ASoC: dapm: fix use-after-free issue with dailink sname

Commit 7620fe91 ("ASoC: topology: fix memory leak in
soc_tplg_dapm_widget_create") fixed a memory leak issue, but
additional tests and KASAN reports show a use-after-free in soc-dapm.

The widgets are created with a kmemdup operating on a template. The
"name" string is also duplicated, but the "sname" string is not. As a
result, when the template is freed after widget creation, its sname
string is still used.

Fix by explicitly duplicating the "sname" string, and freeing it when
required.
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/soc-dapm.c

@@ -295,7 +295,22 @@ EXPORT_SYMBOL_GPL(dapm_mark_endpoints_dirty);
 static inline struct snd_soc_dapm_widget *dapm_cnew_widget(
 	const struct snd_soc_dapm_widget *_widget)
 {
-	return kmemdup(_widget, sizeof(*_widget), GFP_KERNEL);
+	struct snd_soc_dapm_widget *w;
+
+	w = kmemdup(_widget, sizeof(*_widget), GFP_KERNEL);
+	if (!w)
+		return NULL;
+
+	/*
+	 * w->name is duplicated in caller, but w->sname isn't.
+	 * Duplicate it here if defined
+	 */
+	if (_widget->sname) {
+		w->sname = kstrdup_const(_widget->sname, GFP_KERNEL);
+		if (!w->sname)
+			return NULL;
+	}
+	return w;
 }
 
 struct dapm_kcontrol_data {
@@ -2412,6 +2427,7 @@ void snd_soc_dapm_free_widget(struct snd_soc_dapm_widget *w)
 
 	kfree(w->kcontrols);
 	kfree_const(w->name);
+	kfree_const(w->sname);
 	kfree(w);
 }
 
@@ -3469,6 +3485,7 @@ snd_soc_dapm_new_control_unlocked(struct snd_soc_dapm_context *dapm,
 	else
 		w->name = kstrdup_const(widget->name, GFP_KERNEL);
 	if (w->name == NULL) {
+		kfree_const(w->sname);
 		kfree(w);
 		return ERR_PTR(-ENOMEM);
 	}