[PATCH v2 2/2] media: uvcvideo: Avoid partial metadata buffers

[Ricardo Ribalda <ribalda@chromium.org>]

If the metadata queue that is empty receives a new buffer while we are
in the middle of processing a frame, the first metadata buffer will
contain partial information.

Avoid this by tracking the state of the metadata buffer and making sure
that it is in sync with the data buffer.

Now that we are at it, make sure that we skip buffers of size 1 or 0.
They are not allowed by the spec... but it is a simple check to add and
better be safe than sorry.

Fixes: 088ead255245 ("media: uvcvideo: Add a metadata device node")
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
---
 drivers/media/usb/uvc/uvc_video.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
index 5d45c74c6041..cd77ca6f8136 100644
--- a/drivers/media/usb/uvc/uvc_video.c
+++ b/drivers/media/usb/uvc/uvc_video.c
@@ -1149,7 +1149,9 @@ static void uvc_video_stats_stop(struct uvc_streaming *stream)
  * uvc_video_decode_end will never be called with a NULL buffer.
  */
 static int uvc_video_decode_start(struct uvc_streaming *stream,
-		struct uvc_buffer *buf, const u8 *data, int len)
+				  struct uvc_buffer *buf,
+				  struct uvc_buffer *meta_buf,
+				  const u8 *data, int len)
 {
 	u8 header_len;
 	u8 fid;
@@ -1278,6 +1280,8 @@ static int uvc_video_decode_start(struct uvc_streaming *stream,
 
 		/* TODO: Handle PTS and SCR. */
 		buf->state = UVC_BUF_STATE_ACTIVE;
+		if (meta_buf)
+			meta_buf->state = UVC_BUF_STATE_ACTIVE;
 	}
 
 	stream->last_fid = fid;
@@ -1435,7 +1439,7 @@ static void uvc_video_decode_meta(struct uvc_streaming *stream,
 	ktime_t time;
 	const u8 *scr;
 
-	if (!meta_buf || length == 2)
+	if (length <= 2 || !meta_buf || meta_buf->state != UVC_BUF_STATE_ACTIVE)
 		return;
 
 	has_pts = mem[1] & UVC_STREAM_PTS;
@@ -1552,7 +1556,7 @@ static void uvc_video_decode_isoc(struct uvc_urb *uvc_urb,
 		/* Decode the payload header. */
 		mem = urb->transfer_buffer + urb->iso_frame_desc[i].offset;
 		do {
-			ret = uvc_video_decode_start(stream, buf, mem,
+			ret = uvc_video_decode_start(stream, buf, meta_buf, mem,
 				urb->iso_frame_desc[i].actual_length);
 			if (ret == -EAGAIN)
 				uvc_video_next_buffers(stream, &buf, &meta_buf);
@@ -1601,7 +1605,8 @@ static void uvc_video_decode_bulk(struct uvc_urb *uvc_urb,
 	 */
 	if (stream->bulk.header_size == 0 && !stream->bulk.skip_payload) {
 		do {
-			ret = uvc_video_decode_start(stream, buf, mem, len);
+			ret = uvc_video_decode_start(stream, buf, meta_buf, mem,
+						     len);
 			if (ret == -EAGAIN)
 				uvc_video_next_buffers(stream, &buf, &meta_buf);
 		} while (ret == -EAGAIN);

-- 
2.54.0.rc1.513.gad8abe7a5a-goog