[PATCH] pc: fix leak in pc_system_flash_cleanup_unused

[Alexander Bulekov <alxndr@bu.edu>]

fix a leak detected when building with --enable-sanitizers:
./i386-softmmu/qemu-system-i386
Upon exit:
==13576==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 1216 byte(s) in 1 object(s) allocated from:
    #0 0x7f9d2ed5c628 in malloc (/usr/lib/x86_64-linux-gnu/libasan.so.5)
    #1 0x7f9d2e963500 in g_malloc (/usr/lib/x86_64-linux-gnu/libglib-2.0.so.)
    #2 0x55fa646d25cc in object_new_with_type /tmp/qemu/qom/object.c:686
    #3 0x55fa63dbaa88 in qdev_new /tmp/qemu/hw/core/qdev.c:140
    #4 0x55fa638a533f in pc_pflash_create /tmp/qemu/hw/i386/pc_sysfw.c:88
    #5 0x55fa638a54c4 in pc_system_flash_create /tmp/qemu/hw/i386/pc_sysfw.c:106
    #6 0x55fa646caa1d in object_init_with_type /tmp/qemu/qom/object.c:369
    #7 0x55fa646d20b5 in object_initialize_with_type /tmp/qemu/qom/object.c:511
    #8 0x55fa646d2606 in object_new_with_type /tmp/qemu/qom/object.c:687
    #9 0x55fa639431e9 in qemu_init /tmp/qemu/softmmu/vl.c:3878
    #10 0x55fa6335c1b8 in main /tmp/qemu/softmmu/main.c:48
    #11 0x7f9d2cf06e0a in __libc_start_main ../csu/libc-start.c:308
    #12 0x55fa6335f8e9 in _start (/tmp/qemu/build/i386-softmmu/qemu-system-i386)

Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
---

I am not very familiar with the QOM, so maybe this isn't the right way
of going about this. With the call to object_property_add_child in
pc_sysfw.c:pc_pflash_create, object_ref is called on the pflash device.
In the pc_system_flash_cleanup_unused function, there are calls to
object_propery_del and object_unparent, but it seems neither of these
calls object_unref. So do we need to manually decrement the refcount?

 hw/i386/pc_sysfw.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/hw/i386/pc_sysfw.c b/hw/i386/pc_sysfw.c
index ec2a3b3e7e..f69a93671a 100644
--- a/hw/i386/pc_sysfw.c
+++ b/hw/i386/pc_sysfw.c
@@ -123,6 +123,7 @@ static void pc_system_flash_cleanup_unused(PCMachineState *pcms)
             object_property_del(OBJECT(pcms), prop_name);
             g_free(prop_name);
             object_unparent(dev_obj);
+            object_unref(dev_obj);
             pcms->flash[i] = NULL;
         }
     }
-- 
2.26.2