Re: [PATCH] firmware: arm_scmi: Fix OOB in scmi_power_name_get()

[Geert Uytterhoeven <geert@linux-m68k.org>]

Hi Cristian,

On Fri, 15 May 2026 at 13:46, Cristian Marussi <cristian.marussi@arm.com> wrote:
> On Fri, May 15, 2026 at 01:29:27PM +0200, Geert Uytterhoeven wrote:
> > On Fri, 15 May 2026 at 12:28, Dan Carpenter <error27@gmail.com> wrote:
> > > On Fri, May 15, 2026 at 11:59:15AM +0200, Geert Uytterhoeven wrote:
> > > > scmi_power_name_get() does not validate the domain number passed by the
> > > > external caller, which may lead to an out-of-bounds access.
> > >
> > > Is an external caller an out of tree caller?  So far as I can see this
> >
> > I meant a caller outside drivers/firmware/arm_scmi/.
> >
> > > is only called by scmi_pm_domain_probe().
> > >
> > >         scmi_pd->name = power_ops->name_get(ph, i);
> > >
> > > where i < num_domains.
> >
> > You are right. But this seems to be only API implementation in
> > drivers/firmware/arm_scmi/ that does not validate the passed domain
> > number.
>
> Yes we tend to validate protocol operations calls even if apparently
> safe from teh caller perspective...indeed I have this fixed locally
> since ages in an horrible patch, that does a lot more, and that I
> never posted :P
>
> Usually, if it is worth, we also build an internal domain get helper to
> reuse across the protocol unit...but here really there are only 2 call-sites.
>
> What I am not sure is what to return: "unknown" is safer as of now than NULL
> for sure, but really, what happened is NOT that the name was "unknown" (which
> by itself would be out-of-spec behaviour) it is more that the whole domain that
> was referred to that was invalid and NOT existent...
>
> ....mmm I suppose we are opening another can of worms here :P

Like scmi_perf_info_get() returning ERR_PTR(-EINVAL) instead of NULL,
and scmi_perf_domain_probe() never checking the return value anyway?

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds