greybus: audio: Add check for invalid index while mapping control

While mapping control id to define DAPM routes, invalid control index
may cause kernel oops. Add extra check to validate index while mapping
names to control_id.
Signed-off-by: Vaibhav Agarwal <vaibhav.agarwal@linaro.org>
Reviewed-by: Mark Greer <mgreer@animalcreek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/audio_codec.h

@@ -132,6 +132,7 @@ struct gbaudio_control {
 	char *name;
 	char *wname;
 	const char * const *texts;
+	int items;
 	struct list_head list;
 };
 

drivers/staging/greybus/audio_topology.c

@@ -64,6 +64,8 @@ static const char *gbaudio_map_controlid(struct gbaudio_module_info *module,
 		if (control->id == control_id) {
 			if (index == GBAUDIO_INVALID_ID)
 				return control->name;
+			if (index >= control->items)
+				return NULL;
 			return control->texts[index];
 		}
 	}
@@ -71,6 +73,8 @@ static const char *gbaudio_map_controlid(struct gbaudio_module_info *module,
 		if (control->id == control_id) {
 			if (index == GBAUDIO_INVALID_ID)
 				return control->name;
+			if (index >= control->items)
+				return NULL;
 			return control->texts[index];
 		}
 	}
@@ -1038,6 +1042,7 @@ static int gbaudio_tplg_create_widget(struct gbaudio_module_info *module,
 			csize += gbenum->names_length;
 			control->texts = (const char * const *)
 				gb_generate_enum_strings(module, gbenum);
+			control->items = gbenum->items;
 		} else
 			csize = sizeof(struct gb_audio_control);
 		*w_size += csize;
@@ -1184,6 +1189,7 @@ static int gbaudio_tplg_process_kcontrols(struct gbaudio_module_info *module,
 			csize += gbenum->names_length;
 			control->texts = (const char * const *)
 				gb_generate_enum_strings(module, gbenum);
+			control->items = gbenum->items;
 		} else
 			csize = sizeof(struct gb_audio_control);