From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752241AbaEAVP5 (ORCPT ); Thu, 1 May 2014 17:15:57 -0400 Received: from one.firstfloor.org ([193.170.194.197]:58387 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751784AbaEAVPz (ORCPT ); Thu, 1 May 2014 17:15:55 -0400 Date: Thu, 1 May 2014 23:15:54 +0200 From: Andi Kleen To: Andy Lutomirski Cc: "H. Peter Anvin" , Andi Kleen , X86 ML , "linux-kernel@vger.kernel.org" , Andi Kleen Subject: Re: [PATCH 4/7] x86: Add support for rd/wr fs/gs base Message-ID: <20140501211554.GH2382@two.firstfloor.org> References: <1398723161-21968-1-git-send-email-andi@firstfloor.org> <1398723161-21968-5-git-send-email-andi@firstfloor.org> <535FED4D.5000703@amacapital.net> <20140429233950.GE2382@two.firstfloor.org> <53608180.5070800@zytor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > If usergs == kernelgs, then ebx will always be 1 and we'll never end > up in paranoid_userspace. You may miss a reschedule in this obscure case. It shouldn't really happen because loading a kernel pointer is not useful for user space. Doesn't seem like a real issue to me. We only happen need to handle it to avoid crashing. > Alternatively, what if the paranoid entry checked whether we're coming > from userspace at the very beginning and, if so, just jumped to the > non-paranoid entry? That would work, but I doubt it would be worth it. -Andi