From patchwork Wed May 26 09:30:36 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 12281075 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=-16.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 40A16C2B9F7 for ; Wed, 26 May 2021 09:31:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 249816142D for ; Wed, 26 May 2021 09:31:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233419AbhEZJch (ORCPT ); Wed, 26 May 2021 05:32:37 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:30174 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233356AbhEZJch (ORCPT ); Wed, 26 May 2021 05:32:37 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1622021466; 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: in-reply-to:in-reply-to:references:references; bh=/osWbHv9H+D8jMkXYe0YG4c0I4+JjXX9FiaLxBUqIoc=; b=h2WdEny7QWf0X6bBsQZpBkA1zQ6d7c4tKYGcdHfgUER8gjtItSMiDzFIve7LY539cd8Zlf zGRPUs0CEisnX6OfmUeVFyLHatwX1TDTP/ZrXXkQ47whaXnlqKn6au0P+PVgQRdz22Q/AY BJh4CDVCsX5bnN3GS4FHbRY/hZqTqDY= 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-141-Fk8f-plUN86vXtXK6gxEqw-1; Wed, 26 May 2021 05:31:04 -0400 X-MC-Unique: Fk8f-plUN86vXtXK6gxEqw-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 4833879EC1; Wed, 26 May 2021 09:31:01 +0000 (UTC) Received: from t480s.redhat.com (ovpn-113-99.ams2.redhat.com [10.36.113.99]) by smtp.corp.redhat.com (Postfix) with ESMTP id 174745D9CC; Wed, 26 May 2021 09:30:54 +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, Mike Rapoport Subject: [PATCH v3 1/6] fs/proc/kcore: drop KCORE_REMAP and KCORE_OTHER Date: Wed, 26 May 2021 11:30:36 +0200 Message-Id: <20210526093041.8800-2-david@redhat.com> In-Reply-To: <20210526093041.8800-1-david@redhat.com> References: <20210526093041.8800-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Commit db779ef67ffe ("proc/kcore: Remove unused kclist_add_remap()") removed the last user of KCORE_REMAP. Commit 595dd46ebfc1 ("vfs/proc/kcore, x86/mm/kcore: Fix SMAP fault when dumping vsyscall user page") removed the last user of KCORE_OTHER. Let's drop both types. While at it, also drop vaddr in "struct kcore_list", used by KCORE_REMAP only. Reviewed-by: Mike Rapoport Signed-off-by: David Hildenbrand --- fs/proc/kcore.c | 7 ++----- include/linux/kcore.h | 3 --- 2 files changed, 2 insertions(+), 8 deletions(-) diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c index 4d2e64e9016c..09f77d3c6e15 100644 --- a/fs/proc/kcore.c +++ b/fs/proc/kcore.c @@ -380,11 +380,8 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) phdr->p_type = PT_LOAD; phdr->p_flags = PF_R | PF_W | PF_X; phdr->p_offset = kc_vaddr_to_offset(m->addr) + data_offset; - if (m->type == KCORE_REMAP) - phdr->p_vaddr = (size_t)m->vaddr; - else - phdr->p_vaddr = (size_t)m->addr; - if (m->type == KCORE_RAM || m->type == KCORE_REMAP) + phdr->p_vaddr = (size_t)m->addr; + if (m->type == KCORE_RAM) phdr->p_paddr = __pa(m->addr); else if (m->type == KCORE_TEXT) phdr->p_paddr = __pa_symbol(m->addr); diff --git a/include/linux/kcore.h b/include/linux/kcore.h index da676cdbd727..86c0f1d18998 100644 --- a/include/linux/kcore.h +++ b/include/linux/kcore.h @@ -11,14 +11,11 @@ enum kcore_type { KCORE_RAM, KCORE_VMEMMAP, KCORE_USER, - KCORE_OTHER, - KCORE_REMAP, }; struct kcore_list { struct list_head list; unsigned long addr; - unsigned long vaddr; size_t size; int type; }; From patchwork Wed May 26 09:30:37 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 12281077 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=-16.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 D70B1C2B9F7 for ; Wed, 26 May 2021 09:31:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BAF5961432 for ; Wed, 26 May 2021 09:31:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233420AbhEZJcy (ORCPT ); Wed, 26 May 2021 05:32:54 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:53198 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233283AbhEZJcx (ORCPT ); Wed, 26 May 2021 05:32:53 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1622021481; 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: in-reply-to:in-reply-to:references:references; bh=CeyyYgXMaIv1KkLK2Mxpk2s8iuflkxKOKdYcMCECEco=; b=TpHyrTVEgS5UaXirS+e99q40tDkE5n9T0hQtJx3BuwEnP8idZzpqVPFZglK4rR7oCELWK/ 8BzTkBrAfwpKEFPRgLyyHhKivVpjNE6Za4XaRHum8QwY0DCm0NEjPKnL/3Mp5WXkTpRFtK scg1yf1jeyjMamqv+MEeHFnLrnMtgIY= 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-394-KMaDda-lNSilAZz1rrmwcg-1; Wed, 26 May 2021 05:31:19 -0400 X-MC-Unique: KMaDda-lNSilAZz1rrmwcg-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 083AC180FD65; Wed, 26 May 2021 09:31:17 +0000 (UTC) Received: from t480s.redhat.com (ovpn-113-99.ams2.redhat.com [10.36.113.99]) by smtp.corp.redhat.com (Postfix) with ESMTP id 9CB925D9CC; Wed, 26 May 2021 09:31:01 +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, Mike Rapoport Subject: [PATCH v3 2/6] fs/proc/kcore: pfn_is_ram check only applies to KCORE_RAM Date: Wed, 26 May 2021 11:30:37 +0200 Message-Id: <20210526093041.8800-3-david@redhat.com> In-Reply-To: <20210526093041.8800-1-david@redhat.com> References: <20210526093041.8800-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Let's resturcture the code, using switch-case, and checking pfn_is_ram() only when we are dealing with KCORE_RAM. Reviewed-by: Mike Rapoport Signed-off-by: David Hildenbrand --- fs/proc/kcore.c | 35 +++++++++++++++++++++++++++-------- 1 file changed, 27 insertions(+), 8 deletions(-) diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c index 09f77d3c6e15..ed6fbb3bd50c 100644 --- a/fs/proc/kcore.c +++ b/fs/proc/kcore.c @@ -483,25 +483,36 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) goto out; } m = NULL; /* skip the list anchor */ - } else if (!pfn_is_ram(__pa(start) >> PAGE_SHIFT)) { - if (clear_user(buffer, tsz)) { - ret = -EFAULT; - goto out; - } - } else if (m->type == KCORE_VMALLOC) { + goto skip; + } + + switch (m->type) { + case KCORE_VMALLOC: vread(buf, (char *)start, tsz); /* we have to zero-fill user buffer even if no read */ if (copy_to_user(buffer, buf, tsz)) { ret = -EFAULT; goto out; } - } else if (m->type == KCORE_USER) { + break; + case KCORE_USER: /* User page is handled prior to normal kernel page: */ if (copy_to_user(buffer, (char *)start, tsz)) { ret = -EFAULT; goto out; } - } else { + break; + case KCORE_RAM: + if (!pfn_is_ram(__pa(start) >> PAGE_SHIFT)) { + if (clear_user(buffer, tsz)) { + ret = -EFAULT; + goto out; + } + break; + } + fallthrough; + case KCORE_VMEMMAP: + case KCORE_TEXT: if (kern_addr_valid(start)) { /* * Using bounce buffer to bypass the @@ -525,7 +536,15 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) goto out; } } + break; + default: + pr_warn_once("Unhandled KCORE type: %d\n", m->type); + if (clear_user(buffer, tsz)) { + ret = -EFAULT; + goto out; + } } +skip: buflen -= tsz; *fpos += tsz; buffer += tsz; From patchwork Wed May 26 09:30:38 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 12281121 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=-16.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,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 EC4DDC47088 for ; Wed, 26 May 2021 09:32:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D3B8F6117A for ; Wed, 26 May 2021 09:32:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233420AbhEZJdw (ORCPT ); Wed, 26 May 2021 05:33:52 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:54141 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233683AbhEZJdj (ORCPT ); Wed, 26 May 2021 05:33:39 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1622021528; 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: in-reply-to:in-reply-to:references:references; bh=HpQl70FCJrKzkRws/ycp8B14QnuETKoEKh3YFLooSpk=; b=gqiObnwYZBPS9mVSMmPBvXlbdA/lVJynS9Kl15KUOiCLT9XWSndR7bDmW9krIqLejnBxjL hDErOrWJrRSo0Nb/74Iimiox0jl8LP6C0fCtPQossoFesT7O1zVjHbOV4MZjmxIFyauL4Q oycehSI7QW88FB6R4T+F92hRnSqe7So= 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-273-bVRoSnEGNimMg5ofHHzOIg-1; Wed, 26 May 2021 05:31:26 -0400 X-MC-Unique: bVRoSnEGNimMg5ofHHzOIg-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 2C4F0106BB2B; Wed, 26 May 2021 09:31:23 +0000 (UTC) Received: from t480s.redhat.com (ovpn-113-99.ams2.redhat.com [10.36.113.99]) by smtp.corp.redhat.com (Postfix) with ESMTP id 668435D9CC; Wed, 26 May 2021 09:31:17 +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, Mike Rapoport Subject: [PATCH v3 3/6] fs/proc/kcore: don't read offline sections, logically offline pages and hwpoisoned pages Date: Wed, 26 May 2021 11:30:38 +0200 Message-Id: <20210526093041.8800-4-david@redhat.com> In-Reply-To: <20210526093041.8800-1-david@redhat.com> References: <20210526093041.8800-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Let's avoid reading: 1) Offline memory sections: the content of offline memory sections is stale as the memory is effectively unused by the kernel. On s390x with standby memory, offline memory sections (belonging to offline storage increments) are not accessible. With virtio-mem and the hyper-v balloon, we can have unavailable memory chunks that should not be accessed inside offline memory sections. Last but not least, offline memory sections might contain hwpoisoned pages which we can no longer identify because the memmap is stale. 2) PG_offline pages: logically offline pages that are documented as "The content of these pages is effectively stale. Such pages should not be touched (read/write/dump/save) except by their owner.". Examples include pages inflated in a balloon or unavailble memory ranges inside hotplugged memory sections with virtio-mem or the hyper-v balloon. 3) PG_hwpoison pages: Reading pages marked as hwpoisoned can be fatal. As documented: "Accessing is not safe since it may cause another machine check. Don't touch!" Introduce is_page_hwpoison(), adding a comment that it is inherently racy but best we can really do. Reading /proc/kcore now performs similar checks as when reading /proc/vmcore for kdump via makedumpfile: problematic pages are exclude. It's also similar to hibernation code, however, we don't skip hwpoisoned pages when processing pages in kernel/power/snapshot.c:saveable_page() yet. Note 1: we can race against memory offlining code, especially memory going offline and getting unplugged: however, we will properly tear down the identity mapping and handle faults gracefully when accessing this memory from kcore code. Note 2: we can race against drivers setting PageOffline() and turning memory inaccessible in the hypervisor. We'll handle this in a follow-up patch. Reviewed-by: Mike Rapoport Reviewed-by: Oscar Salvador Signed-off-by: David Hildenbrand --- fs/proc/kcore.c | 14 +++++++++++++- include/linux/page-flags.h | 12 ++++++++++++ 2 files changed, 25 insertions(+), 1 deletion(-) diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c index ed6fbb3bd50c..92ff1e4436cb 100644 --- a/fs/proc/kcore.c +++ b/fs/proc/kcore.c @@ -465,6 +465,9 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) m = NULL; while (buflen) { + struct page *page; + unsigned long pfn; + /* * If this is the first iteration or the address is not within * the previous entry, search for a matching entry. @@ -503,7 +506,16 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) } break; case KCORE_RAM: - if (!pfn_is_ram(__pa(start) >> PAGE_SHIFT)) { + pfn = __pa(start) >> PAGE_SHIFT; + page = pfn_to_online_page(pfn); + + /* + * Don't read offline sections, logically offline pages + * (e.g., inflated in a balloon), hwpoisoned pages, + * and explicitly excluded physical ranges. + */ + if (!page || PageOffline(page) || + is_page_hwpoison(page) || !pfn_is_ram(pfn)) { if (clear_user(buffer, tsz)) { ret = -EFAULT; goto out; diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index 04a34c08e0a6..daed82744f4b 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -694,6 +694,18 @@ PAGEFLAG_FALSE(DoubleMap) TESTSCFLAG_FALSE(DoubleMap) #endif +/* + * Check if a page is currently marked HWPoisoned. Note that this check is + * best effort only and inherently racy: there is no way to synchronize with + * failing hardware. + */ +static inline bool is_page_hwpoison(struct page *page) +{ + if (PageHWPoison(page)) + return true; + return PageHuge(page) && PageHWPoison(compound_head(page)); +} + /* * For pages that are never mapped to userspace (and aren't PageSlab), * page_type may be used. Because it is initialised to -1, we invert the From patchwork Wed May 26 09:30:39 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 12281079 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=-16.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,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 E9856C2B9F7 for ; Wed, 26 May 2021 09:31:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CD1AB6117A for ; Wed, 26 May 2021 09:31:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233454AbhEZJdK (ORCPT ); Wed, 26 May 2021 05:33:10 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:26373 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233583AbhEZJdE (ORCPT ); Wed, 26 May 2021 05:33:04 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1622021493; 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: in-reply-to:in-reply-to:references:references; bh=0LN0J8fOWqC6Tk5wkSbpwkNZtNpLvOB+CwQIFMbUdeo=; b=AnIppB8NgblNZ0a7jsbJMwU4h5WyngA5mcaVh/bYm038pee2Ynh2AHzYYiZmMRPTLbdED7 f+U/pL6mfMWmTArjT3FNy7MBw/UyfydjHOTWalvyR+qwWZgpaI+rXhNZQj9ZHcharl2e+4 I/t+TVHMfQL+h54WSNz4h4FhQn7yoss= 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-574-gnXabOTcN2GlrtYNjLBgrQ-1; Wed, 26 May 2021 05:31:31 -0400 X-MC-Unique: gnXabOTcN2GlrtYNjLBgrQ-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 0899D107ACE3; Wed, 26 May 2021 09:31:29 +0000 (UTC) Received: from t480s.redhat.com (ovpn-113-99.ams2.redhat.com [10.36.113.99]) by smtp.corp.redhat.com (Postfix) with ESMTP id 892915D9D3; Wed, 26 May 2021 09:31:23 +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, Mike Rapoport Subject: [PATCH v3 4/6] mm: introduce page_offline_(begin|end|freeze|thaw) to synchronize setting PageOffline() Date: Wed, 26 May 2021 11:30:39 +0200 Message-Id: <20210526093041.8800-5-david@redhat.com> In-Reply-To: <20210526093041.8800-1-david@redhat.com> References: <20210526093041.8800-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org A driver might set a page logically offline -- PageOffline() -- and turn the page inaccessible in the hypervisor; after that, access to page content can be fatal. One example is virtio-mem; while unplugged memory -- marked as PageOffline() can currently be read in the hypervisor, this will no longer be the case in the future; for example, when having a virtio-mem device backed by huge pages in the hypervisor. Some special PFN walkers -- i.e., /proc/kcore -- read content of random pages after checking PageOffline(); however, these PFN walkers can race with drivers that set PageOffline(). Let's introduce page_offline_(begin|end|freeze|thaw) for synchronizing. page_offline_freeze()/page_offline_thaw() allows for a subsystem to synchronize with such drivers, achieving that a page cannot be set PageOffline() while frozen. page_offline_begin()/page_offline_end() is used by drivers that care about such races when setting a page PageOffline(). For simplicity, use a rwsem for now; neither drivers nor users are performance sensitive. Acked-by: Michal Hocko Reviewed-by: Mike Rapoport Reviewed-by: Oscar Salvador Signed-off-by: David Hildenbrand --- include/linux/page-flags.h | 10 ++++++++++ mm/util.c | 40 ++++++++++++++++++++++++++++++++++++++ 2 files changed, 50 insertions(+) diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index daed82744f4b..382464aa3c20 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -769,9 +769,19 @@ PAGE_TYPE_OPS(Buddy, buddy) * relies on this feature is aware that re-onlining the memory block will * require to re-set the pages PageOffline() and not giving them to the * buddy via online_page_callback_t. + * + * There are drivers that mark a page PageOffline() and expect there won't be + * any further access to page content. PFN walkers that read content of random + * pages should check PageOffline() and synchronize with such drivers using + * page_offline_freeze()/page_offline_thaw(). */ PAGE_TYPE_OPS(Offline, offline) +extern void page_offline_freeze(void); +extern void page_offline_thaw(void); +extern void page_offline_begin(void); +extern void page_offline_end(void); + /* * Marks pages in use as page tables. */ diff --git a/mm/util.c b/mm/util.c index a8bf17f18a81..a034525e7ba2 100644 --- a/mm/util.c +++ b/mm/util.c @@ -1010,3 +1010,43 @@ void mem_dump_obj(void *object) } EXPORT_SYMBOL_GPL(mem_dump_obj); #endif + +/* + * A driver might set a page logically offline -- PageOffline() -- and + * turn the page inaccessible in the hypervisor; after that, access to page + * content can be fatal. + * + * Some special PFN walkers -- i.e., /proc/kcore -- read content of random + * pages after checking PageOffline(); however, these PFN walkers can race + * with drivers that set PageOffline(). + * + * page_offline_freeze()/page_offline_thaw() allows for a subsystem to + * synchronize with such drivers, achieving that a page cannot be set + * PageOffline() while frozen. + * + * page_offline_begin()/page_offline_end() is used by drivers that care about + * such races when setting a page PageOffline(). + */ +static DECLARE_RWSEM(page_offline_rwsem); + +void page_offline_freeze(void) +{ + down_read(&page_offline_rwsem); +} + +void page_offline_thaw(void) +{ + up_read(&page_offline_rwsem); +} + +void page_offline_begin(void) +{ + down_write(&page_offline_rwsem); +} +EXPORT_SYMBOL(page_offline_begin); + +void page_offline_end(void) +{ + up_write(&page_offline_rwsem); +} +EXPORT_SYMBOL(page_offline_end); From patchwork Wed May 26 09:30:40 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 12281117 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=-16.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,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 3C5BBC2B9F7 for ; Wed, 26 May 2021 09:31:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 228B2613E1 for ; Wed, 26 May 2021 09:31:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233644AbhEZJd2 (ORCPT ); Wed, 26 May 2021 05:33:28 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:26977 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233592AbhEZJdS (ORCPT ); Wed, 26 May 2021 05:33:18 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1622021507; 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: in-reply-to:in-reply-to:references:references; bh=8Ug1zAPLCqnh6GoayNnsPLQvKUErGoEhMFV9yrDkIMc=; b=DyWnMSmtT6f0JA2O5BHmgpJWNdLNO6snrikz630MkbY5p6CM1JWcK7IIU9kVXc99dBhlr9 +Daf9+xynoFnBcbTxdwupkkxjSpT00f018wLB2xgaKQcQOzDukf6YZ28Zzk391qpnpFLyh JWV2+dJjRSN28w+abpu7DM04DOEK+6U= 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-8-d70cn4qBMKyhYDfqXWiyxg-1; Wed, 26 May 2021 05:31:45 -0400 X-MC-Unique: d70cn4qBMKyhYDfqXWiyxg-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 55FB979EC9; Wed, 26 May 2021 09:31:43 +0000 (UTC) Received: from t480s.redhat.com (ovpn-113-99.ams2.redhat.com [10.36.113.99]) by smtp.corp.redhat.com (Postfix) with ESMTP id 62C095D9D3; Wed, 26 May 2021 09:31:29 +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, Mike Rapoport Subject: [PATCH v3 5/6] virtio-mem: use page_offline_(start|end) when setting PageOffline() Date: Wed, 26 May 2021 11:30:40 +0200 Message-Id: <20210526093041.8800-6-david@redhat.com> In-Reply-To: <20210526093041.8800-1-david@redhat.com> References: <20210526093041.8800-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Let's properly use page_offline_(start|end) to synchronize setting PageOffline(), so we won't have valid page access to unplugged memory regions from /proc/kcore. Existing balloon implementations usually allow reading inflated memory; doing so might result in unnecessary overhead in the hypervisor, which is currently the case with virtio-mem. For future virtio-mem use cases, it will be different when using shmem, huge pages, !anonymous private mappings, ... as backing storage for a VM. virtio-mem unplugged memory must no longer be accessed and access might result in undefined behavior. There will be a virtio spec extension to document this change, including a new feature flag indicating the changed behavior. We really don't want to race against PFN walkers reading random page content. Acked-by: Michael S. Tsirkin Acked-by: Mike Rapoport Reviewed-by: Oscar Salvador Signed-off-by: David Hildenbrand --- drivers/virtio/virtio_mem.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c index 10ec60d81e84..dc2a2e2b2ff8 100644 --- a/drivers/virtio/virtio_mem.c +++ b/drivers/virtio/virtio_mem.c @@ -1065,6 +1065,7 @@ static int virtio_mem_memory_notifier_cb(struct notifier_block *nb, static void virtio_mem_set_fake_offline(unsigned long pfn, unsigned long nr_pages, bool onlined) { + page_offline_begin(); for (; nr_pages--; pfn++) { struct page *page = pfn_to_page(pfn); @@ -1075,6 +1076,7 @@ static void virtio_mem_set_fake_offline(unsigned long pfn, ClearPageReserved(page); } } + page_offline_end(); } /* From patchwork Wed May 26 09:30:41 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 12281119 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=-16.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,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 9F66FC47088 for ; Wed, 26 May 2021 09:32:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 85AA66142D for ; Wed, 26 May 2021 09:32:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233628AbhEZJdb (ORCPT ); Wed, 26 May 2021 05:33:31 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:44671 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233575AbhEZJd0 (ORCPT ); Wed, 26 May 2021 05:33:26 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1622021515; 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: in-reply-to:in-reply-to:references:references; bh=UwY8egmBhFN4ttOumbwiNB+K87+iDRAp24/+Sy47AVY=; b=bdWQTezUW7VSgqzB7Oqcjd4zxTtr7nsMgioeGGEXFwMqDNa4OqW071MiuM4Os/y90V3eiL 5RRg+oncjrt1QcquZ+KMmy1BBI9mPMyItrpEpglRf7Gq6Y43g3ygLtrWW0ogRM5OWX7HVx 1Zlq3PDFrC37RyBV9Q2pAt1GLoT7KyI= 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-154-sylAfsenNgmVBsWBcSkMGg-1; Wed, 26 May 2021 05:31:51 -0400 X-MC-Unique: sylAfsenNgmVBsWBcSkMGg-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 751F7107ACF6; Wed, 26 May 2021 09:31:49 +0000 (UTC) Received: from t480s.redhat.com (ovpn-113-99.ams2.redhat.com [10.36.113.99]) by smtp.corp.redhat.com (Postfix) with ESMTP id B3CF25D9D3; Wed, 26 May 2021 09:31:43 +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, Mike Rapoport Subject: [PATCH v3 6/6] fs/proc/kcore: use page_offline_(freeze|thaw) Date: Wed, 26 May 2021 11:30:41 +0200 Message-Id: <20210526093041.8800-7-david@redhat.com> In-Reply-To: <20210526093041.8800-1-david@redhat.com> References: <20210526093041.8800-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Let's properly synchronize with drivers that set PageOffline(). Unfreeze/thaw every now and then, so drivers that want to set PageOffline() can make progress. Acked-by: Mike Rapoport Reviewed-by: Oscar Salvador Signed-off-by: David Hildenbrand --- fs/proc/kcore.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c index 92ff1e4436cb..982e694aae77 100644 --- a/fs/proc/kcore.c +++ b/fs/proc/kcore.c @@ -313,6 +313,7 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) { char *buf = file->private_data; size_t phdrs_offset, notes_offset, data_offset; + size_t page_offline_frozen = 1; size_t phdrs_len, notes_len; struct kcore_list *m; size_t tsz; @@ -322,6 +323,11 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) int ret = 0; down_read(&kclist_lock); + /* + * Don't race against drivers that set PageOffline() and expect no + * further page access. + */ + page_offline_freeze(); get_kcore_size(&nphdr, &phdrs_len, ¬es_len, &data_offset); phdrs_offset = sizeof(struct elfhdr); @@ -480,6 +486,12 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) } } + if (page_offline_frozen++ % MAX_ORDER_NR_PAGES == 0) { + page_offline_thaw(); + cond_resched(); + page_offline_freeze(); + } + if (&m->list == &kclist_head) { if (clear_user(buffer, tsz)) { ret = -EFAULT; @@ -565,6 +577,7 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) } out: + page_offline_thaw(); up_read(&kclist_lock); if (ret) return ret;