linux-kernel - Re: [PATCH] usb: usb251xb: fix to avoid potential NULL pointer dereference

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Message-ID: <3579fc19-dde7-968b-3918-39f1cc4ee3bc@skidata.com>
Date:   Tue, 19 Mar 2019 14:11:23 +0100
From:   Richard Leitner <richard.leitner@...data.com>
To:     Aditya Pakki <pakki001@....edu>
CC:     <kjlu@....edu>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] usb: usb251xb: fix to avoid potential NULL pointer
 dereference

On 19/03/2019 00:56, Aditya Pakki wrote:
> of_match_device in usb251xb_probe can fail and returns a NULL pointer.
> The patch avoids a potential NULL pointer dereference in this scenario.
> 
> Signed-off-by: Aditya Pakki <pakki001@....edu>
> ---
>   drivers/usb/misc/usb251xb.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/usb/misc/usb251xb.c b/drivers/usb/misc/usb251xb.c
> index 4d72b7d1d383..fe5266dc8864 100644
> --- a/drivers/usb/misc/usb251xb.c
> +++ b/drivers/usb/misc/usb251xb.c
> @@ -612,6 +612,8 @@ static int usb251xb_probe(struct usb251xb *hub)
>   							   dev);
>   	int err;
>   
> +	if (!of_id)
> +		return -ENODEV;

Hi Aditya,
thanks for finding this issue!

Nonetheless I'd prefer to change this to not return here but rather do 
something like:

	if (np && of_id) {

So we still may bring up the hub in its default config in scenarios 
without dt/of...

Any comments/objections on that?

regards;Richard.L

>   	if (np) {
>   		err = usb251xb_get_ofdata(hub,
>   					  (struct usb251xb_data *)of_id->data);
>