[PATCH 2/3] echoaudio: Prevent races in calls to set_audio_format()

[Mark Hills]

The function uses chip->comm_page which needs locking against
other use at the same time.

Signed-off-by: Mark Hills <mark at xwax.org>
---
 sound/pci/echoaudio/echoaudio.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/sound/pci/echoaudio/echoaudio.c b/sound/pci/echoaudio/echoaudio.c
index 82a49dfd2384..8cf08988959f 100644
--- a/sound/pci/echoaudio/echoaudio.c
+++ b/sound/pci/echoaudio/echoaudio.c
@@ -711,9 +711,22 @@ static int pcm_prepare(struct snd_pcm_substream *substream)
 
 	if (snd_BUG_ON(pipe_index >= px_num(chip)))
 		return -EINVAL;
-	if (snd_BUG_ON(!is_pipe_allocated(chip, pipe_index)))
+
+	/*
+	 * We passed checks we can do independently; now take
+	 * exclusive control
+	 */
+
+	spin_lock(&chip->lock);
+
+	if (snd_BUG_ON(!is_pipe_allocated(chip, pipe_index))) {
+		spin_unlock(&chip->lock);
 		return -EINVAL;
+	}
+
 	set_audio_format(chip, pipe_index, &format);
+	spin_unlock(&chip->lock);
+
 	return 0;
 }
 
-- 
2.17.5