linux-kernel - Re: [PATCH] cpufreq: scmi: Avoid overflow of target

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Date: Mon, 20 May 2024 10:55:49 +0530
From: Jagadeesh Kona <quic_jkona@...cinc.com>
To: Sudeep Holla <sudeep.holla@....com>,
        Viresh Kumar
	<viresh.kumar@...aro.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        "Cristian Marussi" <cristian.marussi@....com>
CC: <linux-arm-kernel@...ts.infradead.org>, <linux-pm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, Taniya Das <quic_tdas@...cinc.com>,
        "Ajit
 Pandey" <quic_ajipan@...cinc.com>,
        Imran Shaik <quic_imrashai@...cinc.com>,
        Vivek Aknurwar <quic_viveka@...cinc.com>,
        Mike Tipton
	<quic_mdtipton@...cinc.com>
Subject: Re: [PATCH] cpufreq: scmi: Avoid overflow of target_freq in fast
 switch



On 5/17/2024 12:31 PM, Jagadeesh Kona wrote:
> Conversion of target_freq to HZ in scmi_cpufreq_fast_switch()
> can lead to overflow if the multiplied result is greater than
> UINT_MAX, since type of target_freq is unsigned int. Avoid this
> overflow by assigning target_freq to u64 variable for converting
> it to HZ.
> 
> Signed-off-by: Jagadeesh Kona <quic_jkona@...cinc.com>
> ---
>   drivers/cpufreq/scmi-cpufreq.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/cpufreq/scmi-cpufreq.c b/drivers/cpufreq/scmi-cpufreq.c
> index 3b4f6bfb2f4c..42be87aebe6f 100644
> --- a/drivers/cpufreq/scmi-cpufreq.c
> +++ b/drivers/cpufreq/scmi-cpufreq.c
> @@ -63,9 +63,9 @@ static unsigned int scmi_cpufreq_fast_switch(struct cpufreq_policy *policy,
>   					     unsigned int target_freq)
>   {
>   	struct scmi_data *priv = policy->driver_data;
> +	u64 freq = target_freq;
>   

To keep type of freq consistent with the rate parameter of scmi 
freq_set() callback which is unsigned long, will move the above freq 
variable from u64 to unsigned long and post the v2 series.

Thanks,
Jagadeesh

> -	if (!perf_ops->freq_set(ph, priv->domain_id,
> -				target_freq * 1000, true))
> +	if (!perf_ops->freq_set(ph, priv->domain_id, freq * 1000, true))
>   		return target_freq;
>   
>   	return 0;