--- kernel/bsd/sys/ucred.h	2018/04/24 18:26:01	1.1.1.1
+++ kernel/bsd/sys/ucred.h	2018/04/24 18:28:25	1.1.1.2
@@ -67,7 +67,7 @@
  * Credentials.
  */
 struct ucred {
-	u_short	cr_ref;			/* reference count */
+	u_long	cr_ref;			/* reference count */
 	uid_t	cr_uid;			/* effective user id */
 	short	cr_ngroups;		/* number of groups */
 	gid_t	cr_groups[NGROUPS];	/* groups */
@@ -77,7 +77,11 @@ struct ucred {
 #define FSCRED ((struct ucred *)-1)	/* filesystem credential */
 
 #ifdef _KERNEL
-#define	crhold(cr)	(cr)->cr_ref++
+#define	crhold(cr)			\
+{					\
+	if (++(cr)->cr_ref == 0)	\
+		panic("crhold");	\
+}
 
 struct ucred	*crcopy __P((struct ucred *cr));
 struct ucred	*crdup __P((struct ucred *cr));