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Message-ID: <CAGXu5jLdc7dHbjd1ZTNuc2=Bk3zTNeXd8EGT-YUcG-0gkp3+jg@mail.gmail.com>
Date: Tue, 20 Jun 2017 12:14:34 -0700
From: Kees Cook <keescook@...omium.org>
To: Alexander Popov <alex.popov@...ux.com>
Cc: "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, PaX Team <pageexec@...email.hu>,
Brad Spengler <spender@...ecurity.net>, Tycho Andersen <tycho@...ker.com>
Subject: Re: [PATCH RFC v2 1/1] gcc-plugins: Add stackleak feature erasing the
kernel stack at the end of syscalls
On Fri, Jun 9, 2017 at 7:30 AM, Alexander Popov <alex.popov@...ux.com> wrote:
> diff --git a/scripts/gcc-plugins/stackleak_plugin.c b/scripts/gcc-plugins/stackleak_plugin.c
> new file mode 100644
> index 0000000..2ee49c4
> --- /dev/null
> +++ b/scripts/gcc-plugins/stackleak_plugin.c
> [...]
> + * TODO:
> + * - initialize all local variables
> [...]
> +static bool init_locals;
> +
> +static struct plugin_info stackleak_plugin_info = {
> + .version = "201602181345",
> + .help = "track-lowest-sp=nn\ttrack sp in functions whose frame size is at least nn bytes\n"
> +// "initialize-locals\t\tforcibly initialize all stack frames\n"
> +};
> [...]
> + for (i = 0; i < argc; ++i) {
> + if (!strcmp(argv[i].key, "track-lowest-sp")) {
> + if (!argv[i].value) {
> + error(G_("no value supplied for option '-fplugin-arg-%s-%s'"), plugin_name, argv[i].key);
> + continue;
> + }
> + track_frame_size = atoi(argv[i].value);
> + if (argv[i].value[0] < '0' || argv[i].value[0] > '9' || track_frame_size < 0)
> + error(G_("invalid option argument '-fplugin-arg-%s-%s=%s'"), plugin_name, argv[i].key, argv[i].value);
> + continue;
> + }
> + if (!strcmp(argv[i].key, "initialize-locals")) {
> + if (argv[i].value) {
> + error(G_("invalid option argument '-fplugin-arg-%s-%s=%s'"), plugin_name, argv[i].key, argv[i].value);
> + continue;
> + }
> + init_locals = true;
> + continue;
> + }
> + error(G_("unknown option '-fplugin-arg-%s-%s'"), plugin_name, argv[i].key);
> + }
Just noticed this: there is an undocumented "initialize-locals" plugin
argument that set an unused init_locals variables. (And it's
unused-ness matches the TODO at the top.)
Probably the unused arg/var should be dropped (or better yet:
implemented to do the initialization).
-Kees
--
Kees Cook
Pixel Security
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