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

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Date:   Tue, 6 Jun 2017 20:12:22 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Mark Rutland <mark.rutland@....com>
Cc:     Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        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 6, 2017 at 10:17 AM, Mark Rutland <mark.rutland@....com> wrote:
> 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?

I sent that separately but discovered that my invocation of git
send-email failed to include a CC to you, even though I had it listed
as Suggested-by, etc. I think it's going to get queued for the arm64
tree.

>
> 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.

If it can go through the EFI tree, that'd be great. Less for akpm to wrangle. :)

Thanks!

-Kees

-- 
Kees Cook
Pixel Security