[1/2] clk: Do not register provider with a NULL dev->of_node

commit 6579c8d97ad7 ("clk: Mark fwnodes when their clock provider is added")
revealed that clk/bcm/clk-raspberrypi.c driver calls
devm_of_clk_add_hw_provider(), with a NULL dev->of_node.

devm_of_clk_add_hw_provider() should not register the provider with
a NULL dev->of_node, as there is no of_node. Apart of the NULL pointer
dereference that will result when calling fwnode_dev_initialized() in
of_clk_add_hw_provider(), another problem is that when two drivers calling
of_clk_add_hw_provider() with np = NULL, their unregistration order is not
guaranteed to be correct. Avoid all the problems and just return -ENODEV
when the callers of devm_of_clk_add_hw_provider() use a NULL dev->of_node,
which seems the natural way to do.

Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Fixes: 6579c8d97ad7 ("clk: Mark fwnodes when their clock provider is added")
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
---
 drivers/clk/clk.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

On Fri, Apr 23, 2021 at 10:14 AM Tudor Ambarus
<tudor.ambarus@microchip.com> wrote:
>
> commit 6579c8d97ad7 ("clk: Mark fwnodes when their clock provider is added")
> revealed that clk/bcm/clk-raspberrypi.c driver calls
> devm_of_clk_add_hw_provider(), with a NULL dev->of_node.
>
> devm_of_clk_add_hw_provider() should not register the provider with
> a NULL dev->of_node, as there is no of_node. Apart of the NULL pointer
> dereference that will result when calling fwnode_dev_initialized() in
> of_clk_add_hw_provider(), another problem is that when two drivers calling
> of_clk_add_hw_provider() with np = NULL, their unregistration order is not
> guaranteed to be correct. Avoid all the problems and just return -ENODEV
> when the callers of devm_of_clk_add_hw_provider() use a NULL dev->of_node,
> which seems the natural way to do.
>
> Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
> Fixes: 6579c8d97ad7 ("clk: Mark fwnodes when their clock provider is added")
> Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
> ---
>  drivers/clk/clk.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index e2ec1b745243..8b5077cc5e67 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -4634,11 +4634,10 @@ static struct device_node *get_clk_provider_node(struct device *dev)
>   * @get: callback for decoding clk_hw
>   * @data: context pointer for @get callback
>   *
> - * Registers clock provider for given device's node. If the device has no DT
> - * node or if the device node lacks of clock provider information (#clock-cells)
> - * then the parent device's node is scanned for this information. If parent node
> - * has the #clock-cells then it is used in registration. Provider is
> - * automatically released at device exit.
> + * Registers clock provider for given device's node. If the device node lacks
> + * of clock provider information (#clock-cells) then the parent device's node is
> + * scanned for this information. If parent node has the #clock-cells then it is
> + * used in registration. Provider is automatically released at device exit.
>   *
>   * Return: 0 on success or an errno on failure.
>   */
> @@ -4650,6 +4649,9 @@ int devm_of_clk_add_hw_provider(struct device *dev,
>         struct device_node **ptr, *np;
>         int ret;
>
> +       if (!dev->of_node)
> +               return -ENODEV;
> +

Based on the other discussions, for now, just return 0. The error
might cause other issues in other drivers. We can clean this up later.

-Saravana

>         ptr = devres_alloc(devm_of_clk_release_provider, sizeof(*ptr),
>                            GFP_KERNEL);
>         if (!ptr)
> --
> 2.25.1
>

Hi Saravana, Tudor,

On Fri, 2021-04-23 at 10:24 -0700, Saravana Kannan wrote:
> On Fri, Apr 23, 2021 at 10:14 AM Tudor Ambarus
> <tudor.ambarus@microchip.com> wrote:
> > 
> > commit 6579c8d97ad7 ("clk: Mark fwnodes when their clock provider is added")
> > revealed that clk/bcm/clk-raspberrypi.c driver calls
> > devm_of_clk_add_hw_provider(), with a NULL dev->of_node.
> > 
> > devm_of_clk_add_hw_provider() should not register the provider with
> > a NULL dev->of_node, as there is no of_node. Apart of the NULL pointer
> > dereference that will result when calling fwnode_dev_initialized() in
> > of_clk_add_hw_provider(), another problem is that when two drivers calling
> > of_clk_add_hw_provider() with np = NULL, their unregistration order is not
> > guaranteed to be correct. Avoid all the problems and just return -ENODEV
> > when the callers of devm_of_clk_add_hw_provider() use a NULL dev->of_node,
> > which seems the natural way to do.
> > 
> > Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
> > Fixes: 6579c8d97ad7 ("clk: Mark fwnodes when their clock provider is added")
> > Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
> > ---
> >  drivers/clk/clk.c | 12 +++++++-----
> >  1 file changed, 7 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> > index e2ec1b745243..8b5077cc5e67 100644
> > --- a/drivers/clk/clk.c
> > +++ b/drivers/clk/clk.c
> > @@ -4634,11 +4634,10 @@ static struct device_node *get_clk_provider_node(struct device *dev)
> >   * @get: callback for decoding clk_hw
> >   * @data: context pointer for @get callback
> >   *
> > - * Registers clock provider for given device's node. If the device has no DT
> > - * node or if the device node lacks of clock provider information (#clock-cells)
> > - * then the parent device's node is scanned for this information. If parent node
> > - * has the #clock-cells then it is used in registration. Provider is
> > - * automatically released at device exit.
> > + * Registers clock provider for given device's node. If the device node lacks
> > + * of clock provider information (#clock-cells) then the parent device's node is
> > + * scanned for this information. If parent node has the #clock-cells then it is
> > + * used in registration. Provider is automatically released at device exit.
> >   *
> >   * Return: 0 on success or an errno on failure.
> >   */
> > @@ -4650,6 +4649,9 @@ int devm_of_clk_add_hw_provider(struct device *dev,
> >         struct device_node **ptr, *np;
> >         int ret;
> > 
> > +       if (!dev->of_node)
> > +               return -ENODEV;
> > +
> 
> Based on the other discussions, for now, just return 0. The error
> might cause other issues in other drivers. We can clean this up later.

+1, Let's return 0 and do nothing skip the logic in the driver.

Now, from what I read in devm_of_clk_add_hw_provider(), there is a use case for
entering with '!dev->of_node'. See get_clk_provider_node()'s usage. So I think
we should only bail if that function fails to provide a device_node.

Regards,
Nicolas

On 4/23/21 9:21 PM, nicolas saenz julienne wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe

> 

> Hi Saravana, Tudor,

> 

> On Fri, 2021-04-23 at 10:24 -0700, Saravana Kannan wrote:

>> On Fri, Apr 23, 2021 at 10:14 AM Tudor Ambarus

>> <tudor.ambarus@microchip.com> wrote:

>>>

>>> commit 6579c8d97ad7 ("clk: Mark fwnodes when their clock provider is added")

>>> revealed that clk/bcm/clk-raspberrypi.c driver calls

>>> devm_of_clk_add_hw_provider(), with a NULL dev->of_node.

>>>

>>> devm_of_clk_add_hw_provider() should not register the provider with

>>> a NULL dev->of_node, as there is no of_node. Apart of the NULL pointer

>>> dereference that will result when calling fwnode_dev_initialized() in

>>> of_clk_add_hw_provider(), another problem is that when two drivers calling

>>> of_clk_add_hw_provider() with np = NULL, their unregistration order is not

>>> guaranteed to be correct. Avoid all the problems and just return -ENODEV

>>> when the callers of devm_of_clk_add_hw_provider() use a NULL dev->of_node,

>>> which seems the natural way to do.

>>>

>>> Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>

>>> Fixes: 6579c8d97ad7 ("clk: Mark fwnodes when their clock provider is added")

>>> Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>

>>> ---

>>>  drivers/clk/clk.c | 12 +++++++-----

>>>  1 file changed, 7 insertions(+), 5 deletions(-)

>>>

>>> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c

>>> index e2ec1b745243..8b5077cc5e67 100644

>>> --- a/drivers/clk/clk.c

>>> +++ b/drivers/clk/clk.c

>>> @@ -4634,11 +4634,10 @@ static struct device_node *get_clk_provider_node(struct device *dev)

>>>   * @get: callback for decoding clk_hw

>>>   * @data: context pointer for @get callback

>>>   *

>>> - * Registers clock provider for given device's node. If the device has no DT

>>> - * node or if the device node lacks of clock provider information (#clock-cells)

>>> - * then the parent device's node is scanned for this information. If parent node

>>> - * has the #clock-cells then it is used in registration. Provider is

>>> - * automatically released at device exit.

>>> + * Registers clock provider for given device's node. If the device node lacks

>>> + * of clock provider information (#clock-cells) then the parent device's node is

>>> + * scanned for this information. If parent node has the #clock-cells then it is

>>> + * used in registration. Provider is automatically released at device exit.

>>>   *

>>>   * Return: 0 on success or an errno on failure.

>>>   */

>>> @@ -4650,6 +4649,9 @@ int devm_of_clk_add_hw_provider(struct device *dev,

>>>         struct device_node **ptr, *np;

>>>         int ret;

>>>

>>> +       if (!dev->of_node)

>>> +               return -ENODEV;

>>> +

>>

>> Based on the other discussions, for now, just return 0. The error

>> might cause other issues in other drivers. We can clean this up later.

> 

> +1, Let's return 0 and do nothing skip the logic in the driver.

> 

> Now, from what I read in devm_of_clk_add_hw_provider(), there is a use case for

> entering with '!dev->of_node'. See get_clk_provider_node()'s usage. So I think

> we should only bail if that function fails to provide a device_node.

> 


Oh, yes, the error should have been after the get_clk_provider_node().
Any way, will send the return 0 variant too.

Cheers,
ta