linux-kernel - Re: clk: rockchip: Checking a kmemdup() call in rockchip_clk_register

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Date:   Mon, 14 Oct 2019 09:26:41 +0200
From:   Markus Elfring <Markus.Elfring@....de>
To:     Heiko Stübner <heiko@...ech.de>,
        linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org, kernel-janitors@...r.kernel.org
Cc:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Aditya Pakki <pakki001@....edu>, Kangjie Lu <kjlu@....edu>,
        Navid Emamdoost <emamd001@....edu>,
        Stephen McCamant <smccaman@....edu>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: clk: rockchip: Checking a kmemdup() call in
 rockchip_clk_register_pll()

> The other option would be to panic, but the kernel should not
> panic if other options are available - and continuing with a static
> pll frequency is less invasive in the error case.

I would like to point out that this function implementation contains
the following source code already.

…
	/* name the actual pll */
	snprintf(pll_name, sizeof(pll_name), "pll_%s", name);

	pll = kzalloc(sizeof(*pll), GFP_KERNEL);
	if (!pll)
		return ERR_PTR(-ENOMEM);
…



…
> +++ b/drivers/clk/rockchip/clk-pll.c
> @@ -909,14 +909,16 @@ struct clk *rockchip_clk_register_pll(struct rockchip_clk_provider *ctx,
…
> -		pll->rate_count = len;
>  		pll->rate_table = kmemdup(rate_table,
>  					pll->rate_count *
>  					sizeof(struct rockchip_pll_rate_table),
>  					GFP_KERNEL);
> -		WARN(!pll->rate_table,
> -			"%s: could not allocate rate table for %s\n",
> -			__func__, name);
> +
> +		/*
> +		 * Set num rates to 0 if kmemdup fails. That way the clock
> +		 * at least can report its rate and stays usable.
> +		 */
> +		pll->rate_count = pll->rate_table ? len : 0;

Can an other error handling strategy make sense occasionally?

…
		if (!pll->rate_table) {
			clk_unregister(mux_clk);
			mux_clk = ERR_PTR(-ENOMEM);
			goto err_mux;
		}
…


Would you like to adjust such exception handling another bit?

Regards,
Markus