linux-kernel - Re: [PATCH 2/6] efi: Avoid fortify checks in EFI stub

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Date:   Tue, 6 Jun 2017 18:17:12 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Kees Cook <keescook@...omium.org>
Cc:     Matt Fleming <matt@...eblueprint.co.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/6] efi: Avoid fortify checks in EFI stub

On Tue, Jun 06, 2017 at 05:13:07PM +0000, Ard Biesheuvel wrote:
> (+ Mark, Matt)
> 
> On 6 June 2017 at 04:52, Kees Cook <keescook@...omium.org> wrote:
> > This avoids CONFIG_FORTIFY_SOURCE from being enabled during the EFI stub
> > build, as adding a panic() implementation may not work well. This can be
> > adjusted in the future.
> >
> > Suggested-by: Daniel Micay <danielmicay@...il.com>
> > Signed-off-by: Kees Cook <keescook@...omium.org>
> > Cc; Matt Fleming <matt@...eblueprint.co.uk>
> > Cc: Ard Biesheuvel <ard.biesheuvel@...aro.org>

I believe for arm64 the immediate breakage is implicitly fixed by the
<asm/string.h> definition, but I agree it makes sense to be explicit
anyhow.

FWIW:

Acked-by: Mark Rutland <mark.rutland@....com>

Kees, as an aside, do you want me to patchify the vdso fixup? Or are
you going to handle that?

Thanks,
Mark.

> > ---
> >  drivers/firmware/efi/libstub/Makefile | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
> > index f7425960f6a5..37e24f525162 100644
> > --- a/drivers/firmware/efi/libstub/Makefile
> > +++ b/drivers/firmware/efi/libstub/Makefile
> > @@ -17,6 +17,7 @@ cflags-$(CONFIG_ARM)          := $(subst -pg,,$(KBUILD_CFLAGS)) \
> >  cflags-$(CONFIG_EFI_ARMSTUB)   += -I$(srctree)/scripts/dtc/libfdt
> >
> >  KBUILD_CFLAGS                  := $(cflags-y) -DDISABLE_BRANCH_PROFILING \
> > +                                  -D__NO_FORTIFY \
> >                                    $(call cc-option,-ffreestanding) \
> >                                    $(call cc-option,-fno-stack-protector)
> >
> 
> Reviewed-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
> 
> This is unlikely to conflict with anything going through the EFI tree,
> so feel free to queue it elsewhere.