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Message-ID: <CAB8ipk9wJ-VDHrLMgEoVcdquWptkLnXZ15xFvugC8+WXOf6_Og@mail.gmail.com>
Date: Tue, 15 Aug 2023 14:56:49 +0800
From: Xuewen Yan <xuewen.yan94@...il.com>
To: Xuewen Yan <xuewen.yan@...soc.com>
Cc: rafael@...nel.org, pavel@....cz, len.brown@...el.com,
qyousef@...alina.io, guohua.yan@...soc.com,
linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PM: QOS: Always use "kstrtos32_from_user()" in cpu_latency_qos_write()
Hi rafael
What do you think of this patch?
# echo 500 > /dev/cpu_dma_latency
[T4893] write: qos value=170930229
[T4893] write: count value=4
the value is 170930229 is because it's hex is 0x0A303035, It is
exactly the "500\0"
# echo 200> /dev/cpu_dma_latency
[T4893] write: qos value=170930226
[T4893] write: count value=4
the value is 170930226 is because it's hex is 0x0A303032, It is
exactly the "200\0"
Thanks!
On Mon, Aug 7, 2023 at 3:17 PM Xuewen Yan <xuewen.yan@...soc.com> wrote:
>
> In cpu_latency_qos_write, there is a judgment on whether the count
> value is equal to sizeof(s32). This means that when user write 100~999,
> it would get error value because it would call the "copy_from_user()"
> instead of "kstrtos32".
> Just like:
>
> # echo 500 > /dev/cpu_dma_latency
> [T4893] write: qos value=170930229
> [T4893] write: count value=4
>
> [T4893] write: qos value=170930226
> [T4893] write: count value=4
>
> To prevent this happening, delete the "copy_from_user()" and
> always use "kstrtos32_from_user()".
>
> Signed-off-by: Xuewen Yan <xuewen.yan@...soc.com>
> ---
> kernel/power/qos.c | 14 ++++----------
> 1 file changed, 4 insertions(+), 10 deletions(-)
>
> diff --git a/kernel/power/qos.c b/kernel/power/qos.c
> index 782d3b41c1f3..21a2f873e921 100644
> --- a/kernel/power/qos.c
> +++ b/kernel/power/qos.c
> @@ -379,17 +379,11 @@ static ssize_t cpu_latency_qos_write(struct file *filp, const char __user *buf,
> size_t count, loff_t *f_pos)
> {
> s32 value;
> + int ret;
>
> - if (count == sizeof(s32)) {
> - if (copy_from_user(&value, buf, sizeof(s32)))
> - return -EFAULT;
> - } else {
> - int ret;
> -
> - ret = kstrtos32_from_user(buf, count, 16, &value);
> - if (ret)
> - return ret;
> - }
> + ret = kstrtos32_from_user(buf, count, 16, &value);
> + if (ret)
> + return ret;
>
> cpu_latency_qos_update_request(filp->private_data, value);
>
> --
> 2.25.1
>
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