From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36077) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Wn6jD-0002DF-Kh for qemu-devel@nongnu.org; Wed, 21 May 2014 09:38:48 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Wn6j9-0003Ji-1o for qemu-devel@nongnu.org; Wed, 21 May 2014 09:38:43 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41409) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Wn6j8-0003JW-PN for qemu-devel@nongnu.org; Wed, 21 May 2014 09:38:38 -0400 Date: Wed, 21 May 2014 09:27:47 -0400 From: Luiz Capitulino Message-ID: <20140521092747.2deeffb3@redhat.com> In-Reply-To: <1400606439-19899-1-git-send-email-mdroth@linux.vnet.ibm.com> References: <1400606439-19899-1-git-send-email-mdroth@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] qapi: zero-initialize all QMP command parameters List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Michael Roth Cc: famz@redhat.com, peter.maydell@linaro.org, qemu-devel@nongnu.org, armbru@redhat.com On Tue, 20 May 2014 12:20:39 -0500 Michael Roth wrote: > 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 > --- > scripts/qapi-commands.py | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) Applied to the qmp branch, thanks. > > diff --git a/scripts/qapi-commands.py b/scripts/qapi-commands.py > index 386f17e..7d93d01 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)) >