Subject: Re: [PATCH] cpufreq: powernv: Fix frame-size-overflow in powernv_cpufreq_reboot_notifier

From: Daniel Axtens <[email-masked]>
Date: Thu, 24 Sep 2020 12:35:05 +1000

Hi Srikar,

> The patch avoids allocating cpufreq_policy on stack hence fixing frame
> size overflow in 'powernv_cpufreq_reboot_notifier'
>
> ./drivers/cpufreq/powernv-cpufreq.c: In function _powernv_cpufreq_reboot_notifier_:
> ./drivers/cpufreq/powernv-cpufreq.c:906:1: error: the frame size of 2064 bytes is larger than 2048 bytes [-Werror=frame-larger-than=]
>  }
>  ^
> cc1: all warnings being treated as errors
> make[3]: *** [./scripts/Makefile.build:316: drivers/cpufreq/powernv-cpufreq.o] Error 1
> make[2]: *** [./scripts/Makefile.build:556: drivers/cpufreq] Error 2
> make[1]: *** [./Makefile:1072: drivers] Error 2
> make[1]: *** Waiting for unfinished jobs....
> make: *** [Makefile:157: sub-make] Error 2
>

This looks a lot like commit d95fe371ecd2 ("cpufreq: powernv: Fix frame-size-overflow in powernv_cpufreq_work_fn").

As with that patch, I have checked for matching puts/gets and that all
uses of '&' check out.

I tried to look at the snowpatch tests: they apparently reported a
checkpatch warning but the file has since disappeared so I can't see
what it was. Running checkpatch locally:

$ scripts/checkpatch.pl -g HEAD -strict
WARNING: Possible unwrapped commit description (prefer a maximum 75 chars per line)
#15: 
make[3]: *** [./scripts/Makefile.build:316: drivers/cpufreq/powernv-cpufreq.o] Error 1

This is benign and you shouldn't wrap that line anyway.

On that basis:

Reviewed-by: Daniel Axtens <[email-masked]>

Kind regards,
Daniel

> Fixes: cf30af76 ("cpufreq: powernv: Set the cpus to nominal frequency during reboot/kexec")
> Cc: Pratik Rajesh Sampat <[email-masked]>
> Cc: Daniel Axtens <[email-masked]>
> Cc: Michael Ellerman <[email-masked]>
> Cc: linuxppc-dev <[email-masked]>
> Signed-off-by: Srikar Dronamraju <[email-masked]>
> ---
>  drivers/cpufreq/powernv-cpufreq.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c
> index a9af15e..e439b43 100644
> --- a/drivers/cpufreq/powernv-cpufreq.c
> +++ b/drivers/cpufreq/powernv-cpufreq.c
> @@ -885,12 +885,15 @@ static int powernv_cpufreq_reboot_notifier(struct notifier_block *nb,
>  				unsigned long action, void *unused)
>  {
>  	int cpu;
> -	struct cpufreq_policy cpu_policy;
> +	struct cpufreq_policy *cpu_policy;
>  
>  	rebooting = true;
>  	for_each_online_cpu(cpu) {
> -		cpufreq_get_policy(&cpu_policy, cpu);
> -		powernv_cpufreq_target_index(&cpu_policy, get_nominal_index());
> +		cpu_policy = cpufreq_cpu_get(cpu);
> +		if (!cpu_policy)
> +			continue;
> +		powernv_cpufreq_target_index(cpu_policy, get_nominal_index());
> +		cpufreq_cpu_put(cpu_policy);
>  	}
>  
>  	return NOTIFY_DONE;
> -- 
> 1.8.3.1