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From: Andy Lutomirski <luto@amacapital.net>
To: jwboyer@gmail.com
Cc: Matthew Garrett <mjg@redhat.com>,
	Kees Cook <keescook@chromium.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>,
	x86@kernel.org, linux-efi@vger.kernel.org,
	linux-security-module@vger.kernel.org
Subject: Re: [PATCH] x86: Lock down MSR writing in secure boot
Date: Fri, 08 Feb 2013 15:09:19 -0800	[thread overview]
Message-ID: <5115859F.8070805@amacapital.net> (raw)
In-Reply-To: <CA+5PVA4EbgBRgg+ZDa4+vG0Ngw8wJ3kH6NcmDvZ=+CP=kH82_A@mail.gmail.com>

On 02/08/2013 01:14 PM, Josh Boyer wrote:
> On Fri, Feb 8, 2013 at 4:07 PM, Matthew Garrett
> <matthew.garrett-05XSO3Yj/JvQT0dZR+AlfA@public.gmane.org> wrote:
>> On Fri, 2013-02-08 at 13:02 -0800, Kees Cook wrote:
>>
>>> I don't find it unreasonable to drop all caps and lose access to
>>> sensitive things. :) That's sort of the point, really. I think a cap
>>> is the best match. It seems like it should either be a cap or a
>>> namespace flag, but the latter seems messy.
>>
>> Yeah, I think it's an expected outcome, but it means that if (say) qemu
>> drops privileges, qemu can no longer access PCI resources - even on
>> non-secure boot systems. That breaks existing userspace.
> 
> Right.  We've had a few reports in Fedora of things breaking on non-SB
> systems because of this.  The qemu one is the latest, but the general
> problem is people think dropping all caps blindly is making their apps
> safer.  Then they find they can't do things they could do before the new
> cap was added.  It's messy.

Why not require CAP_COMPROMISE_KERNEL to open (with O_RDWR or O_WRONLY)
/dev/msr?  After all, sudo </dev/null >/dev/msr will cause a privileged
write() call on the fd as long as the capability is in your bounding set.

--Andy

  reply	other threads:[~2013-02-08 23:09 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 [this message]
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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