Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753597AbbGXHZ5 (ORCPT ); Fri, 24 Jul 2015 03:25:57 -0400 Received: from wtarreau.pck.nerim.net ([62.212.114.60]:7994 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753333AbbGXHZz (ORCPT ); Fri, 24 Jul 2015 03:25:55 -0400 Date: Fri, 24 Jul 2015 09:24:51 +0200 From: Willy Tarreau To: Kees Cook Cc: Andy Lutomirski , Andy Lutomirski , Peter Zijlstra , Steven Rostedt , "security@kernel.org" , X86 ML , Borislav Petkov , Sasha Levin , LKML , Konrad Rzeszutek Wilk , Boris Ostrovsky , Andrew Cooper , Jan Beulich , xen-devel Subject: Re: [PATCH v3 2/3] x86/ldt: Make modify_ldt optional Message-ID: <20150724072451.GB3293@1wt.eu> References: <7bfde005b84a90a83bf668a320c7d4ad1b940065.1437592883.git.luto@kernel.org> <20150723102434.GA2929@1wt.eu> <20150723235805.GA3191@1wt.eu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.3i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1629 Lines: 36 On Thu, Jul 23, 2015 at 05:09:21PM -0700, Kees Cook wrote: > > All this to say that probably only a handful of tricky syscalls would > > need an on/off switch but clearly not all of them at all, so I'd rather > > add a few entries just for the relevant ones, mainly to fix compatibility > > issues and nothing more. Eg: what's the point of disabling exit(), wait(), > > kill(), fork() or getpid()... It would only increase the difficulty to > > sort out bug reports. > > > > Just my opinion, > > Well, I would really like to have something like this around so that I > can trivially globally disable syscalls when they have security risks. I understand, but while maybe it could make sense to have the option on any linux-specific syscall, having it on the standard, portable ones will be useless as disabling them will break most applications. > My hack[1] to disable kexec_load, for example, was terrible while I > waited for a kernel that supported the disable_kexec_load sysctl. This typically is one linux-specific syscall which no regular application would rely on and which can come with side effects. I think there are not *that* many, none of them is performance-critical, and they'd rather be dealt with one at a time. > [1] https://outflux.net/blog/archives/2013/12/10/live-patching-the-kernel/ Thanks, that (and the linked articles) was an interesting read. Willy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/