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_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT 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 402C6C46470 for ; Wed, 29 May 2019 09:16:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1AF0420665 for ; Wed, 29 May 2019 09:16:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726330AbfE2JQf (ORCPT ); Wed, 29 May 2019 05:16:35 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:41534 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725861AbfE2JQe (ORCPT ); Wed, 29 May 2019 05:16:34 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 6E45D15AD; Wed, 29 May 2019 02:16:34 -0700 (PDT) Received: from p8cg001049571a15.blr.arm.com (p8cg001049571a15.blr.arm.com [10.162.41.181]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 2E2683F5AF; Wed, 29 May 2019 02:16:28 -0700 (PDT) From: Anshuman Khandual To: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, akpm@linux-foundation.org, catalin.marinas@arm.com, will.deacon@arm.com Cc: mark.rutland@arm.com, mhocko@suse.com, ira.weiny@intel.com, david@redhat.com, cai@lca.pw, logang@deltatee.com, james.morse@arm.com, cpandya@codeaurora.org, arunks@codeaurora.org, dan.j.williams@intel.com, mgorman@techsingularity.net, osalvador@suse.de, ard.biesheuvel@arm.com Subject: [PATCH V5 2/3] arm64/mm: Hold memory hotplug lock while walking for kernel page table dump Date: Wed, 29 May 2019 14:46:26 +0530 Message-Id: <1559121387-674-3-git-send-email-anshuman.khandual@arm.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1559121387-674-1-git-send-email-anshuman.khandual@arm.com> References: <1559121387-674-1-git-send-email-anshuman.khandual@arm.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The arm64 page table dump code can race with concurrent modification of the kernel page tables. When a leaf entries are modified concurrently, the dump code may log stale or inconsistent information for a VA range, but this is otherwise not harmful. When intermediate levels of table are freed, the dump code will continue to use memory which has been freed and potentially reallocated for another purpose. In such cases, the dump code may dereference bogus addresses, leading to a number of potential problems. Intermediate levels of table may by freed during memory hot-remove, which will be enabled by a subsequent patch. To avoid racing with this, take the memory hotplug lock when walking the kernel page table. Acked-by: David Hildenbrand Signed-off-by: Anshuman Khandual --- arch/arm64/mm/ptdump_debugfs.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/arm64/mm/ptdump_debugfs.c b/arch/arm64/mm/ptdump_debugfs.c index 064163f..80171d1 100644 --- a/arch/arm64/mm/ptdump_debugfs.c +++ b/arch/arm64/mm/ptdump_debugfs.c @@ -7,7 +7,10 @@ static int ptdump_show(struct seq_file *m, void *v) { struct ptdump_info *info = m->private; + + get_online_mems(); ptdump_walk_pgd(m, info); + put_online_mems(); return 0; } DEFINE_SHOW_ATTRIBUTE(ptdump); -- 2.7.4