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[209.132.183.28]) by mx.google.com with ESMTPS id x12si4138258qkh.253.2019.03.12.05.43.17 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 12 Mar 2019 05:43:17 -0700 (PDT) Received-SPF: pass (google.com: domain of peterx@redhat.com designates 209.132.183.28 as permitted sender) client-ip=209.132.183.28; Authentication-Results: mx.google.com; spf=pass (google.com: domain of peterx@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=peterx@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 78BAF30842CD; Tue, 12 Mar 2019 12:43:16 +0000 (UTC) Received: from xz-x1 (dhcp-14-116.nay.redhat.com [10.66.14.116]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 45797648C2; Tue, 12 Mar 2019 12:43:05 +0000 (UTC) Date: Tue, 12 Mar 2019 20:43:02 +0800 From: Peter Xu To: "Kirill A. Shutemov" Cc: linux-kernel@vger.kernel.org, Paolo Bonzini , Hugh Dickins , Luis Chamberlain , Maxime Coquelin , kvm@vger.kernel.org, Jerome Glisse , Pavel Emelyanov , Johannes Weiner , Martin Cracauer , Denis Plotnikov , linux-mm@kvack.org, Marty McFadden , Maya Gokhale , Mike Kravetz , Andrea Arcangeli , Mike Rapoport , Kees Cook , Mel Gorman , linux-fsdevel@vger.kernel.org, "Dr . David Alan Gilbert" , Andrew Morton , linux-api@vger.kernel.org Subject: Re: [PATCH 0/3] userfaultfd: allow to forbid unprivileged users Message-ID: <20190312124302.GA2433@xz-x1> References: <20190311093701.15734-1-peterx@redhat.com> <20190312074951.i2md3npcjcceywqj@kshutemo-mobl1> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190312074951.i2md3npcjcceywqj@kshutemo-mobl1> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.40]); Tue, 12 Mar 2019 12:43:17 +0000 (UTC) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hi, Kirill, On Tue, Mar 12, 2019 at 10:49:51AM +0300, Kirill A. Shutemov wrote: > On Mon, Mar 11, 2019 at 05:36:58PM +0800, Peter Xu wrote: > > Hi, > > > > (The idea comes from Andrea, and following discussions with Mike and > > other people) > > > > This patchset introduces a new sysctl flag to allow the admin to > > forbid users from using userfaultfd: > > > > $ cat /proc/sys/vm/unprivileged_userfaultfd > > [disabled] enabled kvm > > CC linux-api@ > > This is unusual way to return current value for sysctl. Does it work fine > with sysctl tool? It can work, though it displays the same as "cat": $ sysctl vm.unprivileged_userfaultfd vm.unprivileged_userfaultfd = disabled enabled [kvm] > > Have you considered to place the switch into /sys/kernel/mm instead? > I doubt it's the last tunable for userfaultfd. Maybe we should have an > directory for it under /sys/kernel/mm? I haven't thought about sysfs, if that's preferred I can consider to switch to that. And yes I think creating a directory should be a good idea. Thanks, -- Peter Xu