qom/object: Don't poll cast cache for NULL objects

object_dynamic_cast_assert used to be tolerant of NULL objects and not
assert. It's clear from the implementation that this is the expected
behavior.

The preceding check of the cast cache dereferences obj however causing
a segfault. Fix by conditionalizing the cast cache logic on obj being
non-null.

Signed-off-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Reviewed-by: Andreas Färber <afaerber@suse.de>
Reviewed-by: Anthony Liguori <aliguori@us.ibm.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@gmail.com>
Message-id: 8e2bef6a55753869c50bfa32226f7fcf0439ca62.1369183592.git.peter.crosthwaite@xilinx.com
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
(cherry picked from commit 95916abcf428fb03644468c7fbce64356c6483c0)

Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

diff --git a/qom/object.c b/qom/object.c
index ec88231fa90ad851b50145f96a6e267067905b72..803b94bb66bad43bd9ae5459f74fb16270e8d5ab 100644 (file)
--- a/qom/object.c
+++ b/qom/object.c
@@ -442,7 +442,7 @@ Object *object_dynamic_cast_assert(Object *obj, const char *typename,
     int i;
     Object *inst;
 
-    for (i = 0; i < OBJECT_CLASS_CAST_CACHE; i++) {
+    for (i = 0; obj && i < OBJECT_CLASS_CAST_CACHE; i++) {
         if (obj->class->cast_cache[i] == typename) {
             goto out;
         }
@@ -458,7 +458,7 @@ Object *object_dynamic_cast_assert(Object *obj, const char *typename,
 
     assert(obj == inst);
 
-    if (obj == inst) {
+    if (obj && obj == inst) {
         for (i = 1; i < OBJECT_CLASS_CAST_CACHE; i++) {
             obj->class->cast_cache[i - 1] = obj->class->cast_cache[i];
         }