From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Garzik Subject: Re: [PATCH] drivers/net: remove network drivers' last few uses of IRQF_SAMPLE_RANDOM Date: Thu, 15 May 2008 14:31:32 -0400 Message-ID: <482C8184.2030906@garzik.org> References: <20080515142154.0595e475@core> <36D9DB17C6DE9E40B059440DB8D95F52052D71BB@orsmsx418.amr.corp.intel.com> <482C7B18.6060003@garzik.org> <482C7E53.3050300@hp.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: "Brandeburg, Jesse" , Alan Cox , Chris Peterson , netdev@vger.kernel.org, linux-kernel@vger.kernel.org To: Rick Jones Return-path: Received: from srv5.dvmed.net ([207.36.208.214]:59761 "EHLO mail.dvmed.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758984AbYEOSbl (ORCPT ); Thu, 15 May 2008 14:31:41 -0400 In-Reply-To: <482C7E53.3050300@hp.com> Sender: netdev-owner@vger.kernel.org List-ID: Rick Jones wrote: > Is there nothing associated with the networking stack - NIC, driver, > protocols, system calls which can be used as a source of entropy? The issue is with being externally observable and controllable, or, with some irq mitigation schemes, be made /too regular/. Interrupts (or timed mitigation events) may be triggered by the outside world, which makes it a very short path from remote attacker to local kernel entropy pool. Finally, with severe load, there are little or no interrupts thanks to heavy mitigation, which means your entropy pool may be externally DoS'd. Or at the very least, when your entropy needs to be INCREASED (due to heavy workload due to heavy traffic), your incoming entropy DECREASES due to decreased interrupts. [I just realized that last one. Heck, I'm even convincing myself even more its a bad idea] Jeff