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

diff --git a/sound/soc/soc-dapm.c b/sound/soc/soc-dapm.c
index bd16010441cc16fdb26aba40ae5326c427705e81..4375c9f2b791006717f807cdddcb343bb0f8074c 100644 (file)
--- 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;