[patch 36/36] BRIDGE: Properly dereference the br_should_route_hook

[Greg KH <gregkh@suse.de>]

2.6.22-stable review patch.  If anyone has any objections, please let us
know.

------------------
From: Pavel Emelyanov <xemul@openvz.org>

[BRIDGE]: Properly dereference the br_should_route_hook

[ Upstream commit: 82de382ce8e1c7645984616728dc7aaa057821e4 ]

This hook is protected with the RCU, so simple

if (br_should_route_hook)
	br_should_route_hook(...)

is not enough on some architectures.

Use the rcu_dereference/rcu_assign_pointer in this case.

Fixed Stephen's comment concerning using the typeof().

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
 net/bridge/br_input.c                 |    7 ++++---
 net/bridge/netfilter/ebtable_broute.c |    4 ++--
 2 files changed, 6 insertions(+), 5 deletions(-)

--- a/net/bridge/br_input.c
+++ b/net/bridge/br_input.c
@@ -127,6 +127,7 @@ static inline int is_link_local(const un
 struct sk_buff *br_handle_frame(struct net_bridge_port *p, struct sk_buff *skb)
 {
 	const unsigned char *dest = eth_hdr(skb)->h_dest;
+	int (*rhook)(struct sk_buff **pskb);
 
 	if (!is_valid_ether_addr(eth_hdr(skb)->h_source))
 		goto drop;
@@ -148,9 +149,9 @@ struct sk_buff *br_handle_frame(struct n
 
 	switch (p->state) {
 	case BR_STATE_FORWARDING:
-
-		if (br_should_route_hook) {
-			if (br_should_route_hook(&skb))
+		rhook = rcu_dereference(br_should_route_hook);
+		if (rhook != NULL) {
+			if (rhook(&skb))
 				return skb;
 			dest = eth_hdr(skb)->h_dest;
 		}
--- a/net/bridge/netfilter/ebtable_broute.c
+++ b/net/bridge/netfilter/ebtable_broute.c
@@ -70,13 +70,13 @@ static int __init ebtable_broute_init(vo
 	if (ret < 0)
 		return ret;
 	/* see br_input.c */
-	br_should_route_hook = ebt_broute;
+	rcu_assign_pointer(br_should_route_hook, ebt_broute);
 	return ret;
 }
 
 static void __exit ebtable_broute_fini(void)
 {
-	br_should_route_hook = NULL;
+	rcu_assign_pointer(br_should_route_hook, NULL);
 	synchronize_net();
 	ebt_unregister_table(&broute_table);
 }

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