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CVE-2017-5754 - ETA?

Started byfrancis picabia <fpicabia@gmail.com>
First post2018-01-04 15:00 +0100
Last post2018-01-13 09:50 +0100
Articles 3 on this page of 23 — 12 participants

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  CVE-2017-5754 - ETA? francis picabia <fpicabia@gmail.com> - 2018-01-04 15:00 +0100
    Re: CVE-2017-5754 - ETA? Don Armstrong <don@debian.org> - 2018-01-04 21:50 +0100
      Re: CVE-2017-5754 - ETA? francis picabia <fpicabia@gmail.com> - 2018-01-08 16:40 +0100
        Re: CVE-2017-5754 - ETA? Jeroen Mathon <jeroenmathonmac@gmail.com> - 2018-01-08 17:20 +0100
        Re: CVE-2017-5754 - ETA? Tixy <tixy@yxit.co.uk> - 2018-01-08 18:10 +0100
          Re: CVE-2017-5754 - ETA? Sven Joachim <svenjoac@gmx.de> - 2018-01-08 18:40 +0100
        Re: CVE-2017-5754 - ETA? Richard Hector <richard@walnut.gen.nz> - 2018-01-08 22:30 +0100
          Re: CVE-2017-5754 - ETA? francis picabia <fpicabia@gmail.com> - 2018-01-10 13:50 +0100
      Re: CVE-2017-5754 - ETA? Vincent Lefevre <vincent@vinc17.net> - 2018-01-12 14:40 +0100
        Re: CVE-2017-5754 - ETA? bw <bwtnguy@yahoo.com> - 2018-01-12 16:10 +0100
          Re: CVE-2017-5754 - ETA? Jack Dangler <tdldev@gmail.com> - 2018-01-12 17:00 +0100
            Re: CVE-2017-5754 - ETA? Roberto C. Sánchez <roberto@debian.org> - 2018-01-12 17:00 +0100
          Re: CVE-2017-5754 - ETA? Vincent Lefevre <vincent@vinc17.net> - 2018-01-12 22:10 +0100
            Re: CVE-2017-5754 - ETA? Roberto C. Sánchez <roberto@debian.org> - 2018-01-12 22:20 +0100
              Re: CVE-2017-5754 - ETA? Vincent Lefevre <vincent@vinc17.net> - 2018-01-12 22:20 +0100
            Re: CVE-2017-5754 - ETA? Nick <debuser@acrasis.net> - 2018-01-12 22:30 +0100
              Re: CVE-2017-5754 - ETA? Vincent Lefevre <vincent@vinc17.net> - 2018-01-12 22:50 +0100
                Re: CVE-2017-5754 - XEN silent_disable? bw <bwtnguy@yahoo.com> - 2018-01-13 02:10 +0100
                  Re: CVE-2017-5754 - XEN silent_disable? <tomas@tuxteam.de> - 2018-01-13 08:30 +0100
                    Re: CVE-2017-5754 - XEN silent_disable? Vincent Lefevre <vincent@vinc17.net> - 2018-01-13 10:50 +0100
                      Re: CVE-2017-5754 - XEN silent_disable? <tomas@tuxteam.de> - 2018-01-13 12:30 +0100
                Re: CVE-2017-5754 - ETA? Tixy <tixy@yxit.co.uk> - 2018-01-13 09:10 +0100
                  Re: CVE-2017-5754 - ETA? Tixy <tixy@yxit.co.uk> - 2018-01-13 09:50 +0100

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#191029 — Re: CVE-2017-5754 - XEN silent_disable?

From<tomas@tuxteam.de>
Date2018-01-13 12:30 +0100
SubjectRe: CVE-2017-5754 - XEN silent_disable?
Message-ID<v7saC-5as-3@gated-at.bofh.it>
In reply to#191026
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On Sat, Jan 13, 2018 at 10:45:31AM +0100, Vincent Lefevre wrote:

[...]

> For the "silent" part, I've reported a wishlist bug here:
> 
>   https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=887061

You're my hero :)

thanks
- -- t
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#191024

FromTixy <tixy@yxit.co.uk>
Date2018-01-13 09:10 +0100
Message-ID<v7p34-3dS-7@gated-at.bofh.it>
In reply to#191012
On Fri, 2018-01-12 at 22:40 +0100, Vincent Lefevre wrote:
> On 2018-01-12 21:21:06 +0000, Nick wrote:
> > It might have aged out of the buffer that dmesg reports on.
> 
> No, there's the beginning of the dmesg output:
> 
> [    0.000000] Linux version 4.9.0-5-amd64 (debian-kernel@lists.debian.org) (gcc version 6.3.0 20170516 (Debian 6.3.0-18) ) #1 SMP Debian 4.9.65-3+deb9u2 (2018-01-04)
> 
> But I think I've found the reason:
> 
> In arch/x86/mm/kaiser.c:
> 
> void __init kaiser_check_boottime_disable(void)
> {
> [...]
>         if (boot_cpu_has(X86_FEATURE_XENPV))
>                 goto silent_disable;
> [...]
> disable:
>         pr_info("disabled\n");
> 
> silent_disable:
>         kaiser_enabled = 0;
>         setup_clear_cpu_cap(X86_FEATURE_KAISER);
> }
> 
> I must be in the "silent_disable" case (this is a Xen guest).
> 
> It's unfortunate that no-one mentions this case!

Hmm. I have a system running under Xen and get the 'page tables
isolation: enabled' message. Here's what I hope are relevant parts from
dmesg output...

[    0.000000] Linux version 4.9.0-5-amd64 (debian-kernel@lists.debian.org) (gcc version 6.3.0 20170
516 (Debian 6.3.0-18) ) #1 SMP Debian 4.9.65-3+deb9u2 (2018-01-04)
...
[    0.000000] DMI: Xen HVM domU, BIOS 4.8.1-pre-memset3 06/07/2017
[    0.000000] Hypervisor detected: Xen
[    0.000000] Xen version 4.8.
...
[    0.000000] Booting paravirtualized kernel on Xen HVM
...
[    0.000000] Kernel/User page tables isolation: enabled

-- 
Tixy

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#191025

FromTixy <tixy@yxit.co.uk>
Date2018-01-13 09:50 +0100
Message-ID<v7pFL-3rR-1@gated-at.bofh.it>
In reply to#191024
On Sat, 2018-01-13 at 08:06 +0000, Tixy wrote:
> On Fri, 2018-01-12 at 22:40 +0100, Vincent Lefevre wrote:
> > On 2018-01-12 21:21:06 +0000, Nick wrote:
> > > It might have aged out of the buffer that dmesg reports on.
> > 
> > No, there's the beginning of the dmesg output:
> > 
> > [    0.000000] Linux version 4.9.0-5-amd64 (debian-kernel@lists.debian.org) (gcc version 6.3.0 20170516 (Debian 6.3.0-18) ) #1 SMP Debian 4.9.65-3+deb9u2 (2018-01-04)
> > 
> > But I think I've found the reason:
> > 
> > In arch/x86/mm/kaiser.c:
> > 
> > void __init kaiser_check_boottime_disable(void)
> > {
> > [...]
> >         if (boot_cpu_has(X86_FEATURE_XENPV))
> >                 goto silent_disable;
> > [...]
> > disable:
> >         pr_info("disabled\n");
> > 
> > silent_disable:
> >         kaiser_enabled = 0;
> >         setup_clear_cpu_cap(X86_FEATURE_KAISER);
> > }
> > 
> > I must be in the "silent_disable" case (this is a Xen guest).
> > 
> > It's unfortunate that no-one mentions this case!
> 
> Hmm. I have a system running under Xen and get the 'page tables
> isolation: enabled' message. Here's what I hope are relevant parts from
> dmesg output...
> 
> [    0.000000] Linux version 4.9.0-5-amd64 (debian-kernel@lists.debian.org) (gcc version 6.3.0 20170
> 516 (Debian 6.3.0-18) ) #1 SMP Debian 4.9.65-3+deb9u2 (2018-01-04)
> ...
> [    0.000000] DMI: Xen HVM domU, BIOS 4.8.1-pre-memset3 06/07/2017
> [    0.000000] Hypervisor detected: Xen
> [    0.000000] Xen version 4.8.
> ...
> [    0.000000] Booting paravirtualized kernel on Xen HVM
> ...
> [    0.000000] Kernel/User page tables isolation: enabled

Replying to myself... The above makes sense as while the Debian kernel
is built with Xen paravirtualisation support, in my case it is running
under hardware virtualisation (HVM) so the paravirtialisation flag
(X86_FEATURE_XENPV) isn't set.

For people who's boot log says 

  Booting paravirtualized kernel on Xen PVH

I would expect not to see any mention of 

  Kernel/User page tables isolation

as the code Vincent identified [1] silently disables it.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/commit/?h=v4.9.76&id=402e63de94afdf7cd64e4eb209a8a77310e02d2c

-- 
Tixy

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