tipc: fix broadcast wakeup contention after congestion

commit 908344cdda ("tipc: fix bug in multicast congestion handling")
introduced a race in the broadcast link wakeup functionality.

This patch eliminates this broadcast link wakeup race caused by
operation on the wakeup list without proper locking. If this race
hit and corrupted the list all subsequent wakeup messages would be
lost, resulting in a considerable memory leak.

Signed-off-by: Richard Alpe <richard.alpe@ericsson.com>
Signed-off-by: Erik Hugne <erik.hugne@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tipc/link.c

@@ -293,7 +293,7 @@ struct tipc_link *tipc_link_create(struct tipc_node *n_ptr,
 	l_ptr->next_out_no = 1;
 	__skb_queue_head_init(&l_ptr->outqueue);
 	__skb_queue_head_init(&l_ptr->deferred_queue);
-	__skb_queue_head_init(&l_ptr->waiting_sks);
+	skb_queue_head_init(&l_ptr->waiting_sks);
 
 	link_reset_statistics(l_ptr);
 
@@ -358,7 +358,7 @@ static bool link_schedule_user(struct tipc_link *link, u32 oport,
 		return false;
 	TIPC_SKB_CB(buf)->chain_sz = chain_sz;
 	TIPC_SKB_CB(buf)->chain_imp = imp;
-	__skb_queue_tail(&link->waiting_sks, buf);
+	skb_queue_tail(&link->waiting_sks, buf);
 	link->stats.link_congs++;
 	return true;
 }
@@ -378,8 +378,8 @@ static void link_prepare_wakeup(struct tipc_link *link)
 		if (pend_qsz >= link->queue_limit[TIPC_SKB_CB(skb)->chain_imp])
 			break;
 		pend_qsz += TIPC_SKB_CB(skb)->chain_sz;
-		__skb_unlink(skb, &link->waiting_sks);
-		__skb_queue_tail(&link->owner->waiting_sks, skb);
+		skb_unlink(skb, &link->waiting_sks);
+		skb_queue_tail(&link->owner->waiting_sks, skb);
 	}
 }
 

net/tipc/node.c

@@ -115,7 +115,7 @@ struct tipc_node *tipc_node_create(u32 addr)
 	INIT_LIST_HEAD(&n_ptr->list);
 	INIT_LIST_HEAD(&n_ptr->publ_list);
 	INIT_LIST_HEAD(&n_ptr->conn_sks);
-	__skb_queue_head_init(&n_ptr->waiting_sks);
+	skb_queue_head_init(&n_ptr->waiting_sks);
 	__skb_queue_head_init(&n_ptr->bclink.deferred_queue);
 
 	hlist_add_head_rcu(&n_ptr->hash, &node_htable[tipc_hashfn(addr)]);