[PATCH] Fix boot crash on xsm/flask enabled builds when no policy module is present

[Tomasz Wroblewski <tomasz.wroblewski@citrix.com>]

Xen crashes on boot of xsm/flask enabled builds, if policy module is not specified.
This seems to have worked on 4.1 at least. Can be fixed by testing whether policy_buffer
is NULL before attempting to load from it - it's a global which is set to non-NULL when
policy module is detected.

Signed-off-by: Tomasz Wroblewski <tomasz.wroblewski@citrix.com>
---
 xen/xsm/flask/hooks.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/xen/xsm/flask/hooks.c b/xen/xsm/flask/hooks.c
index fa0589a..cfa2929 100644
--- a/xen/xsm/flask/hooks.c
+++ b/xen/xsm/flask/hooks.c
@@ -1585,7 +1585,8 @@ static __init int flask_init(void)
     if ( register_xsm(&flask_ops) )
         panic("Flask: Unable to register with XSM.\n");
 
-    ret = security_load_policy(policy_buffer, policy_size);
+    if ( policy_buffer )
+        ret = security_load_policy(policy_buffer, policy_size);
 
     if ( flask_enforcing )
         printk("Flask:  Starting in enforcing mode.\n");
-- 
1.7.10.4