linux-kernel - Re: [PATCH v4 5/5] arm64: Kconfig: select KASAN_VMALLOC if KANSAN

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Date:   Mon, 29 Mar 2021 13:54:49 +0100
From:   Will Deacon <will@...nel.org>
To:     Lecopzer Chen <lecopzer.chen@...iatek.com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kasan-dev@...glegroups.com, catalin.marinas@....com,
        ryabinin.a.a@...il.com, glider@...gle.com, andreyknvl@...il.com,
        dvyukov@...gle.com, akpm@...ux-foundation.org,
        tyhicks@...ux.microsoft.com, maz@...nel.org, rppt@...nel.org,
        linux@...ck-us.net, gustavoars@...nel.org, yj.chiang@...iatek.com
Subject: Re: [PATCH v4 5/5] arm64: Kconfig: select KASAN_VMALLOC if
 KANSAN_GENERIC is enabled

On Wed, Mar 24, 2021 at 12:05:22PM +0800, Lecopzer Chen wrote:
> Before this patch, someone who wants to use VMAP_STACK when
> KASAN_GENERIC enabled must explicitly select KASAN_VMALLOC.
> 
> From Will's suggestion [1]:
>   > I would _really_ like to move to VMAP stack unconditionally, and
>   > that would effectively force KASAN_VMALLOC to be set if KASAN is in use
> 
> Because VMAP_STACK now depends on either HW_TAGS or KASAN_VMALLOC if
> KASAN enabled, in order to make VMAP_STACK selected unconditionally,
> we bind KANSAN_GENERIC and KASAN_VMALLOC together.
> 
> Note that SW_TAGS supports neither VMAP_STACK nor KASAN_VMALLOC now,
> so this is the first step to make VMAP_STACK selected unconditionally.

Do you know if anybody is working on this? It's really unfortunate that
we can't move exclusively to VMAP_STACK just because of SW_TAGS KASAN.

That said, what is there to do? As things stand, won't kernel stack
addresses end up using KASAN_TAG_KERNEL?

Will