batman-adv: Make bat_priv->primary_if an rcu protected pointer

The rcu protected macros rcu_dereference() and rcu_assign_pointer()
for the bat_priv->primary_if need to be used, as well as spin/rcu locking.

Otherwise we might end up using a primary_if pointer pointing to already
freed memory.

Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
Signed-off-by: Sven Eckelmann <sven@narfation.org>

1 files changed, 18 insertions, 0 deletions

diff --git a/net/batman-adv/hard-interface.h b/net/batman-adv/hard-interface.h
index a9ddf36e51c8..64265991460b 100644
--- a/net/batman-adv/hard-interface.h
+++ b/net/batman-adv/hard-interface.h
@@ -45,4 +45,22 @@ static inline void hardif_free_ref(struct hard_iface *hard_iface)
                 call_rcu(&hard_iface->rcu, hardif_free_rcu);
 }
 
+static inline struct hard_iface *primary_if_get_selected(
+                                                struct bat_priv *bat_priv)
+{
+        struct hard_iface *hard_iface;
+
+        rcu_read_lock();
+        hard_iface = rcu_dereference(bat_priv->primary_if);
+        if (!hard_iface)
+                goto out;
+
+        if (!atomic_inc_not_zero(&hard_iface->refcount))
+                hard_iface = NULL;
+
+out:
+        rcu_read_unlock();
+        return hard_iface;
+}
+
 #endif /* _NET_BATMAN_ADV_HARD_INTERFACE_H_ */