Linux Ethernet Bridging - Nov 2007 - [PATCH][BRIDGE] Properly dereference the br_should_route_hook

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.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>

---

diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
index 3cedd4e..b42b192 100644
--- a/net/bridge/br_input.c
+++ b/net/bridge/br_input.c
@@ -122,6 +122,7 @@ static inline int is_link_local(const unsigned char *dest)
 struct sk_buff *br_handle_frame(struct net_bridge_port *p, struct sk_buff *skb)
 {
 	const unsigned char *dest = eth_hdr(skb)->h_dest;
+	typeof(br_should_route_hook) rhook;
 
 	if (!is_valid_ether_addr(eth_hdr(skb)->h_source))
 		goto drop;
@@ -147,9 +148,9 @@ struct sk_buff *br_handle_frame(struct net_bridge_port *p,
struct sk_buff *skb)
 
 	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;
 		}
diff --git a/net/bridge/netfilter/ebtable_broute.c
b/net/bridge/netfilter/ebtable_broute.c
index e44519e..be6f186 100644
--- a/net/bridge/netfilter/ebtable_broute.c
+++ b/net/bridge/netfilter/ebtable_broute.c
@@ -70,13 +70,13 @@ static int __init ebtable_broute_init(void)
 	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);
 }

On Tue, 27 Nov 2007 19:12:11 +0300
Pavel Emelyanov <xemul@openvz.org> wrote:
> 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.
> 
> Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
> 
> ---
> 
> diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
> index 3cedd4e..b42b192 100644
> --- a/net/bridge/br_input.c
> +++ b/net/bridge/br_input.c
> @@ -122,6 +122,7 @@ static inline int is_link_local(const unsigned char
*dest)
>  struct sk_buff *br_handle_frame(struct net_bridge_port *p, struct sk_buff
*skb)
>  {
>  	const unsigned char *dest = eth_hdr(skb)->h_dest;
> +	typeof(br_should_route_hook) rhook;
Okay, but I don't like the typeof() magic. Resubmit with proper declartion.

-- 
Stephen Hemminger <shemminger@linux-foundation.org>