batman-adv: Check ptr for NULL before reducing its refcnt

The commit b37a46683739 ("netdevice: add the case if dev is NULL") changed
the way how the NULL check for net_devices have to be handled when trying
to reduce its reference counter. Before this commit, it was the
responsibility of the caller to check whether the object is NULL or not.
But it was changed to behave more like kfree. Now the callee has to handle
the NULL-case.

The batman-adv code was scanned via cocinelle for similar places. These
were changed to use the paradigm

  @@
  identifier E, T, R, C;
  identifier put;
  @@
   void put(struct T *E)
   {
  +	if (!E)
  +		return;
  	kref_put(&E->C, R);
   }

Functions which were used in other sources files were moved to the header
to allow the compiler to inline the NULL check and the kref_put call.

Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>

1 files changed, 15 insertions, 1 deletions

diff --git a/net/batman-adv/gateway_client.h b/net/batman-adv/gateway_client.h
index 2ae5846ef958..95c2ccdaa554 100644
--- a/net/batman-adv/gateway_client.h
+++ b/net/batman-adv/gateway_client.h
@@ -9,6 +9,7 @@
 
 #include "main.h"
 
+#include <linux/kref.h>
 #include <linux/netlink.h>
 #include <linux/skbuff.h>
 #include <linux/types.h>
@@ -27,7 +28,7 @@ void batadv_gw_node_update(struct batadv_priv *bat_priv,
 void batadv_gw_node_delete(struct batadv_priv *bat_priv,
 			   struct batadv_orig_node *orig_node);
 void batadv_gw_node_free(struct batadv_priv *bat_priv);
-void batadv_gw_node_put(struct batadv_gw_node *gw_node);
+void batadv_gw_node_release(struct kref *ref);
 struct batadv_gw_node *
 batadv_gw_get_selected_gw_node(struct batadv_priv *bat_priv);
 int batadv_gw_dump(struct sk_buff *msg, struct netlink_callback *cb);
@@ -38,4 +39,17 @@ batadv_gw_dhcp_recipient_get(struct sk_buff *skb, unsigned int *header_len,
 struct batadv_gw_node *batadv_gw_node_get(struct batadv_priv *bat_priv,
 					  struct batadv_orig_node *orig_node);
 
+/**
+ * batadv_gw_node_put() - decrement the gw_node refcounter and possibly release
+ *  it
+ * @gw_node: gateway node to free
+ */
+static inline void batadv_gw_node_put(struct batadv_gw_node *gw_node)
+{
+	if (!gw_node)
+		return;
+
+	kref_put(&gw_node->refcount, batadv_gw_node_release);
+}
+
 #endif /* _NET_BATMAN_ADV_GATEWAY_CLIENT_H_ */