[PATCH] v4l2-ctrls.c/uvc: zero v4l2_event

[PATCH] v4l2-ctrls.c/uvc: zero v4l2_event

[Hans Verkuil]

Control events can leak kernel memory since they do not fully zero the
event. The same code is present in both v4l2-ctrls.c and uvc_ctrl.c, so
fix both.

It appears that all other event code is properly zeroing the structure,
it's these two places.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Reported-by: syzbot+4f021cf3697781dbd9fb@syzkaller.appspotmail.com
---
For details see: https://syzkaller.appspot.com/bug?extid=4f021cf3697781dbd9fb
---
diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
index d45415cbe6e7..14cff91b7aea 100644
--- a/drivers/media/usb/uvc/uvc_ctrl.c
+++ b/drivers/media/usb/uvc/uvc_ctrl.c
@@ -1212,7 +1212,7 @@ static void uvc_ctrl_fill_event(struct uvc_video_chain *chain,

 	__uvc_query_v4l2_ctrl(chain, ctrl, mapping, &v4l2_ctrl);

-	memset(ev->reserved, 0, sizeof(ev->reserved));
+	memset(ev, 0, sizeof(*ev));
 	ev->type = V4L2_EVENT_CTRL;
 	ev->id = v4l2_ctrl.id;
 	ev->u.ctrl.value = value;
diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c
index 5e3806feb5d7..8a82427c4d54 100644
--- a/drivers/media/v4l2-core/v4l2-ctrls.c
+++ b/drivers/media/v4l2-core/v4l2-ctrls.c
@@ -1387,7 +1387,7 @@ static u32 user_flags(const struct v4l2_ctrl *ctrl)

 static void fill_event(struct v4l2_event *ev, struct v4l2_ctrl *ctrl, u32 changes)
 {
-	memset(ev->reserved, 0, sizeof(ev->reserved));
+	memset(ev, 0, sizeof(*ev));
 	ev->type = V4L2_EVENT_CTRL;
 	ev->id = ctrl->id;
 	ev->u.ctrl.changes = changes;

Re: [PATCH] v4l2-ctrls.c/uvc: zero v4l2_event

[Laurent Pinchart]

Hi Hans,

Thank you for the patch.

On Tuesday, 18 December 2018 15:37:08 EET Hans Verkuil wrote:
> Control events can leak kernel memory since they do not fully zero the
> event. The same code is present in both v4l2-ctrls.c and uvc_ctrl.c, so
> fix both.
> 
> It appears that all other event code is properly zeroing the structure,
> it's these two places.

Indeed :-(

maybe s/it's these/it's only these/ ?

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

I assume you will merge this directly, without a need for me to take the patch 
in my UVC branch ?

> Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
> Reported-by: syzbot+4f021cf3697781dbd9fb@syzkaller.appspotmail.com
> ---
> For details see:
> https://syzkaller.appspot.com/bug?extid=4f021cf3697781dbd9fb ---
> diff --git a/drivers/media/usb/uvc/uvc_ctrl.c
> b/drivers/media/usb/uvc/uvc_ctrl.c index d45415cbe6e7..14cff91b7aea 100644
> --- a/drivers/media/usb/uvc/uvc_ctrl.c
> +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> @@ -1212,7 +1212,7 @@ static void uvc_ctrl_fill_event(struct uvc_video_chain
> *chain,
> 
>  	__uvc_query_v4l2_ctrl(chain, ctrl, mapping, &v4l2_ctrl);
> 
> -	memset(ev->reserved, 0, sizeof(ev->reserved));
> +	memset(ev, 0, sizeof(*ev));
>  	ev->type = V4L2_EVENT_CTRL;
>  	ev->id = v4l2_ctrl.id;
>  	ev->u.ctrl.value = value;
> diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c
> b/drivers/media/v4l2-core/v4l2-ctrls.c index 5e3806feb5d7..8a82427c4d54
> 100644
> --- a/drivers/media/v4l2-core/v4l2-ctrls.c
> +++ b/drivers/media/v4l2-core/v4l2-ctrls.c
> @@ -1387,7 +1387,7 @@ static u32 user_flags(const struct v4l2_ctrl *ctrl)
> 
>  static void fill_event(struct v4l2_event *ev, struct v4l2_ctrl *ctrl, u32
> changes) {
> -	memset(ev->reserved, 0, sizeof(ev->reserved));
> +	memset(ev, 0, sizeof(*ev));
>  	ev->type = V4L2_EVENT_CTRL;
>  	ev->id = ctrl->id;
>  	ev->u.ctrl.changes = changes;

-- 
Regards,

Laurent Pinchart