linux-kernel - [PATCH v2] bridge: rcu_deref outside read-lock section

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Date:	Tue, 14 Aug 2012 12:08:52 +0400
From:	Denis Efremov <yefremov.denis@...il.com>
To:	Stephen Hemminger <shemminger@...tta.com>
Cc:	Denis Efremov <yefremov.denis@...il.com>,
	"David S. Miller" <davem@...emloft.net>, pablo@...filter.org,
	kaber@...sh.net, netfilter-devel@...r.kernel.org,
	netfilter@...r.kernel.org, coreteam@...filter.org,
	linux-kernel@...r.kernel.org, ldv-project@...ras.ru
Subject: [PATCH v2] bridge: rcu_deref outside read-lock section

As it noted in the comment before the br_handle_frame_finish
function, this function should be called under rcu_read_lock.

The problem callgraph:
br_dev_xmit -> br_nf_pre_routing_finish_bridge_slow ->
-> br_handle_frame_finish -> br_port_get_rcu -> rcu_dereference

And in this case there is no read-lock section.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Denis Efremov <yefremov.denis@...il.com>
---
 net/bridge/br_device.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/net/bridge/br_device.c b/net/bridge/br_device.c
index 3334845..f9ae07f 100644
--- a/net/bridge/br_device.c
+++ b/net/bridge/br_device.c
@@ -33,7 +33,9 @@ netdev_tx_t br_dev_xmit(struct sk_buff *skb, struct net_device *dev)
 
 #ifdef CONFIG_BRIDGE_NETFILTER
 	if (skb->nf_bridge && (skb->nf_bridge->mask & BRNF_BRIDGED_DNAT)) {
+		rcu_read_lock();
 		br_nf_pre_routing_finish_bridge_slow(skb);
+		rcu_read_unlock();
 		return NETDEV_TX_OK;
 	}
 #endif
-- 
1.7.7

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