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

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Message-ID: <1921198.IfoiWgUDIW@kreacher>
Date:   Thu, 19 Mar 2020 11:18:26 +0100
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Pratik Rajesh Sampat <psampat@...ux.ibm.com>
Cc:     linux-pm@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, pratik.r.sampat@...il.com,
        ego@...ux.vnet.ibm.com, dja@...ens.net,
        Michael Ellerman <mpe@...erman.id.au>
Subject: Re: [PATCH] cpufreq: powernv: Fix frame-size-overflow in powernv_cpufreq_work_fn

On Monday, March 16, 2020 2:57:43 PM CET Pratik Rajesh Sampat wrote:
> 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>

Any objections or concerns here?

If not, I'll queue it up.

> ---
>  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();
>