From nobody Fri Dec 19 22:01:10 2025 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 A8BC0C38A2D for ; Mon, 24 Oct 2022 20:25:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233736AbiJXUZX (ORCPT ); Mon, 24 Oct 2022 16:25:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60924 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233454AbiJXUXY (ORCPT ); Mon, 24 Oct 2022 16:23:24 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E217413F48; Mon, 24 Oct 2022 11:38:52 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 21F1AB810B2; Mon, 24 Oct 2022 12:14:33 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 733A1C433C1; Mon, 24 Oct 2022 12:14:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1666613671; bh=NMLKHiEK9NjSAgTP2LcnDOFgdc0G48TbfOyUUvIGw5A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=XRKF8Q06Lv++LwgwFal8wutGEFQP4JUAgBftMbCdaZdqZJCoDYUryystFnh75p6CU 6Wq4AaUJGpVyUIgxXJHfOpfuuuIM/TKLhugTssi054x94TJilQNtlrJV5avscacUQr inK8hIZKCDe51xvI9H3uDHpJx466DXNPxbnA4xZo= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Abhishek Shah , Eric Dumazet , "David S. Miller" , Sasha Levin Subject: [PATCH 5.4 195/255] tcp: annotate data-race around tcp_md5sig_pool_populated Date: Mon, 24 Oct 2022 13:31:45 +0200 Message-Id: <20221024113009.475095136@linuxfoundation.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221024113002.471093005@linuxfoundation.org> References: <20221024113002.471093005@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Eric Dumazet [ Upstream commit aacd467c0a576e5e44d2de4205855dc0fe43f6fb ] tcp_md5sig_pool_populated can be read while another thread changes its value. The race has no consequence because allocations are protected with tcp_md5sig_mutex. This patch adds READ_ONCE() and WRITE_ONCE() to document the race and silence KCSAN. Reported-by: Abhishek Shah Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- net/ipv4/tcp.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 2da4f852fc58..aeeeaf2d6482 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -3770,12 +3770,16 @@ static void __tcp_alloc_md5sig_pool(void) * to memory. See smp_rmb() in tcp_get_md5sig_pool() */ smp_wmb(); - tcp_md5sig_pool_populated =3D true; + /* Paired with READ_ONCE() from tcp_alloc_md5sig_pool() + * and tcp_get_md5sig_pool(). + */ + WRITE_ONCE(tcp_md5sig_pool_populated, true); } =20 bool tcp_alloc_md5sig_pool(void) { - if (unlikely(!tcp_md5sig_pool_populated)) { + /* Paired with WRITE_ONCE() from __tcp_alloc_md5sig_pool() */ + if (unlikely(!READ_ONCE(tcp_md5sig_pool_populated))) { mutex_lock(&tcp_md5sig_mutex); =20 if (!tcp_md5sig_pool_populated) { @@ -3786,7 +3790,8 @@ bool tcp_alloc_md5sig_pool(void) =20 mutex_unlock(&tcp_md5sig_mutex); } - return tcp_md5sig_pool_populated; + /* Paired with WRITE_ONCE() from __tcp_alloc_md5sig_pool() */ + return READ_ONCE(tcp_md5sig_pool_populated); } EXPORT_SYMBOL(tcp_alloc_md5sig_pool); =20 @@ -3802,7 +3807,8 @@ struct tcp_md5sig_pool *tcp_get_md5sig_pool(void) { local_bh_disable(); =20 - if (tcp_md5sig_pool_populated) { + /* Paired with WRITE_ONCE() from __tcp_alloc_md5sig_pool() */ + if (READ_ONCE(tcp_md5sig_pool_populated)) { /* coupled with smp_wmb() in __tcp_alloc_md5sig_pool() */ smp_rmb(); return this_cpu_ptr(&tcp_md5sig_pool); --=20 2.35.1