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

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Date:   Mon, 1 Aug 2022 15:18:50 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     Jassi Brar <jaswinder.singh@...aro.org>
Cc:     Jassi Brar <jassisinghbrar@...il.com>,
        Rob Herring <robh@...nel.org>,
        Sudeep Holla <sudeep.holla@....com>,
        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, Aug 01, 2022 at 08:57:52AM -0500, Jassi Brar wrote:
> 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".
>

True, generally they should have put this in a separate page/range so
TZ could program accordingly and prohibit any access 🙁.

--
Regards,
Sudeep