[alsa-devel] [PATCH 3/6] ASoC: Samsung-dma: Fix potential NULL pointer dereference

[Sachin Kamat]

'substream' was dereferenced before the NULL check.
Moved the check earlier to prevent NULL pointer dereference.

Cc: Sangbeom Kim <sbkim73 at samsung.com>
Cc: Mark Brown <broonie at opensource.wolfsonmicro.com>
Signed-off-by: Sachin Kamat <sachin.kamat at linaro.org>
---
Build tested and based on linux-next 20121115.
---
 sound/soc/samsung/dma.c |   12 +++++++++---
 1 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/sound/soc/samsung/dma.c b/sound/soc/samsung/dma.c
index b70964e..e59a4f4 100644
--- a/sound/soc/samsung/dma.c
+++ b/sound/soc/samsung/dma.c
@@ -114,17 +114,23 @@ static void dma_enqueue(struct snd_pcm_substream *substream)
 static void audio_buffdone(void *data)
 {
 	struct snd_pcm_substream *substream = data;
-	struct runtime_data *prtd = substream->runtime->private_data;
+	struct runtime_data *prtd;
 
 	pr_debug("Entered %s\n", __func__);
 
+	if (substream) {
+		prtd = substream->runtime->private_data;
+	} else {
+		pr_err("%s: Null data received\n", __func__);
+		return;
+	}
+
 	if (prtd->state & ST_RUNNING) {
 		prtd->dma_pos += prtd->dma_period;
 		if (prtd->dma_pos >= prtd->dma_end)
 			prtd->dma_pos = prtd->dma_start;
 
-		if (substream)
-			snd_pcm_period_elapsed(substream);
+		snd_pcm_period_elapsed(substream);
 
 		spin_lock(&prtd->lock);
 		if (!samsung_dma_has_circular()) {
-- 
1.7.4.1