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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 CBE4BC28CF6 for ; Wed, 1 Aug 2018 21:50:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 90EA520840 for ; Wed, 1 Aug 2018 21:50:24 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 90EA520840 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732518AbeHAXiN (ORCPT ); Wed, 1 Aug 2018 19:38:13 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:56910 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726174AbeHAXiN (ORCPT ); Wed, 1 Aug 2018 19:38:13 -0400 Received: from akpm3.svl.corp.google.com (unknown [104.133.9.92]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id 2EA1CD3C; Wed, 1 Aug 2018 21:50:21 +0000 (UTC) Date: Wed, 1 Aug 2018 14:50:20 -0700 From: Andrew Morton To: Jeremy Linton Cc: linux-mm@kvack.org, cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, mhocko@suse.com, vbabka@suse.cz, Punit.Agrawal@arm.com, Lorenzo.Pieralisi@arm.com, linux-arm-kernel@lists.infradead.org, bhelgaas@google.com, linux-kernel@vger.kernel.org Subject: Re: [RFC 0/2] harden alloc_pages against bogus nid Message-Id: <20180801145020.8c76a490c1bf9bef5f87078a@linux-foundation.org> In-Reply-To: <20180801200418.1325826-1-jeremy.linton@arm.com> References: <20180801200418.1325826-1-jeremy.linton@arm.com> X-Mailer: Sylpheed 3.6.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 1 Aug 2018 15:04:16 -0500 Jeremy Linton wrote: > The thread "avoid alloc memory on offline node" > > https://lkml.org/lkml/2018/6/7/251 > > Asked at one point why the kzalloc_node was crashing rather than > returning memory from a valid node. The thread ended up fixing > the immediate causes of the crash but left open the case of bad > proximity values being in DSDT tables without corrisponding > SRAT/SLIT entries as is happening on another machine. > > Its also easy to fix that, but we should also harden the allocator > sufficiently that it doesn't crash when passed an invalid node id. > There are a couple possible ways to do this, and i've attached two > separate patches which individually fix that problem. > > The first detects the offline node before calling > the new_slab code path when it becomes apparent that the allocation isn't > going to succeed. The second actually hardens node_zonelist() and > prepare_alloc_pages() in the face of NODE_DATA(nid) returning a NULL > zonelist. This latter case happens if the node has never been initialized > or is possibly out of range. There are other places (NODE_DATA & > online_node) which should be checking if the node id's are > MAX_NUMNODES. > What is it that leads to a caller requesting memory from an invalid node? A race against offlining? If so then that's a lack of appropriate locking, isn't it? I don't see a problem with emitting a warning and then selecting a different node so we can keep running. But we do want that warning, so we can understand the root cause and fix it?