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From:   Daniel Axtens <dja@axtens.net>
To:     Mark Rutland <mark.rutland@arm.com>
Cc:     Andrey Ryabinin <aryabinin@virtuozzo.com>,
        kasan-dev@googlegroups.com, linux-mm@kvack.org, x86@kernel.org,
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        dvyukov@google.com, christophe.leroy@c-s.fr,
        linuxppc-dev@lists.ozlabs.org, gor@linux.ibm.com
Subject: Re: [PATCH v8 1/5] kasan: support backing vmalloc space with real shadow memory
In-Reply-To: <20191014152717.GA20438@lakrids.cambridge.arm.com>
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Date:   Tue, 15 Oct 2019 17:32:03 +1100
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> There is a potential problem here, as Will Deacon wrote up at:
>
>   https://lore.kernel.org/linux-arm-kernel/20190827131818.14724-1-will@kernel.org/
>
> ... in the section starting:
>
> | *** Other architecture maintainers -- start here! ***
>
> ... whereby the CPU can spuriously fault on an access after observing a
> valid PTE.
>
> For arm64 we handle the spurious fault, and it looks like x86 would need
> something like its vmalloc_fault() applying to the shadow region to
> cater for this.

I'm not really up on x86 - my first thought would be that their stronger
memory ordering might be sufficient but I really don't know. Reading the
thread I see arm and powerpc discussions but nothing from anyone else,
so I'm none the wiser there...

Andy, do you have any thoughts?

Regards,
Daniel

>
> Thanks,
> Mark.