From patchwork Wed Jul 6 05:21:16 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kuniyuki Iwashima X-Patchwork-Id: 12907325 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 A4791CCA47F for ; Wed, 6 Jul 2022 05:22:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230481AbiGFFW3 (ORCPT ); Wed, 6 Jul 2022 01:22:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45192 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230445AbiGFFW2 (ORCPT ); Wed, 6 Jul 2022 01:22:28 -0400 Received: from smtp-fw-9103.amazon.com (smtp-fw-9103.amazon.com [207.171.188.200]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 42AD4205F0; Tue, 5 Jul 2022 22:22:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1657084947; x=1688620947; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=nXgol3t1QpvI6in0uKJ77IASldBl9uWqY9rKUYy3dVc=; b=R5tB7PqpH13hGGQFdzTOcZche8ElVXvks24T1vkKTgFqdom4ixemnmm+ Cb19zPnWbFkW/79WZ08xQnVh9QibyNzo8JZUZBA7aHjM+vvupa524Re56 2INnnJ8vND8rh2veu3gDcF4IdqNdPElkMLwuMoW6K0Te3kdKIKwxR5CVP I=; X-IronPort-AV: E=Sophos;i="5.92,248,1650931200"; d="scan'208";a="1031201485" Received: from pdx4-co-svc-p1-lb2-vlan3.amazon.com (HELO email-inbound-relay-pdx-2c-7d0c7241.us-west-2.amazon.com) ([10.25.36.214]) by smtp-border-fw-9103.sea19.amazon.com with ESMTP; 06 Jul 2022 05:22:10 +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-2c-7d0c7241.us-west-2.amazon.com (Postfix) with ESMTPS id 7134943B52; Wed, 6 Jul 2022 05:22:10 +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 05:22:09 +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 05:22:07 +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 , , , Jia He Subject: [PATCH v1 net 02/16] sysctl: Add proc_dobool_lockless(). Date: Tue, 5 Jul 2022 22:21:16 -0700 Message-ID: <20220706052130.16368-3-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_dobool() to use READ_ONCE()/WRITE_ONCE() internally to fix a data-race on the sysctl side. For now, proc_dobool() 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_dobool() to a wrapper of proc_dobool_lockless(). When we fix a data-race in the other subsystem, we can explicitly set it as a handler. Also, this patch removes proc_dobool()'s document and adds proc_dobool_lockless()'s one so that no one will use proc_dobool() anymore. Fixes: a2071573d634 ("sysctl: introduce new proc handler proc_dobool") Signed-off-by: Kuniyuki Iwashima --- CC: Jia He --- include/linux/sysctl.h | 2 ++ kernel/sysctl.c | 23 ++++++++++++++++------- 2 files changed, 18 insertions(+), 7 deletions(-) diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h index 9beab3a4de3d..fcafc16abbad 100644 --- a/include/linux/sysctl.h +++ b/include/linux/sysctl.h @@ -83,6 +83,8 @@ PROC_HANDLER(proc_dointvec_ms_jiffies); PROC_HANDLER(proc_do_large_bitmap); PROC_HANDLER(proc_do_static_key); +PROC_HANDLER(proc_dobool_lockless); + /* * Register a set of sysctl names by calling register_sysctl_table * with an initialised array of struct ctl_table's. An entry with diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 1082c8bc5ba5..bc6fcc64eeaf 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -424,13 +424,12 @@ static void proc_put_char(void **buf, size_t *size, char c) } static int do_proc_dobool_conv(bool *negp, unsigned long *lvalp, - int *valp, - int write, void *data) + int *valp, int write, void *data) { if (write) { - *(bool *)valp = *lvalp; + WRITE_ONCE(*(bool *)valp, *lvalp); } else { - int val = *(bool *)valp; + int val = READ_ONCE(*(bool *)valp); *lvalp = (unsigned long)val; *negp = false; @@ -701,7 +700,7 @@ int do_proc_douintvec(struct ctl_table *table, int write, } /** - * proc_dobool - read/write a bool + * proc_dobool_lockless - read/write a bool locklessly * @table: the sysctl table * @write: %TRUE if this is a write to the sysctl file * @buffer: the user buffer @@ -713,13 +712,19 @@ int do_proc_douintvec(struct ctl_table *table, int write, * * Returns 0 on success. */ -int proc_dobool(struct ctl_table *table, int write, void *buffer, - size_t *lenp, loff_t *ppos) +int proc_dobool_lockless(struct ctl_table *table, int write, void *buffer, + size_t *lenp, loff_t *ppos) { return do_proc_dointvec(table, write, buffer, lenp, ppos, do_proc_dobool_conv, NULL); } +int proc_dobool(struct ctl_table *table, int write, void *buffer, + size_t *lenp, loff_t *ppos) +{ + return proc_dobool_lockless(table, write, buffer, lenp, ppos); +} + /** * proc_dointvec - read a vector of integers * @table: the sysctl table @@ -1497,6 +1502,8 @@ PROC_HANDLER_ENOSYS(proc_dointvec_ms_jiffies); PROC_HANDLER_ENOSYS(proc_do_cad_pid); PROC_HANDLER_ENOSYS(proc_do_large_bitmap); +PROC_HANDLER_ENOSYS(proc_dobool_lockless); + #endif /* CONFIG_PROC_SYSCTL */ #if defined(CONFIG_SYSCTL) @@ -2405,3 +2412,5 @@ EXPORT_SYMBOL(proc_dointvec_jiffies); EXPORT_SYMBOL(proc_dointvec_userhz_jiffies); EXPORT_SYMBOL(proc_dointvec_ms_jiffies); EXPORT_SYMBOL(proc_do_large_bitmap); + +EXPORT_SYMBOL(proc_dobool_lockless);