From: Matthew Garrett <mjg59@google.com>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>,
James Bottomley <James.Bottomley@hansenpartnership.com>,
Sultan Alsawaf <sultan@kerneltoast.com>,
"Jason A. Donenfeld" <Jason@zx2c4.com>,
Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
kitsunyan <kitsunyan@airmail.cc>,
"Brown, Len" <len.brown@intel.com>, X86 ML <x86@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH] x86/msr: do not warn on writes to OC_MAILBOX
Date: Tue, 8 Sep 2020 15:32:28 -0700 [thread overview]
Message-ID: <CACdnJusOJVb0xpecFgPQB4N2WhUORikv_1eXAcGfJ3xwBVTo9Q@mail.gmail.com> (raw)
In-Reply-To: <025308CD-6E1A-41E1-8B3D-E9842CE00794@amacapital.net>
On Tue, Sep 8, 2020 at 1:35 PM Andy Lutomirski <luto@amacapital.net> wrote:
> Undervolting is a bit different. It’s a genuinely useful configuration that can affect system stability. In general, I think it should be allowed, and it should have a real driver in tree.
Agree that this should be a proper driver rather than permitting
arbitrary poking (especially if this isn't an architecturally defined
MSR - there's no guarantee that it'll have the same functionality
everywhere).
> But this has a tricky interaction with lockdown. An interface that allows root to destabilize a system may well allow root to escalate privileges. But I think that making lockdown=integrity prevent tuning voltages and such would be quite obnoxious.
Indeed - plundervolt.com is a demonstration of this. Any realistic
attack involves being able to drop the voltage enough to interfere
with a calculation and then raise it again before everything else
falls over, so simply applying some rate limiting seems like it would
be sufficient.
> Should there perhaps be a separate lockdown bit for stability?
If it's a sysfs interface then I think it'd be easy enough for people
who care to just add an SELinux or Apparmor rule, tbh.
next prev parent reply other threads:[~2020-09-08 22:32 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-07 9:48 [PATCH] x86/msr: do not warn on writes to OC_MAILBOX Jason A. Donenfeld
2020-09-07 10:06 ` Borislav Petkov
2020-09-07 10:46 ` Jason A. Donenfeld
2020-09-07 11:11 ` Borislav Petkov
2020-09-07 11:15 ` Jason A. Donenfeld
2020-09-07 11:23 ` Borislav Petkov
2020-09-08 17:10 ` Srinivas Pandruvada
2020-09-08 17:12 ` Jason A. Donenfeld
2020-09-08 17:25 ` Borislav Petkov
2020-09-08 17:29 ` Jason A. Donenfeld
2020-09-08 17:36 ` Borislav Petkov
2020-09-08 17:42 ` Jason A. Donenfeld
2020-09-08 18:01 ` Borislav Petkov
2020-09-08 19:07 ` Jason A. Donenfeld
2020-09-08 19:18 ` Sultan Alsawaf
2020-09-08 19:30 ` Borislav Petkov
2020-09-08 20:35 ` Andy Lutomirski
2020-09-08 22:32 ` Matthew Garrett [this message]
2020-09-09 23:56 ` Andy Lutomirski
2020-09-09 1:02 ` Srinivas Pandruvada
2020-09-10 0:08 ` Andy Lutomirski
2020-10-19 17:15 ` Borislav Petkov
2020-10-20 17:21 ` Srinivas Pandruvada
2020-10-20 17:47 ` Borislav Petkov
2020-10-20 18:40 ` Srinivas Pandruvada
2020-10-20 19:40 ` Dave Hansen
2020-10-21 13:11 ` Srinivas Pandruvada
2020-10-22 19:28 ` Borislav Petkov
2020-10-21 13:24 ` Peter Zijlstra
2020-09-08 17:31 ` Borislav Petkov
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