Check and report for incomplete 'global' option format

Qemu might crash when provided incomplete '-global' option.
For example:
     qemu-system-x86_64 -global driver=isa-fdc
     qemu-system-x86_64: ../../devel/qemu/qapi/string-input-visitor.c:394:
     string_input_visitor_new: Assertion `str' failed.
     Aborted (core dumped)

Fixes: 3751d7c4 ("vl: allow full-blown QemuOpts syntax for -global")
Signed-off-by: Rohit Kumar <rohit.kumar3@nutanix.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/604


Message-Id: <20220216071508.412974-1-rohit.kumar3@nutanix.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

softmmu/qdev-monitor.c

@@ -1038,6 +1038,13 @@ int qemu_global_option(const char *str)
     if (!opts) {
         return -1;
     }
+    if (!qemu_opt_get(opts, "driver")
+        || !qemu_opt_get(opts, "property")
+        || !qemu_opt_get(opts, "value")) {
+        error_report("options 'driver', 'property', and 'value'"
+                     " are required");
+        return -1;
+    }
 
     return 0;
 }