Some objects accidentally inherit ObjectClass instead of Object.
They compile silently but may crash after downcasting.

In this patch, we introduce a coccinelle script to find broken
declarations and fix them manually with proper base type.

Signed-off-by: Sergey Nizovtsev <snizovtsev@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 MAINTAINERS                              |  1 +
 include/hw/acpi/vmgenid.h                |  2 +-
 include/hw/misc/vmcoreinfo.h             |  2 +-
 include/net/can_host.h                   |  2 +-
 scripts/coccinelle/qom-parent-type.cocci | 26 ++++++++++++++++++++++++
 5 files changed, 30 insertions(+), 3 deletions(-)
 create mode 100644 scripts/coccinelle/qom-parent-type.cocci

diff --git a/MAINTAINERS b/MAINTAINERS
index 7ef459a33c..fcb2c03c2b 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2462,6 +2462,7 @@ F: include/monitor/qdev.h
 F: include/qom/
 F: qapi/qom.json
 F: qapi/qdev.json
+F: scripts/coccinelle/qom-parent-type.cocci
 F: softmmu/qdev-monitor.c
 F: qom/
 F: tests/check-qom-interface.c
diff --git a/include/hw/acpi/vmgenid.h b/include/hw/acpi/vmgenid.h
index d50fbacb8e..cb4ad37fc5 100644
--- a/include/hw/acpi/vmgenid.h
+++ b/include/hw/acpi/vmgenid.h
@@ -19,7 +19,7 @@
 OBJECT_DECLARE_SIMPLE_TYPE(VmGenIdState, VMGENID)
 
 struct VmGenIdState {
-    DeviceClass parent_obj;
+    DeviceState parent_obj;
     QemuUUID guid;                /* The 128-bit GUID seen by the guest */
     uint8_t vmgenid_addr_le[8];   /* Address of the GUID (little-endian) */
 };
diff --git a/include/hw/misc/vmcoreinfo.h b/include/hw/misc/vmcoreinfo.h
index ebada6617a..0b7b55d400 100644
--- a/include/hw/misc/vmcoreinfo.h
+++ b/include/hw/misc/vmcoreinfo.h
@@ -24,7 +24,7 @@ DECLARE_INSTANCE_CHECKER(VMCoreInfoState, VMCOREINFO,
 typedef struct fw_cfg_vmcoreinfo FWCfgVMCoreInfo;
 
 struct VMCoreInfoState {
-    DeviceClass parent_obj;
+    DeviceState parent_obj;
 
     bool has_vmcoreinfo;
     FWCfgVMCoreInfo vmcoreinfo;
diff --git a/include/net/can_host.h b/include/net/can_host.h
index 4e3ce3f954..caab71bdda 100644
--- a/include/net/can_host.h
+++ b/include/net/can_host.h
@@ -35,7 +35,7 @@
 OBJECT_DECLARE_TYPE(CanHostState, CanHostClass, CAN_HOST)
 
 struct CanHostState {
-    ObjectClass oc;
+    Object oc;
 
     CanBusState *bus;
     CanBusClientState bus_client;
diff --git a/scripts/coccinelle/qom-parent-type.cocci b/scripts/coccinelle/qom-parent-type.cocci
new file mode 100644
index 0000000000..9afb3edd97
--- /dev/null
+++ b/scripts/coccinelle/qom-parent-type.cocci
@@ -0,0 +1,26 @@
+// Highlight object declarations that don't look like object class but
+// accidentally inherit from it.
+
+@match@
+identifier obj_t, fld;
+type parent_t =~ ".*Class$";
+@@
+struct obj_t {
+    parent_t fld;
+    ...
+};
+
+@script:python filter depends on match@
+obj_t << match.obj_t;
+@@
+is_class_obj = obj_t.endswith('Class')
+cocci.include_match(not is_class_obj)
+
+@replacement depends on filter@
+identifier match.obj_t, match.fld;
+type match.parent_t;
+@@
+struct obj_t {
+*   parent_t fld;
+    ...
+};
-- 
2.26.2