linux-kernel - Re: [PATCH v2 3/5] kasan, arm64: don't instrument functions that enable kasan

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Message-ID: <CAAeHK+wVpLvjcwGzD=0FyXiC0+tf6CU0uwh_vfzBXfaCpDyKPg@mail.gmail.com>
Date:   Tue, 4 Aug 2020 15:24:33 +0200
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Catalin Marinas <catalin.marinas@....com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Marco Elver <elver@...gle.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Arvind Sankar <nivedita@...m.mit.edu>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Linux Memory Management List <linux-mm@...ck.org>,
        linux-efi <linux-efi@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Walter Wu <walter-zh.wu@...iatek.com>,
        Elena Petrova <lenaptr@...gle.com>,
        Vincenzo Frascino <vincenzo.frascino@....com>
Subject: Re: [PATCH v2 3/5] kasan, arm64: don't instrument functions that
 enable kasan

On Tue, Aug 4, 2020 at 3:19 PM Catalin Marinas <catalin.marinas@....com> wrote:
>
> On Tue, Aug 04, 2020 at 02:41:26PM +0200, Andrey Konovalov wrote:
> > This patch prepares Software Tag-Based KASAN for stack tagging support.
> >
> > With stack tagging enabled, KASAN tags stack variable in each function
> > in its prologue. In start_kernel() stack variables get tagged before KASAN
> > is enabled via setup_arch()->kasan_init(). As the result the tags for
> > start_kernel()'s stack variables end up in the temporary shadow memory.
> > Later when KASAN gets enabled, switched to normal shadow, and starts
> > checking tags, this leads to false-positive reports, as proper tags are
> > missing in normal shadow.
> >
> > Disable KASAN instrumentation for start_kernel(). Also disable it for
> > arm64's setup_arch() as a precaution (it doesn't have any stack variables
> > right now).
> >
> > Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
>
> I thought I acked this already. Either way:
>
> Acked-by: Catalin Marinas <catalin.marinas@....com>

Sorry, I forgot to include that into v2. Thanks!