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=unavailable 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 58531C432C2 for ; Thu, 26 Sep 2019 07:53:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 382AB222C5 for ; Thu, 26 Sep 2019 07:53:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726460AbfIZHxM (ORCPT ); Thu, 26 Sep 2019 03:53:12 -0400 Received: from mx2.suse.de ([195.135.220.15]:41402 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725815AbfIZHxL (ORCPT ); Thu, 26 Sep 2019 03:53:11 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 2265DAED6; Thu, 26 Sep 2019 07:53:10 +0000 (UTC) Date: Thu, 26 Sep 2019 09:53:07 +0200 From: Oscar Salvador To: Alastair D'Silva Cc: alastair@d-silva.org, Andrew Morton , Michal Hocko , David Hildenbrand , Pavel Tatashin , Dan Williams , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4] memory_hotplug: Add a bounds check to __add_pages Message-ID: <20190926075307.GB17200@linux> References: <20190926013406.16133-1-alastair@au1.ibm.com> <20190926013406.16133-2-alastair@au1.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190926013406.16133-2-alastair@au1.ibm.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 26, 2019 at 11:34:05AM +1000, 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 Reviewed-by: Oscar Salvador Just a nit-picking below: > --- > 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; I would use PFN_PHYS instead: unsigned long max_addr = PFN_PHYS(pfn + nr_pages) - 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, Same here. > + (1ul << (MAX_PHYSMEM_BITS + 1)) - 1); I would use a local variable to hold this computation. > + return -E2BIG; > + } > + > + return 0; -- Oscar Salvador SUSE L3