net: convert inet_peer.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.
This conversion requires overall +1 on the whole
refcounting scheme.

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/include/net/inetpeer.h b/include/net/inetpeer.h
index 235c781..f2a215f 100644
--- a/include/net/inetpeer.h
+++ b/include/net/inetpeer.h
@@ -46,7 +46,7 @@
 		struct rcu_head     gc_rcu;
 	};
 	/*
-	 * Once inet_peer is queued for deletion (refcnt == -1), following field
+	 * Once inet_peer is queued for deletion (refcnt == 0), following field
 	 * is not available: rid
 	 * We can share memory with rcu_head to help keep inet_peer small.
 	 */
@@ -60,7 +60,7 @@
 
 	/* following fields might be frequently dirtied */
 	__u32			dtime;	/* the time of last use of not referenced entries */
-	atomic_t		refcnt;
+	refcount_t		refcnt;
 };
 
 struct inet_peer_base {