linux-kernel - Re: [PATCH v2 1/2] media: uvcvideo: Avoid invalid memory access

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Message-ID: <YacLQ/CNxBaLC+EE@pendragon.ideasonboard.com>
Date:   Wed, 1 Dec 2021 07:42:27 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Ricardo Ribalda <ribalda@...omium.org>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] media: uvcvideo: Avoid invalid memory access

Hi Ricardo,

Thank you for the patch.

On Wed, Dec 01, 2021 at 06:22:17AM +0100, Ricardo Ribalda wrote:
> If mappings points to an invalid memory, we will be invalid accessing
> it.

I'll reflow the commit message.

> Solve it by initializing the value of the variable mapping and by
> changing the order in the conditional statement (to avoid accessing
> mapping->id if not needed).
> 
> Fix:
> kasan: GPF could be caused by NULL-ptr deref or user memory access
> general protection fault: 0000 [#1] PREEMPT SMP KASAN NOPTI
> 
> Fixes: 6350d6a4ed487 ("media: uvcvideo: Set error_idx during ctrl_commit errors")
> Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>

Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>

> ---
>  drivers/media/usb/uvc/uvc_ctrl.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
> index 30bfe9069a1f..9a25d6029255 100644
> --- a/drivers/media/usb/uvc/uvc_ctrl.c
> +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> @@ -1638,7 +1638,7 @@ static int uvc_ctrl_find_ctrl_idx(struct uvc_entity *entity,
>  				  struct v4l2_ext_controls *ctrls,
>  				  struct uvc_control *uvc_control)
>  {
> -	struct uvc_control_mapping *mapping;
> +	struct uvc_control_mapping *mapping = NULL;
>  	struct uvc_control *ctrl_found;
>  	unsigned int i;
>  

-- 
Regards,

Laurent Pinchart