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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 67C3CC432C2 for ; Thu, 26 Sep 2019 07:46:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3B42D21A4A for ; Thu, 26 Sep 2019 07:46:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731325AbfIZHqv (ORCPT ); Thu, 26 Sep 2019 03:46:51 -0400 Received: from mx1.redhat.com ([209.132.183.28]:44270 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726148AbfIZHqv (ORCPT ); Thu, 26 Sep 2019 03:46:51 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id C84F785540; Thu, 26 Sep 2019 07:46:50 +0000 (UTC) Received: from [10.36.116.222] (ovpn-116-222.ams2.redhat.com [10.36.116.222]) by smtp.corp.redhat.com (Postfix) with ESMTP id E4A0B5D9CD; Thu, 26 Sep 2019 07:46:48 +0000 (UTC) Subject: Re: [PATCH v4] memory_hotplug: Add a bounds check to __add_pages To: Michal Hocko Cc: Alastair D'Silva , alastair@d-silva.org, Andrew Morton , Oscar Salvador , Pavel Tatashin , Dan Williams , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20190926013406.16133-1-alastair@au1.ibm.com> <20190926013406.16133-2-alastair@au1.ibm.com> <8e00cf16-76b9-6655-86b6-288b454d6fe5@redhat.com> <20190926074312.GD20255@dhcp22.suse.cz> From: David Hildenbrand Openpgp: preference=signencrypt Autocrypt: addr=david@redhat.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190926074312.GD20255@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.28]); Thu, 26 Sep 2019 07:46:50 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 26.09.19 09:43, Michal Hocko wrote: > On Thu 26-09-19 09:12:50, David Hildenbrand wrote: >> On 26.09.19 03:34, Alastair D'Silva wrote: >>> From: Alastair D'Silva >>> >>> On PowerPC, the address ranges allocated to OpenCAPI LPC memory >>> are allocated from firmware. These address ranges may be higher >>> than what older kernels permit, as we increased the maximum >>> permissable address in commit 4ffe713b7587 >>> ("powerpc/mm: Increase the max addressable memory to 2PB"). It is >>> possible that the addressable range may change again in the >>> future. >>> >>> In this scenario, we end up with a bogus section returned from >>> __section_nr (see the discussion on the thread "mm: Trigger bug on >>> if a section is not found in __section_nr"). >>> >>> Adding a check here means that we fail early and have an >>> opportunity to handle the error gracefully, rather than rumbling >>> on and potentially accessing an incorrect section. >>> >>> Further discussion is also on the thread ("powerpc: Perform a bounds >>> check in arch_add_memory") >>> http://lkml.kernel.org/r/20190827052047.31547-1-alastair@au1.ibm.com >>> >>> Signed-off-by: Alastair D'Silva >>> --- >>> mm/memory_hotplug.c | 20 ++++++++++++++++++++ >>> 1 file changed, 20 insertions(+) >>> >>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c >>> index c73f09913165..212804c0f7f5 100644 >>> --- a/mm/memory_hotplug.c >>> +++ b/mm/memory_hotplug.c >>> @@ -278,6 +278,22 @@ static int check_pfn_span(unsigned long pfn, unsigned long nr_pages, >>> return 0; >>> } >>> >>> +static int check_hotplug_memory_addressable(unsigned long pfn, >>> + unsigned long nr_pages) >>> +{ >>> + unsigned long max_addr = ((pfn + nr_pages) << PAGE_SHIFT) - 1; >>> + >>> + if (max_addr >> MAX_PHYSMEM_BITS) { >>> + WARN(1, >>> + "Hotplugged memory exceeds maximum addressable address, range=%#lx-%#lx, maximum=%#lx\n", >>> + pfn << PAGE_SHIFT, max_addr, >>> + (1ul << (MAX_PHYSMEM_BITS + 1)) - 1); >>> + return -E2BIG; >>> + } >>> + >>> + return 0; >>> +} >>> + >>> /* >>> * Reasonably generic function for adding memory. It is >>> * expected that archs that support memory hotplug will >>> @@ -291,6 +307,10 @@ int __ref __add_pages(int nid, unsigned long pfn, unsigned long nr_pages, >>> unsigned long nr, start_sec, end_sec; >>> struct vmem_altmap *altmap = restrictions->altmap; >>> >>> + err = check_hotplug_memory_addressable(pfn, nr_pages); >>> + if (err) >>> + return err; >>> + >>> if (altmap) { >>> /* >>> * Validate altmap is within bounds of the total request >>> >> >> >> I know Michal suggested this, but I still prefer checking early instead >> of when we're knees-deep into adding of memory. > > What is your concern here? Unwinding the state should be pretty > straightfoward from this failure path. Just the general "check what you can check early without locks" approach. But yeah, this series is probably not worth a v5, so I can live with this change just fine :) -- Thanks, David / dhildenb