xsm: Avoid null dereference in flask get_page_sid

From: Daniel De Graaf <dgdegra@tycho.nsa.gov>

diff --git a/xen/xsm/flask/hooks.c b/xen/xsm/flask/hooks.c
index b2bf4023f1dddea08f1d91700fe70ed6e94a2797..c58f8d71b6deb177c5f96512218c5960d2a186ad 100644 (file)
--- a/xen/xsm/flask/hooks.c
+++ b/xen/xsm/flask/hooks.c
@@ -340,7 +340,10 @@ static int get_page_sid(struct page_info *page, u32 *sid)
         default:
             /*Pages are implicitly labeled by domain ownership!*/
             dsec = d->ssid;
-            *sid = dsec->sid;
+            if (dsec)
+                *sid = dsec->sid;
+            else
+                rc = -ENOENT;
         break;
     }