Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755871AbbGUU2H (ORCPT ); Tue, 21 Jul 2015 16:28:07 -0400 Received: from mail-la0-f49.google.com ([209.85.215.49]:34377 "EHLO mail-la0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754740AbbGUU2E (ORCPT ); Tue, 21 Jul 2015 16:28:04 -0400 MIME-Version: 1.0 In-Reply-To: <55AEA99C.3030608@oracle.com> References: <06f4a63325ac221868770a8d63207d74b160df89.1437508486.git.luto@kernel.org> <55AEA99C.3030608@oracle.com> From: Andy Lutomirski Date: Tue, 21 Jul 2015 13:27:43 -0700 Message-ID: Subject: Re: [PATCH v2 2/3] x86/ldt: Make modify_ldt optional To: Sasha Levin Cc: Andy Lutomirski , Peter Zijlstra , Steven Rostedt , "security@kernel.org" , X86 ML , Borislav Petkov , "linux-kernel@vger.kernel.org" , Konrad Rzeszutek Wilk , Boris Ostrovsky Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1003 Lines: 29 On Tue, Jul 21, 2015 at 1:20 PM, Sasha Levin wrote: > On 07/21/2015 03:59 PM, Andy Lutomirski wrote: >> The modify_ldt syscall exposes a large attack surface and is >> unnecessary for modern userspace. Make it optional. > > Since this a "default y" option I think we need to make the > implications of this a bit clearer. Do you mean improving the help text? To be clear, there's no change on a non-EXPERT of default EXPERT kernel here. > > Do we know what userspace would break? Some Wine and some DOSEMU most likely. Also many of the exploits I've written over the past year or two :) > > Maybe add a WARN_ONCE() in a stub syscall? > I think if we do that then we should do it for all the syscall disabling things. --Andy -- 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/