linux-kernel - Re: KASLR vs. KASAN on x86

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Message-ID: <CAPAsAGzYSi_mCy64rFH=o+m8eT-A9ffttsFO9Wx94=nsj+Q8Jg@mail.gmail.com>
Date:   Mon, 13 Mar 2023 14:40:33 +0100
From:   Andrey Ryabinin <ryabinin.a.a@...il.com>
To:     Michal Koutný <mkoutny@...e.com>
Cc:     Dave Hansen <dave.hansen@...el.com>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Alexander Potapenko <glider@...gle.com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        kasan-dev@...glegroups.com, Kees Cook <keescook@...omium.org>,
        Thomas Garnier <thgarnie@...gle.com>
Subject: Re: KASLR vs. KASAN on x86

On Mon, Mar 13, 2023 at 10:41 AM Michal Koutný <mkoutny@...e.com> wrote:
>
> On Wed, Mar 08, 2023 at 06:24:05PM +0100, Andrey Ryabinin <ryabinin.a.a@...il.com> wrote:
> > So the vmemmap_base and probably some part of vmalloc could easily end
> > up in KASAN shadow.
>
> Would it help to (conditionally) reduce vaddr_end to the beginning of
> KASAN shadow memory?
> (I'm not that familiar with KASAN, so IOW, would KASAN handle
> randomized: linear mapping (__PAGE_OFFSET), vmalloc (VMALLOC_START) and
> vmemmap (VMEMMAP_START) in that smaller range.)
>

Yes, with the vaddr_end = KASAN_SHADOW_START  it should work,
 kaslr_memory_enabled() can be removed in favor of just the kaslr_enabled()

> Thanks,
> Michal