linux-kernel - Re: oops in tcp_xmit_retransmit

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Date:	Mon, 19 Jul 2010 10:06:09 +0200
From:	Lennart Schulte <lennart.schulte@...s.rwth-aachen.de>
To:	Ilpo Järvinen <ilpo.jarvinen@...sinki.fi>
CC:	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Tejun Heo <tj@...nel.org>, lkml <linux-kernel@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"Fehrmann, Henning" <henning.fehrmann@....mpg.de>,
	Carsten Aulbert <carsten.aulbert@....mpg.de>
Subject: Re: oops in tcp_xmit_retransmit_queue() w/ v2.6.32.15

I ran tests for about 2 hours with this patch and I got no output from 
the debug patch. This seems to have solved at least my problem :)

Thanks!
> [PATCH] tcp: fix crash in tcp_xmit_retransmit_queue
>
> It can happen that there are no packets in queue while calling
> tcp_xmit_retransmit_queue(). tcp_write_queue_head() then returns
> NULL and that gets deref'ed to get sacked into a local var.
>
> There is no work to do if no packets are outstanding so we just
> exit early.
>
> There may still be another bug affecting this same function.
>
> Signed-off-by: Ilpo Järvinen<ilpo.jarvinen@...sinki.fi>
> Reported-by: Lennart Schulte<lennart.schulte@...s.rwth-aachen.de>
> ---
>   net/ipv4/tcp_output.c |    3 +++
>   1 files changed, 3 insertions(+), 0 deletions(-)
>
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index b4ed957..7ed9dc1 100644
> --- a/net/ipv4/tcp_output.c
> +++ b/net/ipv4/tcp_output.c
> @@ -2208,6 +2208,9 @@ void tcp_xmit_retransmit_queue(struct sock *sk)
>   	int mib_idx;
>   	int fwd_rexmitting = 0;
>
> +	if (!tp->packets_out)
> +		return;
> +
>   	if (!tp->lost_out)
>   		tp->retransmit_high = tp->snd_una;
>
>    

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