linux-kernel - Re: [PATCH 0/3] arm64: kasan: support CONFIG_KASAN

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Message-ID: <CAAeHK+xaVvvMfd8LhPssYi+mjS-3OVsDaiNq2Li+J7JLF6k3Gg@mail.gmail.com>
Date:   Fri, 8 Jan 2021 19:37:08 +0100
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Lecopzer Chen <lecopzer@...il.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-mediatek@...ts.infradead.org, yj.chiang@...iatek.com,
        Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Lecopzer Chen <lecopzer.chen@...iatek.com>
Subject: Re: [PATCH 0/3] arm64: kasan: support CONFIG_KASAN_VMALLOC

On Sun, Jan 3, 2021 at 6:12 PM Lecopzer Chen <lecopzer@...il.com> wrote:
>
> Linux supports KAsan for VMALLOC since commit 3c5c3cfb9ef4da9
> ("kasan: support backing vmalloc space with real shadow memory")
>
> Acroding to how x86 ported it [1], they early allocated p4d and pgd,
> but in arm64 I just simulate how KAsan supports MODULES_VADDR in arm64
> by not to populate the vmalloc area except for kimg address.
>
> Test environment:
>     4G and 8G Qemu virt,
>     39-bit VA + 4k PAGE_SIZE with 3-level page table,
>     test by lib/test_kasan.ko and lib/test_kasan_module.ko
>
> It also works in Kaslr with CONFIG_RANDOMIZE_MODULE_REGION_FULL,
> but not test for HW_TAG(I have no proper device), thus keep
> HW_TAG and KASAN_VMALLOC mutual exclusion until confirming
> the functionality.

Re this: it makes sense to introduce vmalloc support one step a time
and add SW_TAGS support before taking on HW_TAGS. SW_TAGS doesn't
require any special hardware. Working on SW_TAGS first will also allow
dealing with potential conflicts between vmalloc and tags without
having MTE in the picture as well. Just FYI, no need to include that
in this change.