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=-0.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 C6C97CA9EBC for ; Fri, 25 Oct 2019 21:58:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8AC9C21D82 for ; Fri, 25 Oct 2019 21:58:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572040709; bh=5idHqzI+WDLhPVhG4vI2ZMChGI3hQGDJ+ZfGRxe0PSk=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=KA4etMxn7E0EwF3RnvMUZ/H4S6hObZZxeXOI+Nq5oD4R0qcz+AntHNMzxCSo9tZqD kpWNfNpxwjuYwJ1xksowQSBSWgXuyeqw5KCrRPA6+RveZugcXaRfgiXMhbGqBpugaN ItAH+pwfYDq0jKbFFBntV5bLyGXkpsvOwAoNwctY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726271AbfJYV62 (ORCPT ); Fri, 25 Oct 2019 17:58:28 -0400 Received: from mail.kernel.org ([198.145.29.99]:35712 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725801AbfJYV62 (ORCPT ); Fri, 25 Oct 2019 17:58:28 -0400 Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id CD05B21D7F; Fri, 25 Oct 2019 21:58:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572040707; bh=5idHqzI+WDLhPVhG4vI2ZMChGI3hQGDJ+ZfGRxe0PSk=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=V7hXa31Uos3d+7DomJcDHCsK1tAEa/hKrzpZ6JVU5sh0ejVGcV6AYpTNCCfKj0yGH 9L8NB8JihQZ5Uyo2PehT1vpnOs5+87csqN2nTpkxTNJhNy3nwJy0cf1Q8phBhOyjl5 UIJUHjZz7Qk49FHME8WpQam7ERAEwn2uFD/6TQvE= Date: Fri, 25 Oct 2019 14:58:26 -0700 From: Andrew Morton To: Vlastimil Babka Cc: Michal Hocko , Mel Gorman , Waiman Long , Johannes Weiner , Roman Gushchin , Konstantin Khlebnikov , Jann Horn , Song Liu , Greg Kroah-Hartman , Rafael Aquini , linux-mm@kvack.org, LKML , Michal Hocko , David Rientjes , stable Subject: Re: [PATCH 1/2] mm, vmstat: hide /proc/pagetypeinfo from normal users Message-Id: <20191025145826.acfd34f4eaec65f0525ac40b@linux-foundation.org> In-Reply-To: References: <20191025072610.18526-1-mhocko@kernel.org> <20191025072610.18526-2-mhocko@kernel.org> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 25 Oct 2019 09:33:26 +0200 Vlastimil Babka wrote: > On 10/25/19 9:26 AM, Michal Hocko wrote: > > From: Michal Hocko > > > > /proc/pagetypeinfo is a debugging tool to examine internal page > > allocator state wrt to fragmentation. It is not very useful for > > any other use so normal users really do not need to read this file. > > > > Waiman Long has noticed that reading this file can have negative side > > effects because zone->lock is necessary for gathering data and that > > a) interferes with the page allocator and its users and b) can lead to > > hard lockups on large machines which have very long free_list. > > > > Reduce both issues by simply not exporting the file to regular users. > > > > Reported-by: Waiman Long > > Cc: stable > > Cc: As we don't really know how much damage this will cause, it would be nice to let it bake in mainline for a month or three before committing it to the -stable trees. But we don't have a process for that, apart from remembering to poke Greg at a suitable date. Oh well. I guess that if someone is truly harmed by this change, they can just chmod /proc/pagetypeinfo back to 0444.