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 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 5304DC43142 for ; Fri, 3 Aug 2018 03:15:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0E0E0216EE for ; Fri, 3 Aug 2018 03:15:15 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0E0E0216EE Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com 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 S1727573AbeHCFJX (ORCPT ); Fri, 3 Aug 2018 01:09:23 -0400 Received: from foss.arm.com ([217.140.101.70]:37120 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727392AbeHCFJX (ORCPT ); Fri, 3 Aug 2018 01:09:23 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 987D218A; Thu, 2 Aug 2018 20:15:12 -0700 (PDT) Received: from [192.168.100.241] (usa-sjc-mx-foss1.foss.arm.com [217.140.101.70]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 8FC003F5BA; Thu, 2 Aug 2018 20:15:11 -0700 (PDT) Subject: Re: [RFC 0/2] harden alloc_pages against bogus nid To: Andrew Morton 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 References: <20180801200418.1325826-1-jeremy.linton@arm.com> <20180801145020.8c76a490c1bf9bef5f87078a@linux-foundation.org> <20180801171414.30e54a106733ccaaa566388d@linux-foundation.org> From: Jeremy Linton Message-ID: Date: Thu, 2 Aug 2018 22:15:10 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <20180801171414.30e54a106733ccaaa566388d@linux-foundation.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 08/01/2018 07:14 PM, Andrew Morton wrote: > On Wed, 1 Aug 2018 17:56:46 -0500 Jeremy Linton wrote: > >> Hi, >> >> On 08/01/2018 04:50 PM, Andrew Morton wrote: >>> 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? >> >> There were a couple unrelated cases, both having to do with the PXN >> associated with a PCI port. The first case AFAIK, the domain wasn't >> really invalid if the entire SRAT was parsed and nodes created even when >> there weren't associated CPUs. The second case (a different machine) is >> simply a PXN value that is completely invalid (no associated >> SLIT/SRAT/etc entries) due to firmware making a mistake when a socket >> isn't populated. >> >> There have been a few other suggested or merged patches for the >> individual problems above, this set is just an attempt at avoiding a >> full crash if/when another similar problem happens. > > Please add the above info to the changelog. Sure. > >> >>> >>> 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? >> >> Yes, we do want to know when an invalid id is passed, i will add the >> VM_WARN in the first one. >> >> The second one I wasn't sure about as failing prepare_alloc_pages() >> generates a couple of error messages, but the system then continues >> operation. >> >> I guess my question though is which method (or both/something else?) is >> the preferred way to harden this up? > > The first patch looked neater. Can we get a WARN_ON in there as well? > Yes, Thanks,