linux-hardening - Re: [PATCH 01/64] media: omap3isp: Extract struct group for memcpy() region

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Message-ID: <202107301217.46EA9DA@keescook>
Date:   Fri, 30 Jul 2021 12:18:26 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Dan Carpenter <dan.carpenter@...cle.com>, dsterba@...e.cz,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Bart Van Assche <bvanassche@....org>,
        linux-hardening@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Keith Packard <keithpac@...zon.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, linux-wireless@...r.kernel.org,
        netdev@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-staging@...ts.linux.dev, linux-block@...r.kernel.org,
        linux-kbuild@...r.kernel.org, clang-built-linux@...glegroups.com,
        nborisov@...e.com
Subject: Re: [PATCH 01/64] media: omap3isp: Extract struct group for memcpy()
 region

On Fri, Jul 30, 2021 at 10:08:03AM -0700, Nick Desaulniers wrote:
> On Fri, Jul 30, 2021 at 9:44 AM Kees Cook <keescook@...omium.org> wrote:
> >
> > On Fri, Jul 30, 2021 at 12:00:54PM +0300, Dan Carpenter wrote:
> > > On Fri, Jul 30, 2021 at 10:38:45AM +0200, David Sterba wrote:
> > > > Then is explicit memset the only reliable way accross all compiler
> > > > flavors and supported versions?
> > > >
> > >
> > > The = { } initializer works.  It's only when you start partially
> > > initializing the struct that it doesn't initialize holes.
> >
> > No, partial works. It's when you _fully_ initialize the struct where the
> > padding doesn't get initialized. *sob*
> 
> I'm pretty sure that this has more to do with whether or not the
> compiler applies SROA then observes uses of the individual members or
> not.

Ultimately, it's just not consistent, so thank goodness for
-ftrivial-auto-var-init=zero. :)

-- 
Kees Cook