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

[Sasha Levin]

From: Kieran Bingham <kieran.bingham+rene...@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+rene...@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+rene...@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mche...@s-opensource.com>
Signed-off-by: Sasha Levin <alexander.le...@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