linux-kernel - Re: [PATCH] hwrng: fix division by zero in ks_sa_rng

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Message-ID: <a0cc0a58218478a182b8d32fe9158f143816a7fd.camel@gmail.com>
Date: Sat, 20 Sep 2025 09:23:10 +0200
From: Alexander Sverdlin <alexander.sverdlin@...il.com>
To: Nishanth Menon <nm@...com>, Uwe Kleine-König
	 <u.kleine-koenig@...libre.com>, Herbert Xu <herbert@...dor.apana.org.au>, 
 Olivia Mackall <olivia@...enic.com>
Cc: Alexander Sverdlin <alexander.sverdlin@...ia.com>, 
	linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org
Subject: Re: [PATCH] hwrng: fix division by zero in ks_sa_rng_init

Hi Nishanth,

On Fri, 2025-09-19 at 08:20 -0500, Nishanth Menon wrote:
> Fix division by zero in ks_sa_rng_init caused by missing clock
> pointer initialization. The clk_get_rate() call is performed on
> an uninitialized clk pointer, resulting in division by zero when
> calculating delay values.
> 
> Add clock initialization code before using the clock.
> 
> Fixes: 6d01d8511dce ("hwrng: ks-sa - Add minimum sleep time before ready-polling")
> Signed-off-by: Nishanth Menon <nm@...com>

Reviewed-by: Alexander Sverdlin <alexander.sverdlin@...il.com>

>  drivers/char/hw_random/ks-sa-rng.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> ---
> 
> Noticed this when looking at kci logs:
> https://dashboard.kernelci.org/log-viewer?itemId=ti%3A0af42187f4b24261b0c102f0&org=ti&type=test&url=http%3A%2F%2Ffiles.kernelci.org%2F%2Fti%2Fmainline%2Fmaster%2Fv6.17-rc6-43-g8b789f2b7602%2Farm%2Fmulti_v7_defconfig%2BCONFIG_EFI%3Dy%2BCONFIG_ARM_LPAE%3Dy%2Bdebug%2Bkselftest%2Btinyconfig%2Fgcc-12%2Fbaseline-nfs-boot.nfs-k2hk-evm.txt.gz
> 
> Fixed version boot:
> https://gist.github.com/nmenon/0996e5f7bdbcd3b014cee9921a60d88c
> 
>  drivers/char/hw_random/ks-sa-rng.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/char/hw_random/ks-sa-rng.c b/drivers/char/hw_random/ks-sa-rng.c
> index d8fd8a354482..9e408144a10c 100644
> --- a/drivers/char/hw_random/ks-sa-rng.c
> +++ b/drivers/char/hw_random/ks-sa-rng.c
> @@ -231,6 +231,10 @@ static int ks_sa_rng_probe(struct platform_device *pdev)
>  	if (IS_ERR(ks_sa_rng->regmap_cfg))
>  		return dev_err_probe(dev, -EINVAL, "syscon_node_to_regmap failed\n");
>  
> +	ks_sa_rng->clk = devm_clk_get_enabled(dev, NULL);
> +	if (IS_ERR(ks_sa_rng->clk))
> +		return dev_err_probe(dev, PTR_ERR(ks_sa_rng->clk), "Failed to get clock\n");
> +
>  	pm_runtime_enable(dev);
>  	ret = pm_runtime_resume_and_get(dev);
>  	if (ret < 0) {

-- 
Alexander Sverdlin.