linux-kernel - Re: [PATCH v2 11/17] selftests/x86/ldt

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Message-ID: <CA+55aFxnx98JLdpnjrvPZ+BDY_0dY+1GbCKRVki8b+-af+MM=g@mail.gmail.com>
Date:   Thu, 14 Dec 2017 14:50:02 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        X86 ML <x86@...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 11/17] selftests/x86/ldt_gdt: Prepare for access bit forced

On Thu, Dec 14, 2017 at 2:23 PM, Thomas Gleixner <tglx@...utronix.de> wrote:
>
> The user knows the LDT contents because he put it there and it can be read
> via modify_ldt(0, ) anyway. Or am I misunderstanding what you are trying to
> say?

I don't think they are secret, it's more of a "if they can read it,
they can write it" kind of thing.

The whole "it should be RO" makes no sense. The first choice should be
"it should be inaccessible".

And that actually seems the _simpler_ choice.

             Linus