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=-6.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 B0342C169C4 for ; Tue, 29 Jan 2019 12:08:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8024320881 for ; Tue, 29 Jan 2019 12:08:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548763722; bh=ieLL6maC+/Il3iQvHcB5hGZbFbso1LJG07gmPRNHA2M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=uCd+3ZvrrKxn/wu5C3GrcMfcJDhOKf7u1OxzBf+3ovtImIGmm2G/SmtxaoC1DiYpI 1DFPG7V9XDXg5uTLGNX6gV5WYNQeC4ayTj356Y4PxjPxew2RWkFiCUmh7+aOGs+YeK hqpcEW5smJRWpW+pX6q6HrdVffr869pmflOrNUb4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729373AbfA2LjQ (ORCPT ); Tue, 29 Jan 2019 06:39:16 -0500 Received: from mail.kernel.org ([198.145.29.99]:55934 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729390AbfA2LjQ (ORCPT ); Tue, 29 Jan 2019 06:39:16 -0500 Received: from localhost (5356596B.cm-6-7b.dynamic.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A99CA20844; Tue, 29 Jan 2019 11:39:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548761955; bh=ieLL6maC+/Il3iQvHcB5hGZbFbso1LJG07gmPRNHA2M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=AyJB8Br4+mh5NQnmkO0/4Gy6G7rvPu4tWkRSDG+SW87IVOeygWo0KEm40JltE8oBi lyrdzjW2ZX04MIOLzdTj3CE9kdZXYj5DOF8FG6jvAMP3VBDToGvlFinygT2aB0YwWr conyZm8ZYQkvbW6b3iIFmugP8xfbRH/X3xG+f4m4= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Vitaly Kuznetsov , stable@kernel.org, Sasha Levin Subject: [PATCH 4.20 058/117] hv_balloon: avoid touching uninitialized struct page during tail onlining Date: Tue, 29 Jan 2019 12:35:09 +0100 Message-Id: <20190129113210.571420906@linuxfoundation.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190129113207.477505932@linuxfoundation.org> References: <20190129113207.477505932@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review X-Patchwork-Hint: ignore MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org 4.20-stable review patch. If anyone has any objections, please let me know. ------------------ From: Vitaly Kuznetsov commit da8ced360ca8ad72d8f41f5c8fcd5b0e63e1555f upstream. Hyper-V memory hotplug protocol has 2M granularity and in Linux x86 we use 128M. To deal with it we implement partial section onlining by registering custom page onlining callback (hv_online_page()). Later, when more memory arrives we try to online the 'tail' (see hv_bring_pgs_online()). It was found that in some cases this 'tail' onlining causes issues: BUG: Bad page state in process kworker/0:2 pfn:109e3a page:ffffe08344278e80 count:0 mapcount:1 mapping:0000000000000000 index:0x0 flags: 0xfffff80000000() raw: 000fffff80000000 dead000000000100 dead000000000200 0000000000000000 raw: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 page dumped because: nonzero mapcount ... Workqueue: events hot_add_req [hv_balloon] Call Trace: dump_stack+0x5c/0x80 bad_page.cold.112+0x7f/0xb2 free_pcppages_bulk+0x4b8/0x690 free_unref_page+0x54/0x70 hv_page_online_one+0x5c/0x80 [hv_balloon] hot_add_req.cold.24+0x182/0x835 [hv_balloon] ... Turns out that we now have deferred struct page initialization for memory hotplug so e.g. memory_block_action() in drivers/base/memory.c does pages_correctly_probed() check and in that check it avoids inspecting struct pages and checks sections instead. But in Hyper-V balloon driver we do PageReserved(pfn_to_page()) check and this is now wrong. Switch to checking online_section_nr() instead. Signed-off-by: Vitaly Kuznetsov Cc: stable@kernel.org Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- drivers/hv/hv_balloon.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) --- a/drivers/hv/hv_balloon.c +++ b/drivers/hv/hv_balloon.c @@ -888,12 +888,14 @@ static unsigned long handle_pg_range(uns pfn_cnt -= pgs_ol; /* * Check if the corresponding memory block is already - * online by checking its last previously backed page. - * In case it is we need to bring rest (which was not - * backed previously) online too. + * online. It is possible to observe struct pages still + * being uninitialized here so check section instead. + * In case the section is online we need to bring the + * rest of pfns (which were not backed previously) + * online too. */ if (start_pfn > has->start_pfn && - !PageReserved(pfn_to_page(start_pfn - 1))) + online_section_nr(pfn_to_section_nr(start_pfn))) hv_bring_pgs_online(has, start_pfn, pgs_ol); }