[PATCH] ASoC: sh: rz-ssi: Improve error handling in rz_ssi_dma_request function

[Biju Das]

The rz_ssi_dma_request function only checks the NULL condition for
the value returned by the dma_request_chan function, but this function
can also return an error. If it happens, the subsequent function call to
rz_ssi_dma_slave_config can lead to a kernel crash.

This patch fixes the issue by checking both error and NULL condition
returned by dma_request_chan.

Signed-off-by: Biju Das <biju.das.jz at bp.renesas.com>
---
 sound/soc/sh/rz-ssi.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/sound/soc/sh/rz-ssi.c b/sound/soc/sh/rz-ssi.c
index ea8d33ede5d2..3867e2efd3e0 100644
--- a/sound/soc/sh/rz-ssi.c
+++ b/sound/soc/sh/rz-ssi.c
@@ -676,11 +676,19 @@ static void rz_ssi_release_dma_channels(struct rz_ssi_priv *ssi)
 static int rz_ssi_dma_request(struct rz_ssi_priv *ssi, struct device *dev)
 {
 	ssi->playback.dma_ch = dma_request_chan(dev, "tx");
+	if (IS_ERR_OR_NULL(ssi->playback.dma_ch))
+		ssi->playback.dma_ch = NULL;
+
 	ssi->capture.dma_ch = dma_request_chan(dev, "rx");
+	if (IS_ERR_OR_NULL(ssi->capture.dma_ch))
+		ssi->capture.dma_ch = NULL;
+
 	if (!ssi->playback.dma_ch && !ssi->capture.dma_ch) {
 		ssi->playback.dma_ch = dma_request_chan(dev, "rt");
-		if (!ssi->playback.dma_ch)
+		if (IS_ERR_OR_NULL(ssi->playback.dma_ch)) {
+			ssi->playback.dma_ch = NULL;
 			goto no_dma;
+		}
 
 		ssi->dma_rt = true;
 	}
-- 
2.17.1