batman-adv: Make orig_node->router an rcu protected pointer

The rcu protected macros rcu_dereference() and rcu_assign_pointer()
for the orig_node->router need to be used, as well as spin/rcu locking.
Otherwise we might end up using a router pointer pointing to already
freed memory.

Therefore this commit introduces the safe getter method
orig_node_get_router().

Signed-off-by: Linus Lüssing <linus.luessing@web.de>
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
diff --git a/net/batman-adv/types.h b/net/batman-adv/types.h
index 83445cf..1854cbb 100644
--- a/net/batman-adv/types.h
+++ b/net/batman-adv/types.h
@@ -67,7 +67,7 @@
 struct orig_node {
 	uint8_t orig[ETH_ALEN];
 	uint8_t primary_addr[ETH_ALEN];
-	struct neigh_node *router;
+	struct neigh_node __rcu *router; /* rcu protected pointer */
 	unsigned long *bcast_own;
 	uint8_t *bcast_own_sum;
 	unsigned long last_valid;
@@ -83,7 +83,7 @@
 	uint32_t last_bcast_seqno;
 	struct hlist_head neigh_list;
 	struct list_head frag_list;
-	spinlock_t neigh_list_lock; /* protects neighbor list */
+	spinlock_t neigh_list_lock; /* protects neigh_list and router */
 	atomic_t refcount;
 	struct rcu_head rcu;
 	struct hlist_node hash_entry;