linux-kernel - Re: [PATCH v2 13/17] x86/mm: Force LDT desc accessed bit

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Message-ID: <CALCETrWfm+BXKuRCN44NjpG37NA8+gFNYPK9gVTcUXzckpv9nw@mail.gmail.com>
Date:   Thu, 14 Dec 2017 08:21:40 -0800
From:   Andy Lutomirski <luto@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>, X86 ML <x86@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Lutomirsky <luto@...nel.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Borislav Petkov <bpetkov@...e.de>,
        Greg KH <gregkh@...uxfoundation.org>,
        Kees Cook <keescook@...gle.com>,
        Hugh Dickins <hughd@...gle.com>,
        Brian Gerst <brgerst@...il.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        David Laight <David.Laight@...lab.com>,
        Eduardo Valentin <eduval@...zon.com>,
        "Liguori, Anthony" <aliguori@...zon.com>,
        Will Deacon <will.deacon@....com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Dan Williams <dan.j.williams@...el.com>
Subject: Re: [PATCH v2 13/17] x86/mm: Force LDT desc accessed bit

On Thu, Dec 14, 2017 at 3:27 AM, Peter Zijlstra <peterz@...radead.org> wrote:
> In preparation to mapping the LDT RO, unconditionally set the accessed
> bit.

I like this patch, but only as part of a standalone series to harden
the kernel by making the LDT be RO so we can revert the series if
needed.  I don't like it as a prerequisite to having a working kernel.