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=-17.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT,USER_IN_DEF_DKIM_WL 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 23116CA9EC1 for ; Tue, 29 Oct 2019 00:54:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E23EA21920 for ; Tue, 29 Oct 2019 00:54:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="VNIhRIVz" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727409AbfJ2Ay2 (ORCPT ); Mon, 28 Oct 2019 20:54:28 -0400 Received: from mail-qk1-f202.google.com ([209.85.222.202]:38336 "EHLO mail-qk1-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727336AbfJ2Ay2 (ORCPT ); Mon, 28 Oct 2019 20:54:28 -0400 Received: by mail-qk1-f202.google.com with SMTP id 64so9713665qkm.5 for ; Mon, 28 Oct 2019 17:54:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:message-id:mime-version:subject:from:to:cc; bh=CJNyfCkSt7mazdpKxm+NauccC7aNCXbzHO2WmG+WXZI=; b=VNIhRIVznNTE4231t1PB9Y892IckjdElWezZZVpfEZj80/mzanDBafaCAPwbWdo/2+ A2IlnsRAL2Blt3IvIwX0ISb+ZmFwG9yrBZ55rX1/xuj9NUAqSD3FHneUmyprKlV5yl3q tTlgF3TG2RXMaFaXAlfpSDe9OiAODZDJ/pnsUOZfcjt++CXArvZZTjQ5fY2m5Jz4KDJj UImudqlau9RYfYGT+aEy1/m9RTwJwhjIFgij71FJyZX0avIJ5/L6Yy34dJ5ovk87MzOg vpUccTmI91a3yMxtIvMawk0rByNgb7F2mUfDUfz6Bqs+0lifTZdjCcjDQGftK7LTeiXB t6Tw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=CJNyfCkSt7mazdpKxm+NauccC7aNCXbzHO2WmG+WXZI=; b=j3ZRf6cRMMdwq4VuGTlYlOKt+pBv+9odPRayXVRczixCm3rmJCk7Ui3HZN3SBZZETR m+vUgWeel4vQqn5j40g9rKW6dv3/TwOvKSgx5f2U2eV/Ck0d13UZGBmRoquxB9rATql9 aYyGyLd8pjkVYvMgr9ZG6r6SGlmog55zOfaQRH6u+7uIO0Gr4N3kAlq0MbZdPx0tPZZ/ /vxSzcbUouPsG1pPgY+y9U7gdEevPh5qjKYcz96ZBnnOij4ryUujWVMvBfWd6Se5utoh T4MhjX7BG+4W1+dtUUwObttfoeghS3XBQTMdoiE4xFMObVaKu6Wsw89RLk3UFKy0IhOj 3mEg== X-Gm-Message-State: APjAAAUaMYCYn1sZu2C2qd33wyWgFHdLzS3hA44KAxru+Bdce54D+Lmf tMo7Ti4iUaVUTPV/5UB9726g9t14yYmisg== X-Google-Smtp-Source: APXvYqyuC1vSPb0iXXoyj+RX6tq0hHQYQPJSlVZL8/Xu5SdTk1tHt39Bxai/8EbXawqb+7npXxeAku+T+G4lIw== X-Received: by 2002:a37:9d15:: with SMTP id g21mr4415148qke.71.1572310467233; Mon, 28 Oct 2019 17:54:27 -0700 (PDT) Date: Mon, 28 Oct 2019 17:54:05 -0700 Message-Id: <20191029005405.201986-1-shakeelb@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.24.0.rc0.303.g954a862665-goog Subject: [PATCH] mm: memcontrol: fix data race in mem_cgroup_select_victim_node From: Shakeel Butt To: Roman Gushchin , Johannes Weiner , Michal Hocko , Andrew Morton Cc: linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Shakeel Butt , Eric Dumazet , Greg Thelen , syzbot+13f93c99c06988391efe@syzkaller.appspotmail.com Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Syzbot reported the following bug: BUG: KCSAN: data-race in mem_cgroup_select_victim_node / mem_cgroup_select_victim_node write to 0xffff88809fade9b0 of 4 bytes by task 8603 on cpu 0: mem_cgroup_select_victim_node+0xb5/0x3d0 mm/memcontrol.c:1686 try_to_free_mem_cgroup_pages+0x175/0x4c0 mm/vmscan.c:3376 reclaim_high.constprop.0+0xf7/0x140 mm/memcontrol.c:2349 mem_cgroup_handle_over_high+0x96/0x180 mm/memcontrol.c:2430 tracehook_notify_resume include/linux/tracehook.h:197 [inline] exit_to_usermode_loop+0x20c/0x2c0 arch/x86/entry/common.c:163 prepare_exit_to_usermode+0x180/0x1a0 arch/x86/entry/common.c:194 swapgs_restore_regs_and_return_to_usermode+0x0/0x40 read to 0xffff88809fade9b0 of 4 bytes by task 7290 on cpu 1: mem_cgroup_select_victim_node+0x92/0x3d0 mm/memcontrol.c:1675 try_to_free_mem_cgroup_pages+0x175/0x4c0 mm/vmscan.c:3376 reclaim_high.constprop.0+0xf7/0x140 mm/memcontrol.c:2349 mem_cgroup_handle_over_high+0x96/0x180 mm/memcontrol.c:2430 tracehook_notify_resume include/linux/tracehook.h:197 [inline] exit_to_usermode_loop+0x20c/0x2c0 arch/x86/entry/common.c:163 prepare_exit_to_usermode+0x180/0x1a0 arch/x86/entry/common.c:194 swapgs_restore_regs_and_return_to_usermode+0x0/0x40 mem_cgroup_select_victim_node() can be called concurrently which reads and modifies memcg->last_scanned_node without any synchrnonization. So, read and modify memcg->last_scanned_node with READ_ONCE()/WRITE_ONCE() to stop potential reordering. Signed-off-by: Shakeel Butt Suggested-by: Eric Dumazet Cc: Greg Thelen Reported-by: syzbot+13f93c99c06988391efe@syzkaller.appspotmail.com --- mm/memcontrol.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index c4c555055a72..5a06739dd3e4 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1667,7 +1667,7 @@ int mem_cgroup_select_victim_node(struct mem_cgroup *memcg) int node; mem_cgroup_may_update_nodemask(memcg); - node = memcg->last_scanned_node; + node = READ_ONCE(memcg->last_scanned_node); node = next_node_in(node, memcg->scan_nodes); /* @@ -1678,7 +1678,7 @@ int mem_cgroup_select_victim_node(struct mem_cgroup *memcg) if (unlikely(node == MAX_NUMNODES)) node = numa_node_id(); - memcg->last_scanned_node = node; + WRITE_ONCE(memcg->last_scanned_node, node); return node; } #else -- 2.24.0.rc0.303.g954a862665-goog