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Subject: media: uvcvideo: Avoid NULL pointer dereference at the end of streaming Author: Sakari Ailus sakari.ailus@linux.intel.com Date: Wed Jan 30 05:09:41 2019 -0500

The UVC video driver converts the timestamp from hardware specific unit to one known by the kernel at the time when the buffer is dequeued. This is fine in general, but the streamoff operation consists of the following steps (among other things):

1. uvc_video_clock_cleanup --- the hardware clock sample array is released and the pointer to the array is set to NULL,

2. buffers in active state are returned to the user and

3. buf_finish callback is called on buffers that are prepared. buf_finish includes calling uvc_video_clock_update that accesses the hardware clock sample array.

The above is serialised by a queue specific mutex. Address the problem by skipping the clock conversion if the hardware clock sample array is already released.

Fixes: 9c0863b1cc48 ("[media] vb2: call buf_finish from __queue_cancel")

Reported-by: Chiranjeevi Rapolu chiranjeevi.rapolu@intel.com Tested-by: Chiranjeevi Rapolu chiranjeevi.rapolu@intel.com Signed-off-by: Sakari Ailus sakari.ailus@linux.intel.com Cc: stable@vger.kernel.org Signed-off-by: Laurent Pinchart laurent.pinchart@ideasonboard.com Signed-off-by: Mauro Carvalho Chehab mchehab+samsung@kernel.org

drivers/media/usb/uvc/uvc_video.c | 8 ++++++++ 1 file changed, 8 insertions(+)

---

diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c index 84525ff04745..e314657a1843 100644 --- a/drivers/media/usb/uvc/uvc_video.c +++ b/drivers/media/usb/uvc/uvc_video.c @@ -676,6 +676,14 @@ void uvc_video_clock_update(struct uvc_streaming *stream, if (!uvc_hw_timestamps_param) return;

+ /* + * We will get called from __vb2_queue_cancel() if there are buffers + * done but not dequeued by the user, but the sample array has already + * been released at that time. Just bail out in that case. + */ + if (!clock->samples) + return; + spin_lock_irqsave(&clock->lock, flags);

if (clock->count < clock->size)