[PATCH AUTOSEL for 4.9 140/219] [media] v4l: vsp1: Prevent multiple streamon race commencing pipeline early

Sasha Levin
2018-03-03T22:35:04Z

From: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>

[ Upstream commit 4461c84b52b4a952c657505ef7e4e06b016783df ]

With multiple inputs through the BRU it is feasible for the streams to
race each other at stream-on.

Multiple VIDIOC_STREAMON calls racing each other could have process
N-1 skipping over the pipeline setup section and then start the pipeline
early, if videobuf2 has already enqueued buffers to the driver for
process N but not called the .start_streaming() operation yet

In the case of the video pipelines, this
can present two serious issues.

1) A null-dereference if the pipe->dl is committed at the same time as
the vsp1_video_setup_pipeline() is processing

2) A hardware hang, where a display list is committed without having
called vsp1_video_setup_pipeline() first

Repair this issue, by ensuring that only the stream which configures the
pipeline is able to start it.

Signed-off-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
drivers/media/platform/vsp1/vsp1_video.c | 13 +++++++++++++
1 file changed, 13 insertions(+)

diff --git a/drivers/media/platform/vsp1/vsp1_video.c b/drivers/media/platform/vsp1/vsp1_video.c
index d351b9c768d2..743aa0febc09 100644
--- a/drivers/media/platform/vsp1/vsp1_video.c
+++ b/drivers/media/platform/vsp1/vsp1_video.c
@@ -792,6 +792,7 @@ static int vsp1_video_start_streaming(struct vb2_queue *vq, unsigned int count)
{
struct vsp1_video *video = vb2_get_drv_priv(vq);
struct vsp1_pipeline *pipe = video->rwpf->pipe;
+ bool start_pipeline = false;
unsigned long flags;
int ret;

@@ -802,11 +803,23 @@ static int vsp1_video_start_streaming(struct vb2_queue *vq, unsigned int count)
mutex_unlock(&pipe->lock);
return ret;
}
+
+ start_pipeline = true;
}

pipe->stream_count++;
mutex_unlock(&pipe->lock);

+ /*
+ * vsp1_pipeline_ready() is not sufficient to establish that all streams
+ * are prepared and the pipeline is configured, as multiple streams
+ * can race through streamon with buffers already queued; Therefore we
+ * don't even attempt to start the pipeline until the last stream has
+ * called through here.
+ */
+ if (!start_pipeline)
+ return 0;
+
spin_lock_irqsave(&pipe->irqlock, flags);
if (vsp1_pipeline_ready(pipe))
vsp1_video_pipeline_run(pipe);
--
2.14.1