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Date:   Mon, 8 Jul 2019 07:37:48 -0700
From:   Tejun Heo <tj@kernel.org>
To:     Peng Wang <rocking@whu.edu.cn>
Cc:     gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] kernfs: fix potential null pointer dereference
Message-ID: <20190708143748.GZ657710@devbig004.ftw2.facebook.com>
References: <20190705134730.20833-1-rocking@whu.edu.cn>
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On Fri, Jul 05, 2019 at 09:47:30PM +0800, Peng Wang wrote:
> diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
> index a387534c9577..ea3fc972c48b 100644
> --- a/fs/kernfs/dir.c
> +++ b/fs/kernfs/dir.c
> @@ -430,7 +430,7 @@ struct kernfs_node *kernfs_get_active(struct kernfs_node *kn)
>   */
>  void kernfs_put_active(struct kernfs_node *kn)
>  {
> -	struct kernfs_root *root = kernfs_root(kn);
> +	struct kernfs_root *root;
>  	int v;
>  
>  	if (unlikely(!kn))
> @@ -442,6 +442,7 @@ void kernfs_put_active(struct kernfs_node *kn)
>  	if (likely(v != KN_DEACTIVATED_BIAS))
>  		return;
>  
> +	root = kernfs_root(kn);
>  	wake_up_all(&root->deactivate_waitq);

Maybe just remove the root variable altogether?  Other than that,

Acked-by: Tejun Heo <tj@kernel.org>

Thanks.

-- 
tejun