linux-kernel - Re: [PATCH 1/2] clk: Do not register provider with a NULL dev->of

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Message-ID: <CAGETcx-81hPTW_EVexMWaxGSOknuK-zESqKdiuQvye=n3TaHkA@mail.gmail.com>
Date:   Fri, 23 Apr 2021 10:24:54 -0700
From:   Saravana Kannan <saravanak@...gle.com>
To:     Tudor Ambarus <tudor.ambarus@...rochip.com>
Cc:     mturquette@...libre.com, sboyd@...nel.org, nsaenz@...nel.org,
        maxime@...no.tech, gregkh@...uxfoundation.org, rafael@...nel.org,
        khilman@...nel.org, ulf.hansson@...aro.org, len.brown@...el.com,
        pavel@....cz, robh+dt@...nel.org, frowand.list@...il.com,
        maz@...nel.org, tglx@...utronix.de, geert@...ux-m68k.org,
        nsaenzjulienne@...e.de, linux@...ck-us.net,
        guillaume.tucker@...labora.com, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org, corbet@....net,
        nicolas.ferre@...rochip.com, claudiu.beznea@...rochip.com,
        linux-doc@...r.kernel.org, linux-pm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-acpi@...r.kernel.org,
        kernel-team@...roid.com, linux-rpi-kernel@...ts.infradead.org,
        Marek Szyprowski <m.szyprowski@...sung.com>
Subject: Re: [PATCH 1/2] clk: Do not register provider with a NULL dev->of_node

On Fri, Apr 23, 2021 at 10:14 AM Tudor Ambarus
<tudor.ambarus@...rochip.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@...sung.com>
> Fixes: 6579c8d97ad7 ("clk: Mark fwnodes when their clock provider is added")
> Signed-off-by: Tudor Ambarus <tudor.ambarus@...rochip.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
>