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From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Tue, 8 Jan 2019 05:51:20 +0100
Message-ID: <CACT4Y+a_LB6aVoLEcFVJhP40D9E4MM3T=7-0aBhFvBffXgNZmw@mail.gmail.com>
Subject: Re: [PATCH] kasan: fix kasan_check_read/write definitions
To:     Alexander Potapenko <glider@google.com>
Cc:     Arnd Bergmann <arnd@arndb.de>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Anders Roxell <anders.roxell@linaro.org>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Will Deacon <will.deacon@arm.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Andrey Konovalov <andreyknvl@google.com>,
        Stephen Rothwell <sfr@canb.auug.org.au>,
        kasan-dev <kasan-dev@googlegroups.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Linux-MM <linux-mm@kvack.org>,
        Nathan Chancellor <natechancellor@gmail.com>
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On Tue, Jan 8, 2019 at 3:27 AM Nathan Chancellor
<natechancellor@gmail.com> wrote:
>
> On Tue, Dec 11, 2018 at 02:34:35PM +0100, Arnd Bergmann wrote:
> > Building little-endian allmodconfig kernels on arm64 started failing
> > with the generated atomic.h implementation, since we now try to call
> > kasan helpers from the EFI stub:
> >
> > aarch64-linux-gnu-ld: drivers/firmware/efi/libstub/arm-stub.stub.o: in function `atomic_set':
> > include/generated/atomic-instrumented.h:44: undefined reference to `__efistub_kasan_check_write'
> >
> > I suspect that we get similar problems in other files that explicitly
> > disable KASAN for some reason but call atomic_t based helper functions.
> >
> > We can fix this by checking the predefined __SANITIZE_ADDRESS__ macro
> > that the compiler sets instead of checking CONFIG_KASAN, but this in turn
> > requires a small hack in mm/kasan/common.c so we do see the extern
> > declaration there instead of the inline function.
> >
> > Fixes: b1864b828644 ("locking/atomics: build atomic headers as required")
> > Reported-by: Anders Roxell <anders.roxell@linaro.org>
> > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> > ---
> >  include/linux/kasan-checks.h | 2 +-
> >  mm/kasan/common.c            | 2 ++
> >  2 files changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/include/linux/kasan-checks.h b/include/linux/kasan-checks.h
> > index d314150658a4..a61dc075e2ce 100644
> > --- a/include/linux/kasan-checks.h
> > +++ b/include/linux/kasan-checks.h
> > @@ -2,7 +2,7 @@
> >  #ifndef _LINUX_KASAN_CHECKS_H
> >  #define _LINUX_KASAN_CHECKS_H
> >
> > -#ifdef CONFIG_KASAN
> > +#if defined(__SANITIZE_ADDRESS__) || defined(__KASAN_INTERNAL)
> >  void kasan_check_read(const volatile void *p, unsigned int size);
> >  void kasan_check_write(const volatile void *p, unsigned int size);
> >  #else
> > diff --git a/mm/kasan/common.c b/mm/kasan/common.c
> > index 03d5d1374ca7..51a7932c33a3 100644
> > --- a/mm/kasan/common.c
> > +++ b/mm/kasan/common.c
> > @@ -14,6 +14,8 @@
> >   *
> >   */
> >
> > +#define __KASAN_INTERNAL
> > +
> >  #include <linux/export.h>
> >  #include <linux/interrupt.h>
> >  #include <linux/init.h>
> > --
> > 2.20.0
> >
>
> Hi all,
>
> Was there any other movement on this patch? I am noticing this fail as
> well and I have applied this patch in the meantime; it would be nice for
> it to be merged so I could drop it from my stack.

Alexander, ping, you wanted to double-check re KMSAN asm
instrumentation and then decide on a common approach for KASAN and
KMSAN.