linux-kernel - Re: [PATCH v3 3/5] PM / devfreq: Fix kernel panic with cpu based scaling to passive gov

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Date:   Wed, 15 Jun 2022 08:06:36 +0900
From:   Chanwoo Choi <cwchoi00@...il.com>
To:     Christian 'Ansuel' Marangi <ansuelsmth@...il.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Sibi Sankar <sibis@...eaurora.org>,
        Saravana Kannan <skannan@...eaurora.org>,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/5] PM / devfreq: Fix kernel panic with cpu based
 scaling to passive gov

On 22. 6. 14. 20:06, Christian 'Ansuel' Marangi wrote:
> The cpufreq passive register notifier can PROBE_DEFER and the devfreq
> struct is freed and then reallocaed on probe retry.
> The current logic assume that the code can't PROBE_DEFER so the devfreq
> struct in the this variable in devfreq_passive_data is assumed to be
> (if already set) always correct.
> This cause kernel panic as the code try to access the wrong address.
> To correctly handle this, update the this variable in
> devfreq_passive_data to the devfreq reallocated struct.
> 
> Fixes: a03dacb0316f ("PM / devfreq: Add cpu based scaling support to passive governor")
> Signed-off-by: Christian 'Ansuel' Marangi <ansuelsmth@...il.com>
> ---
>  drivers/devfreq/governor_passive.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/devfreq/governor_passive.c b/drivers/devfreq/governor_passive.c
> index 3c3322adea03..be8aa6830413 100644
> --- a/drivers/devfreq/governor_passive.c
> +++ b/drivers/devfreq/governor_passive.c
> @@ -395,8 +395,7 @@ static int devfreq_passive_event_handler(struct devfreq *devfreq,
>  	if (!p_data)
>  		return -EINVAL;
>  
> -	if (!p_data->this)
> -		p_data->this = devfreq;
> +	p_data->this = devfreq;
>  
>  	switch (event) {
>  	case DEVFREQ_GOV_START:

Applied it to devfreq-fixes. Thanks.

-- 
Best Regards,
Samsung Electronics
Chanwoo Choi