From: Michael Roth Date: Tue, 20 May 2014 17:20:39 +0000 (-0500) Subject: qapi: zero-initialize all QMP command parameters X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=fc13d937269c1cd01a4b7720c1dcce01722727a2;p=qemu.git qapi: zero-initialize all QMP command parameters In general QMP command parameter values are specified by consumers of the QMP/HMP interface, but in the case of optional parameters these values may be left uninitialized. It is considered a bug for code to make use of optional parameters that have not been flagged as being present by the marshalling code (via corresponding has_ parameter), however our marshalling code will still pass these uninitialized values on to the corresponding QMP function (to then be ignored). Some compilers (clang in particular) consider this unsafe however, and generate warnings as a result. As reported by Peter Maydell: This is something clang's -fsanitize=undefined spotted. The code generated by qapi-commands.py in qmp-marshal.c for qmp_marshal_* functions where there are some optional arguments looks like this: bool has_force = false; bool force; mi = qmp_input_visitor_new_strict(QOBJECT(args)); v = qmp_input_get_visitor(mi); visit_type_str(v, &device, "device", errp); visit_start_optional(v, &has_force, "force", errp); if (has_force) { visit_type_bool(v, &force, "force", errp); } visit_end_optional(v, errp); qmp_input_visitor_cleanup(mi); if (error_is_set(errp)) { goto out; } qmp_eject(device, has_force, force, errp); In the case where has_force is false, we never initialize force, but then we use it by passing it to qmp_eject. I imagine we don't then actually use the value, but clang complains in particular for 'bool' variables because the value that ends up being loaded from memory for 'force' is not either 0 or 1 (being uninitialized stack contents). Fix this by initializing all QMP command parameters to {0} in the marshalling code prior to passing them on to the QMP functions. Signed-off-by: Michael Roth Reported-by: Peter Maydell Tested-by: Peter Maydell Reviewed-by: Eric Blake Reviewed-by: Markus Armbruster Signed-off-by: Luiz Capitulino --- diff --git a/scripts/qapi-commands.py b/scripts/qapi-commands.py index 386f17ef44..7d93d01ed2 100644 --- a/scripts/qapi-commands.py +++ b/scripts/qapi-commands.py @@ -111,7 +111,7 @@ bool has_%(argname)s = false; argname=c_var(argname), argtype=c_type(argtype)) else: ret += mcgen(''' -%(argtype)s %(argname)s; +%(argtype)s %(argname)s = {0}; ''', argname=c_var(argname), argtype=c_type(argtype))