Re: [PATCH 0/3] arm64: kasan: support CONFIG_KASAN_VMALLOC

From: Ard Biesheuvel <ardb@kernel.org>
To: Andrey Konovalov <andreyknvl@google.com>
Cc: Lecopzer Chen <lecopzer@gmail.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Lecopzer Chen <lecopzer.chen@mediatek.com>,
	yj.chiang@mediatek.com, linux-mediatek@lists.infradead.org,
	LKML <linux-kernel@vger.kernel.org>,
	kasan-dev <kasan-dev@googlegroups.com>,
	Linux Memory Management List <linux-mm@kvack.org>,
	Alexander Potapenko <glider@google.com>,
	Dmitry Vyukov <dvyukov@google.com>,
	Andrey Ryabinin <aryabinin@virtuozzo.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 0/3] arm64: kasan: support CONFIG_KASAN_VMALLOC
Date: Fri, 8 Jan 2021 19:41:37 +0100	[thread overview]
Message-ID: <CAMj1kXHFOQMV_4pYp9u9u++2jjQbHuLU95KeJTzrWXZWQTe_Tg@mail.gmail.com> (raw)
In-Reply-To: <CAAeHK+y=vEuSe-LFOhxkEu4x0Dy2jYts18R0V6Pbv1-5Cwg9_g@mail.gmail.com>

On Fri, 8 Jan 2021 at 19:31, Andrey Konovalov <andreyknvl@google.com> wrote:
>
> On Sun, Jan 3, 2021 at 6:12 PM Lecopzer Chen <lecopzer@gmail.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.
> >
> >
> > [1]: commit 0609ae011deb41c ("x86/kasan: support KASAN_VMALLOC")
> >
> > Signed-off-by: Lecopzer Chen <lecopzer.chen@mediatek.com>
>
> Hi Lecopzer,
>
> Thanks for working on this!
>
> Acked-by: Andrey Konovalov <andreyknvl@google.com>
> Tested-by: Andrey Konovalov <andreyknvl@google.com>
>
> for the series along with the other two patches minding the nit in patch #3.
>
> Will, Catalin, could you please take a look at the arm changes?
>
> Thanks!
>

If vmalloc can now be backed with real shadow memory, we no longer
have to keep the module region in its default location when KASLR and
KASAN are both enabled.

So the check on line 164 in arch/arm64/kernel/kaslr.c should probably
be updated to reflect this change.