pwm: sun4i: add NULL check on of_match_device() return value

Submitted by Gustavo A. R. Silva on July 7, 2017, 6:39 a.m.

Details

Message ID 20170707063939.GA20510@embeddedgus
State New
Headers show

Commit Message

Gustavo A. R. Silva July 7, 2017, 6:39 a.m.
Check return value from call to of_match_device()
in order to prevent a NULL pointer dereference.

In case of NULL print error message and return -ENODEV

Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
---
 drivers/pwm/pwm-sun4i.c | 4 ++++
 1 file changed, 4 insertions(+)

Comments

Chen-Yu Tsai July 7, 2017, 7:16 a.m.
On Fri, Jul 7, 2017 at 2:39 PM, Gustavo A. R. Silva
<garsilva@embeddedor.com> wrote:
> Check return value from call to of_match_device()
> in order to prevent a NULL pointer dereference.
>
> In case of NULL print error message and return -ENODEV
>
> Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
> ---
>  drivers/pwm/pwm-sun4i.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/drivers/pwm/pwm-sun4i.c b/drivers/pwm/pwm-sun4i.c
> index 1284ffa..295ca19 100644
> --- a/drivers/pwm/pwm-sun4i.c
> +++ b/drivers/pwm/pwm-sun4i.c
> @@ -321,6 +321,10 @@ static int sun4i_pwm_probe(struct platform_device *pdev)
>         const struct of_device_id *match;
>
>         match = of_match_device(sun4i_pwm_dt_ids, &pdev->dev);

AFAIK this simply can not and should not fail with a device tree
only driver with properly populated of_device_id tables.

ChenYu

> +       if (!match) {
> +               dev_err(&pdev->dev, "failed to match device\n");
> +               return -ENODEV;
> +       }
>
>         pwm = devm_kzalloc(&pdev->dev, sizeof(*pwm), GFP_KERNEL);
>         if (!pwm)
> --
> 2.5.0
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
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Thierry Reding July 7, 2017, 9:33 a.m.
On Fri, Jul 07, 2017 at 03:16:23PM +0800, Chen-Yu Tsai wrote:
> On Fri, Jul 7, 2017 at 2:39 PM, Gustavo A. R. Silva
> <garsilva@embeddedor.com> wrote:
> > Check return value from call to of_match_device()
> > in order to prevent a NULL pointer dereference.
> >
> > In case of NULL print error message and return -ENODEV
> >
> > Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
> > ---
> >  drivers/pwm/pwm-sun4i.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/drivers/pwm/pwm-sun4i.c b/drivers/pwm/pwm-sun4i.c
> > index 1284ffa..295ca19 100644
> > --- a/drivers/pwm/pwm-sun4i.c
> > +++ b/drivers/pwm/pwm-sun4i.c
> > @@ -321,6 +321,10 @@ static int sun4i_pwm_probe(struct platform_device *pdev)
> >         const struct of_device_id *match;
> >
> >         match = of_match_device(sun4i_pwm_dt_ids, &pdev->dev);
> 
> AFAIK this simply can not and should not fail with a device tree
> only driver with properly populated of_device_id tables.

Technically this could happen if someone manually created the platform
device. In that case the core will try to match by name if there is no
device node to use for a match against the list of of_device_ids.

In my opinion it's best to let things crash in this situation to make
it really obvious that people have done something wrong.

Thierry
Gustavo A. R. Silva July 10, 2017, 7:26 p.m.
Hi all,

Quoting Thierry Reding <thierry.reding@gmail.com>:

> On Fri, Jul 07, 2017 at 03:16:23PM +0800, Chen-Yu Tsai wrote:
>> On Fri, Jul 7, 2017 at 2:39 PM, Gustavo A. R. Silva
>> <garsilva@embeddedor.com> wrote:
>> > Check return value from call to of_match_device()
>> > in order to prevent a NULL pointer dereference.
>> >
>> > In case of NULL print error message and return -ENODEV
>> >
>> > Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
>> > ---
>> >  drivers/pwm/pwm-sun4i.c | 4 ++++
>> >  1 file changed, 4 insertions(+)
>> >
>> > diff --git a/drivers/pwm/pwm-sun4i.c b/drivers/pwm/pwm-sun4i.c
>> > index 1284ffa..295ca19 100644
>> > --- a/drivers/pwm/pwm-sun4i.c
>> > +++ b/drivers/pwm/pwm-sun4i.c
>> > @@ -321,6 +321,10 @@ static int sun4i_pwm_probe(struct  
>> platform_device *pdev)
>> >         const struct of_device_id *match;
>> >
>> >         match = of_match_device(sun4i_pwm_dt_ids, &pdev->dev);
>>
>> AFAIK this simply can not and should not fail with a device tree
>> only driver with properly populated of_device_id tables.
>
> Technically this could happen if someone manually created the platform
> device. In that case the core will try to match by name if there is no
> device node to use for a match against the list of of_device_ids.
>
> In my opinion it's best to let things crash in this situation to make
> it really obvious that people have done something wrong.
>

I get it.

Thanks for clarifying.
--
Gustavo A. R. Silva





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diff --git a/drivers/pwm/pwm-sun4i.c b/drivers/pwm/pwm-sun4i.c
index 1284ffa..295ca19 100644
--- a/drivers/pwm/pwm-sun4i.c
+++ b/drivers/pwm/pwm-sun4i.c
@@ -321,6 +321,10 @@  static int sun4i_pwm_probe(struct platform_device *pdev)
 	const struct of_device_id *match;
 
 	match = of_match_device(sun4i_pwm_dt_ids, &pdev->dev);
+	if (!match) {
+		dev_err(&pdev->dev, "failed to match device\n");
+		return -ENODEV;
+	}
 
 	pwm = devm_kzalloc(&pdev->dev, sizeof(*pwm), GFP_KERNEL);
 	if (!pwm)