[PATCH 2/2] Fix NULL pointer dereference in ARINC653 free_vdata.

[Nathan Studer <nate.studer@dornerworks.com>]

From: Nathan Studer <nate.studer@dornerworks.com>

The ARINC653 scheduler alloc_vdata function does not add the
idle cpu to its internal vcpu_list, but when the free_vdata
function is called, the scheduler attempted to remove the vcpu
from its internal vcpu_list, regardless of whether or not
the vcpu was the idle vcpu.  Since the idle vcpu's list field
was never initialized, a NULL pointer was passed to list_del.

When using cpupools, this resulted in a crash when moving a cpu
from an arinc653 scheduler pool.

Signed-off-by: Nathan Studer <nate.studer@dornerworks.com>
---
 xen/common/sched_arinc653.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/xen/common/sched_arinc653.c b/xen/common/sched_arinc653.c
index a1d9443..8a5bd9c 100644
--- a/xen/common/sched_arinc653.c
+++ b/xen/common/sched_arinc653.c
@@ -418,7 +418,9 @@ a653sched_free_vdata(const struct scheduler *ops, void *priv)
     if (av == NULL)
         return;
 
-    list_del(&av->list);
+    if ( !is_idle_vcpu(av->vc) )
+        list_del(&av->list);
+
     xfree(av);
     update_schedule_vcpus(ops);
 }
-- 
1.7.9.5