Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934471AbeAOOmG (ORCPT + 1 other); Mon, 15 Jan 2018 09:42:06 -0500 Received: from mga17.intel.com ([192.55.52.151]:33433 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933608AbeAOOmF (ORCPT ); Mon, 15 Jan 2018 09:42:05 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.46,364,1511856000"; d="scan'208";a="19846386" Subject: Re: [tip:x86/pti] x86/retpoline: Fill RSB on context switch for affected CPUs To: David Laight , "dwmw@amazon.co.uk" , "riel@redhat.com" , "tglx@linutronix.de" , "linux-kernel@vger.kernel.org" , "tim.c.chen@linux.intel.com" , "pjt@google.com" , "jpoimboe@redhat.com" , "ak@linux.intel.com" , "gregkh@linux-foundation.org" , "torvalds@linux-foundation.org" , "dave.hansen@intel.com" , "luto@amacapital.net" , "jikos@kernel.org" , "peterz@infradead.org" , "keescook@google.com" , "mingo@kernel.org" , "hpa@zytor.com" , "linux-tip-commits@vger.kernel.org" References: <1515779365-9032-1-git-send-email-dwmw@amazon.co.uk> From: Arjan van de Ven Message-ID: Date: Mon, 15 Jan 2018 06:42:03 -0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.5.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: > > This would means that userspace would see return predictions based > on the values the kernel 'stuffed' into the RSB to fill it. > > Potentially this leaks a kernel address to userspace. KASLR pretty much died in May this year to be honest with the KAISER paper (if not before then) also with KPTI the address won't have a TLB mapping so it wouldn't actually be speculated into.