From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757506AbdACJRy (ORCPT ); Tue, 3 Jan 2017 04:17:54 -0500 Received: from mx2.suse.de ([195.135.220.15]:39320 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757242AbdACJRp (ORCPT ); Tue, 3 Jan 2017 04:17:45 -0500 Date: Tue, 3 Jan 2017 10:17:42 +0100 From: Michal Hocko To: Anshuman Khandual Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, vbabka@suse.cz, akpm@linux-foundation.org Subject: Re: [RFC] nodemask: Consider MAX_NUMNODES inside node_isset Message-ID: <20170103091741.GD30111@dhcp22.suse.cz> References: <20170103082753.25758-1-khandual@linux.vnet.ibm.com> <20170103084418.GC30111@dhcp22.suse.cz> <6c7ecb18-2ad0-f38a-1dc8-3c6c405b87ce@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6c7ecb18-2ad0-f38a-1dc8-3c6c405b87ce@linux.vnet.ibm.com> User-Agent: Mutt/1.6.0 (2016-04-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 03-01-17 14:37:09, Anshuman Khandual wrote: > On 01/03/2017 02:14 PM, Michal Hocko wrote: > > On Tue 03-01-17 13:57:53, Anshuman Khandual wrote: > >> node_isset can give incorrect result if the node number is beyond the > >> bitmask size (MAX_NUMNODES in this case) which is not checked inside > >> test_bit. Hence check for the bit limits (MAX_NUMNODES) inside the > >> node_isset function before calling test_bit. > > Could you be more specific when such a thing might happen? Have you seen > > any in-kernel user who would give such a bogus node? > > Have not seen this through any in-kernel use case. While rebasing the CDM > zonelist rebuilding series, Then fix this particular code path... > I came across this through an error path when > a bogus node value of 256 (MAX_NUMNODES on POWER) is received when we call > first_node() on an empty nodemask (which itself seems weird as well). Does calling first_node on an empty nodemask make any sense? If there is a risk then I would expect nodes_empty() check before doing any mask related operations. -- Michal Hocko SUSE Labs