linux-kernel - Re: [PATCH 41/43] security: kmsan: fix interoperability with auto-initialization

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Date:   Tue, 14 Dec 2021 18:00:41 +0100
From:   Alexander Potapenko <glider@...gle.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
        Christoph Hellwig <hch@....de>,
        Christoph Lameter <cl@...ux.com>,
        David Rientjes <rientjes@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Ilya Leoshkevich <iii@...ux.ibm.com>,
        Ingo Molnar <mingo@...hat.com>, Jens Axboe <axboe@...nel.dk>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Kees Cook <keescook@...omium.org>,
        Marco Elver <elver@...gle.com>,
        Matthew Wilcox <willy@...radead.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Pekka Enberg <penberg@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Vegard Nossum <vegard.nossum@...cle.com>,
        Vlastimil Babka <vbabka@...e.cz>, linux-mm@...ck.org,
        linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 41/43] security: kmsan: fix interoperability with auto-initialization

On Tue, Dec 14, 2021 at 5:38 PM Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
>
> > @@ -124,6 +125,7 @@ choice
> >       config INIT_STACK_ALL_ZERO
> >               bool "zero-init everything (strongest and safest)"
> >               depends on CC_HAS_AUTO_VAR_INIT_ZERO
> > +             depends on !KMSAN
>
> So this means KMSAN is a developer debugging feature only and should
> never be turned on on a real device/server that has users?

100% correct. KMSAN is way slower than KASAN, it also eats 2/3 of your
memory to store the metadata.
I thought it was sort of self-evident, but I can surely mention this
explicitly in the cover letter.