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=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 63543C432C2 for ; Thu, 26 Sep 2019 07:45:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3632E222C7 for ; Thu, 26 Sep 2019 07:45:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1569483903; bh=pZy0b91IcGDUU/4dO2zwKPGS3d79Rbor1u62MgztOHw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=qxoqkA2aLcjsofxOi1NrKxzc12KqRa193S//l5qt+jgyFikrf1srhPF9gYi/O2HbM sAfRAin1DAZ7Jxkpse1JZrFP5zDDdhjJvmyytUcDWRPhUSwBnBN7FmBrsYfNxXt1Lh +q+ECBGwMwSb1/YNjG3Y2OyXkb5kdwPSVjJhw+w8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731237AbfIZHpC (ORCPT ); Thu, 26 Sep 2019 03:45:02 -0400 Received: from mx2.suse.de ([195.135.220.15]:39076 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729053AbfIZHpB (ORCPT ); Thu, 26 Sep 2019 03:45:01 -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 50C9CAE0C; Thu, 26 Sep 2019 07:44:59 +0000 (UTC) Date: Thu, 26 Sep 2019 09:44:58 +0200 From: Michal Hocko To: Alastair D'Silva Cc: alastair@d-silva.org, Andrew Morton , Oscar Salvador , 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: <20190926074458.GE20255@dhcp22.suse.cz> 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 26-09-19 11:34:05, 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 Yes, this looks better to me. E2BIG is a new error code for this path but no callers seem to be deeply concerned about a specific error codes so this should be safe. Acked-by: Michal Hocko > --- > 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 > -- > 2.21.0 -- Michal Hocko SUSE Labs