linux-kernel - Re: [PATCH v3 0/7] dma-buf: heaps: Add secure heap

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Message-ID: <ac8107b8608de25a8d680863b28b075c4cd17140.camel@mediatek.com>
Date: Tue, 9 Jan 2024 03:07:21 +0000
From: Yong Wu (吴勇) <Yong.Wu@...iatek.com>
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Subject: Re: [PATCH v3 0/7] dma-buf: heaps: Add secure heap

On Fri, 2024-01-05 at 10:35 +0100, Christian König wrote:
>  	 
> External email : Please do not click links or open attachments until
> you have verified the sender or the content.
>  Am 04.01.24 um 20:50 schrieb Jeffrey Kardatzke:
> > Any feedback from maintainers on what their preference is?  I'm
> fine
> > with 'restricted' as well, but the main reason we chose secure was
> > because of its use in ARM nomenclature and this is more for ARM
> usage
> > than x86.
> 
> Well AMD calls this "trusted", but I think that's just slightly
> better 
> than "secure".
> 
> +1 for using "restricted" cause that seems to match the technical 
> consequences.

Thanks you all for the discussion and the conclusion. I will send v4 in
this week with "restricted".

> 
> Regards,
> Christian.
> 
> >
> > The main difference with similar buffers on AMD/Intel is that with
> > AMD/Intel the buffers are mappable and readable by the CPU in the
> > kernel. The problem is their contents are encrypted so you get junk
> > back if you do that. On ARM, the buffers are completely
> inaccessible
> > by the kernel and the memory controller prevents access to them
> > completely from the kernel.
> >
> > There are also other use cases for this where the hypervisor is
> what
> > is controlling access (second stage in the MMU is providing
> > isolation)....and in that case I do agree that 'secure' would not
> be
> > the right terminology for those types of buffers.   So I do agree
> > something other than 'secure' is probably a better option overall.
> >
> >
> > On Fri, Dec 22, 2023 at 1:40 AM Simon Ser <contact@...rsion.fr>
> wrote:
> >> On Wednesday, December 13th, 2023 at 15:16, Pekka Paalanen <
> ppaalanen@...il.com> wrote:
> >>
> >>>>> It is protected/shielded/fortified from all the kernel and
> userspace,
> >>>>> but a more familiar word to describe that is inaccessible.
> >>>>> "Inaccessible buffer" per se OTOH sounds like a useless
> concept.
> >>>>>
> >>>>> It is not secure, because it does not involve security in any
> way. In
> >>>>> fact, given it's so fragile, I'd classify it as mildly opposite
> of
> >>>>> secure, as e.g. clients of a Wayland compositor can potentially
> DoS the
> >>>>> compositor with it by simply sending such a dmabuf. Or DoS the
> whole
> >>>>> system.
> >>>> I hear what you are saying and DoS is a known problem and attack
> vector,
> >>>> but regardless, we have use cases where we don't want to expose
> >>>> information in the clear and where we also would like to have
> some
> >>>> guarantees about correctness. That is where various secure
> elements and
> >>>> more generally security is needed.
> >>>>
> >>>> So, it sounds like we have two things here, the first is the
> naming and
> >>>> the meaning behind it. I'm pretty sure the people following and
> >>>> contributing to this thread can agree on a name that makes
> sense. Would
> >>>> you personally be OK with "restricted" as the name? It sounds
> like that.
> >>> I would. I'm also just a by-stander, not a maintainer of kernel
> >>> anything. I have no power to accept nor reject anything here.
> >> I'd also personally be OK with "restricted", I think it's a lot
> better
> >> than "secure".
> >>
> >> In general I agree with everything Pekka said.
>