linux-kernel - Re: [PATCH] [media] pvrusb2: qctrl.flag will be uninitlaized if cx2341x_ctrl

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Date:   Mon, 26 Aug 2019 14:08:52 +0200
From:   Hans Verkuil <hverkuil@...all.nl>
To:     Yizhuo <yzhai003@....edu>
Cc:     csong@...ucr.edu, zhiyunq@...ucr.edu, Mike Isely <isely@...ox.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [media] pvrusb2: qctrl.flag will be uninitlaized if
 cx2341x_ctrl_query() returns error code

On 8/21/19 11:09 PM, Yizhuo wrote:
> Inside function ctrl_cx2341x_getv4lflags(), qctrl.flag
> will be uninitlaized if cx2341x_ctrl_query() returns -EINVAL.
> However, it will be used in the later if statement, which is
> potentially unsafe.
> 
> Signed-off-by: Yizhuo <yzhai003@....edu>
> ---
>  drivers/media/usb/pvrusb2/pvrusb2-hdw.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/media/usb/pvrusb2/pvrusb2-hdw.c b/drivers/media/usb/pvrusb2/pvrusb2-hdw.c
> index ad5b25b89699..1fa05971316a 100644
> --- a/drivers/media/usb/pvrusb2/pvrusb2-hdw.c
> +++ b/drivers/media/usb/pvrusb2/pvrusb2-hdw.c
> @@ -793,6 +793,7 @@ static unsigned int ctrl_cx2341x_getv4lflags(struct pvr2_ctrl *cptr)
>  	struct v4l2_queryctrl qctrl;
>  	struct pvr2_ctl_info *info;
>  	qctrl.id = cptr->info->v4l_id;
> +	memset(&qctr, 0, sizeof(qctrl))

Please compile test your patches! This doesn't compile due to a typo
(qctr -> qctrl).

Also, this would overwrite qctrl.id with 0, not what you want.

Instead, just do:

  	struct v4l2_queryctrl qctrl = {};

to initialize the struct with all 0.

Regards,

	Hans

>  	cx2341x_ctrl_query(&cptr->hdw->enc_ctl_state,&qctrl);
>  	/* Strip out the const so we can adjust a function pointer.  It's
>  	   OK to do this here because we know this is a dynamically created
>