Pull up following revision(s) (requested by kre in ticket #987): bin/sh/trap.c: revision 1.44 PR bin/36532 (perhaps) This is more or less the same patch as provided in the PR (just 11 years later, so changed a bit) by woods@... Since there is no known way to actually cause the reported crash, we may never know if this change actually fixes anything. But even if it doesn't it certainly cannot hurt. There is a potential race which could possibly explain the issue (see commentary in the PR) which is not easy to avoid - if that is the actual cause, this should provide a defence, if not really a fix.

(martin)

@@ -1,4 +1,4 @@
-/*	$NetBSD: trap.c,v 1.40.2.1 2017/07/23 14:58:14 snj Exp $	*/
+/*	$NetBSD: trap.c,v 1.40.2.2 2018/08/25 14:41:21 martin Exp $	*/
 
 /*-
  * Copyright (c) 1991, 1993
@@ -37,7 +37,7 @@
 #if 0
 static char sccsid[] = "@(#)trap.c	8.5 (Berkeley) 6/5/95";
 #else
-__RCSID("$NetBSD: trap.c,v 1.40.2.1 2017/07/23 14:58:14 snj Exp $");
+__RCSID("$NetBSD: trap.c,v 1.40.2.2 2018/08/25 14:41:21 martin Exp $");
 #endif
 #endif /* not lint */
 
@@ -523,9 +523,11 @@
 		savestatus=exitstatus;
 		CTRACE(DBG_TRAP|DBG_SIG, ("dotrap %d: \"%s\"\n", i,
 		    trap[i] ? trap[i] : "-NULL-"));
-		tr = savestr(trap[i]);		/* trap code may free trap[i] */
-		evalstring(tr, 0);
-		ckfree(tr);
+		if ((tr = trap[i]) != NULL) {
+			tr = savestr(tr);	/* trap code may free trap[i] */
+			evalstring(tr, 0);
+			ckfree(tr);
+		}
 		exitstatus=savestatus;
 	}
 }