From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linutronix.de (193.142.43.55:993) by crypto-ml.lab.linutronix.de with IMAP4-SSL for ; 20 Feb 2020 14:27:32 -0000 Received: from mail.kernel.org ([198.145.29.99]) by Galois.linutronix.de with esmtps (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1j4mna-0000VY-Sc for speck@linutronix.de; Thu, 20 Feb 2020 15:27:31 +0100 Date: Thu, 20 Feb 2020 15:27:20 +0100 From: Greg KH Subject: [MODERATED] Re: [PATCH 0/2] more sampling fun 0 Message-ID: <20200220142720.GA3433900@kroah.com> References: <20200220081420.GA3328448@kroah.com> MIME-Version: 1.0 In-Reply-To: <20200220081420.GA3328448@kroah.com> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit To: speck@linutronix.de List-ID: On Thu, Feb 20, 2020 at 09:14:20AM +0100, speck for Greg KH wrote: > On Wed, Feb 19, 2020 at 02:45:22PM -0800, speck for mark gross wrote: > > From: mark gross > > Subject: [PATCH 0/2] Special Register Buffer Data Sampling patch set > > > > Special Register Buffer Data Sampling is a sampling type of vulnerability that > > leaks data across cores sharing the HW-RNG for vulnerable processors. > > > > This leak is fixed by a microcode update and is enabled by default. > > > > This new microcode serializes processor access during execution of RDRAND > > or RDSEED. It ensures that the shared buffer is overwritten before it > > is released for reuse. > > > > The mitigation impacts the throughput of the RDRAND and RDSEED instructions > > and latency of RT processing running on the socket while executing RDRAND or > > RDSEED. The micro bechmark of calling RDRAND many times shows a 10x slowdown. > > Then we need to stop using RDRAND internally for our "give me a random > number api" which has spread to more and more parts of the kernel. > > Here's a patch that does so: > https://lore.kernel.org/lkml/20200216161836.1976-1-Jason@zx2c4.com/ > which I'm going to advise get merged now and backported to the stable > branches. Note, the author of that patch has reached out to me to say they found this same issue. He did so independantly so odds are others already know about this. He found it because he was wondering why rdrand was so slow on newer systems, and then traced things backwards like all the other researchers in this area. So, what's the timeline here? Looks like this is already "in the wild" from what I can tell. greg k-h