Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752642AbdFURyB (ORCPT ); Wed, 21 Jun 2017 13:54:01 -0400 Received: from mail-lf0-f67.google.com ([209.85.215.67]:32899 "EHLO mail-lf0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751114AbdFURx7 (ORCPT ); Wed, 21 Jun 2017 13:53:59 -0400 Date: Wed, 21 Jun 2017 20:53:51 +0300 From: Cyrill Gorcunov To: Oleg Nesterov Cc: Hugh Dickins , Andrey Vagin , LKML , Pavel Emelyanov , Dmitry Safonov , Andrew Morton , Adrian Reber Subject: Re: [criu] 1M guard page ruined restore Message-ID: <20170621175351.GH31050@uranus> References: <20170620075206.GB1909@uranus.lan> <20170621152256.GC31050@uranus> <20170621155730.GA32554@redhat.com> <20170621160410.GF31050@uranus> <20170621170129.GA32752@redhat.com> <20170621171545.GA28664@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170621171545.GA28664@redhat.com> User-Agent: Mutt/1.8.0 (2017-02-23) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1743 Lines: 62 On Wed, Jun 21, 2017 at 07:15:45PM +0200, Oleg Nesterov wrote: > On 06/21, Oleg Nesterov wrote: > > > > On 06/21, Cyrill Gorcunov wrote: > > > > > > On Wed, Jun 21, 2017 at 05:57:30PM +0200, Oleg Nesterov wrote: > > > > > > > > > > p = fake_grow_down; > > > > > *p-- = 'c'; > > > > > > > > I guess this works? I mean, *p-- = 'c' should not fail... > > > > > > It fails. > > > > Hmm. Impossible ;) could you add the additional printf's to re-check? > > Yes, please... I meant of course second store, sorry for confusion :) > > > > p = fake_grow_down; > > > *p-- = 'c'; > > > > once again, I can't believe this STORE can fail... > > > > > *p = 'b'; > > > > Ah. I forgot about another kernel "feature" ;) not related to the recent guard > > page changes... > > On the second thought it is actually connected, and it seems we really need to > remove this code in do_page_fault... I'll re-check tomorrow, need to run away. > > > Could you test the patch below? > > > > Oleg. > > > > > > diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c > > index 8ad91a0..edc5d68 100644 > > --- a/arch/x86/mm/fault.c > > +++ b/arch/x86/mm/fault.c > > @@ -1416,7 +1416,7 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code, > > * and pusha to work. ("enter $65535, $31" pushes > > * 32 pointers and then decrements %sp by 65535.) > > */ > > - if (unlikely(address + 65536 + 32 * sizeof(unsigned long) < regs->sp)) { > > +if (0) if (unlikely(address + 65536 + 32 * sizeof(unsigned long) < regs->sp)) { > > bad_area(regs, error_code, address); > > return; > > } It does the trick [root@fc2 ~]# ~/st2 start_addr 7fce7c3f8000 start_addr 7fce7c529000 test_addr 7fce7c527000 grow_down 7fce7c526000 Cyrill