From: Will Deacon <will@kernel.org>
To: Lecopzer Chen <lecopzer@gmail.com>
Cc: akpm@linux-foundation.org, andreyknvl@google.com,
ardb@kernel.org, aryabinin@virtuozzo.com, broonie@kernel.org,
catalin.marinas@arm.com, dan.j.williams@intel.com,
dvyukov@google.com, glider@google.com, gustavoars@kernel.org,
kasan-dev@googlegroups.com, lecopzer.chen@mediatek.com,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, linux-mediatek@lists.infradead.org,
linux-mm@kvack.org, linux@roeck-us.net, robin.murphy@arm.com,
rppt@kernel.org, tyhicks@linux.microsoft.com,
vincenzo.frascino@arm.com, yj.chiang@mediatek.com
Subject: Re: [PATCH v2 0/4] arm64: kasan: support CONFIG_KASAN_VMALLOC
Date: Thu, 4 Feb 2021 17:57:00 +0000 [thread overview]
Message-ID: <20210204175659.GC21303@willie-the-truck> (raw)
In-Reply-To: <20210204155346.88028-1-lecopzer@gmail.com>
On Thu, Feb 04, 2021 at 11:53:46PM +0800, Lecopzer Chen wrote:
> > On Sat, Jan 09, 2021 at 06:32:48PM +0800, Lecopzer Chen 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.
> >
> > The one thing I've failed to grok from your series is how you deal with
> > vmalloc allocations where the shadow overlaps with the shadow which has
> > already been allocated for the kernel image. Please can you explain?
>
>
> The most key point is we don't map anything in the vmalloc shadow address.
> So we don't care where the kernel image locate inside vmalloc area.
>
> kasan_map_populate(kimg_shadow_start, kimg_shadow_end,...)
>
> Kernel image was populated with real mapping in its shadow address.
> I `bypass' the whole shadow of vmalloc area, the only place you can find
> about vmalloc_shadow is
> kasan_populate_early_shadow((void *)vmalloc_shadow_end,
> (void *)KASAN_SHADOW_END);
>
> ----------- vmalloc_shadow_start
> | |
> | |
> | | <= non-mapping
> | |
> | |
> |-----------|
> |///////////|<- kimage shadow with page table mapping.
> |-----------|
> | |
> | | <= non-mapping
> | |
> ------------- vmalloc_shadow_end
> |00000000000|
> |00000000000| <= Zero shadow
> |00000000000|
> ------------- KASAN_SHADOW_END
>
> vmalloc shadow will be mapped 'ondemend', see kasan_populate_vmalloc()
> in mm/vmalloc.c in detail.
> So the shadow of vmalloc will be allocated later if anyone use its va.
Indeed, but the question I'm asking is what happens when an on-demand shadow
allocation from vmalloc overlaps with the shadow that we allocated early for
the kernel image?
Sounds like I have to go and read the code...
Will
next prev parent reply other threads:[~2021-02-04 17:59 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-09 10:32 [PATCH v2 0/4] arm64: kasan: support CONFIG_KASAN_VMALLOC Lecopzer Chen
2021-01-09 10:32 ` [PATCH v2 1/4] arm64: kasan: don't populate vmalloc area for CONFIG_KASAN_VMALLOC Lecopzer Chen
2021-02-03 18:37 ` Ard Biesheuvel
2021-02-04 6:21 ` Lecopzer Chen
2021-02-04 12:45 ` Will Deacon
2021-02-04 14:46 ` Lecopzer Chen
2021-02-04 15:01 ` Will Deacon
2021-02-04 16:37 ` Lecopzer Chen
2021-02-05 17:18 ` Will Deacon
2021-02-05 17:30 ` Andrey Konovalov
2021-02-05 17:43 ` Will Deacon
2021-02-05 20:50 ` Andrey Konovalov
2021-02-05 18:10 ` Lecopzer Chen
2021-01-09 10:32 ` [PATCH v2 2/4] arm64: kasan: abstract _text and _end to KERNEL_START/END Lecopzer Chen
2021-02-04 12:46 ` Will Deacon
2021-02-04 14:51 ` Lecopzer Chen
2021-02-04 14:55 ` Will Deacon
2021-02-04 16:06 ` Lecopzer Chen
2021-02-05 17:02 ` Will Deacon
2021-01-09 10:32 ` [PATCH v2 3/4] arm64: Kconfig: support CONFIG_KASAN_VMALLOC Lecopzer Chen
2021-01-09 10:32 ` [PATCH v2 4/4] arm64: kaslr: support randomized module area with KASAN_VMALLOC Lecopzer Chen
2021-01-27 23:04 ` Will Deacon
2021-01-28 8:53 ` Lecopzer Chen
2021-01-28 20:26 ` Will Deacon
2021-01-21 10:19 ` [PATCH v2 0/4] arm64: kasan: support CONFIG_KASAN_VMALLOC Lecopzer Chen
2021-01-21 17:44 ` Andrey Konovalov
2021-01-22 19:05 ` Will Deacon
2021-02-03 18:31 ` Ard Biesheuvel
2021-02-04 12:49 ` Will Deacon
2021-02-04 15:53 ` Lecopzer Chen
2021-02-04 17:57 ` Will Deacon [this message]
2021-02-04 18:41 ` Lecopzer Chen
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