From: Kees Cook <keescook@chromium.org>
To: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Alexander Potapenko <glider@google.com>,
Nick Desaulniers <ndesaulniers@google.com>,
Kostya Serebryany <kcc@google.com>,
Dmitry Vyukov <dvyukov@google.com>,
Sandeep Patil <sspatil@android.com>,
Laura Abbott <labbott@redhat.com>,
Randy Dunlap <rdunlap@infradead.org>,
Alexander Popov <alpopov@ptsecurity.com>,
Michal Marek <michal.lkml@markovi.net>,
Emese Revfy <re.emese@gmail.com>,
James Morris <jmorris@namei.org>,
"Serge E. Hallyn" <serge@hallyn.com>,
Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-security-module <linux-security-module@vger.kernel.org>,
Kernel Hardening <kernel-hardening@lists.openwall.com>
Subject: Re: [PATCH 3/3] kbuild: Implement Clang's stack initialization
Date: Thu, 11 Apr 2019 10:07:14 -0700 [thread overview]
Message-ID: <CAGXu5jJYPO7buixedop=8e_e+Pf-4nmkz-iS3EV5CXC0obKpdA@mail.gmail.com> (raw)
In-Reply-To: <CAK7LNAQpm5Tz_Fo0rSq00emB7BLnfYB-+mwXd9GiMKAqKCfkrA@mail.gmail.com>
On Thu, Apr 11, 2019 at 1:06 AM Masahiro Yamada
<yamada.masahiro@socionext.com> wrote:
>
> On Thu, Apr 11, 2019 at 1:16 AM Kees Cook <keescook@chromium.org> wrote:
> >
> > CONFIG_INIT_STACK_ALL turns on stack initialization based on
> > -ftrivial-auto-var-init in Clang builds and on
> > -fplugin-arg-structleak_plugin-byref-all in GCC builds.
>
> Is CONFIG_INIT_STACK_ALL wired up to GCC plugin in any way?
> I could not understand it from the code.
No, it's only available under Clang. Clang is all-or-nothing, and the
GCC plugin has a degrees up to "all passed by reference" which isn't
truly "all" (i.e. Clang will initialize variables that aren't passed
by reference and trigger a compiler warning about being
uninitialized.)
> > choice
> > prompt "Initialize kernel stack variables at function entry"
> > depends on CC_HAS_AUTO_VAR_INIT || GCC_PLUGINS
> > + default INIT_STACK_ALL if CC_HAS_AUTO_VAR_INIT
>
> Why should this be enabled by default?
> Ins't it a performance regression
> since it inserts instructions in function prologue?
There are very few users of Clang right now (mainly Android), so I
figured it'd be nice to start Clang builds from a "protected by
default" here, especially given Linus's thoughts on making this always
happen[1]. I don't want to do it for GCC yet, since that would likely
come as a huge surprise to everyone else. :) But I'm happy to change
this, of course.
-Kees
[1] https://lkml.kernel.org/r/CA+55aFykZL+cSBJjBBts7ebEFfyGPdMzTmLSxKnT_29=j942dA@mail.gmail.com
--
Kees Cook
next prev parent reply other threads:[~2019-04-11 17:07 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-10 16:16 [PATCH 0/3] Kconfig: Refactor memory initialization hardening Kees Cook
2019-04-10 16:16 ` [PATCH 1/3] Kconfig: Create "kernel hardening" config area Kees Cook
2019-04-11 8:50 ` Masahiro Yamada
2019-04-11 16:59 ` Kees Cook
2019-04-10 16:16 ` [PATCH 2/3] kbuild: Move stackleak config to Kconfig.hardening Kees Cook
2019-04-10 16:16 ` [PATCH 3/3] kbuild: Implement Clang's stack initialization Kees Cook
2019-04-11 8:05 ` Masahiro Yamada
2019-04-11 17:07 ` Kees Cook [this message]
2019-04-11 7:59 ` [PATCH 0/3] Kconfig: Refactor memory initialization hardening Masahiro Yamada
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