linux-kernel - Re: [PATCH] media: usb: dvb-usb-v2: check the return value of kstrdup()

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Message-ID: <20211214160334.6e493a32@coco.lan>
Date:   Tue, 14 Dec 2021 16:03:34 +0100
From:   Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
To:     Xiaoke Wang <xkernel.wang@...mail.com>
Cc:     crope@....fi, linux-media@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] media: usb: dvb-usb-v2: check the return value of
 kstrdup()

Em Mon, 13 Dec 2021 15:48:33 +0800
Xiaoke Wang <xkernel.wang@...mail.com> escreveu:

> Note: Compare with the last email, this one is using my full name.
> kstrdup() returns NULL if some internal memory errors happen, it is
> better to check the return value of it. Since the return type of
> dvb_usbv2_disconnect() is void, so only raise the error info.
> 
> Signed-off-by: Xiaoke Wang <xkernel.wang@...mail.com>
> ---
>  drivers/media/usb/dvb-usb-v2/dvb_usb_core.c | 14 +++++++++++---
>  1 file changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/media/usb/dvb-usb-v2/dvb_usb_core.c b/drivers/media/usb/dvb-usb-v2/dvb_usb_core.c
> index f1c79f3..a43a310 100644
> --- a/drivers/media/usb/dvb-usb-v2/dvb_usb_core.c
> +++ b/drivers/media/usb/dvb-usb-v2/dvb_usb_core.c
> @@ -1009,6 +1009,9 @@ void dvb_usbv2_disconnect(struct usb_interface *intf)
>  	const char *devname = kstrdup(dev_name(&d->udev->dev), GFP_KERNEL);
>  	const char *drvname = d->name;
>  
> +	if (!devname)
> +		dev_err(&d->udev->dev, "%s: kstrdup() failed\n", KBUILD_MODNAME);
> +

Don't use KBUILD_MODNAME, as dev_err will already add the driver/device's
name.

>  	dev_dbg(&d->udev->dev, "%s: bInterfaceNumber=%d\n", __func__,
>  			intf->cur_altsetting->desc.bInterfaceNumber);
>  
> @@ -1023,9 +1026,14 @@ void dvb_usbv2_disconnect(struct usb_interface *intf)
>  	kfree(d->priv);
>  	kfree(d);
>  
> -	pr_info("%s: '%s:%s' successfully deinitialized and disconnected\n",
> -		KBUILD_MODNAME, drvname, devname);

Better to use:
	dev_dbg(&d->udev->dev, "successfully deinitialized and disconnected\n");

> -	kfree(devname);

No need to place kfree() inside an if, as kfree(NULL) is safe.

> +	if (devname) {
> +		pr_info("%s: '%s:%s' successfully deinitialized and disconnected\n",
> +			KBUILD_MODNAME, drvname, devname);
> +		kfree(devname);
> +	} else {
> +		pr_info("%s: '%s:UNKNOWN' successfully deinitialized and disconnected\n",
> +			KBUILD_MODNAME, drvname);
> +	}
>  }
>  EXPORT_SYMBOL(dvb_usbv2_disconnect);
> 

Thanks,
Mauro