linux-kernel - Re: [PATCH v3] ARM: fix atags_to_fdt with stack-protector-strong

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Date:	Thu, 7 Jan 2016 11:16:13 -0800
From:	Kees Cook <keescook@...omium.org>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:	Russell King - ARM Linux <linux@....linux.org.uk>,
	Arnd Bergmann <arnd@...db.de>,
	Simon Horman <horms+renesas@...ge.net.au>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Magnus Damm <damm+renesas@...nsource.se>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] ARM: fix atags_to_fdt with stack-protector-strong

On Thu, Jan 7, 2016 at 11:11 AM, Geert Uytterhoeven
<geert@...ux-m68k.org> wrote:
> Hi Kees,
>
> On Thu, Jan 7, 2016 at 7:40 PM, Kees Cook <keescook@...omium.org> wrote:
>>> Also, I suspect that all of the decompressor should be built with
>>> -fno-stack-protector as we don't have sufficient environment here.
>>> Maybe it should be placed in the global CFLAGS for the decompressor?
>>
>> I prefer keeping it disabled in as narrow a range as possible. If
>> other code gains a level of complexity that it triggers the stack
>> protector code insertion, I think that's worth examining when it
>> happens. If this ever becomes an actual burden, then yeah, let's do it
>> for the whole decompressor, but I think it'd be best to revisit it if
>> it happens again.
>
> What's the failure mode if the stack protector code insertion is triggered?

AIUI, this code shouldn't even link if the ssp code gets inserted
since it can't resolve __stack_chk_fail.

-Kees

-- 
Kees Cook
Chrome OS & Brillo Security