linux-kernel - Re: [PATCH] ARM: kasan: Only map modules if CONFIG_KASAN

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Message-ID: <CACRpkdYgZK1oaceme6-EEuV3F=m1L5B3Y8t6z7Yxrx842dgrFw@mail.gmail.com>
Date:   Wed, 31 Aug 2022 11:30:53 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Alexander A Sverdlin <alexander.sverdlin@...ia.com>
Cc:     kasan-dev@...glegroups.com,
        Lecopzer Chen <lecopzer.chen@...iatek.com>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        Alexander Potapenko <glider@...gle.com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Russell King <linux@...linux.org.uk>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ARM: kasan: Only map modules if CONFIG_KASAN_VMALLOC=n

On Sat, Aug 27, 2022 at 11:32 PM Alexander A Sverdlin
<alexander.sverdlin@...ia.com> wrote:

> -       create_mapping((void *)MODULES_VADDR, (void *)(PKMAP_BASE + PMD_SIZE));
> +       if (!IS_ENABLED(CONFIG_KASAN_VMALLOC) && IS_ENABLED(CONFIG_MODULES))
> +               create_mapping((void *)MODULES_VADDR, (void *)(MODULES_END));

So the way I understand it is that modules are first and foremost loaded into
the area MODULES_VADDR .. MODULES_END, and then after that is out,
they get loaded into VMALLOC. See arch/arm/kernel/module.c, module_alloc().

If you do this, how are the addresses between MODULES_VADDR..MODULES_END
shadowed when using CONFIG_KASAN_VMALLOC?

> +       create_mapping((void *)PKMAP_BASE, (void *)(PKMAP_BASE + PMD_SIZE));

(Splitting this in two steps if probably good in any case.)

Pls keep me on CC for Kasan ARM patches, thanks! (Maybe I should add some
MAINTAINERS blurb.)

Yours,
Linus Walleij