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=-16.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS 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 9F114C433B4 for ; Fri, 14 May 2021 17:23:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 79AC86145B for ; Fri, 14 May 2021 17:23:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235098AbhENRY2 (ORCPT ); Fri, 14 May 2021 13:24:28 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:59564 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235099AbhENRYZ (ORCPT ); Fri, 14 May 2021 13:24:25 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1621012994; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=Ht2wahpr6SjLNp0fKa1tB4u5N0RuDTYUAiljNoyrPYg=; b=Vtc3P/2eLmuT70MGR/RrvFqOoR9RTayeDELQUWHUrr4+3BWXLF2kjgeV3VFQybVZggPtFv l5oKCCPquFHfPaSSwYMP5kQ1uDmDWacTg25jK26fuCG2atXOh/kg+d9bNUAmjxPLhEIJxI 3qwhBg1l7JBb+CA78WeacU2aqT6/53I= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-166-bsPGuG-lMOKE43HnSNtgxA-1; Fri, 14 May 2021 13:23:06 -0400 X-MC-Unique: bsPGuG-lMOKE43HnSNtgxA-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id C25181005D47; Fri, 14 May 2021 17:23:03 +0000 (UTC) Received: from t480s.redhat.com (ovpn-114-113.ams2.redhat.com [10.36.114.113]) by smtp.corp.redhat.com (Postfix) with ESMTP id 87E821971B; Fri, 14 May 2021 17:22:48 +0000 (UTC) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: David Hildenbrand , Andrew Morton , "Michael S. Tsirkin" , Jason Wang , Alexey Dobriyan , Mike Rapoport , "Matthew Wilcox (Oracle)" , Oscar Salvador , Michal Hocko , Roman Gushchin , Alex Shi , Steven Price , Mike Kravetz , Aili Yao , Jiri Bohac , "K. Y. Srinivasan" , Haiyang Zhang , Stephen Hemminger , Wei Liu , Naoya Horiguchi , linux-hyperv@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v2 0/6] fs/proc/kcore: don't read offline sections, logically offline pages and hwpoisoned pages Date: Fri, 14 May 2021 19:22:41 +0200 Message-Id: <20210514172247.176750-1-david@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Looking for places where the kernel might unconditionally read PageOffline() pages, I stumbled over /proc/kcore; turns out /proc/kcore needs some more love to not touch some other pages we really don't want to read -- i.e., hwpoisoned ones. Examples for PageOffline() pages are pages inflated in a balloon, memory unplugged via virtio-mem, and partially-present sections in memory added by the Hyper-V balloon. When reading pages inflated in a balloon, we essentially produce unnecessary load in the hypervisor; holes in partially present sections in case of Hyper-V are not accessible and already were a problem for /proc/vmcore, fixed in makedumpfile by detecting PageOffline() pages. In the future, virtio-mem might disallow reading unplugged memory -- marked as PageOffline() -- in some environments, resulting in undefined behavior when accessed; therefore, I'm trying to identify and rework all these (corner) cases. With this series, there is really only access via /dev/mem, /proc/vmcore and kdb left after I ripped out /dev/kmem. kdb is an advanced corner-case use case -- we won't care for now if someone explicitly tries to do nasty things by reading from/writing to physical addresses we better not touch. /dev/mem is a use case we won't support for virtio-mem, at least for now, so we'll simply disallow mapping any virtio-mem memory via /dev/mem next. /proc/vmcore is really only a problem when dumping the old kernel via something that's not makedumpfile (read: basically never), however, we'll try sanitizing that as well in the second kernel in the future. Tested via kcore_dump: https://github.com/schlafwandler/kcore_dump v1 -> v2: - Dropped "mm: rename and move page_is_poisoned()" - "fs/proc/kcore: don't read offline sections, logically offline pages ..." -- Add is_page_hwpoison() in page-flags.h along with a comment - "mm: introduce page_offline_(begin|end|freeze|thaw) to ..." -- s/unfreeze/thaw/ -- Add a comment to PageOffline documentation in page-flags.h - "virtio-mem: use page_offline_(start|end) when setting PageOffline()" -- Extend patch description - "fs/proc/kcore: use page_offline_(freeze|thaw)" -- Simplify freeze/thaw logic - Collected acks/rbs Cc: Andrew Morton Cc: "Michael S. Tsirkin" Cc: Jason Wang Cc: Alexey Dobriyan Cc: Mike Rapoport Cc: "Matthew Wilcox (Oracle)" Cc: Oscar Salvador Cc: Michal Hocko Cc: Roman Gushchin Cc: Alex Shi Cc: Steven Price Cc: Mike Kravetz Cc: Aili Yao Cc: Jiri Bohac Cc: "K. Y. Srinivasan" Cc: Haiyang Zhang Cc: Stephen Hemminger Cc: Wei Liu Cc: Naoya Horiguchi Cc: linux-hyperv@vger.kernel.org Cc: virtualization@lists.linux-foundation.org Cc: linux-fsdevel@vger.kernel.org Cc: linux-mm@kvack.org David Hildenbrand (6): fs/proc/kcore: drop KCORE_REMAP and KCORE_OTHER fs/proc/kcore: pfn_is_ram check only applies to KCORE_RAM fs/proc/kcore: don't read offline sections, logically offline pages and hwpoisoned pages mm: introduce page_offline_(begin|end|freeze|thaw) to synchronize setting PageOffline() virtio-mem: use page_offline_(start|end) when setting PageOffline() fs/proc/kcore: use page_offline_(freeze|thaw) drivers/virtio/virtio_mem.c | 2 ++ fs/proc/kcore.c | 67 ++++++++++++++++++++++++++++++------- include/linux/kcore.h | 3 -- include/linux/page-flags.h | 22 ++++++++++++ mm/util.c | 40 ++++++++++++++++++++++ 5 files changed, 118 insertions(+), 16 deletions(-) base-commit: 6efb943b8616ec53a5e444193dccf1af9ad627b5 -- 2.31.1