From nobody Fri Dec 19 06:29:32 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 E1E22C67871 for ; Mon, 24 Oct 2022 20:31:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232705AbiJXUbc (ORCPT ); Mon, 24 Oct 2022 16:31:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42996 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233258AbiJXUa6 (ORCPT ); Mon, 24 Oct 2022 16:30:58 -0400 Received: from sin.source.kernel.org (sin.source.kernel.org [IPv6:2604:1380:40e1:4800::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 47281115428; Mon, 24 Oct 2022 11:42:36 -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 sin.source.kernel.org (Postfix) with ESMTPS id 819BDCE16E4; Mon, 24 Oct 2022 12:51:30 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 92CC6C433D6; Mon, 24 Oct 2022 12:51:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1666615888; bh=mZqX+tluggld9fSL1i9YkMGAMPOcimbKnVay6bhf3mk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ucnbaAmfdd3QKIoesUigwToxvUb+rKTB1hlWN44CChdVfJ+RmIAsAbDyy8D5IJGAg KR8gUNmboMMPbmKjBKpqZIRuhn/UdkOfpUWJzjDnB2qpslLjTyIwAPmvUVKNfBaJAc NKJ4MaOyMi1x8vikX+ErfxCAyLRXg3DWMzC9XCcA= 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 5.15 421/530] tcp: annotate data-race around tcp_md5sig_pool_populated Date: Mon, 24 Oct 2022 13:32:45 +0200 Message-Id: <20221024113104.149722363@linuxfoundation.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221024113044.976326639@linuxfoundation.org> References: <20221024113044.976326639@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 b604c7664350..5b4e170b6a34 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -4331,12 +4331,16 @@ 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) { @@ -4347,7 +4351,8 @@ 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 @@ -4363,7 +4368,8 @@ 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