From patchwork Thu Apr 29 12:25:13 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 12231149 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=-16.0 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 3D331C433ED for ; Thu, 29 Apr 2021 12:25:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 132B561407 for ; Thu, 29 Apr 2021 12:25:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236110AbhD2M01 (ORCPT ); Thu, 29 Apr 2021 08:26:27 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:46085 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236023AbhD2M0Z (ORCPT ); Thu, 29 Apr 2021 08:26:25 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1619699138; 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=rz9iAnX3OWn2JDFVlZ3RHH7TNXHQH76pK/TxsFgUd8I=; b=hiSafdX0573MwQli02mJjnjRnwFevc5OTQqhLz4crMd+Ak5SPWwfN+gVJasSxdS+ZBWYIH sWQOKgG/fPjpa2O7IIAO47HpO+HoR03e9xiIrI5pbTTOLNhHEjbl/zQXSo2sgMAm9Fj1Ew rO0jZ+agpPq6RBDbfdg8RIx2mk1QaAQ= 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-481-cZMzDWWxMHqEdaZ8aCf0oQ-1; Thu, 29 Apr 2021 08:25:35 -0400 X-MC-Unique: cZMzDWWxMHqEdaZ8aCf0oQ-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 59999803622; Thu, 29 Apr 2021 12:25:32 +0000 (UTC) Received: from t480s.redhat.com (ovpn-114-50.ams2.redhat.com [10.36.114.50]) by smtp.corp.redhat.com (Postfix) with ESMTP id DD6F118796; Thu, 29 Apr 2021 12:25:26 +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 v1 1/7] fs/proc/kcore: drop KCORE_REMAP and KCORE_OTHER Date: Thu, 29 Apr 2021 14:25:13 +0200 Message-Id: <20210429122519.15183-2-david@redhat.com> In-Reply-To: <20210429122519.15183-1-david@redhat.com> References: <20210429122519.15183-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 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. Signed-off-by: David Hildenbrand Reviewed-by: Mike Rapoport --- 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 Thu Apr 29 12:25:14 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 12231151 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=-16.0 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 61BEAC43600 for ; Thu, 29 Apr 2021 12:25:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 28981613F1 for ; Thu, 29 Apr 2021 12:25:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236278AbhD2M0a (ORCPT ); Thu, 29 Apr 2021 08:26:30 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:43781 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236536AbhD2M03 (ORCPT ); Thu, 29 Apr 2021 08:26:29 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1619699143; 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=rlbUJqtDJSJXZ0talu2Z3XFcFBG+/7XBZRlbnxcqpi4=; b=PiMRQ0nkNt7BZ++aqOMIeyx//u2QttYyM9H0iWIJdaJ+U6atoNKQho6bWxx2mh/a0Ccy4A gf7apf85DiRl5oVTWhuv7+j9EkYk1qxdmM5srCgz50YHS6TWRL8a63RswSrLyUU3maULv4 Fxaq+LAlcRcgVt7WSyViJfwV7uGlJnE= 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-405-McSW6JEJMfKG2TeFwvbHRQ-1; Thu, 29 Apr 2021 08:25:41 -0400 X-MC-Unique: McSW6JEJMfKG2TeFwvbHRQ-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id F1D518049FF; Thu, 29 Apr 2021 12:25:37 +0000 (UTC) Received: from t480s.redhat.com (ovpn-114-50.ams2.redhat.com [10.36.114.50]) by smtp.corp.redhat.com (Postfix) with ESMTP id A2ABF18796; Thu, 29 Apr 2021 12:25:32 +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 v1 2/7] fs/proc/kcore: pfn_is_ram check only applies to KCORE_RAM Date: Thu, 29 Apr 2021 14:25:14 +0200 Message-Id: <20210429122519.15183-3-david@redhat.com> In-Reply-To: <20210429122519.15183-1-david@redhat.com> References: <20210429122519.15183-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 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. Signed-off-by: David Hildenbrand Reviewed-by: Mike Rapoport --- 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 Thu Apr 29 12:25:15 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 12231153 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=-16.0 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 79248C43470 for ; Thu, 29 Apr 2021 12:25:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4A81461407 for ; Thu, 29 Apr 2021 12:25:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236984AbhD2M0j (ORCPT ); Thu, 29 Apr 2021 08:26:39 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:28190 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236737AbhD2M0g (ORCPT ); Thu, 29 Apr 2021 08:26:36 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1619699150; 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=9yW4OuKyN35nF4beRa4G0zG5E1KxLWubZR1ZjeP0KtI=; b=YfE4oZdXNKlICUEPNXNRa/7MhrKt/zOHHL43XtfnMZQIKy4EUhw41LPH4evd/Sq7+SFGQf 7uzLLZQT9d2cfE4xAJpZwUWZWTGOtA+8IViaLuu0i+KTUrho3jeJ0Jeu4PlfvBZC5+P0M5 4491uSgVq8tefpjyqZ7RyKHm8OhatLg= 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-216-yxYYYYlMNcONjLFEyhJ5IQ-1; Thu, 29 Apr 2021 08:25:46 -0400 X-MC-Unique: yxYYYYlMNcONjLFEyhJ5IQ-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id B20248042A6; Thu, 29 Apr 2021 12:25:43 +0000 (UTC) Received: from t480s.redhat.com (ovpn-114-50.ams2.redhat.com [10.36.114.50]) by smtp.corp.redhat.com (Postfix) with ESMTP id 5C08A18796; Thu, 29 Apr 2021 12:25:38 +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 v1 3/7] mm: rename and move page_is_poisoned() Date: Thu, 29 Apr 2021 14:25:15 +0200 Message-Id: <20210429122519.15183-4-david@redhat.com> In-Reply-To: <20210429122519.15183-1-david@redhat.com> References: <20210429122519.15183-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Commit d3378e86d182 ("mm/gup: check page posion status for coredump.") introduced page_is_poisoned(), however, v5 [1] of the patch used "page_is_hwpoison()" and something went wrong while upstreaming. Rename the function and move it to page-flags.h, from where it can be used in other -- kcore -- context. Move the comment to the place where it belongs and simplify. [1] https://lkml.kernel.org/r/20210322193318.377c9ce9@alex-virtual-machine Signed-off-by: David Hildenbrand Reviewed-by: Mike Rapoport --- include/linux/page-flags.h | 7 +++++++ mm/gup.c | 6 +++++- mm/internal.h | 20 -------------------- 3 files changed, 12 insertions(+), 21 deletions(-) diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index 04a34c08e0a6..b8c56672a588 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -694,6 +694,13 @@ PAGEFLAG_FALSE(DoubleMap) TESTSCFLAG_FALSE(DoubleMap) #endif +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 diff --git a/mm/gup.c b/mm/gup.c index ef7d2da9f03f..000f3303e7f2 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1536,7 +1536,11 @@ struct page *get_dump_page(unsigned long addr) if (locked) mmap_read_unlock(mm); - if (ret == 1 && is_page_poisoned(page)) + /* + * We might have hwpoisoned pages still mapped into user space. Don't + * read these pages when creating a coredump, access could be fatal. + */ + if (ret == 1 && is_page_hwpoison(page)) return NULL; return (ret == 1) ? page : NULL; diff --git a/mm/internal.h b/mm/internal.h index cb3c5e0a7799..1432feec62df 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -97,26 +97,6 @@ static inline void set_page_refcounted(struct page *page) set_page_count(page, 1); } -/* - * When kernel touch the user page, the user page may be have been marked - * poison but still mapped in user space, if without this page, the kernel - * can guarantee the data integrity and operation success, the kernel is - * better to check the posion status and avoid touching it, be good not to - * panic, coredump for process fatal signal is a sample case matching this - * scenario. Or if kernel can't guarantee the data integrity, it's better - * not to call this function, let kernel touch the poison page and get to - * panic. - */ -static inline bool is_page_poisoned(struct page *page) -{ - if (PageHWPoison(page)) - return true; - else if (PageHuge(page) && PageHWPoison(compound_head(page))) - return true; - - return false; -} - extern unsigned long highest_memmap_pfn; /* From patchwork Thu Apr 29 12:25:16 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 12231155 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=-16.0 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 B8D70C43461 for ; Thu, 29 Apr 2021 12:26:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 88497613C8 for ; Thu, 29 Apr 2021 12:26:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237174AbhD2M1I (ORCPT ); Thu, 29 Apr 2021 08:27:08 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:37581 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237142AbhD2M1H (ORCPT ); Thu, 29 Apr 2021 08:27:07 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1619699180; 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=G3IU63kGkBF+ogRqhIQp/uhSIS003Ny+/n/n+XU3YAE=; b=Oq2len8NqdARgRK8zax6I/WDPypb/GB769cTcNdhVOj9E/YanlvJBLiGNg9cZ2nNFrgu+J 54HHYgDwdAHr1MkKBdPY+itk84ZwA1B7ItD97F/DfmnV1C7McjgDrNRL10hKAWNnTHY9T+ Y+QV/DMvBLgO00kaXGZh+cdRmHA/o2A= 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-342-Q7ZmTdkgPk2x6LTwQLPkjg-1; Thu, 29 Apr 2021 08:26:17 -0400 X-MC-Unique: Q7ZmTdkgPk2x6LTwQLPkjg-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id EA17E8049CE; Thu, 29 Apr 2021 12:26:14 +0000 (UTC) Received: from t480s.redhat.com (ovpn-114-50.ams2.redhat.com [10.36.114.50]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1B31818796; Thu, 29 Apr 2021 12:25:43 +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 Subject: [PATCH v1 4/7] fs/proc/kcore: don't read offline sections, logically offline pages and hwpoisoned pages Date: Thu, 29 Apr 2021 14:25:16 +0200 Message-Id: <20210429122519.15183-5-david@redhat.com> In-Reply-To: <20210429122519.15183-1-david@redhat.com> References: <20210429122519.15183-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 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!" 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. Signed-off-by: David Hildenbrand Reviewed-by: Mike Rapoport --- fs/proc/kcore.c | 14 +++++++++++++- 1 file changed, 13 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; From patchwork Thu Apr 29 12:25:17 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 12231157 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=-16.0 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 B85FAC433ED for ; Thu, 29 Apr 2021 12:26:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8024D613F9 for ; Thu, 29 Apr 2021 12:26:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237142AbhD2M10 (ORCPT ); Thu, 29 Apr 2021 08:27:26 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:60945 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231343AbhD2M10 (ORCPT ); Thu, 29 Apr 2021 08:27:26 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1619699199; 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=OqK47sG85aZfcKTSSN25XorwOXhWot6GcaTYJAm0h7w=; b=BMUB1aYEJXWkmgtPRK/lvs/unrJ2bPdaBzYuCWVwX0d8MoyVX5/5pLvoRnA3PMdVvzXkRn G5UuDRcdd6AeCE6k+lhy5QdE7pmWi2p28wu0A+RWrGht8XGpxDFIBi2DsKg+03+O7RXLD2 ol6HFHLNpKsGkeMAuLxDBNIjm4KlFXM= 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-262-BOB6ZMW4OPaam5VXHtscdg-1; Thu, 29 Apr 2021 08:26:37 -0400 X-MC-Unique: BOB6ZMW4OPaam5VXHtscdg-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 0763910054F6; Thu, 29 Apr 2021 12:26:35 +0000 (UTC) Received: from t480s.redhat.com (ovpn-114-50.ams2.redhat.com [10.36.114.50]) by smtp.corp.redhat.com (Postfix) with ESMTP id 4B8A118796; Thu, 29 Apr 2021 12:26:15 +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 v1 5/7] mm: introduce page_offline_(begin|end|freeze|unfreeze) to synchronize setting PageOffline() Date: Thu, 29 Apr 2021 14:25:17 +0200 Message-Id: <20210429122519.15183-6-david@redhat.com> In-Reply-To: <20210429122519.15183-1-david@redhat.com> References: <20210429122519.15183-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 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|unfreeze) for synchronizing. page_offline_freeze()/page_offline_unfreeze() 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. Signed-off-by: David Hildenbrand Acked-by: Michal Hocko --- include/linux/page-flags.h | 5 +++++ mm/util.c | 38 ++++++++++++++++++++++++++++++++++++++ 2 files changed, 43 insertions(+) diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index b8c56672a588..e3d00c72f459 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -767,6 +767,11 @@ PAGE_TYPE_OPS(Buddy, buddy) */ PAGE_TYPE_OPS(Offline, offline) +extern void page_offline_freeze(void); +extern void page_offline_unfreeze(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 54870226cea6..95395d4e4209 100644 --- a/mm/util.c +++ b/mm/util.c @@ -1013,3 +1013,41 @@ void mem_dump_obj(void *object) } pr_cont(" non-slab/vmalloc memory.\n"); } + +/* + * 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_unfreeze() 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_unfreeze(void) +{ + up_read(&page_offline_rwsem); +} + +void page_offline_begin(void) +{ + down_write(&page_offline_rwsem); +} + +void page_offline_end(void) +{ + up_write(&page_offline_rwsem); +} From patchwork Thu Apr 29 12:25:18 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 12231159 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=-16.0 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 377FBC433B4 for ; Thu, 29 Apr 2021 12:26:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 04086613E1 for ; Thu, 29 Apr 2021 12:26:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237260AbhD2M1g (ORCPT ); Thu, 29 Apr 2021 08:27:36 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:58706 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237206AbhD2M1f (ORCPT ); Thu, 29 Apr 2021 08:27:35 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1619699209; 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=ba5FM83Cpmj9gJNSK1p4e73c9iU8c7zv5ZhHHm+jp5A=; b=cdzjZB9+OS7X7ncEdezdyDbxdJ8y6myUQtRaXAK631ZQa4wAwlZuxYkobshgMKZrG7GH2v FEJ+afzzW+9DSvEw4XizITHNWL+wZUutAkmkVDrjHX8O9FgDrEd5Qdq2O4lybC2/n+sbpE M89b/dRKh8CI4bsuVNXXKUj8gGboB6M= 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-564-61zoBJZfO3q1P9IGYPwAlA-1; Thu, 29 Apr 2021 08:26:45 -0400 X-MC-Unique: 61zoBJZfO3q1P9IGYPwAlA-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 679691926DA3; Thu, 29 Apr 2021 12:26:43 +0000 (UTC) Received: from t480s.redhat.com (ovpn-114-50.ams2.redhat.com [10.36.114.50]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6529C18796; Thu, 29 Apr 2021 12:26:35 +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 v1 6/7] virtio-mem: use page_offline_(start|end) when setting PageOffline() Date: Thu, 29 Apr 2021 14:25:18 +0200 Message-Id: <20210429122519.15183-7-david@redhat.com> In-Reply-To: <20210429122519.15183-1-david@redhat.com> References: <20210429122519.15183-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 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. Signed-off-by: David Hildenbrand Acked-by: Michael S. Tsirkin --- drivers/virtio/virtio_mem.c | 2 ++ mm/util.c | 2 ++ 2 files changed, 4 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(); } /* diff --git a/mm/util.c b/mm/util.c index 95395d4e4209..d0e357bd65e6 100644 --- a/mm/util.c +++ b/mm/util.c @@ -1046,8 +1046,10 @@ 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 Thu Apr 29 12:25:19 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 12231161 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=-16.0 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 DED3BC43461 for ; Thu, 29 Apr 2021 12:27:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A8F596141E for ; Thu, 29 Apr 2021 12:27:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234317AbhD2M2R (ORCPT ); Thu, 29 Apr 2021 08:28:17 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:57318 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230148AbhD2M2R (ORCPT ); Thu, 29 Apr 2021 08:28:17 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1619699250; 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=8j9mBor07Cs8M7oV014u0wi5MvoFT2r3E+Kj0uohzbw=; b=Q2ueY/bfihQWmJVU0cBapVR4RsBG7nHK9D0GbgdWNkPFnsWVzglmQpyvCIqsg8RPj9pC3B jFmoYxNjRIZG73BktbxPRvks+JVYeWGW0wHZ+tpFSIHo6UuamcCnL92t/6R9rRx5z0o44U YY/bgFDkagGsocpfcnnprkgHWeiar7g= 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-412-mextiE51O4S-F0gnYD4sAg-1; Thu, 29 Apr 2021 08:27:26 -0400 X-MC-Unique: mextiE51O4S-F0gnYD4sAg-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 097B8108BD0C; Thu, 29 Apr 2021 12:27:22 +0000 (UTC) Received: from t480s.redhat.com (ovpn-114-50.ams2.redhat.com [10.36.114.50]) by smtp.corp.redhat.com (Postfix) with ESMTP id C62B318811; Thu, 29 Apr 2021 12:26:43 +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 Subject: [PATCH v1 7/7] fs/proc/kcore: use page_offline_(freeze|unfreeze) Date: Thu, 29 Apr 2021 14:25:19 +0200 Message-Id: <20210429122519.15183-8-david@redhat.com> In-Reply-To: <20210429122519.15183-1-david@redhat.com> References: <20210429122519.15183-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Let's properly synchronize with drivers that set PageOffline(). Unfreeze every now and then, so drivers that want to set PageOffline() can make progress. Signed-off-by: David Hildenbrand --- fs/proc/kcore.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c index 92ff1e4436cb..3d7531f47389 100644 --- a/fs/proc/kcore.c +++ b/fs/proc/kcore.c @@ -311,6 +311,7 @@ static void append_kcore_note(char *notes, size_t *i, const char *name, static ssize_t read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) { + size_t page_offline_frozen = 0; char *buf = file->private_data; size_t phdrs_offset, notes_offset, data_offset; size_t phdrs_len, notes_len; @@ -509,6 +510,18 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) pfn = __pa(start) >> PAGE_SHIFT; page = pfn_to_online_page(pfn); + /* + * Don't race against drivers that set PageOffline() + * and expect no further page access. + */ + if (page_offline_frozen == MAX_ORDER_NR_PAGES) { + page_offline_unfreeze(); + page_offline_frozen = 0; + cond_resched(); + } + if (!page_offline_frozen++) + page_offline_freeze(); + /* * Don't read offline sections, logically offline pages * (e.g., inflated in a balloon), hwpoisoned pages, @@ -565,6 +578,8 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) } out: + if (page_offline_frozen) + page_offline_unfreeze(); up_read(&kclist_lock); if (ret) return ret;