From patchwork Wed Jul 6 05:21:18 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kuniyuki Iwashima X-Patchwork-Id: 12907327 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 63DC6C433EF for ; Wed, 6 Jul 2022 05:23:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231181AbiGFFXK (ORCPT ); Wed, 6 Jul 2022 01:23:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46196 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231417AbiGFFXC (ORCPT ); Wed, 6 Jul 2022 01:23:02 -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 AFABA2180D; Tue, 5 Jul 2022 22:22:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1657084976; x=1688620976; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=mKWxbo4eRi3u9tBD8C1LmmWJYH/wd8q8AiV00I6QWKU=; b=ITbuIF+E3OLRzFapurihekpwkaBbR0x6tVc9BIjR28yFkX54anVd6pUB 3YzQuxFiEY2C2Jq80hejs7HPXes0j5ej58mwXiu8oyLFGwz97K3n3tGmV Uar4hvy5wdG4oCSKwZjeiNOwWliiiVkhl/+sN1ARiPOqVgkQLHZ6PJp3R E=; X-IronPort-AV: E=Sophos;i="5.92,248,1650931200"; d="scan'208";a="235270838" Received: from pdx4-co-svc-p1-lb2-vlan2.amazon.com (HELO email-inbound-relay-pdx-2a-1801e169.us-west-2.amazon.com) ([10.25.36.210]) by smtp-border-fw-9102.sea19.amazon.com with ESMTP; 06 Jul 2022 05:22:40 +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-2a-1801e169.us-west-2.amazon.com (Postfix) with ESMTPS id 17506C0858; Wed, 6 Jul 2022 05:22:40 +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 05:22:39 +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 05:22:36 +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 , , , Subash Abhinov Kasiviswanathan Subject: [PATCH v1 net 04/16] sysctl: Add proc_douintvec_lockless(). Date: Tue, 5 Jul 2022 22:21:18 -0700 Message-ID: <20220706052130.16368-5-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_douintvec() to use READ_ONCE()/WRITE_ONCE() internally to fix a data-race on the sysctl side. For now, proc_douintvec() 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_douintvec() to a wrapper of proc_douintvec_lockless(). When we fix a data-race in the other subsystem, we can explicitly set it as a handler. Also, this patch removes proc_douintvec()'s document and adds proc_douintvec_lockless()'s one so that no one will use proc_douintvec() anymore. Fixes: e7d316a02f68 ("sysctl: handle error writing UINT_MAX to u32 fields") Signed-off-by: Kuniyuki Iwashima --- CC: Subash Abhinov Kasiviswanathan --- include/linux/sysctl.h | 1 + kernel/sysctl.c | 20 +++++++++++++++----- 2 files changed, 16 insertions(+), 5 deletions(-) diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h index cb87919b5508..770ee1833c25 100644 --- a/include/linux/sysctl.h +++ b/include/linux/sysctl.h @@ -85,6 +85,7 @@ PROC_HANDLER(proc_do_static_key); PROC_HANDLER(proc_dobool_lockless); PROC_HANDLER(proc_dointvec_lockless); +PROC_HANDLER(proc_douintvec_lockless); /* * Register a set of sysctl names by calling register_sysctl_table diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 50d9b78aa0b3..be8a7d912180 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -474,9 +474,11 @@ static int do_proc_douintvec_conv(unsigned long *lvalp, if (write) { if (*lvalp > UINT_MAX) return -EINVAL; - *valp = *lvalp; + + WRITE_ONCE(*valp, *lvalp); } else { - unsigned int val = *valp; + unsigned int val = READ_ONCE(*valp); + *lvalp = (unsigned long)val; } return 0; @@ -775,7 +777,7 @@ static int proc_dointvec_minmax_warn_RT_change(struct ctl_table *table, #endif /** - * proc_douintvec - read a vector of unsigned integers + * proc_douintvec_lockless - read/write a vector of unsigned integers locklessly * @table: the sysctl table * @write: %TRUE if this is a write to the sysctl file * @buffer: the user buffer @@ -787,13 +789,19 @@ static int proc_dointvec_minmax_warn_RT_change(struct ctl_table *table, * * Returns 0 on success. */ -int proc_douintvec(struct ctl_table *table, int write, void *buffer, - size_t *lenp, loff_t *ppos) +int proc_douintvec_lockless(struct ctl_table *table, int write, void *buffer, + size_t *lenp, loff_t *ppos) { return do_proc_douintvec(table, write, buffer, lenp, ppos, do_proc_douintvec_conv, NULL); } +int proc_douintvec(struct ctl_table *table, int write, void *buffer, + size_t *lenp, loff_t *ppos) +{ + return proc_douintvec_lockless(table, write, buffer, lenp, ppos); +} + /* * Taint values can only be increased * This means we can safely use a temporary. @@ -1513,6 +1521,7 @@ 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); #endif /* CONFIG_PROC_SYSCTL */ @@ -2425,3 +2434,4 @@ EXPORT_SYMBOL(proc_do_large_bitmap); EXPORT_SYMBOL(proc_dobool_lockless); EXPORT_SYMBOL(proc_dointvec_lockless); +EXPORT_SYMBOL(proc_douintvec_lockless);