linux-kernel - Re: [PATCH] drivers: net: remove a dangling pointer in peak_usb_create

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Message-ID: <b5cb1132-2f6b-e2da-78c7-1828b3617bc3@gmail.com>
Date:   Thu, 20 Jan 2022 17:27:51 +0300
From:   Pavel Skripkin <paskripkin@...il.com>
To:     Dongliang Mu <dzm91@...t.edu.cn>,
        Wolfgang Grandegger <wg@...ndegger.com>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Stephane Grosjean <s.grosjean@...k-system.com>,
        Stefan Mätje <stefan.maetje@....eu>,
        Vincent Mailhol <mailhol.vincent@...adoo.fr>
Cc:     Dongliang Mu <mudongliangabcd@...il.com>,
        linux-can@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drivers: net: remove a dangling pointer in
 peak_usb_create_dev

Hi Dongliang,

On 1/20/22 16:05, Dongliang Mu wrote:
> From: Dongliang Mu <mudongliangabcd@...il.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@...il.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