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From: Kees Cook <keescook@chromium.org>
To: Matthew Garrett <matthew.garrett@nebula.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, "x86@kernel.org" <x86@kernel.org>,
	"linux-efi@vger.kernel.org" <linux-efi@vger.kernel.org>,
	"linux-security-module@vger.kernel.org" 
	<linux-security-module@vger.kernel.org>
Subject: Re: [PATCH] x86: Lock down MSR writing in secure boot
Date: Fri, 8 Feb 2013 11:21:39 -0800	[thread overview]
Message-ID: <CAGXu5j+aXxQb_Jyn6G+JUdjNOF2EGo9pTw8dBYuZUTb+S1vWow@mail.gmail.com> (raw)
In-Reply-To: <1360351047.18083.14.camel@x230.lan>

On Fri, Feb 8, 2013 at 11:17 AM, Matthew Garrett
<matthew.garrett@nebula.com> wrote:
> On Fri, 2013-02-08 at 11:12 -0800, Kees Cook wrote:
>> Writing to MSRs should not be allowed unless CAP_COMPROMISE_KERNEL is
>> set since it could lead to execution of arbitrary code in kernel mode.
>
> Willing to buy this, but do you have a description of one potential
> approach? We should probably also figure out what's writing to MSRs at
> the moment (anything other than energy_perf_bias?) and decide what the
> best thing to do there is.

Yes, change the SYSENTER entry point to where-ever you like. There are
examples already written:
http://grsecurity.net/~spender/msr32.c

IMO, _writing_ an MSR from userspace should be considered a bug. If
writing is needed, a kernel driver should be mediating the change.
wrmsr (and rdmsr) are ring-0 only for good reason. :)

-Kees

--
Kees Cook
Chrome OS Security

  reply	other threads:[~2013-02-08 19:21 UTC|newest]

Thread overview: 49+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-02-08 19:12 Kees Cook
2013-02-08 19:17 ` H. Peter Anvin
2013-02-08 19:18   ` Kees Cook
2013-02-08 19:42     ` H. Peter Anvin
2013-02-08 20:14       ` Kees Cook
2013-02-08 20:18         ` H. Peter Anvin
2013-02-08 20:28           ` Kees Cook
2013-02-08 20:34             ` Matthew Garrett
2013-02-08 21:02               ` Kees Cook
2013-02-08 21:07                 ` Matthew Garrett
2013-02-08 21:14                   ` Josh Boyer
2013-02-08 23:09                     ` Andy Lutomirski
2013-02-08 22:30                 ` H. Peter Anvin
2013-02-08 23:06                   ` Borislav Petkov
2013-02-08 23:26                     ` Matthew Garrett
2013-02-09  1:22                       ` H. Peter Anvin
2013-02-09  1:29                         ` Matthew Garrett
2013-02-09  6:45                           ` Kees Cook
2013-02-09  9:29                             ` Borislav Petkov
2013-02-09 15:10                               ` Kees Cook
2013-02-09 15:11                               ` Matthew Garrett
2013-02-13  0:48                                 ` H. Peter Anvin
2013-02-13  5:39                                   ` Matthew Garrett
2013-02-13  6:12                                     ` H. Peter Anvin
2013-02-13  6:27                                       ` Matthew Garrett
2013-02-13  6:33                                         ` H. Peter Anvin
2013-02-13  6:41                                           ` Matthew Garrett
2013-02-13 17:20                                             ` H. Peter Anvin
2013-02-13 17:26                                               ` Matthew Garrett
2013-02-13 17:51                                                 ` Casey Schaufler
2013-02-13 17:56                                                   ` Matthew Garrett
2013-02-13 18:44                                                     ` H. Peter Anvin
2013-02-13 18:51                                                       ` Matthew Garrett
2013-02-13 22:26                                                   ` H. Peter Anvin
2013-02-13 22:58                                                     ` Casey Schaufler
2013-02-14  0:25                                                       ` H. Peter Anvin
2013-02-14  0:44                                                         ` Casey Schaufler
2013-02-14  1:04                                                           ` Matthew Garrett
2013-02-14  1:08                                                             ` H. Peter Anvin
2013-02-14  2:46                                                               ` Matthew Garrett
2013-02-14  1:34                                                             ` Casey Schaufler
2013-02-13  8:27                                           ` Paolo Bonzini
2013-02-13 17:21                                             ` H. Peter Anvin
2013-02-13 17:22                                             ` H. Peter Anvin
2013-02-13 19:55                                               ` Paolo Bonzini
2013-02-13 22:24                                                 ` H. Peter Anvin
2013-02-08 19:17 ` Matthew Garrett
2013-02-08 19:21   ` Kees Cook [this message]
2013-02-08 19:27     ` Matthew Garrett

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