linux-kernel - bridge/netfilter: regression in 2.6.39.1

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Message-ID: <4DE93422.3070000@ahsoftware.de>
Date:	Fri, 03 Jun 2011 21:21:06 +0200
From:	Alexander Holler <holler@...oftware.de>
To:	linux-kernel@...r.kernel.org
CC:	Eric Dumazet <eric.dumazet@...il.com>,
	David Miller <davem@...emloft.net>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	netdev@...r.kernel.org
Subject: bridge/netfilter: regression in 2.6.39.1

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.

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,
  };

-- 
1.7.3.4
--
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