[PATCH v2] cpufreq: cppc: Set fie_disabled to FIE_DISABLED if fails to create kworker_fie

[PATCH v2] cpufreq: cppc: Set fie_disabled to FIE_DISABLED if fails to create kworker_fie

[Liao Chang]

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@huawei.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();
+		fie_disabled = FIE_DISABLED;
 	}
 }
 
-static void cppc_freq_invariance_exit(void)
-{
-	if (fie_disabled)
-		return;
-
-	kthread_destroy_worker(kworker_fie);
-	kworker_fie = NULL;
-}
-
 #else
 static inline void cppc_cpufreq_cpu_fie_init(struct cpufreq_policy *policy)
 {
-- 
2.34.1

Re: [PATCH v2] cpufreq: cppc: Set fie_disabled to FIE_DISABLED if fails to create kworker_fie

[Viresh Kumar]

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@huawei.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

Re: [PATCH v2] cpufreq: cppc: Set fie_disabled to FIE_DISABLED if fails to create kworker_fie

[Liao, Chang]

在 2023/8/16 18:37, Viresh Kumar 写道:
> 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@huawei.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.

OK，I will simplify code in next revisoin.

> 
>> +		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.

I agree with you, when fie_disbaled is set to FIE_DISABLED and kthred_destroy_worker() is called,
the driver has no chance to access the invalid kworker_fie pointer.

Thanks.

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

-- 
BR
Liao, Chang