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=-8.5 required=3.0 tests=INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 94FE1C4360C for ; Thu, 10 Oct 2019 07:35:30 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 60D9C218AC for ; Thu, 10 Oct 2019 07:35:30 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 60D9C218AC Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 0F63F8E0006; Thu, 10 Oct 2019 03:35:30 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 0CDBB6B0007; Thu, 10 Oct 2019 03:35:30 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id F25268E0006; Thu, 10 Oct 2019 03:35:29 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0071.hostedemail.com [216.40.44.71]) by kanga.kvack.org (Postfix) with ESMTP id D4A456B0006 for ; Thu, 10 Oct 2019 03:35:29 -0400 (EDT) Received: from smtpin18.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with SMTP id 5144140E5 for ; Thu, 10 Oct 2019 07:35:29 +0000 (UTC) X-FDA: 76027064778.18.peace16_8730436c8cc54 X-HE-Tag: peace16_8730436c8cc54 X-Filterd-Recvd-Size: 3619 Received: from mx1.suse.de (mx2.suse.de [195.135.220.15]) by imf31.hostedemail.com (Postfix) with ESMTP for ; Thu, 10 Oct 2019 07:35:28 +0000 (UTC) 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 60907B02E; Thu, 10 Oct 2019 07:35:27 +0000 (UTC) Date: Thu, 10 Oct 2019 09:35:26 +0200 From: Michal Hocko To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Naoya Horiguchi , Andrew Morton Subject: Re: [PATCH v2 2/2] mm/memory-failure.c: Don't access uninitialized memmaps in memory_failure() Message-ID: <20191010073526.GC18412@dhcp22.suse.cz> References: <20191009142435.3975-1-david@redhat.com> <20191009142435.3975-3-david@redhat.com> <20191009144323.GH6681@dhcp22.suse.cz> <5a626821-77e9-e26b-c2ee-219670283bf0@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5a626821-77e9-e26b-c2ee-219670283bf0@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) 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 Thu 10-10-19 09:27:32, David Hildenbrand wrote: > On 09.10.19 16:43, Michal Hocko wrote: > > On Wed 09-10-19 16:24:35, David Hildenbrand wrote: > >> We should check for pfn_to_online_page() to not access uninitialized > >> memmaps. Reshuffle the code so we don't have to duplicate the error > >> message. > >> > >> Cc: Naoya Horiguchi > >> Cc: Andrew Morton > >> Cc: Michal Hocko > >> Signed-off-by: David Hildenbrand > >> --- > >> mm/memory-failure.c | 14 ++++++++------ > >> 1 file changed, 8 insertions(+), 6 deletions(-) > >> > >> diff --git a/mm/memory-failure.c b/mm/memory-failure.c > >> index 7ef849da8278..e866e6e5660b 100644 > >> --- a/mm/memory-failure.c > >> +++ b/mm/memory-failure.c > >> @@ -1253,17 +1253,19 @@ int memory_failure(unsigned long pfn, int flags) > >> if (!sysctl_memory_failure_recovery) > >> panic("Memory failure on page %lx", pfn); > >> > >> - if (!pfn_valid(pfn)) { > >> + p = pfn_to_online_page(pfn); > >> + if (!p) { > >> + if (pfn_valid(pfn)) { > >> + pgmap = get_dev_pagemap(pfn, NULL); > >> + if (pgmap) > >> + return memory_failure_dev_pagemap(pfn, flags, > >> + pgmap); > >> + } > >> pr_err("Memory failure: %#lx: memory outside kernel control\n", > >> pfn); > >> return -ENXIO; > > > > Don't we need that earlier at hwpoison_inject level? > > > > Theoretically yes, this is another instance. But pfn_to_online_page(pfn) > alone would not be sufficient as discussed. We would, again, have to > special-case ZONE_DEVICE via things like get_dev_pagemap() ... > > But mm/hwpoison-inject.c:hwpoison_inject() is a pure debug feature either way: > > /* > * Note that the below poison/unpoison interfaces do not involve > * hardware status change, hence do not require hardware support. > * They are mainly for testing hwpoison in software level. > */ > > So it's not that bad compared to memory_failure() called from real HW or > drivers/base/memory.c:soft_offline_page_store()/hard_offline_page_store() Yes, this is just a toy. And yes we need to handle zone device pages here because a) people likely want to test MCE behavior even on these pages and b) HW can really trigger MCEs there as well. I was just pointing that the patch is likely incomplete. -- Michal Hocko SUSE Labs