linux-kernel - Re: [PATCH] arm64: kasan: fix phys_to_virt() false positive on tag-based kasan

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Date:   Mon, 19 Aug 2019 13:56:26 +0100
From:   Will Deacon <will@...nel.org>
To:     Walter Wu <walter-zh.wu@...iatek.com>
Cc:     Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        wsd_upstream@...iatek.com, linux-kernel@...r.kernel.org,
        kasan-dev@...glegroups.com, linux-mediatek@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] arm64: kasan: fix phys_to_virt() false positive on
 tag-based kasan

On Mon, Aug 19, 2019 at 07:44:20PM +0800, Walter Wu wrote:
> __arm_v7s_unmap() call iopte_deref() to translate pyh_to_virt address,
> but it will modify pointer tag into 0xff, so there is a false positive.
> 
> When enable tag-based kasan, phys_to_virt() function need to rewrite
> its original pointer tag in order to avoid kasan report an incorrect
> memory corruption.

Hmm. Which tree did you see this on? We've recently queued a load of fixes
in this area, but I /thought/ they were only needed after the support for
52-bit virtual addressing in the kernel.

Will