[18/26] ASoC: Tegra: tegra_pcm_deallocate_dma_buffer: Dont OOPS

[Greg KH]

3.0-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Stephen Warren <swarren@xxxxxxxxxx>

commit a96edd59b2bc88b3d1ea47e0ba48076d65db9302 upstream.

Not all PCM devices have all sub-streams. Specifically, the SPDIF driver
only supports playback and hence has no capture substream. Check whether
a substream exists before dereferencing it, when de-allocating DMA
buffers in tegra_pcm_deallocate_dma_buffer.

Signed-off-by: Stephen Warren <swarren@xxxxxxxxxx>
Acked-by: Liam Girdwood <lrg@xxxxxx>
Signed-off-by: Mark Brown <broonie@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 sound/soc/tegra/tegra_pcm.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

--- a/sound/soc/tegra/tegra_pcm.c
+++ b/sound/soc/tegra/tegra_pcm.c
@@ -309,9 +309,14 @@ static int tegra_pcm_preallocate_dma_buf
 
 static void tegra_pcm_deallocate_dma_buffer(struct snd_pcm *pcm, int stream)
 {
-	struct snd_pcm_substream *substream = pcm->streams[stream].substream;
-	struct snd_dma_buffer *buf = &substream->dma_buffer;
+	struct snd_pcm_substream *substream;
+	struct snd_dma_buffer *buf;
 
+	substream = pcm->streams[stream].substream;
+	if (!substream)
+		return;
+
+	buf = &substream->dma_buffer;
 	if (!buf->area)
 		return;
 


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