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=-8.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT 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 E35D5C65BAE for ; Thu, 13 Dec 2018 12:59:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A551B2086D for ; Thu, 13 Dec 2018 12:59:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1544705996; bh=xKkoOCOSA26D9EssDh96TQ3hG5lvU/P6r/Im4gA55uA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=Jsu+bxesXQTPaRadC2gj4pDYMCygYEVaTq5b60+UrafjfIA8CrrH0t7VTpZngaDVJ /O/XutiIP8ExciZyiXeqPCu7Fiqni4jYEqdHd+xbHU05VeJLCpOx5rSEL4MQFxZ1xR XNkzRSPe/e/oKzKdH2IFax9Lbz2mu+PU+9fywf00= DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A551B2086D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.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 S1729307AbeLMM7z (ORCPT ); Thu, 13 Dec 2018 07:59:55 -0500 Received: from mx2.suse.de ([195.135.220.15]:60982 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728803AbeLMM7z (ORCPT ); Thu, 13 Dec 2018 07:59:55 -0500 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 9136DAF79; Thu, 13 Dec 2018 12:59:52 +0000 (UTC) Date: Thu, 13 Dec 2018 13:59:52 +0100 From: Michal Hocko To: Mikhail Zaslonko Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Pavel.Tatashin@microsoft.com, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, gerald.schaefer@de.ibm.com Subject: Re: [PATCH v2 1/1] mm, memory_hotplug: Initialize struct pages for the full memory section Message-ID: <20181213125952.GA1286@dhcp22.suse.cz> References: <20181212172712.34019-1-zaslonko@linux.ibm.com> <20181212172712.34019-2-zaslonko@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181212172712.34019-2-zaslonko@linux.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 Wed 12-12-18 18:27:12, Mikhail Zaslonko wrote: > If memory end is not aligned with the sparse memory section boundary, the > mapping of such a section is only partly initialized. This may lead to > VM_BUG_ON due to uninitialized struct page access from > is_mem_section_removable() or test_pages_in_a_zone() function triggered by > memory_hotplug sysfs handlers: > > Here are the the panic examples: > CONFIG_DEBUG_VM=y > CONFIG_DEBUG_VM_PGFLAGS=y > > kernel parameter mem=2050M > -------------------------- > page:000003d082008000 is uninitialized and poisoned > page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p)) > Call Trace: > ([<0000000000385b26>] test_pages_in_a_zone+0xde/0x160) > [<00000000008f15c4>] show_valid_zones+0x5c/0x190 > [<00000000008cf9c4>] dev_attr_show+0x34/0x70 > [<0000000000463ad0>] sysfs_kf_seq_show+0xc8/0x148 > [<00000000003e4194>] seq_read+0x204/0x480 > [<00000000003b53ea>] __vfs_read+0x32/0x178 > [<00000000003b55b2>] vfs_read+0x82/0x138 > [<00000000003b5be2>] ksys_read+0x5a/0xb0 > [<0000000000b86ba0>] system_call+0xdc/0x2d8 > Last Breaking-Event-Address: > [<0000000000385b26>] test_pages_in_a_zone+0xde/0x160 > Kernel panic - not syncing: Fatal exception: panic_on_oops > > kernel parameter mem=3075M > -------------------------- > page:000003d08300c000 is uninitialized and poisoned > page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p)) > Call Trace: > ([<000000000038596c>] is_mem_section_removable+0xb4/0x190) > [<00000000008f12fa>] show_mem_removable+0x9a/0xd8 > [<00000000008cf9c4>] dev_attr_show+0x34/0x70 > [<0000000000463ad0>] sysfs_kf_seq_show+0xc8/0x148 > [<00000000003e4194>] seq_read+0x204/0x480 > [<00000000003b53ea>] __vfs_read+0x32/0x178 > [<00000000003b55b2>] vfs_read+0x82/0x138 > [<00000000003b5be2>] ksys_read+0x5a/0xb0 > [<0000000000b86ba0>] system_call+0xdc/0x2d8 > Last Breaking-Event-Address: > [<000000000038596c>] is_mem_section_removable+0xb4/0x190 > Kernel panic - not syncing: Fatal exception: panic_on_oops > > Fix the problem by initializing the last memory section of each zone > in memmap_init_zone() till the very end, even if it goes beyond the zone > end. > > Signed-off-by: Mikhail Zaslonko > Reviewed-by: Gerald Schaefer > Cc: This has alwways been problem AFAIU. It just went unnoticed because we have zeroed memmaps during allocation before f7f99100d8d9 ("mm: stop zeroing memory during allocation in vmemmap") and so the above test would simply skip these ranges as belonging to zone 0 or provided a garbage. So I guess we do care for post f7f99100d8d9 kernels mostly and therefore Fixes: f7f99100d8d9 ("mm: stop zeroing memory during allocation in vmemmap") Other than that looks good to me. Acked-by: Michal Hocko Thanks! > --- > mm/page_alloc.c | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 2ec9cc407216..e2afdb2dc2c5 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -5542,6 +5542,18 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone, > cond_resched(); > } > } > +#ifdef CONFIG_SPARSEMEM > + /* > + * If the zone does not span the rest of the section then > + * we should at least initialize those pages. Otherwise we > + * could blow up on a poisoned page in some paths which depend > + * on full sections being initialized (e.g. memory hotplug). > + */ > + while (end_pfn % PAGES_PER_SECTION) { > + __init_single_page(pfn_to_page(end_pfn), end_pfn, zone, nid); > + end_pfn++; > + } > +#endif > } > > #ifdef CONFIG_ZONE_DEVICE > -- > 2.16.4 -- Michal Hocko SUSE Labs