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 D3FE2C4332F for ; Wed, 19 Oct 2022 09:25:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233328AbiJSJZM (ORCPT ); Wed, 19 Oct 2022 05:25:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33502 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233469AbiJSJXw (ORCPT ); Wed, 19 Oct 2022 05:23:52 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 136698307D; Wed, 19 Oct 2022 02:10:40 -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 dfw.source.kernel.org (Postfix) with ESMTPS id 212376174B; Wed, 19 Oct 2022 09:08:41 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 33653C433D7; Wed, 19 Oct 2022 09:08:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1666170520; bh=YJW838ei9dUw8KV2RE3LIsOoRby+bBUkYxhtb2Aj2+A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=xn1BQo7WV7bsioPuIUux4hiCjojjGL/kv9NFKwZQBaQKcaH3N1g4iDI/Ocrc/DHGK ObFsHK+2+cO/wjFCdE9gTreNd2/ll3loRpqvaQP1Ii9wHidmdqMNvk0LJdEbg69BJg cbx3fzeZFhSEQX/Dff1I4YDCaNqe7EjOAtURPWp8= 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 6.0 687/862] tcp: annotate data-race around tcp_md5sig_pool_populated Date: Wed, 19 Oct 2022 10:32:54 +0200 Message-Id: <20221019083320.336216418@linuxfoundation.org> X-Mailer: git-send-email 2.38.0 In-Reply-To: <20221019083249.951566199@linuxfoundation.org> References: <20221019083249.951566199@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 997a80ce1e13..5f1d84d901c7 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -4444,12 +4444,16 @@ static void __tcp_alloc_md5sig_pool(void) * to memory. See smp_rmb() in tcp_get_md5sig_pool() */ smp_wmb(); - tcp_md5sig_pool_populated = true; + /* Paired with READ_ONCE() from tcp_alloc_md5sig_pool() + * and tcp_get_md5sig_pool(). + */ + WRITE_ONCE(tcp_md5sig_pool_populated, true); } 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); if (!tcp_md5sig_pool_populated) { @@ -4460,7 +4464,8 @@ bool tcp_alloc_md5sig_pool(void) 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); @@ -4476,7 +4481,8 @@ struct tcp_md5sig_pool *tcp_get_md5sig_pool(void) { local_bh_disable(); - 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); -- 2.35.1