linux-kernel - [177/200] V4L/DVB: uvcvideo: Prevent division by 0 when control step value is 0

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Message-Id: <20100701174301.482848572@clark.site>
Date:	Thu, 01 Jul 2010 10:44:27 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Mauro Carvalho Chehab <mchehab@...hat.com>
Subject: [177/200] V4L/DVB: uvcvideo: Prevent division by 0 when control step value is 0

2.6.34-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Laurent Pinchart <laurent.pinchart@...asonboard.com>

commit cf7a50eeb6f462a0b7d1619fcb27a727a2981769 upstream.

The control step values reported by the device are used as a divisor
unchecked, which can result in a division by zero.

Check the step value and make it 1 when null.

Signed-off-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 drivers/media/video/uvc/uvc_ctrl.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/media/video/uvc/uvc_ctrl.c
+++ b/drivers/media/video/uvc/uvc_ctrl.c
@@ -1047,6 +1047,8 @@ int uvc_ctrl_set(struct uvc_video_chain
 				   uvc_ctrl_data(ctrl, UVC_CTRL_DATA_MAX));
 		step = mapping->get(mapping, UVC_GET_RES,
 				    uvc_ctrl_data(ctrl, UVC_CTRL_DATA_RES));
+		if (step == 0)
+			step = 1;
 
 		xctrl->value = min + (xctrl->value - min + step/2) / step * step;
 		xctrl->value = clamp(xctrl->value, min, max);


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