From owner-freebsd-bugs@FreeBSD.ORG  Sun May 18 22:10:01 2014
Return-Path: <owner-freebsd-bugs@FreeBSD.ORG>
Delivered-To: freebsd-bugs@smarthost.ysv.freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115])
 (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits))
 (No client certificate requested)
 by hub.freebsd.org (Postfix) with ESMTPS id 36C68BBC
 for <freebsd-bugs@smarthost.ysv.freebsd.org>;
 Sun, 18 May 2014 22:10:01 +0000 (UTC)
Received: from freefall.freebsd.org (freefall.freebsd.org
 [IPv6:2001:1900:2254:206c::16:87])
 (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
 (Client did not present a certificate)
 by mx1.freebsd.org (Postfix) with ESMTPS id 22483201F
 for <freebsd-bugs@smarthost.ysv.freebsd.org>;
 Sun, 18 May 2014 22:10:01 +0000 (UTC)
Received: from freefall.freebsd.org (localhost [127.0.0.1])
 by freefall.freebsd.org (8.14.8/8.14.8) with ESMTP id s4IMA0ui086059
 for <freebsd-bugs@freefall.freebsd.org>; Sun, 18 May 2014 22:10:00 GMT
 (envelope-from gnats@freefall.freebsd.org)
Received: (from gnats@localhost)
 by freefall.freebsd.org (8.14.8/8.14.8/Submit) id s4IMA0tL086058;
 Sun, 18 May 2014 22:10:00 GMT (envelope-from gnats)
Date: Sun, 18 May 2014 22:10:00 GMT
Message-Id: <201405182210.s4IMA0tL086058@freefall.freebsd.org>
To: freebsd-bugs@FreeBSD.org
Cc: 
From: Jilles Tjoelker <jilles@stack.nl>
Subject: Re: kern/189845: [kvm] UnNecessary Copy of Error Buffer in _kvm_open
Reply-To: Jilles Tjoelker <jilles@stack.nl>
X-BeenThere: freebsd-bugs@freebsd.org
X-Mailman-Version: 2.1.18
Precedence: list
List-Id: Bug reports <freebsd-bugs.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/options/freebsd-bugs>,
 <mailto:freebsd-bugs-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-bugs/>
List-Post: <mailto:freebsd-bugs@freebsd.org>
List-Help: <mailto:freebsd-bugs-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-bugs>,
 <mailto:freebsd-bugs-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Sun, 18 May 2014 22:10:01 -0000

The following reply was made to PR kern/189845; it has been noted by GNATS.

From: Jilles Tjoelker <jilles@stack.nl>
To: bug-followup@FreeBSD.org, myron.walker@emc.com
Cc:  
Subject: Re: kern/189845: [kvm] UnNecessary Copy of Error Buffer in _kvm_open
Date: Mon, 19 May 2014 00:05:07 +0200

 In FreeBSD PR kern/189845, you wrote:
 > _kvm_open in libkvm always returns 0 on a failure. So writing a
 > message to kd is pointless because it is immediately passed to
 > kvm_close() and the memory is freed. Se the code snippet below from
 > _kvm_open.
 
 >	/*
 >	 * Copy out the error if doing sane error semantics.
 >	 */
 >	if (errout != 0)
 >		strlcpy(errout, kd->errbuf, _POSIX2_LINE_MAX);
 >	(void)kvm_close(kd);
 >	return (0);
 
 The error message is written to errout (if _kvm_open() was called via
 kvm_openfiles()), which stays around.
 
 It may be a bit strange to write an error message to kd->errbuf first
 and then copy it to the user's buffer, but it works fine and may
 slightly reduce code duplication from the two types of error handling
 available to the API client.
 
 -- 
 Jilles Tjoelker