Re: [PATCH v2] cpufreq: initialize policy rwsem before sysfs publication

[Zhongqiu Han]

On 9/1/2026 8:19 PM, Runyu Xiao wrote:
> cpufreq_policy_alloc() initializes policy->rwsem after
> kobject_init_and_add() has created the policy sysfs directory and its
> default attributes. A sysfs access can therefore reach a policy callback
> before the semaphore has been initialized.
>
> Initialize policy->rwsem before publishing the policy kobject so sysfs
> callbacks always see an initialized semaphore.
>
> Fixes: 2fc3384dc75b ("cpufreq: Initialize policy->kobj while allocating policy")
> Cc: stable@xxxxxxxxxxxxxxx
> Link: https://lore.kernel.org/all/20260830155301.2713780-1-runyu.xiao@xxxxxxxxxx/

Nit: It points to V1 Link, but should be okay according by https://
docs.kernel.org/process/submitting-patches.html#describe-your-changes

> Signed-off-by: Runyu Xiao <runyu.xiao@xxxxxxxxxx>
> Assisted-by: Codex:GPT-5

Nit: Sob tag should always be the last tag.


Reviewed-by: Zhongqiu Han <zhongqiu.han@xxxxxxxxxxxxxxxx>


> ---
> v2:
> - Correct the Fixes tag to the commit that introduced policy kobject publication.
> ---
>   drivers/cpufreq/cpufreq.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 0d0df986f..9efbf5b17 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -1258,6 +1258,8 @@ static struct cpufreq_policy *cpufreq_policy_alloc(unsigned int cpu)
>   	if (!zalloc_cpumask_var(&policy->real_cpus, GFP_KERNEL))
>   		goto err_free_rcpumask;
>   
> +	init_rwsem(&policy->rwsem);
> +
>   	init_completion(&policy->kobj_unregister);
>   	ret = kobject_init_and_add(&policy->kobj, &ktype_cpufreq,
>   				   cpufreq_global_kobject, "policy%u", cpu);
> @@ -1272,8 +1274,6 @@ static struct cpufreq_policy *cpufreq_policy_alloc(unsigned int cpu)
>   		goto err_free_real_cpus;
>   	}
>   
> -	init_rwsem(&policy->rwsem);
> -
>   	freq_constraints_init(&policy->constraints);
>   
>   	policy->nb_min.notifier_call = cpufreq_notifier_min;


--
Thx and BRs,
Zhongqiu Han