linux-kernel - Re: [PATCH] driver core: class: properly reference count class_dev

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Date:   Thu, 18 May 2023 21:42:10 +0200
From:   Mirsad Goran Todorovac <mirsad.todorovac@....unizg.hr>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org
Cc:     linux-usb@...r.kernel.org,
        syzbot+e7afd76ad060fa0d2605@...kaller.appspotmail.com,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Alan Stern <stern@...land.harvard.edu>
Subject: Re: [PATCH] driver core: class: properly reference count
 class_dev_iter()

On 5/16/23 21:20, Greg Kroah-Hartman wrote:
> When class_dev_iter is initialized, the reference count for the subsys
> private structure is incremented, but never decremented, causing a
> memory leak over time.  To resolve this, save off a pointer to the
> internal structure into the class_dev_iter structure and then when the
> iterator is finished, drop the reference count.
> 
> Reported-and-tested-by: syzbot+e7afd76ad060fa0d2605@...kaller.appspotmail.com
> Reported-by: Mirsad Goran Todorovac <mirsad.todorovac@....unizg.hr>
> Cc: "Rafael J. Wysocki" <rafael@...nel.org>
> Cc: Alan Stern <stern@...land.harvard.edu>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

Hi, Greg,

Did I forget to give the

Tested-by: Mirsad Goran Todorovac <mirsad.todorovac@....unizg.hr>

I apologise if I did.

Best regards,
Mirsad

> ---
>   drivers/base/class.c         | 2 ++
>   include/linux/device/class.h | 1 +
>   2 files changed, 3 insertions(+)
> 
> diff --git a/drivers/base/class.c b/drivers/base/class.c
> index ac1808d1a2e8..05d9df90f621 100644
> --- a/drivers/base/class.c
> +++ b/drivers/base/class.c
> @@ -320,6 +320,7 @@ void class_dev_iter_init(struct class_dev_iter *iter, const struct class *class,
>   		start_knode = &start->p->knode_class;
>   	klist_iter_init_node(&sp->klist_devices, &iter->ki, start_knode);
>   	iter->type = type;
> +	iter->sp = sp;
>   }
>   EXPORT_SYMBOL_GPL(class_dev_iter_init);
>   
> @@ -361,6 +362,7 @@ EXPORT_SYMBOL_GPL(class_dev_iter_next);
>   void class_dev_iter_exit(struct class_dev_iter *iter)
>   {
>   	klist_iter_exit(&iter->ki);
> +	subsys_put(iter->sp);
>   }
>   EXPORT_SYMBOL_GPL(class_dev_iter_exit);
>   
> diff --git a/include/linux/device/class.h b/include/linux/device/class.h
> index 9deeaeb457bb..abf3d3bfb6fe 100644
> --- a/include/linux/device/class.h
> +++ b/include/linux/device/class.h
> @@ -74,6 +74,7 @@ struct class {
>   struct class_dev_iter {
>   	struct klist_iter		ki;
>   	const struct device_type	*type;
> +	struct subsys_private		*sp;
>   };
>   
>   int __must_check class_register(const struct class *class);