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

[Greg KH]

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

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

From: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxxxx>
Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 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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