net, rds: convert rds_incoming.i_refcount 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: David S. Miller <davem@davemloft.net>
diff --git a/net/rds/rds.h b/net/rds/rds.h
index 4a25db7..35ceaa2 100644
--- a/net/rds/rds.h
+++ b/net/rds/rds.h
@@ -8,6 +8,7 @@
 #include <linux/mutex.h>
 #include <linux/rds.h>
 #include <linux/rhashtable.h>
+#include <linux/refcount.h>
 
 #include "info.h"
 
@@ -261,7 +262,7 @@ struct rds_ext_header_rdma_dest {
 #define	RDS_MSG_RX_CMSG		3
 
 struct rds_incoming {
-	atomic_t		i_refcount;
+	refcount_t		i_refcount;
 	struct list_head	i_item;
 	struct rds_connection	*i_conn;
 	struct rds_conn_path	*i_conn_path;