Re: [PATCH] pinctrl: sh-pfc: fix a null pointer dereference of drive strength information

[Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>]

Hi Niklas,

On Mon, Jul 2, 2018 at 9:48 AM Niklas Söderlund
<niklas.soderlund@xxxxxxxxxxxx> wrote:
> On 2018-06-28 08:57:40 +0200, Geert Uytterhoeven wrote:
> > On Thu, Jun 28, 2018 at 2:41 AM Niklas Söderlund
> > <niklas.soderlund@xxxxxxxxxxxx> wrote:
> > > On 2018-06-27 10:27:54 +0200, Geert Uytterhoeven wrote:
> > > > On Wed, Jun 27, 2018 at 8:01 AM Niklas Söderlund
> > > > <niklas.soderlund+renesas@xxxxxxxxxxxx> wrote:
> > > > > Not all SoCs describes the drive strength registers. When reading the
> > > > > sysfs pinconf-pins file on such a SoC this results in a null pointer
> > > > > dereference. Protect against this dereference and allow reading of the
> > > > > pinconf-pins by adding a check if the drive strength registers are
> > > > > described or not.
> > > > >
> > > > > Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@xxxxxxxxxxxx>
> > > >
> > > > Thanks for your patch!
> > > >
> > > > > This was found on the Eagle board and is based on the latest
> > > > > renesas/devel branch.
> > > >
> > > > I think the real issue is pfc-r8a77990.c setting SH_PFC_PIN_CFG_DRIVE_STRENGTH
> > > > without providing sh_pfc.drive_regs[].
> > > > Without that flag set, sh_pfc_pinconf_validate(..., PIN_CONFIG_DRIVE_STRENGTH)
> > > > would cause an earlier failure.
> > >
> > > Ahh I see, thanks for the pointer. I will explore this option as it
> > > seems like a nicer solution, thanks!
> >
> > To be 100% clear: the proper solution is to add the missing drive_regs[],
> > not to remove the flags ;-)
>
> Normally I would agree with you, but V3M have no drive strength
> registered described in the datasheet so in this instance I do think the
> correct fix is to remove the flags :-)

Thanks, hard evidence is a good way to convince me ;-)

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

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
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