ASoC: dapm: Fix empty list check in dapm_new_mux()

list_first_entry() will always return a valid pointer, even if the list is
empty. So the check whether path is NULL will always be false. So we end up
calling dapm_create_or_share_mixmux_kcontrol() with a path struct that points
right in the middle of the widget struct and by trying to modify the path the
widgets memory will become corrupted. Fix this by using list_emtpy() to check if
the widget doesn't have any paths.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Tested-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Mark Brown <broonie@linaro.org>
Cc: stable@vger.kernel.org

1 files changed, 4 insertions, 3 deletions

diff --git a/sound/soc/soc-dapm.c b/sound/soc/soc-dapm.c
index bd16010441cc..4375c9f2b791 100644
--- a/sound/soc/soc-dapm.c
+++ b/sound/soc/soc-dapm.c
@@ -679,13 +679,14 @@ static int dapm_new_mux(struct snd_soc_dapm_widget *w)
                 return -EINVAL;
         }
 
-        path = list_first_entry(&w->sources, struct snd_soc_dapm_path,
-                                list_sink);
-        if (!path) {
+        if (list_empty(&w->sources)) {
                 dev_err(dapm->dev, "ASoC: mux %s has no paths\n", w->name);
                 return -EINVAL;
         }
 
+        path = list_first_entry(&w->sources, struct snd_soc_dapm_path,
+                                list_sink);
+
         ret = dapm_create_or_share_mixmux_kcontrol(w, 0, path);
         if (ret < 0)
                 return ret;