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From:   Andrey Konovalov <andreyknvl@gmail.com>
Date:   Tue, 8 Mar 2022 16:30:46 +0100
Message-ID: <CA+fCnZdCZ92BxnympNoRP8+3_gGDMZQgTeaUpga3ctuRq8zPYg@mail.gmail.com>
Subject: Re: [PATCH v6 31/39] kasan, vmalloc: only tag normal vmalloc allocations
To:     Vasily Gorbik <gor@linux.ibm.com>
Cc:     andrey.konovalov@linux.dev,
        Andrew Morton <akpm@linux-foundation.org>,
        Marco Elver <elver@google.com>,
        Alexander Potapenko <glider@google.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Andrey Ryabinin <ryabinin.a.a@gmail.com>,
        kasan-dev <kasan-dev@googlegroups.com>,
        Linux Memory Management List <linux-mm@kvack.org>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Peter Collingbourne <pcc@google.com>,
        Evgenii Stepanov <eugenis@google.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Andrey Konovalov <andreyknvl@google.com>,
        Ilya Leoshkevich <iii@linux.ibm.com>
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On Tue, Mar 8, 2022 at 4:17 PM Vasily Gorbik <gor@linux.ibm.com> wrote:
>
> On Mon, Jan 24, 2022 at 07:05:05PM +0100, andrey.konovalov@linux.dev wrote:
> > From: Andrey Konovalov <andreyknvl@google.com>
> >
> > The kernel can use to allocate executable memory. The only supported way
> > to do that is via __vmalloc_node_range() with the executable bit set in
> > the prot argument. (vmap() resets the bit via pgprot_nx()).
> >
> > Once tag-based KASAN modes start tagging vmalloc allocations, executing
> > code from such allocations will lead to the PC register getting a tag,
> > which is not tolerated by the kernel.
> >
> > Only tag the allocations for normal kernel pages.
> >
> > Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
>
> This breaks s390 and produce huge amount of false positives.
> I haven't been testing linux-next with KASAN for while, now tried it with
> next-20220308 and bisected false positives to this commit.
>
> Any idea what is going wrong here?

Hi Vasily,

Could you try the attached fix?

Thanks!

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