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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 34849C433EF for ; Wed, 6 Jul 2022 05:23:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229807AbiGFFX5 (ORCPT ); Wed, 6 Jul 2022 01:23:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47890 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231438AbiGFFXp (ORCPT ); Wed, 6 Jul 2022 01:23:45 -0400 Received: from smtp-fw-2101.amazon.com (smtp-fw-2101.amazon.com [72.21.196.25]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D5017DFA3; Tue, 5 Jul 2022 22:23:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1657085025; x=1688621025; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=uJwiKDdUCE6ejBVfaNJ0Ksuef2MfhE73OPMC2pigcSU=; b=ip44yNYxVTvFZiW5SkFBN+O+hc9hWowPPNP59tYv+z+HnBTUkaaaWcWR FcP9TQWtqHZ95DYu1CCpFDV4W4m4vLaQN1X14zTQnBHc5WNdAFhZFeto0 WCijZyhKROb4mmgyKYE/Vdt5p0q967GUEjpXlETm+T99BbcvgPb9Sn6VI M=; X-IronPort-AV: E=Sophos;i="5.92,248,1650931200"; d="scan'208";a="215167311" Received: from iad12-co-svc-p1-lb1-vlan2.amazon.com (HELO email-inbound-relay-pdx-2c-d9fba5dd.us-west-2.amazon.com) ([10.43.8.2]) by smtp-border-fw-2101.iad2.amazon.com with ESMTP; 06 Jul 2022 05:23:42 +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-2c-d9fba5dd.us-west-2.amazon.com (Postfix) with ESMTPS id 357E043CB2; Wed, 6 Jul 2022 05:23:42 +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 05:23:39 +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 05:23:36 +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 , , Subject: [PATCH v1 net 08/16] sysctl: Add proc_dointvec_jiffies_lockless(). Date: Tue, 5 Jul 2022 22:21:22 -0700 Message-ID: <20220706052130.16368-9-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 Content-Transfer-Encoding: 8bit Content-Type: text/plain 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: linux-kernel@vger.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_jiffies() to use READ_ONCE()/WRITE_ONCE() internally to fix a data-race on the sysctl side. For now, proc_dointvec_jiffies() 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_jiffies() to a wrapper of proc_dointvec_jiffies_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_jiffies()'s document and adds proc_dointvec_jiffies_lockless()'s one so that no one will use proc_dointvec_jiffies() anymore. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Kuniyuki Iwashima --- include/linux/sysctl.h | 1 + kernel/sysctl.c | 26 ++++++++++++++++++++------ 2 files changed, 21 insertions(+), 6 deletions(-) diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h index c23b6beef748..8747dbc721f5 100644 --- a/include/linux/sysctl.h +++ b/include/linux/sysctl.h @@ -89,6 +89,7 @@ PROC_HANDLER(proc_douintvec_lockless); PROC_HANDLER(proc_dointvec_minmax_lockless); PROC_HANDLER(proc_douintvec_minmax_lockless); PROC_HANDLER(proc_doulongvec_minmax_lockless); +PROC_HANDLER(proc_dointvec_jiffies_lockless); /* * Register a set of sysctl names by calling register_sysctl_table diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 931ab58985f2..11a1ce837623 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -1221,10 +1221,15 @@ static int do_proc_dointvec_jiffies_conv(bool *negp, unsigned long *lvalp, if (write) { if (*lvalp > INT_MAX / HZ) return 1; - *valp = *negp ? -(*lvalp*HZ) : (*lvalp*HZ); + + if (*negp) + WRITE_ONCE(*valp, -(*lvalp * HZ)); + else + WRITE_ONCE(*valp, *lvalp * HZ); } else { - int val = *valp; + int val = READ_ONCE(*valp); unsigned long lval; + if (val < 0) { *negp = true; lval = -(unsigned long)val; @@ -1286,7 +1291,8 @@ static int do_proc_dointvec_ms_jiffies_conv(bool *negp, unsigned long *lvalp, } /** - * proc_dointvec_jiffies - read a vector of integers as seconds + * proc_dointvec_jiffies_lockless - read/write a vector of integers as + * seconds locklessly * @table: the sysctl table * @write: %TRUE if this is a write to the sysctl file * @buffer: the user buffer @@ -1294,17 +1300,23 @@ static int do_proc_dointvec_ms_jiffies_conv(bool *negp, unsigned long *lvalp, * @ppos: file position * * Reads/writes up to table->maxlen/sizeof(unsigned int) integer - * values from/to the user buffer, treated as an ASCII string. + * values from/to the user buffer, treated as an ASCII string. * The values read are assumed to be in seconds, and are converted into * jiffies. * * Returns 0 on success. */ +int proc_dointvec_jiffies_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_dointvec_jiffies_conv, NULL); +} + int proc_dointvec_jiffies(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_dointvec_jiffies_conv,NULL); + return proc_dointvec_jiffies_lockless(table, write, buffer, lenp, ppos); } /** @@ -1552,6 +1564,7 @@ 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); +PROC_HANDLER_ENOSYS(proc_dointvec_jiffies_lockless); #endif /* CONFIG_PROC_SYSCTL */ @@ -2468,3 +2481,4 @@ EXPORT_SYMBOL(proc_douintvec_lockless); EXPORT_SYMBOL(proc_dointvec_minmax_lockless); EXPORT_SYMBOL_GPL(proc_douintvec_minmax_lockless); EXPORT_SYMBOL(proc_doulongvec_minmax_lockless); +EXPORT_SYMBOL(proc_dointvec_jiffies_lockless); -- 2.30.2