ASoC: fsl_asrc_dma: fix potential null-ptr-deref

dma_request_slave_channel() may return NULL which will lead to
NULL pointer dereference error in 'tmp_chan->private'.

Correct this behaviour by, first, switching from deprecated function
dma_request_slave_channel() to dma_request_chan(). Secondly, enable
sanity check for the resuling value of dma_request_chan().
Also, fix description that follows the enacted changes and that
concerns the use of dma_request_slave_channel().

Fixes: 706e2c881158 ("ASoC: fsl_asrc_dma: Reuse the dma channel if available in Back-End")
Co-developed-by: Natalia Petrova <n.petrova@fintech.ru>
Signed-off-by: Nikita Zhandarovich <n.zhandarovich@fintech.ru>
Acked-by: Shengjiu Wang <shengjiu.wang@gmail.com>
Link: https://lore.kernel.org/r/20230417133242.53339-1-n.zhandarovich@fintech.ru
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/sound/soc/fsl/fsl_asrc_dma.c b/sound/soc/fsl/fsl_asrc_dma.c
index 3b81a465814a1f777ed0820a853fbd93eceaf018..05a7d1588d204b60a3f41abd9982a20a5527f996 100644 (file)
--- a/sound/soc/fsl/fsl_asrc_dma.c
+++ b/sound/soc/fsl/fsl_asrc_dma.c
@@ -209,14 +209,19 @@ static int fsl_asrc_dma_hw_params(struct snd_soc_component *component,
                be_chan = soc_component_to_pcm(component_be)->chan[substream->stream];
                tmp_chan = be_chan;
        }
-       if (!tmp_chan)
-               tmp_chan = dma_request_slave_channel(dev_be, tx ? "tx" : "rx");
+       if (!tmp_chan) {
+               tmp_chan = dma_request_chan(dev_be, tx ? "tx" : "rx");
+               if (IS_ERR(tmp_chan)) {
+                       dev_err(dev, "failed to request DMA channel for Back-End\n");
+                       return -EINVAL;
+               }
+       }
 
        /*
         * An EDMA DEV_TO_DEV channel is fixed and bound with DMA event of each
         * peripheral, unlike SDMA channel that is allocated dynamically. So no
         * need to configure dma_request and dma_request2, but get dma_chan of
-        * Back-End device directly via dma_request_slave_channel.
+        * Back-End device directly via dma_request_chan.
         */
        if (!asrc->use_edma) {
                /* Get DMA request of Back-End */