netdev - Re: [PATCH net-next] ipv6: protect skb->sk accesses from recursive dereference inside the stack

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Date:	Thu, 02 Apr 2015 02:35:51 +0200
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	Eric Dumazet <eric.dumazet@...il.com>,
	Cong Wang <cwang@...pensource.com>
Cc:	netdev <netdev@...r.kernel.org>, Jiri Pirko <jiri@...nulli.us>
Subject: Re: [PATCH net-next] ipv6: protect skb->sk accesses from recursive
 dereference inside the stack



On Thu, Apr 2, 2015, at 02:27, Eric Dumazet wrote:
> On Wed, 2015-04-01 at 17:06 -0700, Cong Wang wrote:
> 
> > Shouldn't these skb's be orphaned for tunnel cases? Or we still have
> > to keep skb->sk for other valid use?
> 
> skb should not be orphaned, until the very last stage.
> 
> Many layers depend on this, really.
> 
> Simply ask the question to yourself :
> 
> What if I do not associate skb to a socket at first. What possibly
> breaks ?
> 
> orphaning skb just because they traverse a tunnel would be quite
> horrible.

Agreed, but we have some bits in the skb->sk pointer left for signaling
we are only keeping it around for destructor and upper layer
notifications. Destructors should be the only ones having to deal with
skb->sk and they can mask the bit. That would touch a lot of NULL
checks, though.

Bye,
Hannes
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