bootdevice: fix segment fault when booting guest with '-kernel' and '…

…-initrd'

Reproducer:

 $./qemu-system-x86_64 --enable-kvm -kernel /home/vmlinuz-2.6.32.12-0.7-default \
  -initrd /home/initrd-2.6.32.12-0.7-default -append \
 "root=/dev/ram rw console=ttyS0,115200" -dtb guest.dtb -vnc :10 --monitor stdio -smp 2
QEMU 2.2.50 monitor - type 'help' for more information
(qemu) Segmentation fault (core dumped)

Reported-by: Edivaldo de Araujo Pereira <edivaldoapereira@yahoo.com.br>
Signed-off-by: Gonglei <arei.gonglei@huawei.com>
Message-Id: <1425001784-6752-1-git-send-email-arei.gonglei@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

bootdevice.c

@@ -221,10 +221,15 @@ char *get_boot_devices_list(size_t *size, bool ignore_suffixes)
         }
 
         if (!ignore_suffixes) {
-            d = qdev_get_own_fw_dev_path_from_handler(i->dev->parent_bus, i->dev);
-            if (d) {
-                assert(!i->suffix);
-                suffix = d;
+            if (i->dev) {
+                d = qdev_get_own_fw_dev_path_from_handler(i->dev->parent_bus,
+                                                          i->dev);
+                if (d) {
+                    assert(!i->suffix);
+                    suffix = d;
+                } else {
+                    suffix = g_strdup(i->suffix);
+                }
             } else {
                 suffix = g_strdup(i->suffix);
             }