linux-kernel - Re: [PATCH net] net: fman: Use physical address for userspace interfaces

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Message-ID: <Y07guYuGySM6F/us@lunn.ch>
Date:   Tue, 18 Oct 2022 19:22:01 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Sean Anderson <sean.anderson@...o.com>
Cc:     "David S . Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Madalin Bucur <madalin.bucur@....com>,
        Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Camelia Groza <camelia.groza@....com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: Re: [PATCH net] net: fman: Use physical address for userspace
 interfaces

On Mon, Oct 17, 2022 at 12:28:06PM -0400, Sean Anderson wrote:
> For whatever reason, the address of the MAC is exposed to userspace in
> several places. We need to use the physical address for this purpose to
> avoid leaking information about the kernel's memory layout, and to keep
> backwards compatibility.

How does this keep backwards compatibility? Whatever is in user space
using this virtual address expects a virtual address. If it now gets a
physical address it will probably do the wrong thing. Unless there is
a one to one mapping, and you are exposing virtual addresses anyway.

If you are going to break backwards compatibility Maybe it would be
better to return 0xdeadbeef? Or 0?

       Andrew