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

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Message-ID: <87h7yexnu7.fsf@mpe.ellerman.id.au>
Date:   Tue, 24 Mar 2020 17:34:56 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        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
Subject: Re: [PATCH] cpufreq: powernv: Fix frame-size-overflow in powernv_cpufreq_work_fn

"Rafael J. Wysocki" <rjw@...ysocki.net> writes:
> 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.

I have it in my testing branch, but if you pick it up I can drop it.

cheers

>> 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();
>>