linux-kernel - Re: [PATCH v7 7/7] ARM: Enable KASan for ARM

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Date:   Fri, 10 Apr 2020 12:47:23 +0200
From:   Ard Biesheuvel <ardb@...nel.org>
To:     Florian Fainelli <f.fainelli@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>
Cc:     Mark Rutland <mark.rutland@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Michal Hocko <mhocko@...e.com>,
        Julien Thierry <julien.thierry@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        David Howells <dhowells@...hat.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        Alexander Potapenko <glider@...gle.com>,
        kvmarm <kvmarm@...ts.cs.columbia.edu>,
        Jonathan Corbet <corbet@....net>,
        Abbott Liu <liuwenliang@...wei.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Russell King <linux@...linux.org.uk>,
        kasan-dev <kasan-dev@...glegroups.com>,
        bcm-kernel-feedback-list@...adcom.com,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Andrew Jones <drjones@...hat.com>,
        Vladimir Murzin <vladimir.murzin@....com>,
        Kees Cook <keescook@...omium.org>,
        Arnd Bergmann <arnd@...db.de>,
        Marc Zyngier <marc.zyngier@....com>,
        Andre Przywara <andre.przywara@....com>,
        Philip Derrin <philip@....systems>,
        Jinbum Park <jinb.park7@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Nicolas Pitre <nico@...xnic.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux Doc Mailing List <linux-doc@...r.kernel.org>,
        Christoffer Dall <christoffer.dall@....com>,
        Thomas Garnier <thgarnie@...gle.com>,
        Rob Landley <rob@...dley.net>,
        Philippe Ombredanne <pombredanne@...b.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andrey Ryabinin <ryabinin@...tuozzo.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [PATCH v7 7/7] ARM: Enable KASan for ARM

(+ Linus)

On Fri, 10 Apr 2020 at 12:45, Ard Biesheuvel <ardb@...nel.org> wrote:
>
> On Fri, 17 Jan 2020 at 23:52, Florian Fainelli <f.fainelli@...il.com> wrote:
> >
> > From: Andrey Ryabinin <ryabinin@...tuozzo.com>
> >
> > This patch enables the kernel address sanitizer for ARM. XIP_KERNEL has
> > not been tested and is therefore not allowed.
> >
> > Acked-by: Dmitry Vyukov <dvyukov@...gle.com>
> > Tested-by: Linus Walleij <linus.walleij@...aro.org>
> > Signed-off-by: Abbott Liu <liuwenliang@...wei.com>
> > Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
> > ---
> >  Documentation/dev-tools/kasan.rst     | 4 ++--
> >  arch/arm/Kconfig                      | 9 +++++++++
> >  arch/arm/boot/compressed/Makefile     | 1 +
> >  drivers/firmware/efi/libstub/Makefile | 3 ++-
> >  4 files changed, 14 insertions(+), 3 deletions(-)
> >
> > diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst
> > index e4d66e7c50de..6acd949989c3 100644
> > --- a/Documentation/dev-tools/kasan.rst
> > +++ b/Documentation/dev-tools/kasan.rst
> > @@ -21,8 +21,8 @@ global variables yet.
> >
> >  Tag-based KASAN is only supported in Clang and requires version 7.0.0 or later.
> >
> > -Currently generic KASAN is supported for the x86_64, arm64, xtensa and s390
> > -architectures, and tag-based KASAN is supported only for arm64.
> > +Currently generic KASAN is supported for the x86_64, arm, arm64, xtensa and
> > +s390 architectures, and tag-based KASAN is supported only for arm64.
> >
> >  Usage
> >  -----
> > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> > index 96dab76da3b3..70a7eb50984e 100644
> > --- a/arch/arm/Kconfig
> > +++ b/arch/arm/Kconfig
> > @@ -65,6 +65,7 @@ config ARM
> >         select HAVE_ARCH_BITREVERSE if (CPU_32v7M || CPU_32v7) && !CPU_32v6
> >         select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL && !CPU_ENDIAN_BE32 && MMU
> >         select HAVE_ARCH_KGDB if !CPU_ENDIAN_BE32 && MMU
> > +       select HAVE_ARCH_KASAN if MMU && !XIP_KERNEL
> >         select HAVE_ARCH_MMAP_RND_BITS if MMU
> >         select HAVE_ARCH_SECCOMP_FILTER if AEABI && !OABI_COMPAT
> >         select HAVE_ARCH_THREAD_STRUCT_WHITELIST
> > @@ -212,6 +213,14 @@ config ARCH_MAY_HAVE_PC_FDC
> >  config ZONE_DMA
> >         bool
> >
> > +config KASAN_SHADOW_OFFSET
> > +       hex
> > +       depends on KASAN
> > +       default 0x1f000000 if PAGE_OFFSET=0x40000000
> > +       default 0x5f000000 if PAGE_OFFSET=0x80000000
> > +       default 0x9f000000 if PAGE_OFFSET=0xC0000000
> > +       default 0xffffffff
> > +
> >  config ARCH_SUPPORTS_UPROBES
> >         def_bool y
> >
> > diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile
> > index 83991a0447fa..efda24b00a44 100644
> > --- a/arch/arm/boot/compressed/Makefile
> > +++ b/arch/arm/boot/compressed/Makefile
> > @@ -25,6 +25,7 @@ endif
> >
> >  GCOV_PROFILE           := n
> >  KASAN_SANITIZE         := n
> > +CFLAGS_KERNEL          += -D__SANITIZE_ADDRESS__
> >
> >  # Prevents link failures: __sanitizer_cov_trace_pc() is not linked in.
> >  KCOV_INSTRUMENT                := n
> > diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
> > index c35f893897e1..c8b36824189b 100644
> > --- a/drivers/firmware/efi/libstub/Makefile
> > +++ b/drivers/firmware/efi/libstub/Makefile
> > @@ -20,7 +20,8 @@ cflags-$(CONFIG_ARM64)                := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \
> >                                    -fpie $(DISABLE_STACKLEAK_PLUGIN)
> >  cflags-$(CONFIG_ARM)           := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \
> >                                    -fno-builtin -fpic \
> > -                                  $(call cc-option,-mno-single-pic-base)
> > +                                  $(call cc-option,-mno-single-pic-base) \
> > +                                  -D__SANITIZE_ADDRESS__
> >
>
> I am not too crazy about this need to unconditionally 'enable' KASAN
> on the command line like this, in order to be able to disable it again
> when CONFIG_KASAN=y.
>
> Could we instead add something like this at the top of
> arch/arm/boot/compressed/string.c?
>
> #ifdef CONFIG_KASAN
> #undef memcpy
> #undef memmove
> #undef memset
> void *__memcpy(void *__dest, __const void *__src, size_t __n) __alias(memcpy);
> void *__memmove(void *__dest, __const void *__src, size_t count)
> __alias(memmove);
> void *__memset(void *s, int c, size_t count) __alias(memset);
> #endif
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

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