From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B3616CA9EAF for ; Thu, 24 Oct 2019 15:55:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 897DD222CB for ; Thu, 24 Oct 2019 15:55:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Slhwk2iV" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2503414AbfJXPzA (ORCPT ); Thu, 24 Oct 2019 11:55:00 -0400 Received: from us-smtp-1.mimecast.com ([205.139.110.61]:57013 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2503392AbfJXPy5 (ORCPT ); Thu, 24 Oct 2019 11:54:57 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1571932496; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=T2ExiigEByCtsmRRvNsGaGfhM9mM9F5zlr4YhPOUDug=; b=Slhwk2iVkogSau2UovSoFzTFDf8kgcKFe2LUv/K41U/tRIYekv/IZrhEgLwINFL1mD14yc Uy2QdBHLm3vqFWsU+L2vfmuYarNV2CmSKFHwUtLEZzn0VzG3QUCx50rep1/RwXiu2YhQQ9 JlWZcMPU/YmcwbDO0COLhph1QDQ5O+8= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-74-gGkffQx-MgiQBUn_hUtQng-1; Thu, 24 Oct 2019 11:54:52 -0400 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 5A6E885EE90; Thu, 24 Oct 2019 15:10:55 +0000 (UTC) Received: from mail (ovpn-123-192.rdu2.redhat.com [10.10.123.192]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 25B35196B2; Thu, 24 Oct 2019 15:10:55 +0000 (UTC) Date: Thu, 24 Oct 2019 11:10:54 -0400 From: Andrea Arcangeli To: Mike Rapoport Cc: Andy Lutomirski , Jann Horn , Daniel Colascione , Linus Torvalds , Pavel Emelyanov , Lokesh Gidra , Nick Kralevich , Nosh Minwalla , Tim Murray , Mike Rapoport , Linux API , LKML Subject: Re: [PATCH 3/7] Add a UFFD_SECURE flag to the userfaultfd API. Message-ID: <20191024151054.GJ9902@redhat.com> References: <20191012191602.45649-1-dancol@google.com> <20191012191602.45649-4-dancol@google.com> <20191023190959.GA9902@redhat.com> <20191024090258.GA9802@linux.ibm.com> MIME-Version: 1.0 In-Reply-To: <20191024090258.GA9802@linux.ibm.com> User-Agent: Mutt/1.12.2 (2019-09-21) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-MC-Unique: gGkffQx-MgiQBUn_hUtQng-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On Thu, Oct 24, 2019 at 12:02:59PM +0300, Mike Rapoport wrote: > That's no the reason that UFFD_FEATURE_EVENT_FORK does not show up in > Debian code search, CRIU simply is not there. Debian packages CRIU only i= n > experimental and I believe that's not indexed by the code search. >=20 > As for the limitations, the races were fixed, I just forgot to update the > wiki. As for the supported memory types and COW pages, these only affect > efficiency of post-copy, but not the correctness. That's what I was hoping for. If the wiki information is stale and there are no races it is totally plausible that it's being actively used in production so we need to fix the kernel bug. I was just checking because I wasn't sure anymore of the status after I read the wiki. If the CRIU initialization code that issues the uffd syscall runs as global root the ABI breaking permission check from Andy sounds the simplest for a short term fix, because it will be unnoticed by any production usage with CIRU --lazy-pages. Then later we could add a UFFD_FEATURE_EVENT_FORK2 that will not require root permission. Thanks, Andrea