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=-6.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 C2C28C433E7 for ; Wed, 14 Oct 2020 21:03:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7AEEE221FF for ; Wed, 14 Oct 2020 21:03:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1602709383; bh=c9A5aONVgXWgFc5n+CxTM9SJIGfdRFBMNHql759pizg=; h=Date:From:To:Subject:Reply-To:List-ID:From; b=TuzFrMTtxlmbyBbn7sSiLQUPpVdw/Gjj2rzfpWlh2dSDXHq/AKDk2B8Mp4K2dwUtp GyDJqRFJUNfTF+X2aQC0mcfETv79ERiT9e37unmL8z29IRUNQn17hrBe6tsqWlMLyv Bg3i0ZlEbdxQSA4d5gsfNMMx9pg1ZG02PLizCZEw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730511AbgJNVDD (ORCPT ); Wed, 14 Oct 2020 17:03:03 -0400 Received: from mail.kernel.org ([198.145.29.99]:52862 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726099AbgJNVDD (ORCPT ); Wed, 14 Oct 2020 17:03:03 -0400 Received: from localhost.localdomain (c-71-198-47-131.hsd1.ca.comcast.net [71.198.47.131]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 9195E206B2; Wed, 14 Oct 2020 21:03:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1602709381; bh=c9A5aONVgXWgFc5n+CxTM9SJIGfdRFBMNHql759pizg=; h=Date:From:To:Subject:From; b=XixIiHjszmzVNvdAsx9HLqNBC7YyRc/sSrITJVjSWjdktJhGfDRbLp3TL5dTtTnRb TIylKV6fBqQOEQ6PobUarB06Kh+1ijQMNbYO1wx7yhnuHnyU5lLuLbDqXnT09KHgMA mDImMqqEBA5gNzStLBZsiDc7+3CTs3AqDe7nPZhE= Date: Wed, 14 Oct 2020 14:03:01 -0700 From: akpm@linux-foundation.org To: hughd@google.com, mm-commits@vger.kernel.org, npiggin@gmail.com, peterz@infradead.org, rppt@linux.ibm.com, willy@infradead.org Subject: [merged] page_alloc-fix-freeing-non-compound-pages.patch removed from -mm tree Message-ID: <20201014210301.w32vWqDux%akpm@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 The patch titled Subject: mm/page_alloc.c: fix freeing non-compound pages has been removed from the -mm tree. Its filename was page_alloc-fix-freeing-non-compound-pages.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: "Matthew Wilcox (Oracle)" Subject: mm/page_alloc.c: fix freeing non-compound pages Here is a very rare race which leaks memory: Page P0 is allocated to the page cache. Page P1 is free. Thread A Thread B Thread C find_get_entry(): xas_load() returns P0 Removes P0 from page cache P0 finds its buddy P1 alloc_pages(GFP_KERNEL, 1) returns P0 P0 has refcount 1 page_cache_get_speculative(P0) P0 has refcount 2 __free_pages(P0) P0 has refcount 1 put_page(P0) P1 is not freed Fix this by freeing all the pages in __free_pages() that won't be freed by the call to put_page(). It's usually not a good idea to split a page, but this is a very unlikely scenario. Link: https://lkml.kernel.org/r/20200926213919.26642-1-willy@infradead.org Fixes: e286781d5f2e ("mm: speculative page references") Signed-off-by: Matthew Wilcox (Oracle) Acked-by: Mike Rapoport Cc: Nick Piggin Cc: Hugh Dickins Cc: Peter Zijlstra Signed-off-by: Andrew Morton --- lib/Kconfig.debug | 9 ++++++++ lib/Makefile | 1 lib/test_free_pages.c | 42 ++++++++++++++++++++++++++++++++++++++++ mm/page_alloc.c | 3 ++ 4 files changed, 55 insertions(+) --- a/lib/Kconfig.debug~page_alloc-fix-freeing-non-compound-pages +++ a/lib/Kconfig.debug @@ -2367,6 +2367,15 @@ config TEST_HMM If unsure, say N. +config TEST_FREE_PAGES + tristate "Test freeing pages" + help + Test that a memory leak does not occur due to a race between + freeing a block of pages and a speculative page reference. + Loading this module is safe if your kernel has the bug fixed. + If the bug is not fixed, it will leak gigabytes of memory and + probably OOM your system. + config TEST_FPU tristate "Test floating point operations in kernel space" depends on X86 && !KCOV_INSTRUMENT_ALL --- a/lib/Makefile~page_alloc-fix-freeing-non-compound-pages +++ a/lib/Makefile @@ -101,6 +101,7 @@ obj-$(CONFIG_TEST_BLACKHOLE_DEV) += test obj-$(CONFIG_TEST_MEMINIT) += test_meminit.o obj-$(CONFIG_TEST_LOCKUP) += test_lockup.o obj-$(CONFIG_TEST_HMM) += test_hmm.o +obj-$(CONFIG_TEST_FREE_PAGES) += test_free_pages.o # # CFLAGS for compiling floating point code inside the kernel. x86/Makefile turns --- /dev/null +++ a/lib/test_free_pages.c @@ -0,0 +1,42 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * test_free_pages.c: Check that free_pages() doesn't leak memory + * Copyright (c) 2020 Oracle + * Author: Matthew Wilcox + */ + +#include +#include +#include + +static void test_free_pages(gfp_t gfp) +{ + unsigned int i; + + for (i = 0; i < 1000 * 1000; i++) { + unsigned long addr = __get_free_pages(gfp, 3); + struct page *page = virt_to_page(addr); + + /* Simulate page cache getting a speculative reference */ + get_page(page); + free_pages(addr, 3); + put_page(page); + } +} + +static int m_in(void) +{ + test_free_pages(GFP_KERNEL); + test_free_pages(GFP_KERNEL | __GFP_COMP); + + return 0; +} + +static void m_ex(void) +{ +} + +module_init(m_in); +module_exit(m_ex); +MODULE_AUTHOR("Matthew Wilcox "); +MODULE_LICENSE("GPL"); --- a/mm/page_alloc.c~page_alloc-fix-freeing-non-compound-pages +++ a/mm/page_alloc.c @@ -4952,6 +4952,9 @@ void __free_pages(struct page *page, uns { if (put_page_testzero(page)) free_the_page(page, order); + else if (!PageHead(page)) + while (order-- > 0) + free_the_page(page + (1 << order), order); } EXPORT_SYMBOL(__free_pages); _ Patches currently in -mm which might be from willy@infradead.org are xarray-add-xa_get_order.patch xarray-add-xas_split.patch xarray-add-xas_split-fix-2.patch xarray-add-xas_split-fix-3patch.patch mm-filemap-fix-storing-to-a-thp-shadow-entry.patch mm-filemap-fix-page-cache-removal-for-arbitrary-sized-thps.patch mm-memory-remove-page-fault-assumption-of-compound-page-size.patch mm-memory-remove-page-fault-assumption-of-compound-page-size-fix.patch mm-page_owner-change-split_page_owner-to-take-a-count.patch mm-huge_memory-fix-page_trans_huge_mapcount-assumption-of-thp-size.patch mm-huge_memory-fix-can_split_huge_page-assumption-of-thp-size.patch mm-rmap-fix-assumptions-of-thp-size.patch mm-truncate-fix-truncation-for-pages-of-arbitrary-size.patch mm-page-writeback-support-tail-pages-in-wait_for_stable_page.patch mm-vmscan-allow-arbitrary-sized-pages-to-be-paged-out.patch fs-add-a-filesystem-flag-for-thps.patch fs-do-not-update-nr_thps-for-mappings-which-support-thps.patch mm-readahead-add-define_readahead.patch mm-readahead-make-page_cache_ra_unbounded-take-a-readahead_control.patch mm-readahead-make-do_page_cache_ra-take-a-readahead_control.patch mm-readahead-add-page_cache_sync_ra-and-page_cache_async_ra.patch mm-rename-page_order-to-buddy_order.patch ramfs-fix-nommu-mmap-with-gaps-in-the-page-cache.patch harden-autofs-ioctl-table.patch mm-update-the-documentation-for-vfree.patch