acpi: check for pxm_to_node_map overflow

It is hardly (if ever) possible but in case of broken _PXM entry we could
reach out of pxm_to_node_map array bounds in acpi_map_pxm_to_node() call.
Signed-off-by: NCyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLen Brown <len.brown@intel.com>

drivers/acpi/numa.c

@@ -277,7 +277,7 @@ int acpi_get_node(acpi_handle *handle)
 	int pxm, node = -1;
 
 	pxm = acpi_get_pxm(handle);
-	if (pxm >= 0)
+	if (pxm >= 0 && pxm < MAX_PXM_DOMAINS)
 		node = acpi_map_pxm_to_node(pxm);
 
 	return node;