcg->local.exceptions);
> }
>
> here?
>
> > + if (devcg->local.behavior == devcg->behavior)
> > + rc = revalidate_exceptions(devcg);
I think:
else
dev_exception_clean(&devcg->local.exceptions);
here instead
--
Aristeu
next prev parent reply other threads:[~2013-01-31 22:00 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-30 17:11 [PATCH v4 0/9] devcg: introduce proper hierarchy support aris
2013-01-30 17:11 ` [PATCH v4 1/9] device_cgroup: prepare exception list handling functions for two lists aris
2013-01-30 19:34 ` Serge E. Hallyn
2013-01-30 17:11 ` [PATCH v4 2/9] devcg: reorder device exception functions aris
2013-01-30 19:44 ` Serge E. Hallyn
2013-01-30 17:11 ` [PATCH v4 3/9] device_cgroup: keep track of local group settings aris
2013-01-30 20:01 ` Serge E. Hallyn
2013-01-30 17:11 ` [PATCH v4 4/9] devcg: expand may_access() logic aris
2013-01-30 20:09 ` Serge E. Hallyn
2013-01-30 17:11 ` [PATCH v4 5/9] devcg: prepare may_access() for hierarchy support aris
2013-01-30 20:30 ` Serge E. Hallyn
2013-01-30 17:11 ` [PATCH v4 6/9] devcg: use css_online and css_offline aris
2013-01-30 20:40 ` Serge E. Hallyn
2013-01-30 17:11 ` [PATCH v4 7/9] devcg: split single exception copy from dev_exceptions_copy() aris
2013-01-30 20:42 ` Serge E. Hallyn
2013-01-30 17:11 ` [PATCH v4 8/9] devcg: refactor dev_exception_clean() aris
2013-01-30 20:47 ` Serge E. Hallyn
2013-01-30 20:49 ` Aristeu Rozanski
2013-01-30 20:50 ` Tejun Heo
2013-01-31 2:15 ` Li Zefan
2013-01-31 15:13 ` Aristeu Rozanski
2013-01-30 17:11 ` [PATCH v4 9/9] devcg: propagate local changes down the hierarchy aris
2013-01-30 21:35 ` Serge E. Hallyn
2013-01-31 4:19 ` Serge E. Hallyn
2013-01-31 22:00 ` Aristeu Rozanski [this message]
2013-01-31 4:38 ` Serge E. Hallyn
2013-01-31 22:03 ` Aristeu Rozanski
2013-02-01 19:09 ` [PATCH v5 " Aristeu Rozanski
2013-02-02 16:13 ` Serge E. Hallyn
2013-02-04 15:03 ` Aristeu Rozanski
2013-02-04 15:17 ` Serge Hallyn
2013-02-02 16:20 ` Serge E. Hallyn
2013-02-04 15:09 ` Aristeu Rozanski
2013-02-05 18:36 ` [PATCH v6 " Aristeu Rozanski
2013-02-09 3:53 ` Serge E. Hallyn
2013-02-11 14:30 ` Aristeu Rozanski
2013-02-09 4:04 ` Serge E. Hallyn
2013-02-11 14:32 ` Aristeu Rozanski
2013-02-11 17:42 ` Serge E. Hallyn
2013-02-11 18:38 ` Aristeu Rozanski
2013-02-11 18:52 ` Serge E. Hallyn
2013-02-11 19:02 ` Aristeu Rozanski
2013-02-11 20:47 ` Serge Hallyn
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