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From:   Haibo Li <haibo.li@mediatek.com>
To:     <jannh@google.com>
CC:     <akpm@linux-foundation.org>, <andreyknvl@gmail.com>,
        <angelogioacchino.delregno@collabora.com>, <dvyukov@google.com>,
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        <ryabinin.a.a@gmail.com>, <vincenzo.frascino@arm.com>,
        <xiaoming.yu@mediatek.com>
Subject: Re: [PATCH] kasan:fix access invalid shadow address when input is illegal
Date:   Mon, 18 Sep 2023 16:12:50 +0800
Message-ID: <20230918081250.143237-1-haibo.li@mediatek.com>
In-Reply-To: <CAG48ez3GSubTFA8+hw=YDZoVHC79JVwNi+xFTQt9ssy_+O1aaw@mail.gmail.com>
References: <CAG48ez3GSubTFA8+hw=YDZoVHC79JVwNi+xFTQt9ssy_+O1aaw@mail.gmail.com>
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> On Fri, Sep 15, 2023 at 6:51 PM Andrey Konovalov <andreyknvl@gmail.com> wrote:
> > On Fri, Sep 15, 2023 at 4:46 AM 'Haibo Li' via kasan-dev
> > <kasan-dev@googlegroups.com> wrote:
> > >
> > > The patch checks each shadow address,so it introduces extra overhead.
> >
> > Ack. Could still be fine, depends on the overhead.
> >
> > But if the message printed by kasan_non_canonical_hook is good enough
> > for your use case, I would rather stick to that.
If we check shadow address before invalid access,
we get below message before oops:
"
BUG: KASAN: invalid-access in do_ib_ob+0xf4/0x110
Read of size 8 at addr caffff80aaaaaaaa by task sh/100
"

We get below message while using kasan_non_canonical_hook:
"
Unable to handle kernel paging request at virtual address ffffff80aaaaaaaa
KASAN: maybe wild-memory-access in range [0xfffffc0aaaaaaaa0-0xfffffc0aaaaaaaaf]
"

Both indicate the original accessed address which causes oops.

> >
> > > Now kasan_non_canonical_hook only works for CONFIG_KASAN_INLINE.
> > >
> > > And CONFIG_KASAN_OUTLINE is set in my case.
> > >
> > > Is it possible to make kasan_non_canonical_hook works for both
> > > INLINE and OUTLINE by simply remove the "#ifdef CONFIG_KASAN_INLINE"?
> >
> > Yes, it should just work if you remove the ifdefs in mm/kasan/report.c
> > and in include/linux/kasan.h.
> >
> > Jann, do you have any objections to enabling kasan_non_canonical_hook
> > for the outline mode too?
>
> No objections from me.

Thanks.
Shall I send a new patch to fix this problem by using kasan_non_canonical_hook