Quoting Li Zefan ([EMAIL PROTECTED]):
> During the use of a dev_cgroup, we should guarantee the corresponding
> cgroup won't be deleted (i.e. via rmdir). This can be done through
> css_get(&dev_cgroup->css), but here we can just get and use the
> dev_cgroup under rcu_read_lock.
> 
> And also remove checking NULL dev_cgroup, it won't be NULL since a task
> always belongs to a cgroup.
> 
> Signed-off-by: Li Zefan <[EMAIL PROTECTED]>

Looks good.  Thanks, Li.

Acked-by: Serge Hallyn <[EMAIL PROTECTED]>

> ---
>  security/device_cgroup.c |   18 +++++++++---------
>  1 files changed, 9 insertions(+), 9 deletions(-)
> 
> diff --git a/security/device_cgroup.c b/security/device_cgroup.c
> index 7bd296c..46f2397 100644
> --- a/security/device_cgroup.c
> +++ b/security/device_cgroup.c
> @@ -508,12 +508,11 @@ int devcgroup_inode_permission(struct inode *inode, int 
> mask)
>               return 0;
>       if (!S_ISBLK(inode->i_mode) && !S_ISCHR(inode->i_mode))
>               return 0;
> -     dev_cgroup = css_to_devcgroup(task_subsys_state(current,
> -                             devices_subsys_id));
> -     if (!dev_cgroup)
> -             return 0;
> 
>       rcu_read_lock();
> +
> +     dev_cgroup = task_devcgroup(current);
> +
>       list_for_each_entry_rcu(wh, &dev_cgroup->whitelist, list) {
>               if (wh->type & DEV_ALL)
>                       goto acc_check;
> @@ -533,6 +532,7 @@ acc_check:
>               rcu_read_unlock();
>               return 0;
>       }
> +
>       rcu_read_unlock();
> 
>       return -EPERM;
> @@ -543,12 +543,10 @@ int devcgroup_inode_mknod(int mode, dev_t dev)
>       struct dev_cgroup *dev_cgroup;
>       struct dev_whitelist_item *wh;
> 
> -     dev_cgroup = css_to_devcgroup(task_subsys_state(current,
> -                             devices_subsys_id));
> -     if (!dev_cgroup)
> -             return 0;
> -
>       rcu_read_lock();
> +
> +     dev_cgroup = task_devcgroup(current);
> +
>       list_for_each_entry(wh, &dev_cgroup->whitelist, list) {
>               if (wh->type & DEV_ALL)
>                       goto acc_check;
> @@ -566,6 +564,8 @@ acc_check:
>               rcu_read_unlock();
>               return 0;
>       }
> +
>       rcu_read_unlock();
> +
>       return -EPERM;
>  }
> -- 
> 1.5.4.rc3
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