From: Thomas Garnier <thgarnie@google.com>
To: Andy Lutomirski <luto@kernel.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H . Peter Anvin" <hpa@zytor.com>,
Kees Cook <keescook@chromium.org>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave@sr71.net>, Chen Yucong <slaoub@gmail.com>,
Paul Gortmaker <paul.gortmaker@windriver.com>,
Andrew Morton <akpm@linux-foundation.org>,
Masahiro Yamada <yamada.masahiro@socionext.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Anna-Maria Gleixner <anna-maria@linutronix.de>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
Michael Ellerman <mpe@ellerman.id.au>,
Juergen Gross <jgross@suse.com>,
Richard Weinberger <richard@nod.at>, X86 ML <x86@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"kernel-hardening@lists.openwall.com"
<kernel-hardening@lists.openwall.com>
Subject: Re: [RFC] x86/mm/KASLR: Remap GDTs at fixed location
Date: Thu, 5 Jan 2017 13:08:21 -0800 [thread overview]
Message-ID: <CAJcbSZHAtxbRzhTcZtBSabW0t+Cj7a1z-xJk8d310a2h8pkG=g@mail.gmail.com> (raw)
In-Reply-To: <CALCETrXymLa1_u90XE6dinhOfiecEJjbUGYn8apXGkiRFuwrZQ@mail.gmail.com>
On Thu, Jan 5, 2017 at 12:18 PM, Andy Lutomirski <luto@kernel.org> wrote:
> On Thu, Jan 5, 2017 at 11:03 AM, Thomas Garnier <thgarnie@google.com> wrote:
>> On Thu, Jan 5, 2017 at 10:58 AM, Arjan van de Ven <arjan@linux.intel.com> wrote:
>>> On 1/5/2017 9:54 AM, Thomas Garnier wrote:
>>>
>>>>
>>>> That's my goal too. I started by doing a RO remap and got couple
>>>> problems with hibernation. I can try again for the next iteration or
>>>> delay it for another patch. I also need to look at KVM GDT usage, I am
>>>> not familiar with it yet.
>>>
>>>
>>> don't we write to the GDT as part of the TLS segment stuff for glibc ?
>>>
>>
>> Not sure which glibc feature it is.
>>
>> In this design, you can write to the GDT per-cpu variable that will
>> remain read-write. You just need to make the remapping writeable when
>> we load task registers (ltr) then the processor use the current GDT
>> address. At least that the case I know, I might find more through
>> testing.
>
> Hmm. I bet that if we preset the accessed bits in all the segments
> then we don't need it to be writable in general. But your point about
> set_thread_area (TLS) is well taken. However, I strongly suspect that
> we could make set_thread_area unconditionally set the accessed bit and
> no one would ever notice.
Not sure I fully understood and I don't want to miss an important
point. Do you mean making GDT (remapping and per-cpu) read-only and
switch the writeable flag only when we write to the per-cpu entry?
--
Thomas
next prev parent reply other threads:[~2017-01-05 21:08 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-04 22:16 [RFC] x86/mm/KASLR: Remap GDTs at fixed location Thomas Garnier
2017-01-05 8:11 ` Ingo Molnar
2017-01-05 15:08 ` Arjan van de Ven
2017-01-05 16:40 ` Thomas Garnier
2017-01-05 18:56 ` Arjan van de Ven
2017-01-05 19:00 ` Thomas Garnier
2017-01-06 17:44 ` Borislav Petkov
2017-01-06 18:04 ` Thomas Garnier
2017-01-05 16:39 ` Thomas Garnier
2017-01-06 6:34 ` Ingo Molnar
2017-01-05 17:51 ` Andy Lutomirski
2017-01-05 17:54 ` Thomas Garnier
2017-01-05 18:01 ` Andy Lutomirski
2017-01-05 18:35 ` Thomas Garnier
2017-01-05 18:58 ` Arjan van de Ven
2017-01-05 19:03 ` Thomas Garnier
2017-01-05 20:18 ` Andy Lutomirski
2017-01-05 21:08 ` Thomas Garnier [this message]
2017-01-05 21:19 ` Andy Lutomirski
2017-01-05 21:58 ` Thomas Garnier
2017-01-06 6:49 ` Ingo Molnar
2017-01-06 18:03 ` Thomas Garnier
2017-01-06 21:59 ` Andy Lutomirski
2017-01-06 22:54 ` Thomas Garnier
2017-01-06 23:39 ` Andy Lutomirski
2017-01-07 7:45 ` Ingo Molnar
2017-01-07 15:58 ` Andy Lutomirski
2017-01-07 7:35 ` Ingo Molnar
2017-01-07 16:02 ` Andy Lutomirski
2017-01-09 22:32 ` Thomas Garnier
2017-01-10 10:27 ` Ingo Molnar
2017-01-10 17:13 ` Thomas Garnier
2017-01-05 23:05 ` Linus Torvalds
2017-01-05 23:16 ` Thomas Garnier
2017-01-06 2:34 ` Andy Lutomirski
2017-01-06 18:02 ` Thomas Garnier
2017-01-06 21:53 ` Andy Lutomirski
2017-01-07 7:46 ` Ingo Molnar
2017-01-06 6:45 ` Ingo Molnar
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