linux-kernel - Re: [x86] 45fc8757d1: BUG:unable_to_handle

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Message-ID: <CA+55aFxrbQpisKU1ZuymdpYgSdxSUZ98k-fXjHZy9G9DwCXtgA@mail.gmail.com>
Date:   Fri, 17 Mar 2017 12:36:22 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     kernel test robot <xiaolong.ye@...el.com>,
        Thomas Garnier <thgarnie@...gle.com>,
        Ingo Molnar <mingo@...nel.org>,
        Alexander Potapenko <glider@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Borislav Petkov <bp@...e.de>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Jiri Kosina <jikos@...nel.org>, Joerg Roedel <joro@...tes.org>,
        Jonathan Corbet <corbet@....net>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Juergen Gross <jgross@...e.com>,
        Kees Cook <keescook@...omium.org>,
        Len Brown <len.brown@...el.com>,
        Lorenzo Stoakes <lstoakes@...il.com>,
        "Luis R . Rodriguez" <mcgrof@...nel.org>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        Michal Hocko <mhocko@...e.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        Pavel Machek <pavel@....cz>,
        Peter Zijlstra <peterz@...radead.org>,
        Radim Krčmář <rkrcmar@...hat.com>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Rusty Russell <rusty@...tcorp.com.au>,
        Stanislaw Gruszka <sgruszka@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        zijun_hu <zijun_hu@....com>, LKML <linux-kernel@...r.kernel.org>,
        "H. Peter Anvin" <hpa@...or.com>, tipbuild@...or.com,
        LKP <lkp@...org>
Subject: Re: [x86] 45fc8757d1: BUG:unable_to_handle_kernel

On Fri, Mar 17, 2017 at 11:20 AM, Andy Lutomirski <luto@...nel.org> wrote:
>
> I can easily imagine that breaking WINE or DOSEMU because it'll affect
> the LDT, too.

Can they even *read* the LDT contents, though? The whole accessed bit
doesn't show up in 'struct user_desc', so you can neither set it nor
read it.

> How about this:

I don't think that's _wrong_, but..

I'd really rather just do it in fill_ldt() itself, unless you can
explain how it would be visible to anybody..

               Linus