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From: Linus Torvalds <torvalds@linux-foundation.org>
To: Borislav Petkov <bp@alien8.de>
Cc: x86-ml <x86@kernel.org>, lkml <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH] x86/msr: Filter MSR writes
Date: Fri, 12 Jun 2020 10:20:03 -0700	[thread overview]
Message-ID: <CAHk-=wjKr+eAdPg3q7S6N4Cwd1aMEOHc5qLaKE-wwhouZRo=uw@mail.gmail.com> (raw)
In-Reply-To: <20200612105026.GA22660@zn.tnic>

On Fri, Jun 12, 2020 at 3:50 AM Borislav Petkov <bp@alien8.de> wrote:
>
> Disable writing to MSRs from userspace by default. Writes can still be
> allowed by supplying the allow_writes=1 module parameter and the kernel
> will be tainted so that it shows in oopses.

Since you already added the filtering, this looks fairly sane.

IOW, what MSR's do we expect people to maybe write to normally? You
added MSR_IA32_ENERGY_PERF_BIAS as an allowed MST, maybe there are
others?

So I'm not against this, but I suspect the whitelist should be thought
through more, and then maybe the "allow_writes" parameter should be
yes/no/default/<msr-list>, where "default" is that list of
known-normal MSR's.

And I suspect it's a lot longer list than your single one. IIRC,
people were working around CPU bugs or features by doing MSR writes at
startup.

So the first phase might be to introduce this, but have the default
for non-recognized MSR's be "log", not "deny".

                Linus

  parent reply	other threads:[~2020-06-12 17:20 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-12 10:50 [RFC PATCH] x86/msr: Filter MSR writes Borislav Petkov
2020-06-12 16:34 ` Sean Christopherson
2020-06-12 16:46   ` Borislav Petkov
2020-06-12 16:57     ` Sean Christopherson
2020-06-12 17:03       ` Borislav Petkov
2020-06-12 17:43         ` Sean Christopherson
2020-06-12 17:52           ` Borislav Petkov
2020-06-12 17:20 ` Linus Torvalds [this message]
2020-06-12 17:48   ` Borislav Petkov
2020-06-12 19:47     ` Borislav Petkov
2020-06-12 20:39     ` Peter Zijlstra
2020-06-13  5:40       ` Tony Luck
2020-06-13  9:39       ` Borislav Petkov
2020-06-13 15:48 ` [PATCH -v2] " Borislav Petkov
2020-06-15  6:38   ` [PATCH -v2.1] " Borislav Petkov
2020-06-25  5:51     ` Sean Christopherson
2020-06-25  8:37       ` Borislav Petkov
2020-07-14 12:19     ` Chris Down
2020-07-14 15:47       ` Borislav Petkov
2020-07-14 16:04         ` Chris Down
2020-07-14 16:46           ` Luck, Tony
2020-07-14 16:58             ` Borislav Petkov
2020-07-14 17:02             ` Chris Down
2020-07-14 16:56           ` Borislav Petkov
2020-07-14 17:04             ` Chris Down
2020-07-14 18:52             ` Srinivas Pandruvada
2020-07-15  4:26               ` Borislav Petkov
2020-07-14 19:17           ` Matthew Garrett
2020-11-17 21:00             ` Mathieu Chouquet-Stringer
2020-11-17 21:20               ` Borislav Petkov
2020-11-18  8:58                 ` Mathieu Chouquet-Stringer
2020-11-18  9:09                 ` Mathieu Chouquet-Stringer
2020-11-18 11:50                   ` Borislav Petkov
2020-11-18 14:04                     ` [PATCH] " Mathieu Chouquet-Stringer
2020-11-18 17:50                       ` Borislav Petkov
2020-11-19 10:53                         ` Mathieu Chouquet-Stringer
2020-11-25 21:41                           ` Mathieu Chouquet-Stringer
2020-11-26 10:03                           ` Borislav Petkov
2020-11-17 21:21               ` [PATCH -v2.1] " Matthew Garrett
2020-11-17 21:22                 ` Matthew Garrett
2020-11-18  9:02                   ` Mathieu Chouquet-Stringer
2020-06-17 15:06 ` [tip: x86/misc] " tip-bot2 for Borislav Petkov
2020-06-25  8:45 ` tip-bot2 for Borislav Petkov

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