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=-4.3 required=3.0 tests=BAYES_00,DATE_IN_PAST_12_24, DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLACK 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 75A2DC433DF for ; Sat, 15 Aug 2020 22:12:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5274E20639 for ; Sat, 15 Aug 2020 22:12:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597529551; bh=7Kmtoss9B2wqqJa6OYhDZvxmObVoM3fZi1CVnChqzxc=; h=Date:From:To:Subject:In-Reply-To:Reply-To:List-ID:From; b=SO58jjYrxUPDHkNMfyOBwCwqu33KOotrvQ1du48Ra46wdMhvf6JrTyZTVD63QcHsw /03O0Hf0efc7VC6IW2rzp/hvqYbixXZuvqsoHl3k8CCbOhqkdi8p6oDvaTly6sOYHT eXjKeavTFR72HESpBlk+oOfUD/4mo75sYoeDA7H8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729197AbgHOWMU (ORCPT ); Sat, 15 Aug 2020 18:12:20 -0400 Received: from mail.kernel.org ([198.145.29.99]:41792 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729042AbgHOWK2 (ORCPT ); Sat, 15 Aug 2020 18:10:28 -0400 Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (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 D383022D0B; Sat, 15 Aug 2020 00:31:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597451495; bh=7Kmtoss9B2wqqJa6OYhDZvxmObVoM3fZi1CVnChqzxc=; h=Date:From:To:Subject:In-Reply-To:From; b=J8dFhBRQXXcoVEPKDX2P9sDGwGAkOADOEeUAEwBB4SDl+8IVTqQavG6LLG4p7I6rb lhdP5+qhDCOZrwyldArCcLIgIKcC7oW2QZ25VfnSJBnV1pAf27n8YsdpPdOgdHYdnN 4a2m4uHSR2V+F9EYKAwDhjTSFJQGW0cF1yDsLv5s= Date: Fri, 14 Aug 2020 17:31:34 -0700 From: Andrew Morton To: akpm@linux-foundation.org, cai@lca.pw, david@redhat.com, dvyukov@google.com, elver@google.com, hannes@cmpxchg.org, linux-mm@kvack.org, mhocko@suse.com, mm-commits@vger.kernel.org, penguin-kernel@I-love.SAKURA.ne.jp, torvalds@linux-foundation.org Subject: [patch 26/39] mm/page_counter: fix various data races at memsw Message-ID: <20200815003134.sVViWEyRz%akpm@linux-foundation.org> In-Reply-To: <20200814172939.55d6d80b6e21e4241f1ee1f3@linux-foundation.org> User-Agent: s-nail v14.8.16 Sender: mm-commits-owner@vger.kernel.org Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org From: Qian Cai Subject: mm/page_counter: fix various data races at memsw Commit 3e32cb2e0a12 ("mm: memcontrol: lockless page counters") could had memcg->memsw->watermark and memcg->memsw->failcnt been accessed concurrently as reported by KCSAN, BUG: KCSAN: data-race in page_counter_try_charge / page_counter_try_charge read to 0xffff8fb18c4cd190 of 8 bytes by task 1081 on cpu 59: page_counter_try_charge+0x4d/0x150 mm/page_counter.c:138 try_charge+0x131/0xd50 mm/memcontrol.c:2405 __memcg_kmem_charge_memcg+0x58/0x140 __memcg_kmem_charge+0xcc/0x280 __alloc_pages_nodemask+0x1e1/0x450 alloc_pages_current+0xa6/0x120 pte_alloc_one+0x17/0xd0 __pte_alloc+0x3a/0x1f0 copy_p4d_range+0xc36/0x1990 copy_page_range+0x21d/0x360 dup_mmap+0x5f5/0x7a0 dup_mm+0xa2/0x240 copy_process+0x1b3f/0x3460 _do_fork+0xaa/0xa20 __x64_sys_clone+0x13b/0x170 do_syscall_64+0x91/0xb47 entry_SYSCALL_64_after_hwframe+0x49/0xbe write to 0xffff8fb18c4cd190 of 8 bytes by task 1153 on cpu 120: page_counter_try_charge+0x5b/0x150 mm/page_counter.c:139 try_charge+0x131/0xd50 mm/memcontrol.c:2405 mem_cgroup_try_charge+0x159/0x460 mem_cgroup_try_charge_delay+0x3d/0xa0 wp_page_copy+0x14d/0x930 do_wp_page+0x107/0x7b0 __handle_mm_fault+0xce6/0xd40 handle_mm_fault+0xfc/0x2f0 do_page_fault+0x263/0x6f9 page_fault+0x34/0x40 BUG: KCSAN: data-race in page_counter_try_charge / page_counter_try_charge write to 0xffff88809bbf2158 of 8 bytes by task 11782 on cpu 0: page_counter_try_charge+0x100/0x170 mm/page_counter.c:129 try_charge+0x185/0xbf0 mm/memcontrol.c:2405 __memcg_kmem_charge_memcg+0x4a/0xe0 mm/memcontrol.c:2837 __memcg_kmem_charge+0xcf/0x1b0 mm/memcontrol.c:2877 __alloc_pages_nodemask+0x26c/0x310 mm/page_alloc.c:4780 read to 0xffff88809bbf2158 of 8 bytes by task 11814 on cpu 1: page_counter_try_charge+0xef/0x170 mm/page_counter.c:129 try_charge+0x185/0xbf0 mm/memcontrol.c:2405 __memcg_kmem_charge_memcg+0x4a/0xe0 mm/memcontrol.c:2837 __memcg_kmem_charge+0xcf/0x1b0 mm/memcontrol.c:2877 __alloc_pages_nodemask+0x26c/0x310 mm/page_alloc.c:4780 Since watermark could be compared or set to garbage due to a data race which would change the code logic, fix it by adding a pair of READ_ONCE() and WRITE_ONCE() in those places. The "failcnt" counter is tolerant of some degree of inaccuracy and is only used to report stats, a data race will not be harmful, thus mark it as an intentional data race using the data_race() macro. Link: http://lkml.kernel.org/r/1581519682-23594-1-git-send-email-cai@lca.pw Fixes: 3e32cb2e0a12 ("mm: memcontrol: lockless page counters") Signed-off-by: Qian Cai Reported-by: syzbot+f36cfe60b1006a94f9dc@syzkaller.appspotmail.com Acked-by: Michal Hocko Cc: David Hildenbrand Cc: Tetsuo Handa Cc: Marco Elver Cc: Dmitry Vyukov Cc: Johannes Weiner Signed-off-by: Andrew Morton --- mm/page_counter.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) --- a/mm/page_counter.c~mm-page_counter-fix-various-data-races-at-memsw +++ a/mm/page_counter.c @@ -77,8 +77,8 @@ void page_counter_charge(struct page_cou * This is indeed racy, but we can live with some * inaccuracy in the watermark. */ - if (new > c->watermark) - c->watermark = new; + if (new > READ_ONCE(c->watermark)) + WRITE_ONCE(c->watermark, new); } } @@ -119,9 +119,10 @@ bool page_counter_try_charge(struct page propagate_protected_usage(c, new); /* * This is racy, but we can live with some - * inaccuracy in the failcnt. + * inaccuracy in the failcnt which is only used + * to report stats. */ - c->failcnt++; + data_race(c->failcnt++); *fail = c; goto failed; } @@ -130,8 +131,8 @@ bool page_counter_try_charge(struct page * Just like with failcnt, we can live with some * inaccuracy in the watermark. */ - if (new > c->watermark) - c->watermark = new; + if (new > READ_ONCE(c->watermark)) + WRITE_ONCE(c->watermark, new); } return true; _