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

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

[Niklas Söderlund]

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@ragnatech.se>
---
 drivers/pinctrl/sh-pfc/pinctrl.c | 3 +++
 1 file changed, 3 insertions(+)

---

Hi Geert,

This was found on the Eagle board and is based on the latest 
renesas/devel branch.

Regards,
Niklas

diff --git a/drivers/pinctrl/sh-pfc/pinctrl.c b/drivers/pinctrl/sh-pfc/pinctrl.c
index 654dc20e171b9363..ef837676d0312e8d 100644
--- 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];
-- 
2.17.0

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

[Geert Uytterhoeven]

Hi Niklas,

On Wed, Jun 27, 2018 at 8:01 AM Niklas Söderlund
<niklas.soderlund+renesas@ragnatech.se> 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@ragnatech.se>

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@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

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

[Niklas Söderlund]

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 S�derlund
> <niklas.soderlund+renesas@ragnatech.se> 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 S�derlund <niklas.soderlund+renesas@ragnatech.se>
> 
> 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@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

-- 
Regards,
Niklas S�derlund

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

[Geert Uytterhoeven]

Hi Niklas,

On Thu, Jun 28, 2018 at 2:41 AM Niklas Söderlund
<niklas.soderlund@ragnatech.se> 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@ragnatech.se> 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@ragnatech.se>
> >
> > 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 ;-)

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

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

[Niklas Söderlund]

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 S�derlund
> <niklas.soderlund@ragnatech.se> wrote:
> > On 2018-06-27 10:27:54 +0200, Geert Uytterhoeven wrote:
> > > On Wed, Jun 27, 2018 at 8:01 AM Niklas S�derlund
> > > <niklas.soderlund+renesas@ragnatech.se> 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 S�derlund <niklas.soderlund+renesas@ragnatech.se>
> > >
> > > 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@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

-- 
Regards,
Niklas S�derlund

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

[Geert Uytterhoeven]

Hi Niklas,

On Mon, Jul 2, 2018 at 9:48 AM Niklas Söderlund
<niklas.soderlund@ragnatech.se> 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@ragnatech.se> 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@ragnatech.se> 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@ragnatech.se>
> > > >
> > > > 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@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