linux-kernel - Re: [PATCH] PM: QoS: Add check to make sure CPU freq is non-negative

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Message-ID: <91421440-578a-ccd1-21b3-7b8e2e8e2e8d@quicinc.com>
Date:   Wed, 6 Jul 2022 12:00:07 +0530
From:   Shivnandan Kumar <quic_kshivnan@...cinc.com>
To:     <rafael@...nel.org>, <len.brown@...el.com>, <pavel@....cz>
CC:     <linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] PM: QoS: Add check to make sure CPU freq is non-negative

Gentle reminder,

Thanks,

Shivnandan

On 6/23/2022 12:16 PM, Shivnandan Kumar wrote:
> 	CPU frequency should never be non-negative.
> 	If some client driver calls freq_qos_update_request with some
> 	value greater than INT_MAX, then it will set max CPU freq at
> 	fmax but it will add plist node with some negative priority.
> 	plist node has priority from INT_MIN (highest) to INT_MAX
> 	(lowest). Once priority is set as negative, another client
> 	will not be able to reduce max CPU frequency. Adding check
> 	to make sure CPU freq is non-negative will fix this problem.
> Signed-off-by: Shivnandan Kumar <quic_kshivnan@...cinc.com>
>
> ---
>   kernel/power/qos.c | 6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/power/qos.c b/kernel/power/qos.c
> index ec7e1e85923e..41e96fe34bfd 100644
> --- a/kernel/power/qos.c
> +++ b/kernel/power/qos.c
> @@ -531,7 +531,8 @@ int freq_qos_add_request(struct freq_constraints *qos,
>   {
>   	int ret;
>   
> -	if (IS_ERR_OR_NULL(qos) || !req)
> +	if (IS_ERR_OR_NULL(qos) || !req || value < FREQ_QOS_MIN_DEFAULT_VALUE
> +		|| value > FREQ_QOS_MAX_DEFAULT_VALUE)
>   		return -EINVAL;
>   
>   	if (WARN(freq_qos_request_active(req),
> @@ -563,7 +564,8 @@ EXPORT_SYMBOL_GPL(freq_qos_add_request);
>    */
>   int freq_qos_update_request(struct freq_qos_request *req, s32 new_value)
>   {
> -	if (!req)
> +	if (!req || new_value < FREQ_QOS_MIN_DEFAULT_VALUE ||
> +		new_value > FREQ_QOS_MAX_DEFAULT_VALUE)
>   		return -EINVAL;
>   
>   	if (WARN(!freq_qos_request_active(req),