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Date:   Wed, 8 Nov 2017 17:12:31 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Laura Abbott <labbott@...hat.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Arnd Bergmann <arnd@...db.de>,
        Josh Triplett <josh@...htriplett.org>,
        Nicholas Piggin <npiggin@...il.com>,
        linux-kbuild <linux-kbuild@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 0/3] Makefile: Introduce CONFIG_CC_STACKPROTECTOR_AUTO

On Wed, Nov 8, 2017 at 11:43 AM, Laura Abbott <labbott@...hat.com> wrote:
> On 11/07/2017 09:38 AM, Kees Cook wrote:
>>
>> As described in the final patch:
>>
>> Nearly all modern compilers support a stack-protector option, and nearly
>> all modern distributions enable the kernel stack-protector, so enabling
>> this by default in kernel builds would make sense. However, Kconfig does
>> not have knowledge of available compiler features, so it isn't safe to
>> force on, as this would unconditionally break builds for the compilers
>> or architectures that don't have support. Instead, this introduces a new
>> option, CONFIG_CC_STACKPROTECTOR_AUTO, which attempts to discover the best
>> possible stack-protector available, and will allow builds to proceed even
>> if the compiler doesn't support any stack-protector.
>>
>> This option is made the default so that kernels built with modern
>> compilers will be protected-by-default against stack buffer overflows,
>> avoiding things like the recent BlueBorne attack. Selection of a specific
>> stack-protector option remains available, including disabling it.
>>
>>
>> This has lived over the last several days without any unfixed 0day
>> failures.
>>
>> v2:
>> - under ..._AUTO, warn and continue on _all_ stack protector failure cases
>> - fix 32-bit boot regression due to lazy gz.
>> - set CONFIG_CC_STACKPROTECTOR_NONE for tiny.config.
>>
>> Thanks,
>>
>> -Kees
>>
>
> This passed a test build on all Fedora arches, including s390 and ppc.
> On x86 it picks up the strong option correctly.
>
> You're welcome to add
>
> Tested-by: Laura Abbott <labbott@...hat.com>

Awesome, thanks for testing!

-Kees

-- 
Kees Cook
Pixel Security

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