linux-kernel - Re: [PATCH v4 1/4] uacce: fix for cdev memory leak

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Message-ID: <CABQgh9HFHSstR19NtOw5c6E+qS7_d_=6qnCYq9VY6DNKT6o3ng@mail.gmail.com>
Date: Wed, 22 Oct 2025 14:17:38 +0800
From: Zhangfei Gao <zhangfei.gao@...aro.org>
To: Chenghai Huang <huangchenghai2@...wei.com>
Cc: gregkh@...uxfoundation.org, wangzhou1@...ilicon.com, 
	linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org, 
	fanghao11@...wei.com, shenyang39@...wei.com, liulongfang@...wei.com, 
	qianweili@...wei.com, linwenkai6@...ilicon.com
Subject: Re: [PATCH v4 1/4] uacce: fix for cdev memory leak

On Wed, 22 Oct 2025 at 10:12, Chenghai Huang <huangchenghai2@...wei.com> wrote:
>
> From: Wenkai Lin <linwenkai6@...ilicon.com>
>
> In uacce_register(), if cdev_device_add() fails, we should properly
> decrease the reference count of the cdev kobject and set uacce->cdev
> to NULL to avoid potential use-after-free or double free issues.
>
> This change adds proper error handling after cdev_device_add() fails,
> ensuring that kobject_put() is called and uacce->cdev is cleared.
>
> Fixes: 015d239ac014 ("uacce: add uacce driver")
> Cc: stable@...r.kernel.org
> Signed-off-by: Wenkai Lin <linwenkai6@...ilicon.com>
> Signed-off-by: Chenghai Huang <huangchenghai2@...wei.com>
> ---
>  drivers/misc/uacce/uacce.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/misc/uacce/uacce.c b/drivers/misc/uacce/uacce.c
> index 42e7d2a2a90c..9b82a6731832 100644
> --- a/drivers/misc/uacce/uacce.c
> +++ b/drivers/misc/uacce/uacce.c
> @@ -519,6 +519,8 @@ EXPORT_SYMBOL_GPL(uacce_alloc);
>   */
>  int uacce_register(struct uacce_device *uacce)
>  {
> +       int ret;
> +
>         if (!uacce)
>                 return -ENODEV;
>
> @@ -529,7 +531,14 @@ int uacce_register(struct uacce_device *uacce)
>         uacce->cdev->ops = &uacce_fops;
>         uacce->cdev->owner = THIS_MODULE;
>
> -       return cdev_device_add(uacce->cdev, &uacce->dev);
> +       ret = cdev_device_add(uacce->cdev, &uacce->dev);
> +       if (ret) {
> +               kobject_put(&uacce->cdev->kobj);

Not understanding this,
What if kobject_put(&p->kobj) is called twice?
cdev_device_add would call cdev_del->kobject_put(&p->kobj) as well.

If you think cdev_device_add has an issue, maybe fixing
cdev_device_add itself is better?

Thanks