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=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 E4513C4361B for ; Tue, 15 Dec 2020 03:16:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A680D223C8 for ; Tue, 15 Dec 2020 03:16:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728068AbgLODPg (ORCPT ); Mon, 14 Dec 2020 22:15:36 -0500 Received: from mail.kernel.org ([198.145.29.99]:36850 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728078AbgLODNA (ORCPT ); Mon, 14 Dec 2020 22:13:00 -0500 Date: Mon, 14 Dec 2020 19:11:48 -0800 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1608001909; bh=Lw1/k2xehFo/+jFeojB9G/herfyQAxgwBP0HikYKmq0=; h=From:To:Subject:In-Reply-To:From; b=XuLETQgnKwJeRdekMQ5D5HjAFZQwoffp6xFc3utJOkpcEC/sxZkOAIfOQS/XN5um5 cQsfEXS5oxZ8pzD71+GXUOkJeN6/0ZZlvWuk+QmYB7rBztAXp2wJHvVv/UQHvSUdch 6JdM+8jxflnaCw4lLcWGx9mz8nh1Y1TMCLUeJ7HU= From: Andrew Morton To: akpm@linux-foundation.org, dan.j.williams@intel.com, linux-mm@kvack.org, mm-commits@vger.kernel.org, naoya.horiguchi@nec.com, osalvador@suse.de, torvalds@linux-foundation.org, vbabka@suse.cz Subject: [patch 144/200] mm,memory_failure: always pin the page in madvise_inject_error Message-ID: <20201215031148.G2lE81l-O%akpm@linux-foundation.org> In-Reply-To: <20201214190237.a17b70ae14f129e2dca3d204@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org From: Oscar Salvador Subject: mm,memory_failure: always pin the page in madvise_inject_error madvise_inject_error() uses get_user_pages_fast to translate the address we specified to a page. After [1], we drop the extra reference count for memory_failure() path. That commit says that memory_failure wanted to keep the pin in order to take the page out of circulation. The truth is that we need to keep the page pinned, otherwise the page might be re-used after the put_page() and we can end up messing with someone else's memory. E.g: CPU0 process X CPU1 madvise_inject_error get_user_pages put_page page gets reclaimed process Y allocates the page memory_failure // We mess with process Y memory madvise() is meant to operate on a self address space, so messing with pages that do not belong to us seems the wrong thing to do. To avoid that, let us keep the page pinned for memory_failure as well. Pages for DAX mappings will release this extra refcount in memory_failure_dev_pagemap. [1] ("23e7b5c2e271: mm, madvise_inject_error: Let memory_failure() optionally take a page reference") Link: https://lkml.kernel.org/r/20201207094818.8518-1-osalvador@suse.de Fixes: 23e7b5c2e271 ("mm, madvise_inject_error: Let memory_failure() optionally take a page reference") Signed-off-by: Oscar Salvador Suggested-by: Vlastimil Babka Acked-by: Naoya Horiguchi Cc: Vlastimil Babka Cc: Dan Williams Signed-off-by: Andrew Morton --- mm/madvise.c | 9 +-------- mm/memory-failure.c | 6 ++++++ 2 files changed, 7 insertions(+), 8 deletions(-) --- a/mm/madvise.c~mmmemory_failure-always-pin-the-page-in-madvise_inject_error +++ a/mm/madvise.c @@ -907,14 +907,7 @@ static int madvise_inject_error(int beha } else { pr_info("Injecting memory failure for pfn %#lx at process virtual address %#lx\n", pfn, start); - /* - * Drop the page reference taken by get_user_pages_fast(). In - * the absence of MF_COUNT_INCREASED the memory_failure() - * routine is responsible for pinning the page to prevent it - * from being released back to the page allocator. - */ - put_page(page); - ret = memory_failure(pfn, 0); + ret = memory_failure(pfn, MF_COUNT_INCREASED); } if (ret) --- a/mm/memory-failure.c~mmmemory_failure-always-pin-the-page-in-madvise_inject_error +++ a/mm/memory-failure.c @@ -1302,6 +1302,12 @@ static int memory_failure_dev_pagemap(un loff_t start; dax_entry_t cookie; + if (flags & MF_COUNT_INCREASED) + /* + * Drop the extra refcount in case we come from madvise(). + */ + put_page(page); + /* * Prevent the inode from being freed while we are interrogating * the address_space, typically this would be handled by _