From: Mark Rutland <mark.rutland@arm.com>
To: Kees Cook <keescook@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Masahiro Yamada <yamada.masahiro@socionext.com>,
Michal Marek <mmarek@suse.com>,
Yoshinori Sato <ysato@users.sourceforge.jp>,
Rich Felker <dalias@libc.org>, Ingo Molnar <mingo@kernel.org>,
"David S. Miller" <davem@davemloft.net>,
Nicholas Piggin <npiggin@gmail.com>,
Al Viro <viro@zeniv.linux.org.uk>,
Laura Abbott <labbott@redhat.com>,
linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-sh@vger.kernel.org, kernel-hardening@lists.openwall.com
Subject: Re: [kernel-hardening] [PATCH 0/3] Makefile: Introduce CONFIG_CC_STACKPROTECTOR_AUTO
Date: Tue, 3 Oct 2017 11:04:33 +0100 [thread overview]
Message-ID: <20171003100433.GA4931@leverpostej> (raw)
In-Reply-To: <1506972007-80614-1-git-send-email-keescook@chromium.org>
Hi Kees,
On Mon, Oct 02, 2017 at 12:20:04PM -0700, 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.
I gave this a spin atop of v4.14-rc3 with a few arm64 toolchains I had
installed:
* Linaro 17.08 GCC 7.1 // strong
* Linaro 17.05 GCC 6.1 // strong
* Linaro 15.08 GCC 5.1 // strong
* Linaro 14.09 GCC 4.9 // strong
* Linaro 13.06 GCC 4.8 // none
* Linaro 13.01 GCC 4.7 // none
AFAICT, the detection is correct, and arm64 toolchains only gained stack
protector support in GCC 4.9. I manually tested GCC 4.8 and 4.7, and
got:
warning: -fstack-protector not supported for this target [enabled by default]
... so that looks good to me.
One thing I noticed was taht even when the build system detects no
support for stack-protector, it still passes -DCONFIG_CC_STACKPROTECTOR
to the toolchain. Is that expected?
Thanks,
Mark.
next prev parent reply other threads:[~2017-10-03 10:06 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-02 19:20 [PATCH 0/3] Makefile: Introduce CONFIG_CC_STACKPROTECTOR_AUTO Kees Cook
2017-10-02 19:20 ` [PATCH 1/3] sh/boot: Add static stack-protector to pre-kernel Kees Cook
2017-10-02 19:20 ` [PATCH 2/3] Makefile: Move stackprotector availability out of Kconfig Kees Cook
2017-10-04 14:33 ` Masahiro Yamada
2017-10-04 15:13 ` [kernel-hardening] " Greg KH
2017-10-04 16:22 ` Kees Cook
2017-10-04 17:15 ` Greg KH
2017-10-02 19:20 ` [PATCH 3/3] Makefile: Introduce CONFIG_CC_STACKPROTECTOR_AUTO Kees Cook
2017-10-03 10:04 ` Mark Rutland [this message]
2017-10-03 15:51 ` [kernel-hardening] [PATCH 0/3] " Kees Cook
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