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

[Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>]

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.

> --- 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
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