linux-kernel - Re: [PATCH v5 1/4] uacce: fix cdev handling in register and remove paths

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Message-ID: <CABQgh9GeqxyBPwe-posbstbGy2RBQdfGGBR27tr6+S+5dYzBDQ@mail.gmail.com>
Date: Wed, 12 Nov 2025 17:46:04 +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 v5 1/4] uacce: fix cdev handling in register and remove paths

On Tue, 11 Nov 2025 at 17:35, Chenghai Huang <huangchenghai2@...wei.com> wrote:
>
> From: Wenkai Lin <linwenkai6@...ilicon.com>
>
> This patch addresses a potential issue in the uacce driver where the
> cdev was not properly managed during error handling and cleanup paths.
Can we clarify that it was caused by cdev_device_add?

>
> Changes made:
> 1. In uacce_register(), store the return value of cdev_device_add()
>    and clear the cdev owner as a flag if registration fails.
> 2. In uacce_remove(), add additional check for cdev owner before
>    calling cdev_device_del() to prevent potential issues.
>
> 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 | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/misc/uacce/uacce.c b/drivers/misc/uacce/uacce.c
> index 42e7d2a2a90c..688050c35d88 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 +531,11 @@ 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)
> +               uacce->cdev->owner = NULL;
If uacce is build in, THIS_MODULE = 0.


how about this, handle cdev_device_add fail for no device_add case.

+       if (ret) {
+               if (!device_is_registered(&uacce->dev)) {
+                       cdev_del(uacce->cdev);
+                       uacce->cdev = NULL;
+               }
+       }



> +
> +       return ret;
>  }
>  EXPORT_SYMBOL_GPL(uacce_register);
>
> @@ -568,7 +574,7 @@ void uacce_remove(struct uacce_device *uacce)
>                 unmap_mapping_range(q->mapping, 0, 0, 1);
>         }
>
> -       if (uacce->cdev)
> +       if (uacce->cdev && uacce->cdev->owner)
>                 cdev_device_del(uacce->cdev, &uacce->dev);
is there an potential issue, uacce->cdev is not freed?

Thanks