linux-kernel - Re: [PATCH] efi/libstub: Only disable stackleak plugin for arm64

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Date:   Mon, 30 Jul 2018 12:09:49 -0700
From:   Kees Cook <keescook@...gle.com>
To:     Laura Abbott <labbott@...hat.com>
Cc:     Will Deacon <will.deacon@....com>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Linux-Next Mailing List <linux-next@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Alexander Popov <alex.popov@...ux.com>,
        Catalin Marinas <catalin.marinas@....com>
Subject: Re: [PATCH] efi/libstub: Only disable stackleak plugin for arm64

On Mon, Jul 30, 2018 at 11:31 AM, Laura Abbott <labbott@...hat.com> wrote:
> arm64 uses the full KBUILD_CFLAGS for building libstub as opposed
> to x86 which doesn't. This means that x86 doesn't pick up
> the gcc-plugins. We need to disable the stackleak plugin but
> doing this unconditionally breaks x86 build since it doesn't
> have any plugins. Switch to disabling the stackleak plugin for
> arm64 only.
>
> Signed-off-by: Laura Abbott <labbott@...hat.com>

Reviewed-by: Kees Cook <keescook@...omium.org>

Thanks!

-Kees

> ---
>  drivers/firmware/efi/libstub/Makefile | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
> index 25dd2a14560d..88c322d7c71e 100644
> --- a/drivers/firmware/efi/libstub/Makefile
> +++ b/drivers/firmware/efi/libstub/Makefile
> @@ -11,7 +11,10 @@ cflags-$(CONFIG_X86)         += -m$(BITS) -D__KERNEL__ -O2 \
>                                    -fPIC -fno-strict-aliasing -mno-red-zone \
>                                    -mno-mmx -mno-sse -fshort-wchar
>
> -cflags-$(CONFIG_ARM64)         := $(subst -pg,,$(KBUILD_CFLAGS)) -fpie
> +# arm64 uses the full KBUILD_CFLAGS so it's necessary to explicitly
> +# disable the stackleak plugin
> +cflags-$(CONFIG_ARM64)         := $(subst -pg,,$(KBUILD_CFLAGS)) -fpie \
> +                                  $(DISABLE_STACKLEAK_PLUGIN)
>  cflags-$(CONFIG_ARM)           := $(subst -pg,,$(KBUILD_CFLAGS)) \
>                                    -fno-builtin -fpic -mno-single-pic-base
>
> @@ -21,7 +24,6 @@ KBUILD_CFLAGS                 := $(cflags-y) -DDISABLE_BRANCH_PROFILING \
>                                    -D__NO_FORTIFY \
>                                    $(call cc-option,-ffreestanding) \
>                                    $(call cc-option,-fno-stack-protector) \
> -                                  $(DISABLE_STACKLEAK_PLUGIN)
>
>  GCOV_PROFILE                   := n
>  KASAN_SANITIZE                 := n
> --
> 2.17.1
>



-- 
Kees Cook
Pixel Security