linux-kernel - Re: [PATCH 1/2] gcc-plugins: structleak: Generalize to all variable types

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Date:   Sat, 2 Mar 2019 23:15:53 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Kees Cook <keescook@...omium.org>
Cc:     Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Emese Revfy <re.emese@...il.com>,
        Alexander Popov <alex.popov@...ux.com>,
        Laura Abbott <labbott@...hat.com>,
        Jann Horn <jannh@...gle.com>,
        Alexander Potapenko <glider@...gle.com>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>
Subject: Re: [PATCH 1/2] gcc-plugins: structleak: Generalize to all variable types

On Sat, Mar 2, 2019 at 4:43 PM Kees Cook <keescook@...omium.org> wrote:
>
> On Sat, Mar 2, 2019 at 1:05 AM Ard Biesheuvel <ard.biesheuvel@...aro.org> wrote:
> >
> > On Thu, 28 Feb 2019 at 21:27, Arnd Bergmann <arnd@...db.de> wrote:
> > > I get similar results with asan-stack=1 but without your plugin, only
> > > the combination of the two has the explosive stack size growth.
>
> I can look more closely, but I'm not sure it's entirely worth it:
> these two may not make sense to build at the same time. (e.g. the
> use-after-scope config was disallowed to work with this plugin.)

Well, I still want to make sure all 'randconfig' builds complete without
warnings, and without having to turn off the otherwise useful
stack overflow warnings.

One thing I noticed is that your patch removes the 'depends on
!COMPILE_TEST' check for GCC_PLUGIN_STRUCTLEAK_BYREF_ALL,
so if we add that back in, it would at least take care of the
allmodconfig and randconfig cases.

> > > I can help analyze this further, but maybe you can have a look first,
> > > there might be something obvious when you read the input to the
> > > plugin.
> > >
> >
> > Is this before or after use-after-scope was disabled entirely?
>
> I was wondering the same thing, but I assumed it didn't matter: it
> wasn't possible to use both before it was entirely disabled.

Right. I already had the use-after-scope stuff disabled for
build testing, using the same 'depends on !COMPILE_TEST'
check, so one more reason it did not make a difference.

      Arnd