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From: Borislav Petkov <bp@alien8.de>
To: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: x86-ml <x86@kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	lkml <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH] x86/msr: Filter MSR writes
Date: Fri, 12 Jun 2020 19:52:51 +0200	[thread overview]
Message-ID: <20200612175251.GF22660@zn.tnic> (raw)
In-Reply-To: <20200612174307.GD1026@linux.intel.com>

On Fri, Jun 12, 2020 at 10:43:07AM -0700, Sean Christopherson wrote:
> The problem is a fault on WRMSR doesn't mean the MSR doesn't exist, it only
> means WRMSR faulted.  WRMSR can for all intents and purpose trigger completely
> arbitrary microcode flows, e.g. WRMSR 0x79 can fundamentally change the
> behavior of the CPU.

Yes, that case is in the commit message.

> And it's not like the WRMSR->taint is atomic, e.g. changing a platform scoped
> MSR that affects voltage settings or something of that nature could easily
> tank the system on a successful WRMSR before the kernel can be marked tainted.

Yes, yes, I'll taint before the WRMSR.

> 0400 only allows a privelged user to read the parameter, e.g. for parameters
> that are snapshotted at module load time and/or changing the param while the
> module is running would cause breakage.
> 
> 0600 allows a priveleged user to read and write the parameter, which AFAICT
> is safe here.

Ok, we can do that.

> 0644 allows a priveleged user to read and write the parameter, and allows an
> unpriveleged user to read the param.

Not so sure about that. Why would the unprivileged user need to read it?

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

  reply	other threads:[~2020-06-12 17:52 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 [this message]
2020-06-12 17:20 ` Linus Torvalds
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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