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 2C35BC43465 for ; Fri, 18 Sep 2020 02:59:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EA56C206B6 for ; Fri, 18 Sep 2020 02:59:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1600397997; bh=vrHzzj0NJ4cs62aCcsnRTYbtKwEJBxuDPemCWbUZoIw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=n3rB6j5eHcM0tE8WJUQyVY1ULxs38YWPXiW5G+TgSYaXfC0d8AbrOxzFivBeUS0xT vgXC5hdaO311K9xmy/ZZulO2Cwl7ILQW7V61AIXQcC1pt86pOVA8iD4EO77xf6IUwO JSljLIXOGcZAGAioczdMTiZZfS5LakNG/4cSlF/g= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730381AbgIRC7v (ORCPT ); Thu, 17 Sep 2020 22:59:51 -0400 Received: from mail.kernel.org ([198.145.29.99]:54476 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727647AbgIRCFt (ORCPT ); Thu, 17 Sep 2020 22:05:49 -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 B9FC22388E; Fri, 18 Sep 2020 02:05:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1600394748; bh=vrHzzj0NJ4cs62aCcsnRTYbtKwEJBxuDPemCWbUZoIw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=v1C6OeIqjeJ1Fa+8R4+GvcsiR7aBsVsAuUUqj9pPpXNY+z9wjYH9dMONnbAAh+yrL FREMVPwUCAPpKvDB/psTLPptbCVEDTx+hLIIxj/w1M4pfHAm+uIs9uRXrnkCqQGvxc 9YT7C9B42CtrQjmkcEz5qIUL7EZKXCJNB5FeBGBA= 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 5.4 227/330] mm/swapfile: fix data races in try_to_unuse() Date: Thu, 17 Sep 2020 21:59:27 -0400 Message-Id: <20200918020110.2063155-227-sashal@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200918020110.2063155-1-sashal@kernel.org> References: <20200918020110.2063155-1-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 218209487c3da2f6d861b236c11226b6eca7b7b7 ] si->inuse_pages could be accessed concurrently as noticed by KCSAN, write to 0xffff98b00ebd04dc of 4 bytes by task 82262 on cpu 92: swap_range_free+0xbe/0x230 swap_range_free at mm/swapfile.c:719 swapcache_free_entries+0x1be/0x250 free_swap_slot+0x1c8/0x220 __swap_entry_free.constprop.19+0xa3/0xb0 free_swap_and_cache+0x53/0xa0 unmap_page_range+0x7e0/0x1ce0 unmap_single_vma+0xcd/0x170 unmap_vmas+0x18b/0x220 exit_mmap+0xee/0x220 mmput+0xe7/0x240 do_exit+0x598/0xfd0 do_group_exit+0x8b/0x180 get_signal+0x293/0x13d0 do_signal+0x37/0x5d0 prepare_exit_to_usermode+0x1b7/0x2c0 ret_from_intr+0x32/0x42 read to 0xffff98b00ebd04dc of 4 bytes by task 82499 on cpu 46: try_to_unuse+0x86b/0xc80 try_to_unuse at mm/swapfile.c:2185 __x64_sys_swapoff+0x372/0xd40 do_syscall_64+0x91/0xb05 entry_SYSCALL_64_after_hwframe+0x49/0xbe The plain reads in try_to_unuse() are outside si->lock critical section which result in data races that could be dangerous to be used in a loop. Fix them by adding READ_ONCE(). Signed-off-by: Qian Cai Signed-off-by: Andrew Morton Reviewed-by: Andrew Morton Cc: Marco Elver Cc: Hugh Dickins Link: http://lkml.kernel.org/r/1582578903-29294-1-git-send-email-cai@lca.pw Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- mm/swapfile.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/mm/swapfile.c b/mm/swapfile.c index 646fd0a8e3202..2f59495782dd4 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -2132,7 +2132,7 @@ int try_to_unuse(unsigned int type, bool frontswap, swp_entry_t entry; unsigned int i; - if (!si->inuse_pages) + if (!READ_ONCE(si->inuse_pages)) return 0; if (!frontswap) @@ -2148,7 +2148,7 @@ retry: spin_lock(&mmlist_lock); p = &init_mm.mmlist; - while (si->inuse_pages && + while (READ_ONCE(si->inuse_pages) && !signal_pending(current) && (p = p->next) != &init_mm.mmlist) { @@ -2177,7 +2177,7 @@ retry: mmput(prev_mm); i = 0; - while (si->inuse_pages && + while (READ_ONCE(si->inuse_pages) && !signal_pending(current) && (i = find_next_to_unuse(si, i, frontswap)) != 0) { @@ -2219,7 +2219,7 @@ retry: * been preempted after get_swap_page(), temporarily hiding that swap. * It's easy and robust (though cpu-intensive) just to keep retrying. */ - if (si->inuse_pages) { + if (READ_ONCE(si->inuse_pages)) { if (!signal_pending(current)) goto retry; retval = -EINTR; -- 2.25.1