netdev - Re: [net] net: fix double free issue of skbuff

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Date:	Mon, 29 Feb 2016 22:16:37 +0800
From:	张胜举 <zhangshengju@...s.chinamobile.com>
To:	"'Paolo Abeni'" <pabeni@...hat.com>
Cc:	<davem@...emloft.net>, <netdev@...r.kernel.org>
Subject: Re: [net] net: fix double free issue of skbuff

> On Mon, 2016-02-29 at 12:22 +0000, Zhang Shengju wrote:
> > If skb_reorder_vlan_header() failed, skb is freed and NULL is returned.
> > Then at skb_vlan_untag(), it will free skbuff again which cause double
> > free.
> 
> On skb_reorder_vlan_header() failure, skb_vlan_untag() will call
> kfree_skb() using the return value of skb_reorder_vlan_header(), that is
> NULL. kfree_skb() is a noop when the argument is NULL.
> 
> The current code seams safe.
> 
> Paolo
Hi Paolo, even current code is safe, this's still a potential problem. We should make an
assumption that inner function doesn't free skb, and let outside function take care of this.

BRs, 
Shengju