linux-kernel - Re: [PATCH] structleak: disable BYREF_ALL in combination with KASAN

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Date:   Thu, 20 Jun 2019 10:35:56 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>, kasan-dev@...glegroups.com,
        Alexander Popov <alex.popov@...ux.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] structleak: disable BYREF_ALL in combination with
 KASAN_STACK

On Tue, Jun 18, 2019 at 11:47:13AM +0200, Arnd Bergmann wrote:
> The combination of KASAN_STACK and GCC_PLUGIN_STRUCTLEAK_BYREF_ALL
> leads to much larger kernel stack usage, as seen from the warnings
> about functions that now exceed the 2048 byte limit:

Is the preference that this go into v5.2 (there's not much time left),
or should this be v5.3? (You didn't mark it as Cc: stable?)

> one. I picked the dependency in GCC_PLUGIN_STRUCTLEAK_BYREF_ALL, as
> this option is designed to make uninitialized stack usage less harmful
> when enabled on its own, but it also prevents KASAN from detecting those
> cases in which it was in fact needed.

Right -- there's not much sense in both being enabled. I'd agree with
this rationale.

-- 
Kees Cook