linux-kernel - Re: [PATCH] net: can: usb: peak_usb: pcan_usb_core.c: Cleaning up missing null-terminate in conjunction with strncpy

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Message-ID: <5416A65D.6010500@pengutronix.de>
Date:	Mon, 15 Sep 2014 10:42:05 +0200
From:	Marc Kleine-Budde <mkl@...gutronix.de>
To:	David Laight <David.Laight@...LAB.COM>,
	'Rickard Strandqvist' <rickard_strandqvist@...ctrumdigital.se>,
	Wolfgang Grandegger <wg@...ndegger.com>
CC:	Oliver Hartkopp <socketcan@...tkopp.net>,
	Stephane Grosjean <s.grosjean@...k-system.com>,
	Alexey Khoroshilov <khoroshilov@...ras.ru>,
	"Christopher R. Baker" <cbaker@....ri.cmu.edu>,
	"linux-can@...r.kernel.org" <linux-can@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] net: can: usb: peak_usb: pcan_usb_core.c:  Cleaning up
 missing null-terminate in conjunction with strncpy

On 09/15/2014 10:28 AM, David Laight wrote:
> From: Rickard Strandqvist
> ...
>> Replacing strncpy with strlcpy to avoid strings that lacks null terminate.
> ...
>> 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 644e6ab..d4fe8ac 100644
>> --- a/drivers/net/can/usb/peak_usb/pcan_usb_core.c
>> +++ b/drivers/net/can/usb/peak_usb/pcan_usb_core.c
>> @@ -830,7 +830,7 @@ static void peak_usb_disconnect(struct usb_interface *intf)
>>  		char name[IFNAMSIZ];
>>
>>  		dev->state &= ~PCAN_USB_STATE_CONNECTED;
>> -		strncpy(name, netdev->name, IFNAMSIZ);
>> +		strlcpy(name, netdev->name, IFNAMSIZ);
>>
>>  		unregister_netdev(netdev);
>>  		free_candev(netdev);
> 
> Or:
> 	char name[sizeof netdev->name];
> 	memcpy(name, netdev->name, sizeof netdev->name);

I would be "sizeof(foo)" in kernel coding style, but let's have a look
at the original code:

                struct net_device *netdev = dev->netdev;
                char name[IFNAMSIZ];

                dev->state &= ~PCAN_USB_STATE_CONNECTED;
                strncpy(name, netdev->name, IFNAMSIZ);

                unregister_netdev(netdev);
                free_candev(netdev);

                kfree(dev->cmd_buf);
                dev->next_siblings = NULL;
                if (dev->adapter->dev_free)
                        dev->adapter->dev_free(dev);

                dev_info(&intf->dev, "%s removed\n", name);

I think it's save to use:

    dev_info(&intf->dev, "%s removed\n", netdev_name(dev->netdev));

instead of doing the str?cpy() in the first place. But why not use:

    netdev_info(dev->netdev, "removed\n");

Is the USB device information lost when using netdev_info()?

Marc

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