Re: [PATCH] drivers: net: remove a dangling pointer in peak_usb_create_dev

From: Pavel Skripkin <paskripkin@gmail.com>
To: "Dongliang Mu" <dzm91@hust.edu.cn>,
	"Wolfgang Grandegger" <wg@grandegger.com>,
	"Marc Kleine-Budde" <mkl@pengutronix.de>,
	"David S. Miller" <davem@davemloft.net>,
	"Jakub Kicinski" <kuba@kernel.org>,
	"Stephane Grosjean" <s.grosjean@peak-system.com>,
	"Stefan Mätje" <stefan.maetje@esd.eu>,
	"Vincent Mailhol" <mailhol.vincent@wanadoo.fr>
Cc: Dongliang Mu <mudongliangabcd@gmail.com>,
	linux-can@vger.kernel.org, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] drivers: net: remove a dangling pointer in peak_usb_create_dev
Date: Thu, 20 Jan 2022 17:27:51 +0300	[thread overview]
Message-ID: <b5cb1132-2f6b-e2da-78c7-1828b3617bc3@gmail.com> (raw)
In-Reply-To: <20220120130605.55741-1-dzm91@hust.edu.cn>

Hi Dongliang,

On 1/20/22 16:05, Dongliang Mu wrote:
> From: Dongliang Mu <mudongliangabcd@gmail.com>
> 
> The error handling code of peak_usb_create_dev forgets to reset the
> next_siblings of previous entry.
> 
> Fix this by nullifying the (dev->prev_siblings)->next_siblings in the
> error handling code.
> 
> Signed-off-by: Dongliang Mu <mudongliangabcd@gmail.com>
> ---
>   drivers/net/can/usb/peak_usb/pcan_usb_core.c | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/net/can/usb/peak_usb/pcan_usb_core.c b/drivers/net/can/usb/peak_usb/pcan_usb_core.c
> index b850ff8fe4bd..f858810221b6 100644
> --- a/drivers/net/can/usb/peak_usb/pcan_usb_core.c
> +++ b/drivers/net/can/usb/peak_usb/pcan_usb_core.c
> @@ -894,6 +894,9 @@ static int peak_usb_create_dev(const struct peak_usb_adapter *peak_usb_adapter,
>   		dev->adapter->dev_free(dev);
>   
>   lbl_unregister_candev:
> +	/* remove the dangling pointer in next_siblings */
> +	if (dev->prev_siblings)
> +		(dev->prev_siblings)->next_siblings = NULL;
>   	unregister_candev(netdev);
>   
>   lbl_restore_intf_data:

Is this pointer used somewhere? I see, that couple of
struct peak_usb_adapter::dev_free() functions use it, but
peak_usb_disconnect() sets dev->next_siblings to NULL before calling 
->dev_free().

Do you have a calltrace or oops log?

With regards,
Pavel Skripkin