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

[Niklas Söderlund <niklas.soderlund@xxxxxxxxxxxx>]

Hi Geert,

On 2018-06-28 08:57:40 +0200, Geert Uytterhoeven wrote:
> Hi Niklas,
> 
> 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 :-)

> 
> 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
--
To unsubscribe from this list: send the line "unsubscribe linux-gpio" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html