From fc13d937269c1cd01a4b7720c1dcce01722727a2 Mon Sep 17 00:00:00 2001 From: Michael Roth Date: Tue, 20 May 2014 12:20:39 -0500 Subject: [PATCH] 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 --- scripts/qapi-commands.py | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) 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 @@ def gen_visitor_input_vars_decl(args): 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))