net, bridge: convert net_bridge_vlan.refcnt 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/bridge/br_private.h b/net/bridge/br_private.h
index c18682f..fd9ee73 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -21,6 +21,7 @@
 #include <net/ip6_fib.h>
 #include <linux/if_vlan.h>
 #include <linux/rhashtable.h>
+#include <linux/refcount.h>
 
 #define BR_HASH_BITS 8
 #define BR_HASH_SIZE (1 << BR_HASH_BITS)
@@ -127,7 +128,7 @@ struct net_bridge_vlan {
 		struct net_bridge_port	*port;
 	};
 	union {
-		atomic_t		refcnt;
+		refcount_t		refcnt;
 		struct net_bridge_vlan	*brvlan;
 	};