linux-kernel - Re: [PATCH] cpufreq: powernv: Fix frame-size-overflow in powernv_cpufreq_work

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Message-ID: <87fte6obqo.fsf@dja-thinkpad.axtens.net>
Date:   Wed, 18 Mar 2020 09:30:39 +1100
From:   Daniel Axtens <dja@...ens.net>
To:     Pratik Rajesh Sampat <psampat@...ux.ibm.com>,
        linux-pm@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, psampat@...ux.ibm.com,
        pratik.r.sampat@...il.com, ego@...ux.vnet.ibm.com
Subject: Re: [PATCH] cpufreq: powernv: Fix frame-size-overflow in powernv_cpufreq_work_fn

Hi Pratik,

Thanks.

I have checked:

 - for matching puts/gets
 - that all the '.' to '->' conversions, aud uses of '&' check out
 - that the Snowpatch checks pass (https://patchwork.ozlabs.org/patch/1255580/)

On that basis:

Reviewed-by: Daniel Axtens <dja@...ens.net>

Regards,
Daniel

> The patch avoids allocating cpufreq_policy on stack hence fixing frame
> size overflow in 'powernv_cpufreq_work_fn'
>
> Fixes: 227942809b52 ("cpufreq: powernv: Restore cpu frequency to policy->cur on unthrottling")
> Signed-off-by: Pratik Rajesh Sampat <psampat@...ux.ibm.com>
> ---
>  drivers/cpufreq/powernv-cpufreq.c | 13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c
> index 56f4bc0d209e..20ee0661555a 100644
> --- a/drivers/cpufreq/powernv-cpufreq.c
> +++ b/drivers/cpufreq/powernv-cpufreq.c
> @@ -902,6 +902,7 @@ static struct notifier_block powernv_cpufreq_reboot_nb = {
>  void powernv_cpufreq_work_fn(struct work_struct *work)
>  {
>  	struct chip *chip = container_of(work, struct chip, throttle);
> +	struct cpufreq_policy *policy;
>  	unsigned int cpu;
>  	cpumask_t mask;
>  
> @@ -916,12 +917,14 @@ void powernv_cpufreq_work_fn(struct work_struct *work)
>  	chip->restore = false;
>  	for_each_cpu(cpu, &mask) {
>  		int index;
> -		struct cpufreq_policy policy;
>  
> -		cpufreq_get_policy(&policy, cpu);
> -		index = cpufreq_table_find_index_c(&policy, policy.cur);
> -		powernv_cpufreq_target_index(&policy, index);
> -		cpumask_andnot(&mask, &mask, policy.cpus);
> +		policy = cpufreq_cpu_get(cpu);
> +		if (!policy)
> +			continue;
> +		index = cpufreq_table_find_index_c(policy, policy->cur);
> +		powernv_cpufreq_target_index(policy, index);
> +		cpumask_andnot(&mask, &mask, policy->cpus);
> +		cpufreq_cpu_put(policy);
>  	}
>  out:
>  	put_online_cpus();
> -- 
> 2.24.1