drivers, firewire: convert fw_node.ref_count from atomic_t to refcount_t

refcount_t type and corresponding API should be
used instead of atomic_t when the variable is used as
a reference counter. This allows to avoid accidental
refcounter overflows that might lead to use-after-free
situations.

Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David Windsor <dwindsor@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/firewire/core-topology.c

@@ -124,7 +124,7 @@ static struct fw_node *fw_node_create(u32 sid, int port_count, int color)
 	node->initiated_reset = SELF_ID_PHY_INITIATOR(sid);
 	node->port_count = port_count;
 
-	atomic_set(&node->ref_count, 1);
+	refcount_set(&node->ref_count, 1);
 	INIT_LIST_HEAD(&node->link);
 
 	return node;

drivers/firewire/core.h

@@ -12,7 +12,7 @@
 #include <linux/slab.h>
 #include <linux/types.h>
 
-#include <linux/atomic.h>
+#include <linux/refcount.h>
 
 struct device;
 struct fw_card;
@@ -184,7 +184,7 @@ struct fw_node {
 			 * local node to this node. */
 	u8 max_depth:4;	/* Maximum depth to any leaf node */
 	u8 max_hops:4;	/* Max hops in this sub tree */
-	atomic_t ref_count;
+	refcount_t ref_count;
 
 	/* For serializing node topology into a list. */
 	struct list_head link;
@@ -197,14 +197,14 @@ struct fw_node {
 
 static inline struct fw_node *fw_node_get(struct fw_node *node)
 {
-	atomic_inc(&node->ref_count);
+	refcount_inc(&node->ref_count);
 
 	return node;
 }
 
 static inline void fw_node_put(struct fw_node *node)
 {
-	if (atomic_dec_and_test(&node->ref_count))
+	if (refcount_dec_and_test(&node->ref_count))
 		kfree(node);
 }