linux-kernel - Re: [PATCH v3 35/75] x86/head/64: Build k/head64.c with -fno-stack-protector

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Date:   Wed, 3 Jun 2020 13:14:11 -0400
From:   Brian Gerst <brgerst@...il.com>
To:     Joerg Roedel <joro@...tes.org>
Cc:     "the arch/x86 maintainers" <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Hellstrom <thellstrom@...are.com>,
        Jiri Slaby <jslaby@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Juergen Gross <jgross@...e.com>,
        Kees Cook <keescook@...omium.org>,
        David Rientjes <rientjes@...gle.com>,
        Cfir Cohen <cfir@...gle.com>,
        Erdem Aktas <erdemaktas@...gle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mike Stunes <mstunes@...are.com>,
        Joerg Roedel <jroedel@...e.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        kvm list <kvm@...r.kernel.org>,
        Linux Virtualization <virtualization@...ts.linux-foundation.org>
Subject: Re: [PATCH v3 35/75] x86/head/64: Build k/head64.c with -fno-stack-protector

On Wed, Jun 3, 2020 at 11:18 AM Joerg Roedel <joro@...tes.org> wrote:
>
> On Tue, May 19, 2020 at 09:58:18AM -0400, Brian Gerst wrote:
> > On Tue, Apr 28, 2020 at 11:28 AM Joerg Roedel <joro@...tes.org> wrote:
>
> > The proper fix would be to initialize MSR_GS_BASE earlier.
>
> That'll mean to initialize it two times during boot, as the first C
> function with stack-protection is called before the kernel switches to
> its high addresses (early_idt_setup call-path). But okay, I can do that.

Good point.  Since this is boot code which isn't subject to stack
smashing attacks, disabling stack protector is probably the simpler
option.

--
Brian Gerst