linux-kernel - Re: [PATCH v2] cpufreq: cppc: Set fie_disabled to FIE_DISABLED if fails to create kworker

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Date:   Wed, 16 Aug 2023 16:07:31 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Liao Chang <liaochang1@...wei.com>
Cc:     rafael@...nel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] cpufreq: cppc: Set fie_disabled to FIE_DISABLED if
 fails to create kworker_fie

On 16-08-23, 09:49, Liao Chang wrote:
> The function cppc_freq_invariance_init() may failed to create
> kworker_fie, make it more robust by setting fie_disabled to FIE_DISBALED
> to prevent an invalid pointer dereference in kthread_destroy_worker(),
> which called from cppc_freq_invariance_exit().
> 
> Link: https://lore.kernel.org/all/20230816034630.a4hvsj373q6aslk3@vireshk-i7/
> 
> Signed-off-by: Liao Chang <liaochang1@...wei.com>
> ---
>  drivers/cpufreq/cppc_cpufreq.c | 28 ++++++++++++++++------------
>  1 file changed, 16 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
> index 022e3555407c..bff4cde06083 100644
> --- a/drivers/cpufreq/cppc_cpufreq.c
> +++ b/drivers/cpufreq/cppc_cpufreq.c
> @@ -220,6 +220,15 @@ static void cppc_cpufreq_cpu_fie_exit(struct cpufreq_policy *policy)
>  	}
>  }
>  
> +static void cppc_freq_invariance_exit(void)
> +{
> +	if (fie_disabled)
> +		return;
> +
> +	kthread_destroy_worker(kworker_fie);
> +	kworker_fie = NULL;
> +}
> +
>  static void __init cppc_freq_invariance_init(void)
>  {
>  	struct sched_attr attr = {
> @@ -249,27 +258,22 @@ static void __init cppc_freq_invariance_init(void)
>  		return;
>  
>  	kworker_fie = kthread_create_worker(0, "cppc_fie");
> -	if (IS_ERR(kworker_fie))
> +	if (IS_ERR(kworker_fie)) {
> +		pr_warn("%s: failed to create kworker_fie: %ld\n", __func__,
> +			PTR_ERR(kworker_fie));
> +		fie_disabled = FIE_DISABLED;
>  		return;
> +	}
>  
>  	ret = sched_setattr_nocheck(kworker_fie->task, &attr);
>  	if (ret) {
>  		pr_warn("%s: failed to set SCHED_DEADLINE: %d\n", __func__,
>  			ret);
> -		kthread_destroy_worker(kworker_fie);
> -		return;
> +		cppc_freq_invariance_exit();

I don't really like this change, there aren't a lot of things that we
need to do here on cleanup, but just kthread_destroy_worker(). Calling
it directly makes more sense I guess.

> +		fie_disabled = FIE_DISABLED;
>  	}
>  }
>  
> -static void cppc_freq_invariance_exit(void)
> -{
> -	if (fie_disabled)
> -		return;
> -
> -	kthread_destroy_worker(kworker_fie);

> -	kworker_fie = NULL;

I don't see the point of this line. Probably it can be dropped.

> -}
> -
>  #else
>  static inline void cppc_cpufreq_cpu_fie_init(struct cpufreq_policy *policy)
>  {
> -- 
> 2.34.1

-- 
viresh