linux-kernel - [RFC] ASoC: soc-pcm: crash in snd_soc_dapm_new

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Date:   Sun, 19 Jan 2020 19:49:23 +0530
From:   Sameer Pujar <spujar@...dia.com>
To:     <tiwai@...e.com>, <perex@...ex.cz>
CC:     <broonie@...nel.org>, <alsa-devel@...a-project.org>,
        <linux-kernel@...r.kernel.org>, Sameer Pujar <spujar@...dia.com>
Subject: [RFC] ASoC: soc-pcm: crash in snd_soc_dapm_new_dai

Crash happens in snd_soc_dapm_new_dai() when substream->private_data
access is made and substream is NULL here. This is seen for DAIs where
only playback or capture stream is defined. This seems to be happening
for codec2codec DAI link.

Both playback and capture are 0 during soc_new_pcm(). This is probably
happening because cpu_dai and codec_dai are both validated either for
SNDRV_PCM_STREAM_PLAYBACK or SNDRV_PCM_STREAM_CAPTURE.

Shouldn't be playback = 1 when,
 - playback stream is available for codec_dai AND
 - capture stream is available for cpu_dai

and vice-versa for capture = 1?

Signed-off-by: Sameer Pujar <spujar@...dia.com>
---
 sound/soc/soc-pcm.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c
index 74d340d..5aa9c0b 100644
--- a/sound/soc/soc-pcm.c
+++ b/sound/soc/soc-pcm.c
@@ -2855,10 +2855,10 @@ int soc_new_pcm(struct snd_soc_pcm_runtime *rtd, int num)
 
 		for_each_rtd_codec_dai(rtd, i, codec_dai) {
 			if (snd_soc_dai_stream_valid(codec_dai, SNDRV_PCM_STREAM_PLAYBACK) &&
-			    snd_soc_dai_stream_valid(cpu_dai,   SNDRV_PCM_STREAM_PLAYBACK))
+			    snd_soc_dai_stream_valid(cpu_dai,   SNDRV_PCM_STREAM_CAPTURE))
 				playback = 1;
 			if (snd_soc_dai_stream_valid(codec_dai, SNDRV_PCM_STREAM_CAPTURE) &&
-			    snd_soc_dai_stream_valid(cpu_dai,   SNDRV_PCM_STREAM_CAPTURE))
+			    snd_soc_dai_stream_valid(cpu_dai,   SNDRV_PCM_STREAM_PLAYBACK))
 				capture = 1;
 		}
 
-- 
2.7.4