dell-wmi, hp-wmi, msi-wmi: check wmi_get_event_data() return value

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.

Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/drivers/platform/x86/dell-wmi.c b/drivers/platform/x86/dell-wmi.c
index 4c7e702..500af8c 100644
--- a/drivers/platform/x86/dell-wmi.c
+++ b/drivers/platform/x86/dell-wmi.c
@@ -202,8 +202,13 @@
 	struct acpi_buffer response = { ACPI_ALLOCATE_BUFFER, NULL };
 	static struct key_entry *key;
 	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 "dell-wmi: bad event status 0x%x\n", status);
+		return;
+	}
 
 	obj = (union acpi_object *)response.pointer;