linux-kernel - Re: [PATCH] clk: microchip: check for null return of devm

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Date:   Sat, 19 Nov 2022 10:43:06 +0000
From:   Conor Dooley <conor@...nel.org>
To:     Hui Tang <tanghui20@...wei.com>
Cc:     mturquette@...libre.com, sboyd@...nel.org,
        linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org,
        yusongping@...wei.com, claudiu.beznea@...rochip.com,
        conor.dooley@...rochip.com
Subject: Re: [PATCH] clk: microchip: check for null return of devm_kzalloc()

On Sat, Nov 19, 2022 at 01:48:58PM +0800, Hui Tang wrote:
> Because of the possilble failure of devm_kzalloc(), name might be NULL and
> will cause null pointer derefrence later.

In theory, yeah?

(note to self, s/refrence/reference/, s/possilble/possible)

> Therefore, it might be better to check it and directly return -ENOMEM.

I agree with your use of might here. If the allocations do fail, we
likely aren't getting the system off the ground anyway - but there is
no harm in checking.

Reviewed-by: Conor Dooley <conor.dooley@...rochip.com>

@Claudiu, supposedly I can push to the at91 repo now so I will try to do
that.

Thanks,
Conor.

> 
> Fixes: d39fb172760e ("clk: microchip: add PolarFire SoC fabric clock support")
> Signed-off-by: Hui Tang <tanghui20@...wei.com>
> ---
>  drivers/clk/microchip/clk-mpfs-ccc.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/clk/microchip/clk-mpfs-ccc.c b/drivers/clk/microchip/clk-mpfs-ccc.c
> index 7be028dced63..32aae880a14f 100644
> --- a/drivers/clk/microchip/clk-mpfs-ccc.c
> +++ b/drivers/clk/microchip/clk-mpfs-ccc.c
> @@ -166,6 +166,9 @@ static int mpfs_ccc_register_outputs(struct device *dev, struct mpfs_ccc_out_hw_
>  		struct mpfs_ccc_out_hw_clock *out_hw = &out_hws[i];
>  		char *name = devm_kzalloc(dev, 23, GFP_KERNEL);
>  
> +		if (!name)
> +			return -ENOMEM;
> +
>  		snprintf(name, 23, "%s_out%u", parent->name, i);
>  		out_hw->divider.hw.init = CLK_HW_INIT_HW(name, &parent->hw, &clk_divider_ops, 0);
>  		out_hw->divider.reg = data->pll_base[i / MPFS_CCC_OUTPUTS_PER_PLL] +
> @@ -200,6 +203,9 @@ static int mpfs_ccc_register_plls(struct device *dev, struct mpfs_ccc_pll_hw_clo
>  		struct mpfs_ccc_pll_hw_clock *pll_hw = &pll_hws[i];
>  		char *name = devm_kzalloc(dev, 18, GFP_KERNEL);
>  
> +		if (!name)
> +			return -ENOMEM;
> +
>  		pll_hw->base = data->pll_base[i];
>  		snprintf(name, 18, "ccc%s_pll%u", strchrnul(dev->of_node->full_name, '@'), i);
>  		pll_hw->name = (const char *)name;
> -- 
> 2.17.1
>