Re: [PATCH 13/14] device_cgroup: use css_has_online_children() instead of has_children()

Aristeu Rozanski
2014-05-13T12:57:06Z

On Fri, May 09, 2014 at 05:31:30PM -0400, Tejun Heo wrote:
> devcgroup_update_access() wants to know whether there are child
> cgroups which are online and visible to userland and has_children()
> may return false positive. Replace it with css_has_online_children().
>
> Signed-off-by: Tejun Heo <tj@kernel.org>
> Cc: Aristeu Rozanski <aris@redhat.com>
> Cc: Serge Hallyn <serge.hallyn@ubuntu.com>
> ---
> security/device_cgroup.c | 19 ++-----------------
> 1 file changed, 2 insertions(+), 17 deletions(-)
>
> diff --git a/security/device_cgroup.c b/security/device_cgroup.c
> index 75b4b18..22de334 100644
> --- a/security/device_cgroup.c
> +++ b/security/device_cgroup.c
> @@ -475,21 +475,6 @@ static int propagate_exception(struct dev_cgroup *devcg_root,
> return rc;
> }
>
> -static inline bool has_children(struct dev_cgroup *devcgroup)
> -{
> - bool ret;
> -
> - /*
> - * FIXME: There may be lingering offline csses and this function
> - * may return %true when there isn't any userland-visible child
> - * which is incorrect for our purposes.
> - */
> - rcu_read_lock();
> - ret = css_next_child(NULL, &devcgroup->css);
> - rcu_read_unlock();
> - return ret;
> -}
> -
> /*
> * Modify the exception list using allow/deny rules.
> * CAP_SYS_ADMIN is needed for this. It's at least separate from CAP_MKNOD
> @@ -522,7 +507,7 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup,
> case 'a':
> switch (filetype) {
> case DEVCG_ALLOW:
> - if (has_children(devcgroup))
> + if (css_has_online_children(&devcgroup->css))
> return -EINVAL;
>
> if (!may_allow_all(parent))
> @@ -538,7 +523,7 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup,
> return rc;
> break;
> case DEVCG_DENY:
> - if (has_children(devcgroup))
> + if (css_has_online_children(&devcgroup->css))
> return -EINVAL;
>
> dev_exception_clean(devcgroup);

Acked-by: Aristeu Rozanski <aris@redhat.com>

--
Aristeu