netdev - Re: race in skb_splice

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Message-Id: <200805271833.55880.opurdila@ixiacom.com>
Date:	Tue, 27 May 2008 18:33:55 +0300
From:	Octavian Purdila <opurdila@...acom.com>
To:	Evgeniy Polyakov <johnpol@....mipt.ru>
Cc:	Ben Hutchings <bhutchings@...arflare.com>, netdev@...r.kernel.org,
	davem@...emloft.net
Subject: Re: race in skb_splice_bits?

On Tuesday 27 May 2008, Evgeniy Polyakov wrote:
>
> The same wrong one, sorry about that.
>
> Idea is to hold skb between release/lock sock calls and thus do not
> allow to free it by core stack when it is being released. Patch still
> misses the case, when socket is released and skb was dequeued, so splice
> will try to dequeue it again, which will crash. I will think on how to
> fix the issue.

Yes, I think I got the idea you are trying to use here. But, somehow I feel 
uneasy with this approach :) Isn't it cleaner to keep the lock and try to 
avoid the deadlock on the sendfile() side? Or is that unfeasible?

I don't think we can drop the socket lock, it will introduce at least on type 
of races: since the skb we are processing is still on the socket queue, any 
entity accessing the socket queue will possible collide with us. 

Thanks,
tavi
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