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From: "H. Peter Anvin" <hpa@zytor.com>
To: Kees Cook <keescook@chromium.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Matthew Garrett <matthew.garrett@nebula.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 <linux-security-module@vger.kernel.org>
Subject: Re: [PATCH] x86: Lock down MSR writing in secure boot
Date: Fri, 08 Feb 2013 12:18:27 -0800	[thread overview]
Message-ID: <dee64752-850c-4d78-b703-f47a985bc13e@email.android.com> (raw)
In-Reply-To: <CAGXu5j+_mGzR+72YqORhErMUY1aF1H2urczZ8SwuJHZK-oZL6g@mail.gmail.com>

Analogy fail.  The /dev/mem lockout applies to system RAM, not MMIO.

I fear COMPROMISE_KERNEL is becoming the new SYS_ADMIN, which in turn is the new root.  Why?  Because it is inhebtly about a usage model, not about a specific resource.

Kees Cook <keescook@chromium.org> wrote:

>On Fri, Feb 8, 2013 at 11:42 AM, H. Peter Anvin <hpa@zytor.com> wrote:
>> On 02/08/2013 11:18 AM, Kees Cook wrote:
>>>
>>> No. CAP_RAWIO is for reading. Writing needs a much stronger check.
>>
>> If so, I suspect we need to do this for *all* raw I/O... but I keep
>> wondering how much more sensitive writing really is than reading.
>
>Well, I think there's a reasonable distinction between systems that
>expect to strictly enforce user-space/kernel-space separation
>(CAP_COMPROMISE_KERNEL) and things that are fiddling with hardware
>(CAP_SYS_RAWIO).
>
>For example, even things like /dev/mem already have this separation
>(although it is stronger). You can't open /dev/mem without
>CAP_SYS_RAWIO, but if you do, you still can't write to RAM in
>/dev/mem. This might be one of the earliest examples of this
>distinction, actually.
>
>I think it's likely that after a while, we can convert some of these
>proposed CAP_COMPROMISE_KERNEL checks in always-deny once we figure
>out how to deal with those areas more safely.
>
>-Kees
>
>--
>Kees Cook
>Chrome OS Security

-- 
Sent from my mobile phone. Please excuse brevity and lack of formatting.

  reply	other threads:[~2013-02-08 20:18 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 [this message]
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
2013-02-08 19:27     ` Matthew Garrett

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