linux-kernel - Re: [PATCH] /dev/mem: Fix wrong error on accessing beyond valid memory addresses.

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Message-ID: <379707293.52012.1321309988256.JavaMail.root@zimbra-prod-mbox-2.vmware.com>
Date:	Mon, 14 Nov 2011 14:33:08 -0800 (PST)
From:	Andrei Warkentin <awarkentin@...are.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] /dev/mem: Fix wrong error on accessing beyond valid
 memory addresses.

Hi,

----- Original Message -----
> From: "H. Peter Anvin" <hpa@...or.com>
> To: "Andrei Warkentin" <awarkentin@...are.com>
> Cc: linux-kernel@...r.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
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