netdev - Moving frags and SKBTX_DEV

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Date:	Wed, 14 May 2014 14:40:54 +0100
From:	Zoltan Kiss <zoltan.kiss@...rix.com>
To:	<netdev@...r.kernel.org>
CC:	"xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>,
	<kvm@...r.kernel.org>, Eric Dumazet <eric.dumazet@...il.com>,
	David Miller <davem@...emloft.net>
Subject: Moving frags and SKBTX_DEV_ZEROCOPY skbs

Hi,

Recently I've investigated issues around SKBTX_DEV_ZEROCOPY skbs where 
the frags list were modified. I came across this function skb_shift(), 
which moves frags between skbs. And there are a lot more of such kind, 
skb_split or skb_try_coalesce, for example.
It could be a dangerous thing if a frag is referenced from an skb which 
doesn't have the original destructor_arg, and to avoid that 
skb_orphan_frags should be called. Although probably these functions are 
not normally touched in usual usecases, I think it would be useful to 
review core skb functions proactively and add an skb_orphan_frags 
everywhere where the frags could be referenced from other places.
Any opinion about this?

Regards,

Zoltan
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