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Message-ID: <alpine.LFD.2.03.1304082350540.25182@linux-mips.org>
Date: Mon, 8 Apr 2013 23:56:29 +0100 (BST)
From: "Maciej W. Rozycki" <macro@...ux-mips.org>
To: Kees Cook <keescook@...omium.org>
cc: Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
Thomas Gleixner <tglx@...utronix.de>,
"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
Jeremy Fitzhardinge <jeremy@...p.org>,
Marcelo Tosatti <mtosatti@...hat.com>,
Alex Shi <alex.shi@...el.com>,
Borislav Petkov <borislav.petkov@....com>,
Alexander Duyck <alexander.h.duyck@...el.com>,
Frederic Weisbecker <fweisbec@...il.com>,
Steven Rostedt <rostedt@...dmis.org>,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
xen-devel@...ts.xensource.com,
virtualization@...ts.linux-foundation.org,
kernel-hardening@...ts.openwall.com,
Dan Rosenberg <drosenberg@...curity.com>,
Julien Tinnes <jln@...gle.com>, Will Drewry <wad@...omium.org>,
Eric Northup <digitaleric@...gle.com>
Subject: Re: [PATCH] x86: make IDT read-only
On Mon, 8 Apr 2013, Kees Cook wrote:
> This makes the IDT unconditionally read-only. This primarily removes
> the IDT from being a target for arbitrary memory write attacks. It has
> an added benefit of also not leaking (via the "sidt" instruction) the
> kernel base offset, if it has been relocated.
[...]
> --- a/arch/x86/kernel/cpu/intel.c
> +++ b/arch/x86/kernel/cpu/intel.c
> @@ -215,7 +201,6 @@ static void __cpuinit intel_workarounds(struct cpuinfo_x86 *c)
>
> c->f00f_bug = 1;
> if (!f00f_workaround_enabled) {
> - trap_init_f00f_bug();
> printk(KERN_NOTICE "Intel Pentium with F0 0F bug - workaround enabled.\n");
> f00f_workaround_enabled = 1;
> }
FWIW the change looks reasonable to me, however given that that it makes
the arrangement unconditional and there is no longer a workaround to
enable I think it would make sense to remove the conditional block quoted
above altogether, along with the f00f_workaround_enabled variable itself
(alternatively "Intel Pentium with F0 0F bug" alone could be printed
instead and the name of the variable adjusted to make sense with the new
meaning -- up to you to decide).
Maciej
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