From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:52619) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1V59sI-0000Lt-IC for qemu-devel@nongnu.org; Fri, 02 Aug 2013 03:34:16 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1V59sC-0000Uw-FA for qemu-devel@nongnu.org; Fri, 02 Aug 2013 03:34:10 -0400 Received: from oxygen.pond.sub.org ([2a01:4f8:121:10e4::3]:56190) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1V59sC-0000Tu-5G for qemu-devel@nongnu.org; Fri, 02 Aug 2013 03:34:04 -0400 From: Markus Armbruster Date: Fri, 2 Aug 2013 09:34:00 +0200 Message-Id: <1375428840-5275-1-git-send-email-armbru@redhat.com> Subject: [Qemu-devel] [PATCH] qemu-option: Guard against qemu_opts_set_defaults() misuse List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: peter.maydell@linaro.org, aliguori@us.ibm.com Commit 6d4cd40 fixed qemu_opts_set_defaults() for an existing corner case, but broke it for another one that can't be reached in current code. Quote from its commit message: I believe [opts_parse()] attempts to do the following: If options don't yet exist, create new options Else, if defaults, modify the existing options Else, if list->merge_lists, modify the existing options Else, fail The only caller that passes true for defaults is qemu_opts_set_defaults(). The commit message then claims: A straightforward call of qemu_opts_create() does exactly that. Wrong. When !list->merge_lists, and the option string doesn't contain id=, and options without ID exist, then we don't actually modify the existing options, we create new ones. Not reachable, because we never pass lists with !list->merge_lists to qemu_opts_set_defaults(). Guard against possible (if unlikely) future misuse with assert(). Reported-by: Peter Maydell Signed-off-by: Markus Armbruster --- util/qemu-option.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/util/qemu-option.c b/util/qemu-option.c index 7a1552a..4ebdc4c 100644 --- a/util/qemu-option.c +++ b/util/qemu-option.c @@ -928,6 +928,15 @@ static QemuOpts *opts_parse(QemuOptsList *list, const char *params, get_opt_value(value, sizeof(value), p+4); id = value; } + + /* + * This code doesn't work for defaults && !list->merge_lists: when + * params has no id=, and list has an element with !opts->id, it + * appends a new element instead of returning the existing opts. + * However, we got no use for this case. Guard against possible + * (if unlikely) future misuse: + */ + assert(!defaults || list->merge_lists); opts = qemu_opts_create(list, id, !defaults, &local_err); if (opts == NULL) { if (error_is_set(&local_err)) { -- 1.7.11.7