linux-kernel - Re: [PATCH] dt-bindings: mailbox: arm,mhu: Make secure interrupt optional

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Date:   Mon, 1 Aug 2022 08:57:52 -0500
From:   Jassi Brar <jaswinder.singh@...aro.org>
To:     Sudeep Holla <sudeep.holla@....com>
Cc:     Jassi Brar <jassisinghbrar@...il.com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH] dt-bindings: mailbox: arm,mhu: Make secure interrupt optional

On Mon, 1 Aug 2022 at 05:23, Sudeep Holla <sudeep.holla@....com> wrote:
> On Fri, Jul 29, 2022 at 10:18:04AM -0500, Jassi Brar wrote:
>
> > > Anyways I can insert a module that requests this channel and bring down
> > > the system as accessing anything configure secure from non-secure side
> > > on Juno results in system hang/error.
> > >
> > Why go to those lengths? These are already simpler options available  ;-)
> > 1)   while (1) ;      // preferably in some atomic context
> > 2)   *((int *) 0) = 0;   // you might want to iterate over offset for
> > guaranteed results
> > 3) Slightly more work, but you also have the opportunity to erase your
> > storage device
>
> I know these simple methods but can I hinder secure side services with
> these ?
>
Ideally, no. And neither if we enumerate the secure-channel in dt and driver.

See, even if you remove support for the secure channel in the kernel,
a doped super-user could always insmod a module that attempts to
access the secure address space that you want to "hide".

cheers.