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=-16.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 E2EA0C43465 for ; Fri, 18 Sep 2020 02:30:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A2B0823770 for ; Fri, 18 Sep 2020 02:30:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1600396229; bh=M9BLECcRmg4gwlCqeaZTtuc1dLUoMa95rWXGsAzJuMo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=EycTlRjWebPPAqzm1H1x2+p0QbM8kfNexISldgV2L/+H65E5clTDscOFxJ3OE0CWQ pwQu7TSV9kkbHp76rz9yItRfdM4FWSrYzh1NaTfDH1wwavfBCN5u41Tvc8uqUM1Lxu D9pW7QRSOGGLv577aaJAKJZDqN42T3ygHpfvrda0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729531AbgIRCaZ (ORCPT ); Thu, 17 Sep 2020 22:30:25 -0400 Received: from mail.kernel.org ([198.145.29.99]:43050 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728024AbgIRCOn (ORCPT ); Thu, 17 Sep 2020 22:14:43 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 4076A239E5; Fri, 18 Sep 2020 02:14:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1600395281; bh=M9BLECcRmg4gwlCqeaZTtuc1dLUoMa95rWXGsAzJuMo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=PINfCAC44F2cZNRYUSTu6IVDSPP06R+TdagIUZvMnQh7GDD4dwdwVNmiwxM6xqDsA iZ+4AIll1zH2//qYvpLvDYPFPs7VGkIvE+7pkaxXmY+9u+Cvug+9LDZvuBy4C9Qnwa EBj8fkJRiE80jnr0QjeWzbu86mFtIIlzFCpxSxFs= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Qian Cai , Andrew Morton , Marco Elver , Hugh Dickins , Linus Torvalds , Sasha Levin , linux-mm@kvack.org Subject: [PATCH AUTOSEL 4.14 117/127] mm/swap_state: fix a data race in swapin_nr_pages Date: Thu, 17 Sep 2020 22:12:10 -0400 Message-Id: <20200918021220.2066485-117-sashal@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200918021220.2066485-1-sashal@kernel.org> References: <20200918021220.2066485-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Qian Cai [ Upstream commit d6c1f098f2a7ba62627c9bc17cda28f534ef9e4a ] "prev_offset" is a static variable in swapin_nr_pages() that can be accessed concurrently with only mmap_sem held in read mode as noticed by KCSAN, BUG: KCSAN: data-race in swap_cluster_readahead / swap_cluster_readahead write to 0xffffffff92763830 of 8 bytes by task 14795 on cpu 17: swap_cluster_readahead+0x2a6/0x5e0 swapin_readahead+0x92/0x8dc do_swap_page+0x49b/0xf20 __handle_mm_fault+0xcfb/0xd70 handle_mm_fault+0xfc/0x2f0 do_page_fault+0x263/0x715 page_fault+0x34/0x40 1 lock held by (dnf)/14795: #0: ffff897bd2e98858 (&mm->mmap_sem#2){++++}-{3:3}, at: do_page_fault+0x143/0x715 do_user_addr_fault at arch/x86/mm/fault.c:1405 (inlined by) do_page_fault at arch/x86/mm/fault.c:1535 irq event stamp: 83493 count_memcg_event_mm+0x1a6/0x270 count_memcg_event_mm+0x119/0x270 __do_softirq+0x365/0x589 irq_exit+0xa2/0xc0 read to 0xffffffff92763830 of 8 bytes by task 1 on cpu 22: swap_cluster_readahead+0xfd/0x5e0 swapin_readahead+0x92/0x8dc do_swap_page+0x49b/0xf20 __handle_mm_fault+0xcfb/0xd70 handle_mm_fault+0xfc/0x2f0 do_page_fault+0x263/0x715 page_fault+0x34/0x40 1 lock held by systemd/1: #0: ffff897c38f14858 (&mm->mmap_sem#2){++++}-{3:3}, at: do_page_fault+0x143/0x715 irq event stamp: 43530289 count_memcg_event_mm+0x1a6/0x270 count_memcg_event_mm+0x119/0x270 __do_softirq+0x365/0x589 irq_exit+0xa2/0xc0 Signed-off-by: Qian Cai Signed-off-by: Andrew Morton Cc: Marco Elver Cc: Hugh Dickins Link: http://lkml.kernel.org/r/20200402213748.2237-1-cai@lca.pw Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- mm/swap_state.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/mm/swap_state.c b/mm/swap_state.c index 755be95d52f9c..3ceea86818bd4 100644 --- a/mm/swap_state.c +++ b/mm/swap_state.c @@ -524,10 +524,11 @@ static unsigned long swapin_nr_pages(unsigned long offset) return 1; hits = atomic_xchg(&swapin_readahead_hits, 0); - pages = __swapin_nr_pages(prev_offset, offset, hits, max_pages, + pages = __swapin_nr_pages(READ_ONCE(prev_offset), offset, hits, + max_pages, atomic_read(&last_readahead_pages)); if (!hits) - prev_offset = offset; + WRITE_ONCE(prev_offset, offset); atomic_set(&last_readahead_pages, pages); return pages; -- 2.25.1