[Qemu-devel] [PATCH] pc: fix possible NULL pointer dereference in pc_machine_get_device_memory_region_size()

[Igor Mammedov <imammedo@redhat.com>]

QEMU will crash when device-memory-region-size property is read if ms->device_memory
wasn't initialized yet.

Crash can be reproduced with:
 $QEMU -preconfig -qmp unix:qmp_socket,server,nowait &
 ./scripts/qmp/qom-get -s qmp_socket /machine.device-memory-region-size

Instead of crashing return 0 if ms->device_memory hasn't been initialized.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
---
v2:
  add reproducer to commit message
   (Markus Armbruster <armbru@redhat.com>)

 hw/i386/pc.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index edc240b..1b7ead9 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -2459,7 +2459,11 @@ pc_machine_get_device_memory_region_size(Object *obj, Visitor *v,
                                          Error **errp)
 {
     MachineState *ms = MACHINE(obj);
-    int64_t value = memory_region_size(&ms->device_memory->mr);
+    int64_t value = 0;
+
+    if (ms->device_memory) {
+        memory_region_size(&ms->device_memory->mr);
+    }
 
     visit_type_int(v, name, &value, errp);
 }
-- 
2.7.4