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=-8.2 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_SANE_1 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 11A65C3F2D1 for ; Wed, 4 Mar 2020 10:12:53 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id CDB3220848 for ; Wed, 4 Mar 2020 10:12:52 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CDB3220848 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 6D0116B0006; Wed, 4 Mar 2020 05:12:52 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 65A166B0007; Wed, 4 Mar 2020 05:12:52 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4FA666B0008; Wed, 4 Mar 2020 05:12:52 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0159.hostedemail.com [216.40.44.159]) by kanga.kvack.org (Postfix) with ESMTP id 33AF06B0006 for ; Wed, 4 Mar 2020 05:12:52 -0500 (EST) Received: from smtpin06.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id B35D2181AC9C6 for ; Wed, 4 Mar 2020 10:12:51 +0000 (UTC) X-FDA: 76557266142.06.party95_703fda27bd91c X-HE-Tag: party95_703fda27bd91c X-Filterd-Recvd-Size: 4183 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf29.hostedemail.com (Postfix) with ESMTP for ; Wed, 4 Mar 2020 10:12:51 +0000 (UTC) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id AC46B30E; Wed, 4 Mar 2020 02:12:50 -0800 (PST) Received: from [10.1.195.32] (e112269-lin.cambridge.arm.com [10.1.195.32]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 037CD3F534; Wed, 4 Mar 2020 02:12:47 -0800 (PST) Subject: Re: [PATCH V14 1/2] arm64/mm: Hold memory hotplug lock while walking for kernel page table dump To: Anshuman Khandual , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "akpm@linux-foundation.org" , Catalin Marinas , "will@kernel.org" , "rppt@linux.ibm.com" Cc: Mark Rutland , "david@redhat.com" , "cai@lca.pw" , "logang@deltatee.com" , "arunks@codeaurora.org" , "mgorman@techsingularity.net" , "osalvador@suse.de" , Ard Biesheuvel , Steve Capper , "broonie@kernel.org" , Valentin Schneider , Robin Murphy , Suzuki Poulose , "ira.weiny@intel.com" , "dan.j.williams@intel.com" References: <1583296123-18546-1-git-send-email-anshuman.khandual@arm.com> <1583296123-18546-2-git-send-email-anshuman.khandual@arm.com> From: Steven Price Message-ID: <91e4cbd0-0f1d-30c6-2796-d2fb91ba6720@arm.com> Date: Wed, 4 Mar 2020 10:12:46 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <1583296123-18546-2-git-send-email-anshuman.khandual@arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 04/03/2020 04:28, Anshuman Khandual wrote: > 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 > Acked-by: Mark Rutland > Acked-by: Catalin Marinas > Signed-off-by: Anshuman Khandual Reviewed-by: Steven Price Thanks, Steve > --- > arch/arm64/mm/ptdump_debugfs.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/arch/arm64/mm/ptdump_debugfs.c b/arch/arm64/mm/ptdump_debugfs.c > index 1f2eae3e988b..d29d722ec3ec 100644 > --- a/arch/arm64/mm/ptdump_debugfs.c > +++ b/arch/arm64/mm/ptdump_debugfs.c > @@ -1,5 +1,6 @@ > // SPDX-License-Identifier: GPL-2.0 > #include > +#include > #include > > #include > @@ -7,7 +8,10 @@ > static int ptdump_show(struct seq_file *m, void *v) > { > struct ptdump_info *info = m->private; > + > + get_online_mems(); > ptdump_walk(m, info); > + put_online_mems(); > return 0; > } > DEFINE_SHOW_ATTRIBUTE(ptdump); >