netdev - Re: [PATCH] tcp: assign the sock correctly to an outgoing SYNACK packet

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Date:	Mon, 08 Apr 2013 12:14:34 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	pmoore@...hat.com
Cc:	netdev@...r.kernel.org, mvadkert@...hat.com
Subject: Re: [PATCH] tcp: assign the sock correctly to an outgoing SYNACK
 packet

From: Paul Moore <pmoore@...hat.com>
Date: Mon, 08 Apr 2013 11:45:19 -0400

> Commit 90ba9b1986b5ac4b2d184575847147ea7c4280a2 converted
> tcp_make_synack() to use alloc_skb() directly instead of calling
> sock_wmalloc(), the goal being the elimination of two atomic
> operations.  Unfortunately, in doing so the change broke certain
> SELinux/NetLabel configurations by no longer correctly assigning
> the sock to the outgoing packet.
> 
> This patch fixes this regression by doing the skb->sk assignment
> directly inside tcp_make_synack().
> 
> Reported-by: Miroslav Vadkerti <mvadkert@...hat.com>
> Signed-off-by: Paul Moore <pmoore@...hat.com>

Setting skb->sk without the destructor results in an SKB that can live
potentially forever with a stale reference to a destroyed socket.

You cannot fix the problem in this way.
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