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[140.211.169.12]) by mx.google.com with ESMTPS id v34si12624571plg.176.2019.03.19.11.02.38 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 19 Mar 2019 11:02:38 -0700 (PDT) Received-SPF: pass (google.com: domain of akpm@linux-foundation.org designates 140.211.169.12 as permitted sender) client-ip=140.211.169.12; Authentication-Results: mx.google.com; spf=pass (google.com: domain of akpm@linux-foundation.org designates 140.211.169.12 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org Received: from akpm3.svl.corp.google.com (unknown [104.133.8.65]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id 3CA3F3802; Tue, 19 Mar 2019 18:02:37 +0000 (UTC) Date: Tue, 19 Mar 2019 11:02:36 -0700 From: Andrew Morton To: Peter Xu Cc: linux-kernel@vger.kernel.org, Paolo Bonzini , Hugh Dickins , Luis Chamberlain , Maxime Coquelin , Maya Gokhale , Jerome Glisse , Pavel Emelyanov , Johannes Weiner , Martin Cracauer , Denis Plotnikov , linux-mm@kvack.org, Marty McFadden , Mike Kravetz , Andrea Arcangeli , Mike Rapoport , Kees Cook , Mel Gorman , "Kirill A . Shutemov" , linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, "Dr . David Alan Gilbert" Subject: Re: [PATCH v2 1/1] userfaultfd/sysctl: add vm.unprivileged_userfaultfd Message-Id: <20190319110236.b6169d6b469a587a852c7e09@linux-foundation.org> In-Reply-To: <20190319030722.12441-2-peterx@redhat.com> References: <20190319030722.12441-1-peterx@redhat.com> <20190319030722.12441-2-peterx@redhat.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit 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: On Tue, 19 Mar 2019 11:07:22 +0800 Peter Xu wrote: > Add a global sysctl knob "vm.unprivileged_userfaultfd" to control > whether userfaultfd is allowed by unprivileged users. When this is > set to zero, only privileged users (root user, or users with the > CAP_SYS_PTRACE capability) will be able to use the userfaultfd > syscalls. Please send along a full description of why you believe Linux needs this feature, for me to add to the changelog. What is the benefit to our users? How will it be used? etcetera. As it was presented I'm seeing no justification for adding the patch!