From patchwork Wed Jul 6 05:21:17 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kuniyuki Iwashima X-Patchwork-Id: 12907326 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 CF0ABC43334 for ; Wed, 6 Jul 2022 05:22:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230301AbiGFFWp (ORCPT ); Wed, 6 Jul 2022 01:22:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45724 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231150AbiGFFWm (ORCPT ); Wed, 6 Jul 2022 01:22:42 -0400 Received: from smtp-fw-6001.amazon.com (smtp-fw-6001.amazon.com [52.95.48.154]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0047020F71; Tue, 5 Jul 2022 22:22:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1657084959; x=1688620959; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=vvTkQI5kZROfLMtnVMR0jXY5cgp4oarvGhfx+4aDV60=; b=FgBALXTashDb6KrKBVo2VYGUIdBd3WG231pg8K2CNFINgdZMfZByEBqP PKoCy2eO+NmRegISezQC19THxkOfmMtvJVi6PbsLG+1PfinnSq18lwlg6 kOElMSGPBpR2ait61eUEfYtc32o8TIVVfBdQGyF9eTvMVxtVzXWMAZhSI 8=; Received: from iad12-co-svc-p1-lb1-vlan3.amazon.com (HELO email-inbound-relay-pdx-2a-6a4112b2.us-west-2.amazon.com) ([10.43.8.6]) by smtp-border-fw-6001.iad6.amazon.com with ESMTP; 06 Jul 2022 05:22:25 +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-2a-6a4112b2.us-west-2.amazon.com (Postfix) with ESMTPS id 63C684C0077; Wed, 6 Jul 2022 05:22:25 +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 05:22:24 +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 05:22:22 +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 03/16] sysctl: Add proc_dointvec_lockless(). Date: Tue, 5 Jul 2022 22:21:17 -0700 Message-ID: <20220706052130.16368-4-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() to use READ_ONCE()/WRITE_ONCE() internally to fix a data-race on the sysctl side. For now, proc_dointvec() 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() to a wrapper of proc_dointvec_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()'s document and adds proc_dointvec_lockless()'s one so that no one will use proc_dointvec() anymore. While we are on it, we remove some trailing spaces. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Kuniyuki Iwashima --- include/linux/sysctl.h | 1 + kernel/sysctl.c | 27 +++++++++++++++++++-------- 2 files changed, 20 insertions(+), 8 deletions(-) diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h index fcafc16abbad..cb87919b5508 100644 --- a/include/linux/sysctl.h +++ b/include/linux/sysctl.h @@ -84,6 +84,7 @@ PROC_HANDLER(proc_do_large_bitmap); PROC_HANDLER(proc_do_static_key); PROC_HANDLER(proc_dobool_lockless); +PROC_HANDLER(proc_dointvec_lockless); /* * Register a set of sysctl names by calling register_sysctl_table diff --git a/kernel/sysctl.c b/kernel/sysctl.c index bc6fcc64eeaf..50d9b78aa0b3 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -445,14 +445,17 @@ static int do_proc_dointvec_conv(bool *negp, unsigned long *lvalp, if (*negp) { if (*lvalp > (unsigned long) INT_MAX + 1) return -EINVAL; - *valp = -*lvalp; + + WRITE_ONCE(*valp, -*lvalp); } else { if (*lvalp > (unsigned long) INT_MAX) return -EINVAL; - *valp = *lvalp; + + WRITE_ONCE(*valp, *lvalp); } } else { - int val = *valp; + int val = READ_ONCE(*valp); + if (val < 0) { *negp = true; *lvalp = -(unsigned long)val; @@ -491,12 +494,12 @@ static int __do_proc_dointvec(void *tbl_data, struct ctl_table *table, int *i, vleft, first = 1, err = 0; size_t left; char *p; - + if (!tbl_data || !table->maxlen || !*lenp || (*ppos && !write)) { *lenp = 0; return 0; } - + i = (int *) tbl_data; vleft = table->maxlen / sizeof(*i); left = *lenp; @@ -726,7 +729,7 @@ int proc_dobool(struct ctl_table *table, int write, void *buffer, } /** - * proc_dointvec - read a vector of integers + * proc_dointvec_lockless - read/write a vector of integers locklessly * @table: the sysctl table * @write: %TRUE if this is a write to the sysctl file * @buffer: the user buffer @@ -734,14 +737,20 @@ int proc_dobool(struct ctl_table *table, int write, void *buffer, * @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. * * Returns 0 on success. */ +int proc_dointvec_lockless(struct ctl_table *table, int write, void *buffer, + size_t *lenp, loff_t *ppos) +{ + return do_proc_dointvec(table, write, buffer, lenp, ppos, NULL, NULL); +} + int proc_dointvec(struct ctl_table *table, int write, void *buffer, size_t *lenp, loff_t *ppos) { - return do_proc_dointvec(table, write, buffer, lenp, ppos, NULL, NULL); + return proc_dointvec_lockless(table, write, buffer, lenp, ppos); } #ifdef CONFIG_COMPACTION @@ -1503,6 +1512,7 @@ PROC_HANDLER_ENOSYS(proc_do_cad_pid); PROC_HANDLER_ENOSYS(proc_do_large_bitmap); PROC_HANDLER_ENOSYS(proc_dobool_lockless); +PROC_HANDLER_ENOSYS(proc_dointvec_lockless); #endif /* CONFIG_PROC_SYSCTL */ @@ -2414,3 +2424,4 @@ EXPORT_SYMBOL(proc_dointvec_ms_jiffies); EXPORT_SYMBOL(proc_do_large_bitmap); EXPORT_SYMBOL(proc_dobool_lockless); +EXPORT_SYMBOL(proc_dointvec_lockless);