From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752202AbdKZOFi (ORCPT ); Sun, 26 Nov 2017 09:05:38 -0500 Received: from mail-wr0-f194.google.com ([209.85.128.194]:46163 "EHLO mail-wr0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752070AbdKZOFh (ORCPT ); Sun, 26 Nov 2017 09:05:37 -0500 X-Google-Smtp-Source: AGs4zMY0XFx80GGxZWaX0aqjvRjmX+R3OAxSbJYIv8DVSNeMhOG33uZeXJ1UovaDNxOsUv61kZ5Wkw== Date: Sun, 26 Nov 2017 15:05:33 +0100 From: Ingo Molnar To: Andy Lutomirski Cc: Borislav Petkov , "linux-kernel@vger.kernel.org" , Dave Hansen , Thomas Gleixner , "H . Peter Anvin" , Peter Zijlstra , Linus Torvalds Subject: Re: [PATCH 12/43] x86/espfix/64: Stop assuming that pt_regs is on the entry stack Message-ID: <20171126140533.d77hroi7jjvaf42g@gmail.com> References: <20171124172411.19476-1-mingo@kernel.org> <20171124172411.19476-13-mingo@kernel.org> <20171124182517.s266w4ppg4csrjrn@pd.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Andy Lutomirski wrote: > On Fri, Nov 24, 2017 at 10:25 AM, Borislav Petkov wrote: > > On Fri, Nov 24, 2017 at 06:23:40PM +0100, Ingo Molnar wrote: > >> From: Andy Lutomirski > >> > >> When we start using an entry trampoline, a #GP from userspace will > >> be delivered on the entry stack, not on the task stack. Fix the > >> espfix64 #DF fixup to set up #GP according to TSS.SP0, rather than > >> assuming that pt_regs + 1 == SP0. This won't change anything > >> without an entry stack, but it will make the code continue to work > >> when an entry stack is added. > >> > >> Signed-off-by: Andy Lutomirski > >> Signed-off-by: Thomas Gleixner > >> Reviewed-by: Thomas Gleixner > >> Cc: Borislav Petkov > >> Cc: Brian Gerst > >> Cc: Dave Hansen > >> Cc: Josh Poimboeuf > >> Cc: Linus Torvalds > >> Cc: Peter Zijlstra > >> Link: https://lkml.kernel.org/r/b1ef4136616c6bd2a75d1fd2736d1d54437d65a8.1511497875.git.luto@kernel.org > >> Signed-off-by: Ingo Molnar > >> --- > >> arch/x86/kernel/traps.c | 5 +++-- > >> 1 file changed, 3 insertions(+), 2 deletions(-) > >> > >> diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c > >> index 2008dd0f8ccb..1bd43f044c62 100644 > >> --- a/arch/x86/kernel/traps.c > >> +++ b/arch/x86/kernel/traps.c > >> @@ -359,7 +359,8 @@ dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code) > >> regs->cs == __KERNEL_CS && > >> regs->ip == (unsigned long)native_irq_return_iret) > >> { > >> - struct pt_regs *normal_regs = task_pt_regs(current); > >> + struct pt_regs *normal_regs = > >> + (struct pt_regs *)this_cpu_read(cpu_tss.x86_tss.sp0) - 1; > > > > Just let that line stick out. Also, you can shorten it by renaming > > normal_regs to something much shorter - it is a local variable and the > > comment already explains everything you you can just as well have: > > > > struct pt_regs *r = (struct pt_regs *)this_cpu_read(cpu_tss.x86_tss.sp0) - 1; > > > > Done, along with much better comments. > > https://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git/commit/?h=x86/entry_stack&id=6510485d026abdd144d170b1bc8508327acb5648 I have added Boris's reviewed-by tag: Reviewed-by: Borislav Petkov which I suspect applies now? Thanks, Ingo