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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=ham 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 1EB9DECE58D for ; Sat, 12 Oct 2019 01:06:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EA4B32089F for ; Sat, 12 Oct 2019 01:06:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727345AbfJLBGR (ORCPT ); Fri, 11 Oct 2019 21:06:17 -0400 Received: from mx2a.mailbox.org ([80.241.60.219]:57995 "EHLO mx2a.mailbox.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726863AbfJLBGR (ORCPT ); Fri, 11 Oct 2019 21:06:17 -0400 Received: from smtp2.mailbox.org (smtp2.mailbox.org [80.241.60.241]) (using TLSv1.2 with cipher ECDHE-RSA-CHACHA20-POLY1305 (256/256 bits)) (No client certificate requested) by mx2a.mailbox.org (Postfix) with ESMTPS id B4EABA1585; Sat, 12 Oct 2019 03:06:14 +0200 (CEST) X-Virus-Scanned: amavisd-new at heinlein-support.de Received: from smtp2.mailbox.org ([80.241.60.241]) by hefe.heinlein-support.de (hefe.heinlein-support.de [91.198.250.172]) (amavisd-new, port 10030) with ESMTP id HpnuEwOz63oE; Sat, 12 Oct 2019 03:06:11 +0200 (CEST) From: Aleksa Sarai To: Tejun Heo , Li Zefan , Johannes Weiner Cc: cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Aleksa Sarai , stable@vger.kernel.org Subject: [PATCH] cgroup: pids: use {READ,WRITE}_ONCE for pids->limit operations Date: Sat, 12 Oct 2019 12:05:39 +1100 Message-Id: <20191012010539.6131-1-cyphar@cyphar.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org Because pids->limit can be changed concurrently (but we don't want to take a lock because it would be needlessly expensive), use the appropriate memory barriers. Fixes: commit 49b786ea146f ("cgroup: implement the PIDs subsystem") Cc: stable@vger.kernel.org # v4.3+ Signed-off-by: Aleksa Sarai --- kernel/cgroup/pids.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/kernel/cgroup/pids.c b/kernel/cgroup/pids.c index 8e513a573fe9..a726e4a20177 100644 --- a/kernel/cgroup/pids.c +++ b/kernel/cgroup/pids.c @@ -152,7 +152,7 @@ static int pids_try_charge(struct pids_cgroup *pids, int num) * p->limit is %PIDS_MAX then we know that this test will never * fail. */ - if (new > p->limit) + if (new > READ_ONCE(p->limit)) goto revert; } @@ -277,7 +277,7 @@ static ssize_t pids_max_write(struct kernfs_open_file *of, char *buf, * Limit updates don't need to be mutex'd, since it isn't * critical that any racing fork()s follow the new limit. */ - pids->limit = limit; + WRITE_ONCE(pids->limit, limit); return nbytes; } @@ -285,7 +285,7 @@ static int pids_max_show(struct seq_file *sf, void *v) { struct cgroup_subsys_state *css = seq_css(sf); struct pids_cgroup *pids = css_pids(css); - int64_t limit = pids->limit; + int64_t limit = READ_ONCE(pids->limit); if (limit >= PIDS_MAX) seq_printf(sf, "%s\n", PIDS_MAX_STR); -- 2.23.0