linux-kernel - Re: cgroup/next tree: reference to uninitialized percpu ref

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Date:	Mon, 19 Aug 2013 11:46:31 +0800
From:	Li Zefan <lizefan@...wei.com>
To:	Ming Lei <ming.lei@...onical.com>
CC:	Tejun Heo <tj@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: cgroup/next tree: reference to uninitialized percpu ref

On 2013/8/19 11:32, Ming Lei wrote:
> Hi,
> 
> The kernel oops[1] is triggered during kernel boot with the latest next
> tree(3.11.0-rc5-next-20130816), looks it is caused by reference to uninitialized
> percpu ref of root cgroup, and below patch can fix the problem:
> 

Thanks for the report. Li Zhong has summited a patch to fix it:

www.spinics.net/lists/linux-next/msg26414.html

and it should show up in linux-next tree when next is updated.

> diff --git a/kernel/cgroup.c b/kernel/cgroup.c
> index 723194f..0e8954b 100644
> --- a/kernel/cgroup.c
> +++ b/kernel/cgroup.c
> @@ -4485,7 +4485,8 @@ static long cgroup_create(struct cgroup *parent,
> struct dentry *dentry,
>   struct cgroup_subsys_state *css = css_ar[ss->subsys_id];
> 
>   dget(dentry);
> - percpu_ref_get(&css->parent->refcnt);
> + if (!(css->parent->flags & CSS_ROOT))
> + percpu_ref_get(&css->parent->refcnt);
>   }
> 


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