netdev - Re: bridge/netfilter: regression in 2.6.39.1

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Date:	Fri, 03 Jun 2011 21:42:47 +0200
From:	Alexander Holler <holler@...oftware.de>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	linux-kernel@...r.kernel.org, David Miller <davem@...emloft.net>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	netdev@...r.kernel.org
Subject: Re: bridge/netfilter: regression in 2.6.39.1

Am 03.06.2011 21:34, schrieb Eric Dumazet:
> Le vendredi 03 juin 2011 à 21:21 +0200, Alexander Holler a écrit :
>> Hello,
>>
>> I'm getting a oops in the bridge code in br_change_mtu() with 2.6.39.1.
>> The patch below seems to fix that.
>>
>> I'm not sure about the usage of dst_cow_metrics_generic() in
>> fake_dst_ops, but after having a quick look at it seems to be ok to use
>> that here.
>>
>> Regards,
>>
>> Alexander
>>
>> -----
>>   From 3c1d5951af73389798afeea672ec224e195b8e8d Mon Sep 17 00:00:00 2001
>> From: Alexander Holler<holler@...oftware.de>
>> Date: Fri, 3 Jun 2011 20:43:06 +0200
>> Subject: [PATCH] bridge: add dst_cow_metrics_generic to fake_dst_ops
>>
>> Commit 42923465fb8d025a2b5153f2e7ab1e6e1058bf00 does here what it
>> should prevent, it introduces NULL a dereference.
>>
>
> I cant find this commit in known trees. Could you give the real commit
> id and its title ?
>
>> The above commit uses dst_init_metrics() which sets the metrics as
>> read only. As result br_change_mtu() dies in dst_metric_set()
>> which calls dst_metrics_write_ptr() which calls
>> dst->ops->cow_metrics() if the metrics are read only.
>> ---
>>    net/bridge/br_netfilter.c |    1 +
>>    1 files changed, 1 insertions(+), 0 deletions(-)
>>
>> diff --git a/net/bridge/br_netfilter.c b/net/bridge/br_netfilter.c
>> index 5f9c091..de982a1 100644
>> --- a/net/bridge/br_netfilter.c
>> +++ b/net/bridge/br_netfilter.c
>> @@ -107,6 +107,7 @@ static void fake_update_pmtu(struct dst_entry *dst,
>> u32 mtu)
>>    static struct dst_ops fake_dst_ops = {
>>           .family =               AF_INET,
>>           .protocol =             cpu_to_be16(ETH_P_IP),
>> +       .cow_metrics =          dst_cow_metrics_generic,
>>           .update_pmtu =          fake_update_pmtu,
>>    };
>>
>
> Your patch is mangled (white spaces instead of tabulations)

The patch had a tab, so either c&p failed or something else removed the 
tab. Maybe Thunderbird, don't know. Normally I'm using git send-email.

If someone gives a feedback about the content and not the style, I'm 
willing to send a nice patch which too includes the forgotten Signed-off-by.

Regards,

Alexander

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