From: Andi Kleen <ak@suse.de>
To: Alexey Toptygin <alexeyt@freeshell.org>
Cc: linux-kernel@vger.kernel.org, tony.luck@intel.com
Subject: Re: [PATCH] sendfile compat functions on x86_64 and ia64
Date: Fri, 5 May 2006 23:28:21 +0200 [thread overview]
Message-ID: <200605052328.21370.ak@suse.de> (raw)
In-Reply-To: <Pine.NEB.4.62.0605052040250.27826@ukato.freeshell.org>
On Friday 05 May 2006 22:44, Alexey Toptygin wrote:
> On Fri, 5 May 2006, Andi Kleen wrote:
>
> > With your change there wouldn't be any sign extension and rw_verify_area
> > couldn't reject negative values them anymore.
> >
> > I think it would be a wrong change because it would differ from a native
> > 32bit kernel.
>
> No...
>
> On a 32 bit kernel (and on a 64 bit kernel using the native interface),
> count is passed to sendfile as unsigned. rw_verify_area explicitly casts
> to signed
To a 64bit signed.
> before checking for negativeness. The only place anywhere in the
> kernel that count is signed (other than where rw_verify area explicitly
> casts it for one test) is in the declaration of sys32_sendfile in the
> x86_64 compat code. I'm pretty sure it's supposed to be unsigned there
> too, and the current code is a typo.
It's a 32bit signed.
Somehow the 32bit signed has to become a 64bit signed to be caught
by rw_verify_area(). The only place that can do that is the compat
layer.
-Andi
next prev parent reply other threads:[~2006-05-05 21:28 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-05-05 0:45 [PATCH] sendfile compat functions on x86_64 and ia64 Alexey Toptygin
2006-05-05 20:38 ` Andi Kleen
2006-05-05 20:44 ` Alexey Toptygin
2006-05-05 21:28 ` Andi Kleen [this message]
2006-05-05 22:19 ` Alexey Toptygin
2006-05-06 8:46 ` Andi Kleen
2006-05-06 22:43 ` Alexey Toptygin
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