wmi: fix a memory leak in wmi_notify_debug

When acpi_evaluate_object() is passed ACPI_ALLOCATE_BUFFER,
the caller must kfree the returned buffer if AE_OK is returned.

The callers of wmi_get_event_data() pass ACPI_ALLOCATE_BUFFER,
and thus must check its return value before accessing
or kfree() on the buffer.

This patch adds return value checking for wmi_get_event_data()
and adds a missing kfree(obj) in the end of wmi_notify_debug

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Acked-by: Thomas Renninger <trenn@suse.de>
Signed-off-by: Matthew Garrett <mjg@redhat.com>

drivers/platform/x86/wmi.c

@@ -518,8 +518,13 @@ static void wmi_notify_debug(u32 value, void *context)
 {
 	struct acpi_buffer response = { ACPI_ALLOCATE_BUFFER, NULL };
 	union acpi_object *obj;
+	acpi_status status;
 
-	wmi_get_event_data(value, &response);
+	status = wmi_get_event_data(value, &response);
+	if (status != AE_OK) {
+		printk(KERN_INFO "wmi: bad event status 0x%x\n", status);
+		return;
+	}
 
 	obj = (union acpi_object *)response.pointer;
 
@@ -543,6 +548,7 @@ static void wmi_notify_debug(u32 value, void *context)
 	default:
 		printk("object type 0x%X\n", obj->type);
 	}
+	kfree(obj);
 }
 
 /**