Re: [PATCH] x86: Lock down MSR writing in secure boot
[Posted March 12, 2013 by mkerrisk]
| From: |
| Matthew Garrett <matthew.garrett-05XSO3Yj/JvQT0dZR+AlfA-AT-public.gmane.org> |
| To: |
| "H. Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w-AT-public.gmane.org> |
| Subject: |
| Re: [PATCH] x86: Lock down MSR writing in secure boot |
| Date: |
| Wed, 13 Feb 2013 06:41:54 +0000 |
| Message-ID: |
| <1360737709.18083.36.camel@x230.lan> |
| Cc: |
| Borislav Petkov <bp-Gina5bIWoIWzQB+pC5nmwQ-AT-public.gmane.org>, Kees Cook <keescook-F7+t8E8rja9g9hUCZPvPmw-AT-public.gmane.org>,
LKML <linux-kernel-u79uwXL29TY76Z2rM5mHXA-AT-public.gmane.org>,
Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ-AT-public.gmane.org>,
Ingo Molnar <mingo-H+wXaHxf7aLQT0dZR+AlfA-AT-public.gmane.org>,
"x86-DgEjT+Ai2ygdnm+yROfE0A-AT-public.gmane.org" <x86-DgEjT+Ai2ygdnm+yROfE0A-AT-public.gmane.org>,
"linux-efi-u79uwXL29TY76Z2rM5mHXA-AT-public.gmane.org" <linux-efi-u79uwXL29TY76Z2rM5mHXA-AT-public.gmane.org>,
linux-security-module <linux-security-module-u79uwXL29TY76Z2rM5mHXA-AT-public.gmane.org> |
| Archive‑link: | |
Article |
On Tue, 2013-02-12 at 22:33 -0800, H. Peter Anvin wrote:
> That is just batshit crazy. If you have CAP_SYS_RAWIO you can do iopl()
> which means you can reprogram your northbridge, at which point you most
> definitely *can* modify the running kernel.
Well right, that's the point of this patchset - it adds some extra
permission checks to some of the existing CAP_SYS_RAWIO checks.
CAP_SYS_RAWIO hasn't meant "I can perform arbitrary pio and mmio" for
years - it means "I can do things that might maybe break something
somehow". So sure, removing CAP_SYS_RAWIO would give us basically all
the security we want in a secure boot environment, but it would also
block things that we *want* to work.
