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

[Andrew Davis]

On 10/18/22 12:37 PM, Sean Anderson wrote:
> Hi Andrew,
>
> On 10/18/22 1:22 PM, Andrew Lunn wrote:
> > 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
>
> The fixed commit was added in v6.1-rc1 and switched from physical to
> virtual. So this is effectively a partial revert to the previous
> behavior (but keeping the other changes). See [1] for discussion.
>
> --Sean
>
> [1] https://lore.kernel.org/netdev/20220902215737.981341-1-sean.anderson@xxxxxxxx/T/#md5c6b66bc229c09062d205352a7d127c02b8d262

I see it asked in that thread, but not answered. Why are you exposing
"physical" addresses to userspace? There should be no reason for that.

Andrew