From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752863AbbC2MPm (ORCPT ); Sun, 29 Mar 2015 08:15:42 -0400 Received: from mail.skyhub.de ([78.46.96.112]:34319 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751904AbbC2MPk (ORCPT ); Sun, 29 Mar 2015 08:15:40 -0400 Date: Sun, 29 Mar 2015 14:13:47 +0200 From: Borislav Petkov To: Ingo Molnar Cc: Denys Vlasenko , Andy Lutomirski , "H. Peter Anvin" , Brad Spengler , Linus Torvalds , "linux-kernel@vger.kernel.org" , Thomas Gleixner , Andrew Lutomirski , "linux-tip-commits@vger.kernel.org" Subject: Re: [PATCH] x86/asm/entry: Remove user_mode_ignore_vm86() Message-ID: <20150329121347.GC4973@pd.tnic> References: <202c56ca63823c338af8e2e54948dbe222da6343.1426728647.git.luto@kernel.org> <20150324194402.GA27598@gmail.com> <55155F9E.3030605@redhat.com> <20150329070816.GD18007@gmail.com> <20150329090233.GA1963@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20150329090233.GA1963@gmail.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Mar 29, 2015 at 11:02:34AM +0200, Ingo Molnar wrote: > So how about doing the patch below? > > Thanks, > > Ingo > > ===================================> > From 6677d6f073cfda7f1036eb06d13faaad5c6742cc Mon Sep 17 00:00:00 2001 > From: Ingo Molnar > Date: Sun, 29 Mar 2015 09:10:08 +0200 > Subject: [PATCH] x86/asm/entry: Remove user_mode_ignore_vm86() > > user_mode_ignore_vm86() can be used instead of user_mode(), in > places where we have already done a v8086_mode() security > check of ptregs. > > But doing this check in the wrong place would be a bug that could > result in security problems, and also the naming still isn't very clear. > > Furthermore, it only affects 32-bit kernels, while most development > happens on 64-bit kernels. > > If we replace them with user_mode() checks then the cost is only a > very minor increase in various slowpaths: > > text data bss dec hex filename > 10573391 703562 1753042 13029995 c6d26b vmlinux.o.before > 10573423 703562 1753042 13030027 c6d28b vmlinux.o.after > > So lets get rid of this distinction once and for all. > > Cc: Andy Lutomirski > Cc: Borislav Petkov > Cc: Denys Vlasenko > Cc: H. Peter Anvin > Cc: Linus Torvalds > Cc: Oleg Nesterov > Cc: Thomas Gleixner > Signed-off-by: Ingo Molnar > --- > arch/x86/include/asm/ptrace.h | 17 ----------------- > arch/x86/kernel/cpu/perf_event.c | 2 +- > arch/x86/kernel/traps.c | 6 +++--- > 3 files changed, 4 insertions(+), 21 deletions(-) I had some doubts about people using user_mode_ignore_vm86() in the wrong way and thus introducing sec. bugs. Since this is only on the slow path, simplifying the code makes sense to me. Acked-by: Borislav Petkov -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply. --