Re: [PATCH v2] clk: Skip clk provider registration when np is NULL

[Saravana Kannan <saravanak@google.com>]

On Sun, Apr 25, 2021 at 11:56 PM 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, which resulted in a
> NULL pointer dereference in of_clk_add_hw_provider() when calling
> fwnode_dev_initialized().
>
> Returning 0 is reducing the if conditions in driver code and is being
> consistent with the CONFIG_OF=n inline stub that returns 0 when CONFIG_OF
> is disabled. The downside is that drivers will maybe register clkdev lookups
> when they don't need to and waste some memory.
>
> Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
> Fixes: 6579c8d97ad7 ("clk: Mark fwnodes when their clock provider is added")
> Fixes: 3c9ea42802a1 ("clk: Mark fwnodes when their clock provider is added/removed")
> Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
> Reviewed-by: Stephen Boyd <sboyd@kernel.org>
> ---

Reviewed-by: Saravana Kannan <saravanak@google.com>

-Saravana

> v2:
> - s/return 0;/return; in void of_clk_del_provider()
> - add second fixes tag and Stephen's R-b tag
> The opinions on whether to return an error or zero were split. Returning 0
> and skipping the logic was considered safer as we don't know for sure if
> other drivers are affected. See:
> https://lore.kernel.org/lkml/d24bebc5-0f78-021f-293f-e58defa32531@samsung.com/
> https://lore.kernel.org/lkml/20210423171335.262316-1-tudor.ambarus@microchip.com/
>
>  drivers/clk/clk.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
>
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index a3b30f7de2ef..b47460b40d14 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -4552,6 +4552,9 @@ int of_clk_add_provider(struct device_node *np,
>         struct of_clk_provider *cp;
>         int ret;
>
> +       if (!np)
> +               return 0;
> +
>         cp = kzalloc(sizeof(*cp), GFP_KERNEL);
>         if (!cp)
>                 return -ENOMEM;
> @@ -4591,6 +4594,9 @@ int of_clk_add_hw_provider(struct device_node *np,
>         struct of_clk_provider *cp;
>         int ret;
>
> +       if (!np)
> +               return 0;
> +
>         cp = kzalloc(sizeof(*cp), GFP_KERNEL);
>         if (!cp)
>                 return -ENOMEM;
> @@ -4688,6 +4694,9 @@ void of_clk_del_provider(struct device_node *np)
>  {
>         struct of_clk_provider *cp;
>
> +       if (!np)
> +               return;
> +
>         mutex_lock(&of_clk_mutex);
>         list_for_each_entry(cp, &of_clk_providers, link) {
>                 if (cp->node == np) {
> --
> 2.25.1
>