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: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/drivers/acpi/numa.c b/drivers/acpi/numa.c
index c5e292a..3a0d8ef 100644
--- a/drivers/acpi/numa.c
+++ b/drivers/acpi/numa.c
@@ -277,7 +277,7 @@
 	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;