From patchwork Wed Jul 6 05:21:19 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kuniyuki Iwashima X-Patchwork-Id: 12907329 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 0C7A9C433EF for ; Wed, 6 Jul 2022 05:23:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231280AbiGFFXY (ORCPT ); Wed, 6 Jul 2022 01:23:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46784 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231382AbiGFFXN (ORCPT ); Wed, 6 Jul 2022 01:23:13 -0400 Received: from smtp-fw-80007.amazon.com (smtp-fw-80007.amazon.com [99.78.197.218]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B4CBA2124F; Tue, 5 Jul 2022 22:23:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1657084992; x=1688620992; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=YXuh7vJXEQMSPq64wbRPnqP7B9hkeIKY5sqtiuHZaPc=; b=r/p2tNZc9GUR1jWFc6Uh3tZUs2CmBV6xKaAa+VKyB/OrNQN0ztRO9iW9 4BMMrEh7F1Z5yvLXM5NljwCA06rhQAp+3Q7xq43ONhg+Z3XYUJTnGp3Yy e6VYT2YBAJ9VBKTwNVlb4W9H0Ea3JU9/C+sbnntIwZ7xRyKiGB/nvDS3B U=; X-IronPort-AV: E=Sophos;i="5.92,248,1650931200"; d="scan'208";a="105282277" Received: from pdx4-co-svc-p1-lb2-vlan3.amazon.com (HELO email-inbound-relay-pdx-2b-1f9d5b26.us-west-2.amazon.com) ([10.25.36.214]) by smtp-border-fw-80007.pdx80.corp.amazon.com with ESMTP; 06 Jul 2022 05:22:56 +0000 Received: from EX13MTAUWB001.ant.amazon.com (pdx1-ws-svc-p6-lb9-vlan3.pdx.amazon.com [10.236.137.198]) by email-inbound-relay-pdx-2b-1f9d5b26.us-west-2.amazon.com (Postfix) with ESMTPS id A9B5942040; Wed, 6 Jul 2022 05:22:56 +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 05:22:56 +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 05:22:53 +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 05/16] sysctl: Add proc_dointvec_minmax_lockless(). Date: Tue, 5 Jul 2022 22:21:19 -0700 Message-ID: <20220706052130.16368-6-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_dointvec_minmax() to use READ_ONCE()/WRITE_ONCE() internally to fix a data-race on the sysctl side. For now, proc_dointvec_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_dointvec_minmax() to a wrapper of proc_dointvec_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_dointvec_minmax()'s document and adds proc_dointvec_minmax_lockless()'s one so that no one will use proc_dointvec_minmax() anymore. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Kuniyuki Iwashima --- include/linux/sysctl.h | 1 + kernel/sysctl.c | 19 +++++++++++++++---- 2 files changed, 16 insertions(+), 4 deletions(-) diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h index 770ee1833c25..7f91cc625d56 100644 --- a/include/linux/sysctl.h +++ b/include/linux/sysctl.h @@ -86,6 +86,7 @@ PROC_HANDLER(proc_do_static_key); PROC_HANDLER(proc_dobool_lockless); PROC_HANDLER(proc_dointvec_lockless); PROC_HANDLER(proc_douintvec_lockless); +PROC_HANDLER(proc_dointvec_minmax_lockless); /* * Register a set of sysctl names by calling register_sysctl_table diff --git a/kernel/sysctl.c b/kernel/sysctl.c index be8a7d912180..aead731ae74b 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -879,14 +879,16 @@ static int do_proc_dointvec_minmax_conv(bool *negp, unsigned long *lvalp, if ((param->min && *param->min > tmp) || (param->max && *param->max < tmp)) return -EINVAL; - *valp = tmp; + + WRITE_ONCE(*valp, tmp); } return 0; } /** - * proc_dointvec_minmax - read a vector of integers with min/max values + * proc_dointvec_minmax_lockless - read/write a vector of 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 @@ -901,8 +903,8 @@ static int do_proc_dointvec_minmax_conv(bool *negp, unsigned long *lvalp, * * Returns 0 on success or -EINVAL on write when the range check fails. */ -int proc_dointvec_minmax(struct ctl_table *table, int write, - void *buffer, size_t *lenp, loff_t *ppos) +int proc_dointvec_minmax_lockless(struct ctl_table *table, int write, + void *buffer, size_t *lenp, loff_t *ppos) { struct do_proc_dointvec_minmax_conv_param param = { .min = (int *) table->extra1, @@ -912,6 +914,13 @@ int proc_dointvec_minmax(struct ctl_table *table, int write, do_proc_dointvec_minmax_conv, ¶m); } +int proc_dointvec_minmax(struct ctl_table *table, int write, + void *buffer, size_t *lenp, loff_t *ppos) +{ + return proc_dointvec_minmax_lockless(table, write, buffer, + lenp, ppos); +} + /** * struct do_proc_douintvec_minmax_conv_param - proc_douintvec_minmax() range checking structure * @min: pointer to minimum allowable value @@ -1522,6 +1531,7 @@ PROC_HANDLER_ENOSYS(proc_do_large_bitmap); PROC_HANDLER_ENOSYS(proc_dobool_lockless); PROC_HANDLER_ENOSYS(proc_dointvec_lockless); PROC_HANDLER_ENOSYS(proc_douintvec_lockless); +PROC_HANDLER_ENOSYS(proc_dointvec_minmax_lockless); #endif /* CONFIG_PROC_SYSCTL */ @@ -2435,3 +2445,4 @@ EXPORT_SYMBOL(proc_do_large_bitmap); EXPORT_SYMBOL(proc_dobool_lockless); EXPORT_SYMBOL(proc_dointvec_lockless); EXPORT_SYMBOL(proc_douintvec_lockless); +EXPORT_SYMBOL(proc_dointvec_minmax_lockless);