From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751333Ab3FDSRe (ORCPT ); Tue, 4 Jun 2013 14:17:34 -0400 Received: from terminus.zytor.com ([198.137.202.10]:36636 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751286Ab3FDSRc (ORCPT ); Tue, 4 Jun 2013 14:17:32 -0400 Message-ID: <51AE2EDF.3000505@zytor.com> Date: Tue, 04 Jun 2013 11:15:59 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130514 Thunderbird/17.0.6 MIME-Version: 1.0 To: Steven Rostedt CC: Seiji Aguchi , linux-kernel@vger.kernel.org, x86@kernel.org, tglx@linutronix.de, mingo@elte.hu, bp@alien8.de, linux-edac@vger.kernel.org, tony.luck@intel.com, dle-develop@lists.sourceforge.net, tomoki.sekiyama@hds.com Subject: Re: [PATCH v13 3/3] trace,x86: Add irq vector tracepoints References: <51ACEDBB.6040706@hds.com> <51ACEEB4.1010302@hds.com> <1370303581.26799.109.camel@gandalf.local.home> In-Reply-To: <1370303581.26799.109.camel@gandalf.local.home> X-Enigmail-Version: 1.5.1 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/03/2013 04:53 PM, Steven Rostedt wrote: > > This way we wont be opening up any easy root holes where if a process > finds a way to modify some arbitrary kernel memory, we can prevent it > from modifying the current_idt_descr_ptr and have a nice way to exploit > the IDT. Sure, one can argue that if they can modify arbitrary kernel > memory, we may already be lost, but lets not make it easier for them > than need be. > I don't like current_idt_descr_ptr if we can avoid it. It is a direct proxy for reading and writing the original IDT, in other words, it really hasn't really addressed the issue. What I'm thinking we really should have is a function that returns the IDT that we currently should be using, based on the current state. If that state is, say, tracing on/off and NMI on/off, then that can be indicated by bits in a state vector. The point is that the IDT address itself should not be mutable state if it can be at all avoided. -hpa