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=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, USER_AGENT_NEOMUTT 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 C81C3C169C4 for ; Tue, 29 Jan 2019 09:09:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A21732177E for ; Tue, 29 Jan 2019 09:09:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727844AbfA2JJK (ORCPT ); Tue, 29 Jan 2019 04:09:10 -0500 Received: from charybdis-ext.suse.de ([195.135.221.2]:28560 "EHLO suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725355AbfA2JJK (ORCPT ); Tue, 29 Jan 2019 04:09:10 -0500 Received: by suse.de (Postfix, from userid 1000) id 559E540B3; Tue, 29 Jan 2019 10:09:09 +0100 (CET) Date: Tue, 29 Jan 2019 10:09:08 +0100 From: Oscar Salvador To: Michal Hocko Cc: Mikhail Zaslonko , Mikhail Gavrilov , Andrew Morton , Pavel Tatashin , schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, gerald.schaefer@de.ibm.com, linux-mm@kvack.org, LKML , Michal Hocko Subject: Re: [PATCH 2/2] mm, memory_hotplug: test_pages_in_a_zone do not pass the end of zone Message-ID: <20190129090908.oms43oyjicozkvzu@d104.suse.de> References: <20190128144506.15603-1-mhocko@kernel.org> <20190128144506.15603-3-mhocko@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190128144506.15603-3-mhocko@kernel.org> User-Agent: NeoMutt/20170421 (1.8.2) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 28, 2019 at 03:45:06PM +0100, Michal Hocko wrote: > From: Mikhail Zaslonko > > 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 pages access from test_pages_in_a_zone() > function triggered by memory_hotplug sysfs handlers. > > Here are the the panic examples: > 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 > > Fix this by checking whether the pfn to check is within the zone. > > [mhocko@suse.com: separated this change from > http://lkml.kernel.org/r/20181105150401.97287-2-zaslonko@linux.ibm.com] > Signed-off-by: Mikhail Zaslonko > Signed-off-by: Michal Hocko Looks good to me: Reviewed-by: Oscar Salvador > --- > mm/memory_hotplug.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 07872789d778..7711d0e327b6 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1274,6 +1274,9 @@ int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn, > i++; > if (i == MAX_ORDER_NR_PAGES || pfn + i >= end_pfn) > continue; > + /* Check if we got outside of the zone */ > + if (zone && !zone_spans_pfn(zone, pfn + i)) > + return 0; > page = pfn_to_page(pfn + i); Since we are already checking if the zone spans that pfn, is it safe to get rid of the below check? Or maybe not because we might have intersected zones? > if (zone && page_zone(page) != zone) > return 0; -- Oscar Salvador SUSE L3