From: Lecopzer Chen <lecopzer@gmail.com>
To: Will Deacon <will@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Andrey Konovalov <andreyknvl@google.com>,
ardb@kernel.org, aryabinin@virtuozzo.com, broonie@kernel.org,
Catalin Marinas <catalin.marinas@arm.com>,
dan.j.williams@intel.com, Dmitry Vyukov <dvyukov@google.com>,
Alexander Potapenko <glider@google.com>,
gustavoars@kernel.org, kasan-dev@googlegroups.com,
Jian-Lin Chen <lecopzer.chen@mediatek.com>,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
Linux Kernel Mailing List <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: Fri, 5 Feb 2021 02:41:34 +0800 [thread overview]
Message-ID: <CANr2M19xc+9UE3dZB5UA8HvgTGAcoSLOPAkeepExcUrKkNHt+g@mail.gmail.com> (raw)
In-Reply-To: <20210204175659.GC21303@willie-the-truck>
> 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...
oh, sorry I misunderstood your question.
FWIW,
I think this won't happend because this mean vmalloc() provides va
which already allocated by kimg, as I know, vmalloc_init() will insert
early allocated vma into its vmalloc rb tree
, and this early allocated vma will include kernel image.
After quick review of mm init code,
this early allocated for vma is at map_kernel() in arch/arm64/mm/mmu.c
BRs
Lecopzer
prev parent reply other threads:[~2021-02-04 18:46 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
2021-02-04 18:41 ` Lecopzer Chen [this message]
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