From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754922AbeD3Qlj (ORCPT ); Mon, 30 Apr 2018 12:41:39 -0400 Received: from mail.kernel.org ([198.145.29.99]:45906 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754613AbeD3Qli (ORCPT ); Mon, 30 Apr 2018 12:41:38 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1C6A522BDA Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=rostedt@goodmis.org Date: Mon, 30 Apr 2018 12:41:35 -0400 From: Steven Rostedt To: Linus Torvalds Cc: Kees Cook , Anna-Maria Gleixner , Linux Kernel Mailing List , tcharding Subject: Re: Hashed pointer issues Message-ID: <20180430124135.0cce92e3@gandalf.local.home> In-Reply-To: References: X-Mailer: Claws Mail 3.16.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 30 Apr 2018 16:31:52 +0000 Linus Torvalds wrote: > On Mon, Apr 30, 2018 at 9:11 AM Kees Cook wrote: > > > I (or other folks?) had proposed this before, but, AIUI, Linus remains > > opposed. > > Yeah, I hate this, because it will make people paper over their problems by > just booting with that option. > > I think it should just be fixed. > > Is there really any reason why trace buffers have to be dumped so early > that the entropy hasn't even taken yet? In this case, an RCU stall was triggering and a "dump on oops" would dump the trace buffers, (before entropy was established). > > And if we really want a command line option, can we make that still hash > the pointer, just force the entropy early. That way kernel developers that > test that command line option are still testing the *hashing*, they just > are missing the good entropy. > That may work too. Even with bad entropy, pointers at start up are hard to come by, and I can't see a hacker being able to use them as it only happens once during boot. -- Steve