1 files changed, 17 insertions, 4 deletions

diff --git a/net/llc/llc_input.c b/net/llc/llc_input.c
index e32cab44ea9..dd3e83328ad 100644
--- a/net/llc/llc_input.c
+++ b/net/llc/llc_input.c
@@ -42,6 +42,7 @@ static void (*llc_type_handlers[2])(struct llc_sap *sap,
 void llc_add_pack(int type, void (*handler)(struct llc_sap *sap,
 					    struct sk_buff *skb))
 {
+	smp_wmb(); /* ensure initialisation is complete before it's called */
 	if (type == LLC_DEST_SAP || type == LLC_DEST_CONN)
 		llc_type_handlers[type - 1] = handler;
 }
@@ -50,11 +51,19 @@ void llc_remove_pack(int type)
 {
 	if (type == LLC_DEST_SAP || type == LLC_DEST_CONN)
 		llc_type_handlers[type - 1] = NULL;
+	synchronize_net();
 }
 
 void llc_set_station_handler(void (*handler)(struct sk_buff *skb))
 {
+	/* Ensure initialisation is complete before it's called */
+	if (handler)
+		smp_wmb();
+
 	llc_station_handler = handler;
+
+	if (!handler)
+		synchronize_net();
 }
 
 /**
@@ -150,6 +159,8 @@ int llc_rcv(struct sk_buff *skb, struct net_device *dev,
 	int dest;
 	int (*rcv)(struct sk_buff *, struct net_device *,
 		   struct packet_type *, struct net_device *);
+	void (*sta_handler)(struct sk_buff *skb);
+	void (*sap_handler)(struct llc_sap *sap, struct sk_buff *skb);
 
 	if (!net_eq(dev_net(dev), &init_net))
 		goto drop;
@@ -182,7 +193,8 @@ int llc_rcv(struct sk_buff *skb, struct net_device *dev,
 	 */
 	rcv = rcu_dereference(sap->rcv_func);
 	dest = llc_pdu_type(skb);
-	if (unlikely(!dest || !llc_type_handlers[dest - 1])) {
+	sap_handler = dest ? ACCESS_ONCE(llc_type_handlers[dest - 1]) : NULL;
+	if (unlikely(!sap_handler)) {
 		if (rcv)
 			rcv(skb, dev, pt, orig_dev);
 		else
@@ -193,7 +205,7 @@ int llc_rcv(struct sk_buff *skb, struct net_device *dev,
 			if (cskb)
 				rcv(cskb, dev, pt, orig_dev);
 		}
-		llc_type_handlers[dest - 1](sap, skb);
+		sap_handler(sap, skb);
 	}
 	llc_sap_put(sap);
 out:
@@ -202,9 +214,10 @@ drop:
 	kfree_skb(skb);
 	goto out;
 handle_station:
-	if (!llc_station_handler)
+	sta_handler = ACCESS_ONCE(llc_station_handler);
+	if (!sta_handler)
 		goto drop;
-	llc_station_handler(skb);
+	sta_handler(skb);
 	goto out;
 }