kernel-hardening - Re: [PATCH v6 20/27] x86: Support global stack cookie

Follow @Openwall on Twitter for new release announcements and other news

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAJcbSZH3-TVxDsoRLKSuFLU2bHVV9FgDXtUaZFMim3k+4QU8Cg@mail.gmail.com>
Date: Fri, 1 Feb 2019 12:21:44 -0800
From: Thomas Garnier <thgarnie@...omium.org>
To: Andy Lutomirski <luto@...nel.org>
Cc: Kernel Hardening <kernel-hardening@...ts.openwall.com>, 
	Kristen Carlson Accardi <kristen@...ux.intel.com>, Thomas Gleixner <tglx@...utronix.de>, 
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>, 
	X86 ML <x86@...nel.org>, Masahiro Yamada <yamada.masahiro@...ionext.com>, 
	Juergen Gross <jgross@...e.com>, Joerg Roedel <jroedel@...e.de>, 
	Jia Zhang <qianyue.zj@...baba-inc.com>, Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>, 
	Tim Chen <tim.c.chen@...ux.intel.com>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 20/27] x86: Support global stack cookie

On Fri, Feb 1, 2019 at 11:27 AM Andy Lutomirski <luto@...nel.org> wrote:
>
> On Thu, Jan 31, 2019 at 11:29 AM Thomas Garnier <thgarnie@...omium.org> wrote:
> >
> > Add an off-by-default configuration option to use a global stack cookie
> > instead of the default TLS. This configuration option will only be used
> > with PIE binaries.
> >
> > For kernel stack cookie, the compiler uses the mcmodel=kernel to switch
> > between the fs segment to gs segment. A PIE binary does not use
> > mcmodel=kernel because it can be relocated anywhere, therefore the
> > compiler will default to the fs segment register. This is fixed on the
> > latest version of gcc.
>
> I hate all these gcc-sucks-so-we-hack-it-and-change-nasty-semantics
> options.  How about just preventing use of both stack protector and
> PIE unless the version of gcc in use is new enough.

So fail the build in this scenario?

>
> Also, does -mstack-protector-guard-reg not solve this?  See
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81708.  Or is there
> another bug?  Or are you worried about gcc versions that don't have
> that feature yet?

I am worried about gcc versions that don't have this feature, yes.

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.