MIME-Version: 1.0
In-Reply-To: <CA+55aFxGEQroSYmSgEQefNUhJfmvMRg8XAy3TrtYoiLwUQNwKA@mail.gmail.com>
References: <20170329203908.GA39222@beast> <ea0a7663-7318-6086-1cb8-25fd9a252f83@zytor.com>
 <CAGXu5jLQfS6gK2MyetWPjyJDOg8NdACXsPXLt7OasQE03VUwPg@mail.gmail.com> <CA+55aFxGEQroSYmSgEQefNUhJfmvMRg8XAy3TrtYoiLwUQNwKA@mail.gmail.com>
From: Andy Lutomirski <luto@amacapital.net>
Date: Wed, 29 Mar 2017 14:35:16 -0700
Message-ID: <CALCETrVudF5-buAHqGd3y1g8X3mnf6tmB5Av50k9WFL-yrbZmQ@mail.gmail.com>
Subject: Re: [PATCH] x86/fpu: move FPU state into separate cache
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Kees Cook <keescook@chromium.org>, "H. Peter Anvin" <hpa@zytor.com>,
        LKML <linux-kernel@vger.kernel.org>, Rik van Riel <riel@redhat.com>,
        Andy Lutomirski <luto@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        "x86@kernel.org" <x86@kernel.org>, Paolo Bonzini <pbonzini@redhat.com>,
        =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= <rkrcmar@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Yu-cheng Yu <yu-cheng.yu@intel.com>,
        Masahiro Yamada <yamada.masahiro@socionext.com>,
        Borislav Petkov <bp@suse.de>,
        Christian Borntraeger <borntraeger@de.ibm.com>,
        Thomas Garnier <thgarnie@google.com>, Brian Gerst <brgerst@gmail.com>,
        He Chen <he.chen@linux.intel.com>,
        Mathias Krause <minipli@googlemail.com>,
        Fenghua Yu <fenghua.yu@intel.com>, Piotr Luc <piotr.luc@intel.com>,
        Kyle Huey <me@kylehuey.com>, Len Brown <len.brown@intel.com>,
        KVM <kvm@vger.kernel.org>,
        "kernel-hardening@lists.openwall.com" 
        <kernel-hardening@lists.openwall.com>
Content-Type: text/plain; charset=UTF-8
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1024
Lines: 27

On Wed, Mar 29, 2017 at 2:30 PM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
> On Wed, Mar 29, 2017 at 2:09 PM, Kees Cook <keescook@chromium.org> wrote:
>>
>> They're adjacent already, which poses a problem for the struct layout
>> randomization plugin, since adjacency may no longer be true (after
>> layout randomization). T
>
> What?
>
> The layout randomization can't change anything, if you just make the
> adjacency be done explicitly instead of by having the thing be a fixed
> member.
>
> The trivial model might be to just declare the fpu part as an unsized
> array at the end:
>
>         /* Floating point and extended processor state */
>         struct fpu              fpu[];
>
> because there is no way in hell that any randomization code can move
> those kinds of unsized arrays around. If it does, the gcc plugin is
> such unbelievable garbage that it would be insane to depend on such
> shit in the first place.
>

Randomization also needs to leave thread_info at the beginning.  Can it do that?