Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756748Ab1FIDy0 (ORCPT ); Wed, 8 Jun 2011 23:54:26 -0400 Received: from mail-wy0-f174.google.com ([74.125.82.174]:39834 "EHLO mail-wy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755799Ab1FIDyY (ORCPT ); Wed, 8 Jun 2011 23:54:24 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=subject:from:to:cc:in-reply-to:references:content-type:date :message-id:mime-version:x-mailer:content-transfer-encoding; b=ddxC8l2Va7KGvdceZ0sBvrFofldOefkjIHGsPZCLWJ09ogoQ1wBhrWOB9PNl0FWYrw tgl5ZaVLewz+nDhF8KBpSDL+OvDNQVXjgZtTmSisQ8zxmcJq/CbXP0aM9rqNHQjrCdGR XJXNxe2AlGdXhvH5BLf4v7Tc8cVCV3wuadnxY= Subject: Re: Change in functionality of futex() system call. From: Eric Dumazet To: Andrew Lutomirski Cc: Darren Hart , George Spelvin , david@rgmadvisors.com, kyle@moffetthome.net, linux-kernel@vger.kernel.org In-Reply-To: References: <20110609004435.14550.qmail@science.horizon.com> <4DF037C6.4000507@linux.intel.com> Content-Type: text/plain; charset="UTF-8" Date: Thu, 09 Jun 2011 05:54:19 +0200 Message-ID: <1307591659.3980.37.camel@edumazet-laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.32.2 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1316 Lines: 32 Le mercredi 08 juin 2011 à 23:38 -0400, Andrew Lutomirski a écrit : > Huh? > > I still don't understand why userspace ought to need to deny read > access to a file to prevent DoS. I think it's entirely reasonable for > userspace to make the assumption that users with read access cannot > make changes visible to writers unless explicitly documented (i.e. > file locking, which is so thoroughly broken that it shouldn't be taken > as an example of how to design anything). > > Given that current kernels make this use safe and the proposal is to > make it unsafe, I think it's worth designing the interface to avoid > introducing new security problems. I am very tired of this discussion, you repeat the same arguments over and over. You can not prevent DOS on a machine if you allow a process to RO map your critical files (where you put futexes), because you allow this process to interfere with critical cache lines bouncing between cpus. Really, please forget about this crazy idea of allowing foreigners to _read_ or memory _map_ your files. Dont do it. -- 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/