netdev - Re: OOP in ip_cmsg

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Message-Id: <20100503.152351.181464355.davem@davemloft.net>
Date:	Mon, 03 May 2010 15:23:51 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	shemminger@...tta.com, netdev@...r.kernel.org
Subject: Re: OOP in ip_cmsg_recv (net-next)

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Mon, 03 May 2010 19:21:09 +0200

>  
> -	/* skb is now orphaned, might be freed outside of locked section */
> -	consume_skb(skb);
> +	/* skb is now orphaned, can be freed outside of locked section */
> +	__kfree_skb(skb);
>  }
>  EXPORT_SYMBOL(skb_free_datagram_locked);

Eric, if you do this you undo the utility of the SKB packet drop tracing
that Neil wrote.

consome_skb() says that the application actually took in the packet and
we didn't drop it due to some error or similar.

Whereas __kfree_skb() is going to be tagged as a packet drop and the
data didn't reach the application.

So if you need to use __kfree_skb() to fix this you'll need to somehow
add some appropriate annotations for the tracer.  Perhaps add a
__consume_skb() that is marked for the tracing stuff and does what
you need.
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