linux-kernel - Re: [PATCH 0/3] arm64: kasan: support CONFIG_KASAN

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Message-ID: <20210109100205.11359-1-lecopzer.chen@mediatek.com>
Date:   Sat, 9 Jan 2021 18:02:05 +0800
From:   Lecopzer Chen <lecopzer.chen@...iatek.com>
To:     <ardb@...nel.org>
CC:     <akpm@...ux-foundation.org>, <andreyknvl@...gle.com>,
        <aryabinin@...tuozzo.com>, <catalin.marinas@....com>,
        <dan.j.williams@...el.com>, <dvyukov@...gle.com>,
        <glider@...gle.com>, <kasan-dev@...glegroups.com>,
        <lecopzer.chen@...iatek.com>, <lecopzer@...il.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-mediatek@...ts.infradead.org>, <linux-mm@...ck.org>,
        <will@...nel.org>, <yj.chiang@...iatek.com>
Subject: Re: [PATCH 0/3] arm64: kasan: support CONFIG_KASAN_VMALLOC

Hi Ard,

> On Fri, 8 Jan 2021 at 19:31, Andrey Konovalov <andreyknvl@...gle.com> wrote:
> >
> > On Sun, Jan 3, 2021 at 6:12 PM Lecopzer Chen <lecopzer@...il.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@...iatek.com>
> >
> > Hi Lecopzer,
> >
> > Thanks for working on this!
> >
> > Acked-by: Andrey Konovalov <andreyknvl@...gle.com>
> > Tested-by: Andrey Konovalov <andreyknvl@...gle.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.
> 

I've tested supporting module region randomized and It looks fine
in some easy test(insmod some modules).

I'll add this to patch v2, thanks for your suggestion.

BRs,
Lecopzer