linux-kernel - Re: [PATCH] PM: EM: Fix uninitialized power in em_create_perf

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Message-ID: <ZyiQ1YS81ZjE1Qlu@google.com>
Date: Mon, 4 Nov 2024 09:16:05 +0000
From: Quentin Perret <qperret@...gle.com>
To: Lukasz Luba <lukasz.luba@....com>
Cc: Jinjie Ruan <ruanjinjie@...wei.com>, rafael@...nel.org, pavel@....cz,
	len.brown@...el.com, linux-pm@...r.kernel.org,
	daniel.lezcano@...aro.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PM: EM: Fix uninitialized power in em_create_perf_table

On Monday 04 Nov 2024 at 09:14:36 (+0000), Lukasz Luba wrote:
> Hi Jinjie,
> 
> On 11/4/24 09:03, Jinjie Ruan wrote:
> > In em_create_perf_table(), power is uninitialized and passed the pointer
> > to active_power() hook, but the hook function may not assign it and
> > return 0, such as mtk_cpufreq_get_cpu_power(), so the later zero check for
> 
> Please fix the driver. I have checked that function. It must return
> -EINVAL when the 'policy' is not found. We cannot progress with power=0.
> 
> 
> > power is not invalid, initialize power to zero to fix it.
> > 
> > Cc: stable@...r.kernel.org
> > Fixes: 7d9895c7fbfc ("PM / EM: introduce em_dev_register_perf_domain function")
> > Signed-off-by: Jinjie Ruan <ruanjinjie@...wei.com>
> > ---
> >   kernel/power/energy_model.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/kernel/power/energy_model.c b/kernel/power/energy_model.c
> > index 927cc55ba0b3..866a3e9c05b2 100644
> > --- a/kernel/power/energy_model.c
> > +++ b/kernel/power/energy_model.c
> > @@ -344,7 +344,7 @@ static int em_create_perf_table(struct device *dev, struct em_perf_domain *pd,
> >   				struct em_data_callback *cb,
> >   				unsigned long flags)
> >   {
> > -	unsigned long power, freq, prev_freq = 0;
> > +	unsigned long power = 0, freq, prev_freq = 0;
> >   	int nr_states = pd->nr_perf_states;
> >   	int i, ret;
> 
> 
> This patch proposal is just a workaround.
> 
> When you send a patch to that MTK driver, I can review it for you so
> please add me on CC.

We raced, but +1 to the above :-)