From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1756546Ab1KNWdK (ORCPT <rfc822;w@1wt.eu>);
	Mon, 14 Nov 2011 17:33:10 -0500
Received: from smtp-outbound-2.vmware.com ([65.115.85.73]:49940 "EHLO
	smtp-outbound-2.vmware.com" rhost-flags-OK-OK-OK-OK)
	by vger.kernel.org with ESMTP id S1751775Ab1KNWdI (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Mon, 14 Nov 2011 17:33:08 -0500
Date: Mon, 14 Nov 2011 14:33:08 -0800 (PST)
From: Andrei Warkentin <awarkentin@vmware.com>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: linux-kernel@vger.kernel.org
Message-ID: <379707293.52012.1321309988256.JavaMail.root@zimbra-prod-mbox-2.vmware.com>
In-Reply-To: <4EC19253.6080201@zytor.com>
Subject: Re: [PATCH] /dev/mem: Fix wrong error on accessing beyond valid
 memory addresses.
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit
X-Originating-IP: [10.113.60.13]
X-Mailer: Zimbra 7.1.3_GA_3374 (ZimbraWebClient - FF3.0 (Linux)/7.1.3_GA_3346)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Hi,

----- Original Message -----
> From: "H. Peter Anvin" <hpa@zytor.com>
> To: "Andrei Warkentin" <awarkentin@vmware.com>
> Cc: linux-kernel@vger.kernel.org
> Sent: Monday, November 14, 2011 5:12:35 PM
> Subject: Re: [PATCH] /dev/mem: Fix wrong error on accessing beyond valid memory addresses.
> 
> On 11/14/2011 02:11 PM, Andrei Warkentin wrote:
> >>
> >> EOF seems wrong to me (not as bad as EFAULT, but still wrong).
> >
> > Although that was what we had discussed, I do not return -EOF in
> > the patch. As you
> > mention - that would be wrong. I played around with other devices
> > (block, actually),
> > and if you attempt to read(2) beyond the end, read(2) simply
> > returns 0, as in
> > zero bytes read out. Of course, lseek(2) beyond the end should
> > return -EINVAL, as
> > well, so that is what that patch I CCd you on accomplishes.
> >
> 
> 0 is EOF.
> 

Ah, whoops, silly me.

> This is not a block device -- comparing to block devices is
> pointless.
> There is no "end" to /dev/mem, so this is a totally meaningless
> comparison.

Oh ok, I looked at other arches, like IA64, and now see why
using valid_phys_addr_range as an "end" test is meaningless.

Thanks,
A