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 D2DA5C433FE for ; Mon, 10 Oct 2022 00:16:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232065AbiJJAQx (ORCPT ); Sun, 9 Oct 2022 20:16:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42400 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232048AbiJJAQD (ORCPT ); Sun, 9 Oct 2022 20:16:03 -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 20831A1AE; Sun, 9 Oct 2022 16:52:20 -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 8961060DC7; Sun, 9 Oct 2022 22:24:45 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D37D4C4314C; Sun, 9 Oct 2022 22:24:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1665354285; bh=+pZ2BQgE4cajppLO56oT5anENuedhpOpwPn6ToGpfCc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=V007bbVyvtOvXmL0tD5iq2WQ1F/ti6lZLML3DizZIrJqh3y5vzzhPMLvUsM2dXmbW wivOMKv5WV6XuPm/v3QTieuQAHRfLKOz2S9stVs8R0AXuGcLlZzxwvCCjTNq8ol+t7 qhKN6XwBEZhiR1ha2GgEDDvcKvWyWRstq/DrAvwdu4VfW5PrvqmzFnGmBpG5H+508Q ztv49DeHsdUXC0pOHWyKEmYLz0eQ75hzSKffVCUF+2Tk6YDXFUHculSsSasHiOuAGM ByajJZ7QWvhxXJQqfFDL5EJvETsu3MSW6Ogp8r9K9M7yL2U0XXMtBLxQ/LMU9eXhhc UzakcxICZ9mLA== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Eric Dumazet , Abhishek Shah , "David S . Miller" , Sasha Levin , yoshfuji@linux-ipv6.org, dsahern@kernel.org, kuba@kernel.org, pabeni@redhat.com, netdev@vger.kernel.org Subject: [PATCH AUTOSEL 4.19 04/25] tcp: annotate data-race around tcp_md5sig_pool_populated Date: Sun, 9 Oct 2022 18:24:09 -0400 Message-Id: <20221009222436.1219411-4-sashal@kernel.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20221009222436.1219411-1-sashal@kernel.org> References: <20221009222436.1219411-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore 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 768a7daab559..73745d9e6dda 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -3690,12 +3690,16 @@ 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) @@ -3703,7 +3707,8 @@ 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); @@ -3719,7 +3724,8 @@ 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