netdev - Re: [PATCH 1/1] tproxy: do not assign timewait sockets to skb->sk

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Message-ID: <4D594F9E.2090100@trash.net>
Date:	Mon, 14 Feb 2011 16:51:58 +0100
From:	Patrick McHardy <kaber@...sh.net>
To:	Florian Westphal <fw@...len.de>
CC:	netfilter-devel@...r.kernel.org, netdev@...r.kernel.org,
	Balazs Scheidler <bazsi@...abit.hu>,
	KOVACS Krisztian <hidden@...abit.hu>
Subject: Re: [PATCH 1/1] tproxy: do not assign timewait sockets to skb->sk

Am 14.02.2011 12:44, schrieb Florian Westphal:
> Assigning a socket in timewait state to skb->sk can trigger
> kernel oops, e.g. in nfnetlink_log, which does:
> 
> if (skb->sk) {
>         read_lock_bh(&skb->sk->sk_callback_lock);
>         if (skb->sk->sk_socket && skb->sk->sk_socket->file) ...
> 
> in the timewait case, accessing sk->sk_callback_lock and sk->sk_socket
> is invalid.
> 
> Either all of these spots will need to add a test for sk->sk_state != TCP_TIME_WAIT,
> or xt_TPROXY must not assign a timewait socket to skb->sk.
> 
> This does the latter.
> 
> If a TW socket is found, assign the tproxy nfmark, but skip the skb->sk assignment,
> thus mimicking behaviour of a '-m socket .. -j MARK/ACCEPT' re-routing rule.
> 
> The 'SYN to TW socket' case is left unchanged -- we try to redirect to the
> listener socket.
> 
> Cc: Balazs Scheidler <bazsi@...abit.hu>
> Cc: KOVACS Krisztian <hidden@...abit.hu>
> Signed-off-by: Florian Westphal <fwestphal@...aro.com>

Looks fine to me. Balazs. Krisztian, any objections?
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