From patchwork Tue Sep 29 10:59:12 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 263151 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=-13.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, 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 B87A2C4727C for ; Tue, 29 Sep 2020 12:00:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6F304206F7 for ; Tue, 29 Sep 2020 12:00:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601380842; bh=vrHzzj0NJ4cs62aCcsnRTYbtKwEJBxuDPemCWbUZoIw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=CX8BgiBiowVG/5cRpwv5OKLK8OWQogs8Dzt+s1TXf4P9xIgzys3aQhPAe6wXqY6eX 4QMLCDiHqmL6KM4mg3hZ93O60jCVjd2SpM8DbrhnySnpLsm4d0Bikx7wsPm//bhMKi rosmhuoh6aJ5SkAKr6XJpq1mgpxfzWNPs6Uih91E= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730702AbgI2MA1 (ORCPT ); Tue, 29 Sep 2020 08:00:27 -0400 Received: from mail.kernel.org ([198.145.29.99]:36568 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730575AbgI2Lkx (ORCPT ); Tue, 29 Sep 2020 07:40:53 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (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 5BC142065C; Tue, 29 Sep 2020 11:40:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601379635; bh=vrHzzj0NJ4cs62aCcsnRTYbtKwEJBxuDPemCWbUZoIw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=iSDDuKwi141jINaFg8maaqlUU4aO8WzDBuT8Cn0qoBd7pAJhoQ5T8Pij+QekXOUQ9 rfEqNlx0f5CdXsNZeRygbIxXooJV5YmGdiowtExYVBACVNVoNz885T+vRGFvSa9nFy baHr6Ic5juQHfsv7nfBgGDjp9vRg9/uyo9FJLtxg= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Qian Cai , Andrew Morton , Marco Elver , Hugh Dickins , Linus Torvalds , Sasha Levin Subject: [PATCH 5.4 221/388] mm/swapfile: fix data races in try_to_unuse() Date: Tue, 29 Sep 2020 12:59:12 +0200 Message-Id: <20200929110021.176039912@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200929110010.467764689@linuxfoundation.org> References: <20200929110010.467764689@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@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;