From patchwork Wed Jul 6 05:21:21 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kuniyuki Iwashima X-Patchwork-Id: 12907331 X-Patchwork-Delegate: kuba@kernel.org Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 48846C433EF for ; Wed, 6 Jul 2022 05:23:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231382AbiGFFXj (ORCPT ); Wed, 6 Jul 2022 01:23:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47322 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231370AbiGFFX1 (ORCPT ); Wed, 6 Jul 2022 01:23:27 -0400 Received: from smtp-fw-9102.amazon.com (smtp-fw-9102.amazon.com [207.171.184.29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 39F333B0; Tue, 5 Jul 2022 22:23:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1657085006; x=1688621006; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=FH3JnsOgIqucU/O/kiHTcxh5RtV6tKMeFYEzhhc+/GI=; b=F8GbKNSV/eaqqyE+MlfTPBvXX07vN4cyB+wfd8dJM2VXW/BIQV4L1HgM KGvbkd2v235X4bzzppgTEeVl9GKnpk6HU2MqQM6IGTxOqOhEIrnZoPPWn f4Gq3GaluuNfpLXNtD5UmEA4+lPPMxBzBZJpcV0lhHwQRk1rqIDhoH1/r I=; X-IronPort-AV: E=Sophos;i="5.92,248,1650931200"; d="scan'208";a="235270987" Received: from pdx4-co-svc-p1-lb2-vlan2.amazon.com (HELO email-inbound-relay-pdx-2b-22c2b493.us-west-2.amazon.com) ([10.25.36.210]) by smtp-border-fw-9102.sea19.amazon.com with ESMTP; 06 Jul 2022 05:23:26 +0000 Received: from EX13MTAUWB001.ant.amazon.com (pdx1-ws-svc-p6-lb9-vlan2.pdx.amazon.com [10.236.137.194]) by email-inbound-relay-pdx-2b-22c2b493.us-west-2.amazon.com (Postfix) with ESMTPS id B321F43A09; Wed, 6 Jul 2022 05:23:25 +0000 (UTC) Received: from EX19D004ANA001.ant.amazon.com (10.37.240.138) by EX13MTAUWB001.ant.amazon.com (10.43.161.207) with Microsoft SMTP Server (TLS) id 15.0.1497.36; Wed, 6 Jul 2022 05:23:25 +0000 Received: from 88665a182662.ant.amazon.com (10.43.162.55) by EX19D004ANA001.ant.amazon.com (10.37.240.138) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.1118.9; Wed, 6 Jul 2022 05:23:22 +0000 From: Kuniyuki Iwashima To: "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Luis Chamberlain , Kees Cook , Iurii Zaikin CC: Kuniyuki Iwashima , Kuniyuki Iwashima , , Subject: [PATCH v1 net 07/16] sysctl: Add proc_doulongvec_minmax_lockless(). Date: Tue, 5 Jul 2022 22:21:21 -0700 Message-ID: <20220706052130.16368-8-kuniyu@amazon.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20220706052130.16368-1-kuniyu@amazon.com> References: <20220706052130.16368-1-kuniyu@amazon.com> MIME-Version: 1.0 X-Originating-IP: [10.43.162.55] X-ClientProxiedBy: EX13D18UWA004.ant.amazon.com (10.43.160.45) To EX19D004ANA001.ant.amazon.com (10.37.240.138) Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: kuba@kernel.org A sysctl variable is accessed concurrently, and there is always a chance of data-race. So, all readers and writers need some basic protection to avoid load/store-tearing. This patch changes proc_doulongvec_minmax() to use READ_ONCE()/WRITE_ONCE() internally to fix a data-race on the sysctl side. For now, proc_doulongvec_minmax() itself is tolerant to a data-race, but we still need to add annotations on the other subsystem's side. In case we miss such fixes, this patch converts proc_doulongvec_minmax() to a wrapper of proc_doulongvec_minmax_lockless(). When we fix a data-race in the other subsystem, we can explicitly set it as a handler. Also, this patch removes proc_doulongvec_minmax()'s document and adds proc_doulongvec_minmax_lockless()'s one so that no one will use proc_doulongvec_minmax() anymore. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Kuniyuki Iwashima --- include/linux/sysctl.h | 1 + kernel/sysctl.c | 21 +++++++++++++++++---- 2 files changed, 18 insertions(+), 4 deletions(-) diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h index 830d1a8f21d4..c23b6beef748 100644 --- a/include/linux/sysctl.h +++ b/include/linux/sysctl.h @@ -88,6 +88,7 @@ PROC_HANDLER(proc_dointvec_lockless); PROC_HANDLER(proc_douintvec_lockless); PROC_HANDLER(proc_dointvec_minmax_lockless); PROC_HANDLER(proc_douintvec_minmax_lockless); +PROC_HANDLER(proc_doulongvec_minmax_lockless); /* * Register a set of sysctl names by calling register_sysctl_table diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 8ff57b8d1212..931ab58985f2 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -1127,9 +1127,11 @@ static int __do_proc_doulongvec_minmax(void *data, struct ctl_table *table, err = -EINVAL; break; } - *i = val; + + WRITE_ONCE(*i, val); } else { - val = convdiv * (*i) / convmul; + val = convdiv * READ_ONCE(*i) / convmul; + if (!first) proc_put_char(&buffer, &left, '\t'); proc_put_long(&buffer, &left, val, false); @@ -1157,7 +1159,8 @@ static int do_proc_doulongvec_minmax(struct ctl_table *table, int write, } /** - * proc_doulongvec_minmax - read a vector of long integers with min/max values + * proc_doulongvec_minmax_lockless - read/write a vector of long integers + * with min/max values locklessly * @table: the sysctl table * @write: %TRUE if this is a write to the sysctl file * @buffer: the user buffer @@ -1172,10 +1175,18 @@ static int do_proc_doulongvec_minmax(struct ctl_table *table, int write, * * Returns 0 on success. */ +int proc_doulongvec_minmax_lockless(struct ctl_table *table, int write, + void *buffer, size_t *lenp, loff_t *ppos) +{ + return do_proc_doulongvec_minmax(table, write, buffer, lenp, ppos, + 1l, 1l); +} + int proc_doulongvec_minmax(struct ctl_table *table, int write, void *buffer, size_t *lenp, loff_t *ppos) { - return do_proc_doulongvec_minmax(table, write, buffer, lenp, ppos, 1l, 1l); + return proc_doulongvec_minmax_lockless(table, write, buffer, + lenp, ppos); } /** @@ -1540,6 +1551,7 @@ PROC_HANDLER_ENOSYS(proc_dointvec_lockless); PROC_HANDLER_ENOSYS(proc_douintvec_lockless); PROC_HANDLER_ENOSYS(proc_dointvec_minmax_lockless); PROC_HANDLER_ENOSYS(proc_douintvec_minmax_lockless); +PROC_HANDLER_ENOSYS(proc_doulongvec_minmax_lockless); #endif /* CONFIG_PROC_SYSCTL */ @@ -2455,3 +2467,4 @@ EXPORT_SYMBOL(proc_dointvec_lockless); EXPORT_SYMBOL(proc_douintvec_lockless); EXPORT_SYMBOL(proc_dointvec_minmax_lockless); EXPORT_SYMBOL_GPL(proc_douintvec_minmax_lockless); +EXPORT_SYMBOL(proc_doulongvec_minmax_lockless);