Index: sys/kern/vfs_lookup.c
===================================================================
--- sys/kern/vfs_lookup.c	(revisione 238701)
+++ sys/kern/vfs_lookup.c	(copia locale)
@@ -202,6 +202,7 @@ namei(struct nameidata *ndp)
 #ifdef DIAGNOSTIC
 		cnp->cn_pnbuf = NULL;
 		cnp->cn_nameptr = NULL;
+		MPASS(error != 0 || cnp->cn_namelen == 0);
 #endif
 		ndp->ni_vp = NULL;
 		return (error);
@@ -260,6 +261,7 @@ namei(struct nameidata *ndp)
 #ifdef DIAGNOSTIC
 			cnp->cn_pnbuf = NULL;
 			cnp->cn_nameptr = NULL;
+			MPASS(error != 0 || cnp->cn_namelen == 0);
 #endif
 			return (error);
 		}
@@ -310,6 +312,7 @@ namei(struct nameidata *ndp)
 #ifdef DIAGNOSTIC
 			cnp->cn_pnbuf = NULL;
 			cnp->cn_nameptr = NULL;
+			MPASS(error != 0 || cnp->cn_namelen == 0);
 #endif
 			SDT_PROBE(vfs, namei, lookup, return, error, NULL, 0,
 			    0, 0);
@@ -326,6 +329,7 @@ namei(struct nameidata *ndp)
 #ifdef DIAGNOSTIC
 				cnp->cn_pnbuf = NULL;
 				cnp->cn_nameptr = NULL;
+				MPASS(error != 0 || cnp->cn_namelen == 0);
 #endif
 			} else
 				cnp->cn_flags |= HASBUF;
@@ -396,6 +400,7 @@ namei(struct nameidata *ndp)
 #ifdef DIAGNOSTIC
 	cnp->cn_pnbuf = NULL;
 	cnp->cn_nameptr = NULL;
+	MPASS(error != 0 || cnp->cn_namelen == 0);
 #endif
 	vput(ndp->ni_vp);
 	ndp->ni_vp = NULL;