Index: head/sys/kern/kern_descrip.c
===================================================================
--- head/sys/kern/kern_descrip.c
+++ head/sys/kern/kern_descrip.c
@@ -788,6 +788,12 @@
 			break;
 		}
 		vp = fp->f_vnode;
+		if (vp->v_type != VREG) {
+			fdrop(fp, td);
+			error = ENOTTY;
+			break;
+		}
+
 		/*
 		 * Exclusive lock synchronizes against f_seqcount reads and
 		 * writes in sequential_heuristic().