--- kernel/bsd/kern/uipc_usrreq.c	2018/04/24 18:26:01	1.1.1.1
+++ kernel/bsd/kern/uipc_usrreq.c	2018/04/24 18:27:38	1.1.1.2
@@ -678,7 +678,11 @@ unp_internalize(control, p)
 	for (i = 0; i < oldfds; i++) {
 		(void) fdgetf(p, *(int *)rp, &fp);
 		*rp++ = fp;
-		fp->f_count++;
+		if (++fp->f_count <= 0)
+			panic("unp_internalize f_count");
+		/* The following line needs no overflow check
+		 * as if f_msgcount overflows we already
+		 * panic with the f_count overflow above */
 		fp->f_msgcount++;
 		unp_rights++;
 	}
@@ -791,7 +795,8 @@ unp_gc()
 		if (fp->f_count == fp->f_msgcount && !(fp->f_flag & FMARK)) {
 			*fpp++ = fp;
 			nunref++;
-			fp->f_count++;
+			if (++fp->f_count <= 0)
+				panic("unp_gc f_count");
 		}
 	}
 	for (i = nunref, fpp = extra_ref; --i >= 0; ++fpp)