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

["Niklas Söderlund" <niklas.soderlund@xxxxxxxxxxxx>]

Hi Geert,

On 2018-06-27 10:27:54 +0200, Geert Uytterhoeven wrote:
> Hi Niklas,
> 
> 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!

> 
> > --- a/drivers/pinctrl/sh-pfc/pinctrl.c
> > +++ b/drivers/pinctrl/sh-pfc/pinctrl.c
> > @@ -483,6 +483,9 @@ static u32 sh_pfc_pinconf_find_drive_strength_reg(struct sh_pfc *pfc,
> >         const struct pinmux_drive_reg *reg;
> >         unsigned int i;
> >
> > +       if (!pfc->info->drive_regs)
> > +               return 0;
> > +
> >         for (reg = pfc->info->drive_regs; reg->reg; ++reg) {
> >                 for (i = 0; i < ARRAY_SIZE(reg->fields); ++i) {
> >                         field = &reg->fields[i];
> 
> 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

-- 
Regards,
Niklas Söderlund
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