Re: [PATCH v6 3/9] clk: fixed-factor: Rework initialization with parent clocks

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] A fixed-factor clock registered with no parent and the CLK_SET_RATE_PARENT flag will cause a NULL pointer dereference.
--

commit c84e53359c0d9461f122802c5a6acb3dc1fc8cf7
Author: Benoît Monin <benoit.monin@bootlin.com>

clk: fixed-factor: Rework initialization with parent clocks

This commit reworks fixed-factor clock initialization to follow the standard
sequence for setting parent details in the init struct. When a fixed-factor
clock is provided without a parent, it now registers with zero parents
instead of relying on a dummy parent data struct with an invalid index.

> diff --git a/drivers/clk/clk-fixed-factor.c b/drivers/clk/clk-fixed-factor.c
> index 850e8b95f3527..359e91441c740 100644
> --- a/drivers/clk/clk-fixed-factor.c
> +++ b/drivers/clk/clk-fixed-factor.c
> @@ -124,13 +124,13 @@ __clk_hw_register_fixed_factor(struct device *dev, struct device_node *np,
>  	init.name = name;
>  	init.ops = &clk_fixed_factor_ops;
>  	init.flags = flags;
> -	if (parent_name)
> -		init.parent_names = &parent_name;
> -	else if (parent_hw)
> -		init.parent_hws = &parent_hw;
> +	init.parent_names = parent_name ? &parent_name : NULL;
> +	init.parent_hws = parent_hw ? &parent_hw : NULL;
> +	init.parent_data = pdata;
> +	if (parent_name || parent_hw || pdata)
> +		init.num_parents = 1;
>  	else
> -		init.parent_data = pdata;
> -	init.num_parents = 1;
> +		init.num_parents = 0;

This problem wasn't introduced by this patch, but does this expose an
issue if a fixed-factor clock is registered with no parent and the
CLK_SET_RATE_PARENT flag?

If num_parents is 0, clk_factor_determine_rate() will evaluate
clk_hw_get_parent(hw), which will return NULL.

This NULL pointer is then passed directly into clk_hw_round_rate(), which
dereferences it via hw->core without any NULL checks.

Should the clock framework protect against this gracefully, similar to how
divider_ro_determine_rate() in clk-divider.c handles it by checking if
!req->best_parent_hw?

[ ... ]

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260512-clk-eyeq7-v6-0-0540cce18fb2@bootlin.com?part=3