linux-kernel - Re: Badness at net/ipv4/inet_connection

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Message-Id: <1260817033.9141.8.camel@merlyn>
Date:	Mon, 14 Dec 2009 18:57:13 +0000
From:	John Dykstra <john.dykstra1@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	David Miller <davem@...emloft.net>, lists@...dbynature.de,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: Badness at net/ipv4/inet_connection_sock.c:293

On Mon, 2009-12-14 at 18:34 +0100, Eric Dumazet wrote:
> Le 14/12/2009 08:45, David Miller a écrit :
> > From: Eric Dumazet <eric.dumazet@...il.com>
> > Date: Mon, 14 Dec 2009 06:56:31 +0100
> > 
> >> It seems to me tcp_create_openreq_child() doesnt properly initialize
> >> newtp->cookie_values to NULL, but this should not produce warnings like that ?
> > 
> > If oldtp->cookie_values is NULL, the child's should be as well
> > because of sk_clone().
> 
> Right, maybe then its a tcp_ack() or a syncookie validation change ?
> 
> 
> tcp_v4_rcv()
>         bh_lock_sock_nested(sk);
>         if (!sock_owned_by_user(sk)) {
> 
>         -> tcp_v4_do_rcv()
>                 -> tcp_v4_hnd_req()
>                         -> cookie_v4_check()
>                                 -> get_cookie_sock()
>                                         -> child = syn_recv_sock()
>                                         -> inet_csk_reqsk_queue_add(child) (TCP_SYN_RECV socket queued into parent)
>                 -> tcp_child_process() (backlog... not)
>                         -> tcp_rcv_state_process()
>                                 -> acceptable = tcp_ack() > 0;
>                                 -> if (acceptable) -> sk_state = TCP_ESTABLISHED
>                                         (but if tcp_ack() returned <= 0, state unchanged : TCP_SYN_RECV)
> 
> 
> And commit 96e0bf4b5193d0d97d139f99e2dd128763d55521
> (tcp: Discard segments that ack data not yet sent)
> 
> Did change this area a bit :
> 
> @@ -5632,7 +5639,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
>  
>         /* step 5: check the ACK field */
>         if (th->ack) {
> -               int acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH);
> +               int acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH) > 0;
>  
>                 switch (sk->sk_state) {
>                 case TCP_SYN_RECV:

That test was changed to match a change in the return values of
tcp_ack().  No logic change was intended.

I won't be able to catch up on this thread and take a look at the code
until this evening, CST.

  --  John

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