From patchwork Fri Mar 19 01:06:02 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Pablo Neira Ayuso X-Patchwork-Id: 405852 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1362FC4361A for ; Fri, 19 Mar 2021 01:07:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E9F2D60C3E for ; Fri, 19 Mar 2021 01:07:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233068AbhCSBGk (ORCPT ); Thu, 18 Mar 2021 21:06:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52036 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231618AbhCSBGV (ORCPT ); Thu, 18 Mar 2021 21:06:21 -0400 Received: from mail.netfilter.org (mail.netfilter.org [IPv6:2001:4b98:dc0:41:216:3eff:fe8c:2bda]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id AC5AEC061760; Thu, 18 Mar 2021 18:06:20 -0700 (PDT) Received: from localhost.localdomain (unknown [90.77.255.23]) by mail.netfilter.org (Postfix) with ESMTPSA id 4A748630BE; Fri, 19 Mar 2021 02:06:14 +0100 (CET) From: Pablo Neira Ayuso To: netfilter-devel@vger.kernel.org Cc: davem@davemloft.net, netdev@vger.kernel.org, kuba@kernel.org Subject: [PATCH net 3/9] netfilter: x_tables: Use correct memory barriers. Date: Fri, 19 Mar 2021 02:06:02 +0100 Message-Id: <20210319010608.9758-4-pablo@netfilter.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20210319010608.9758-1-pablo@netfilter.org> References: <20210319010608.9758-1-pablo@netfilter.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Mark Tomlinson When a new table value was assigned, it was followed by a write memory barrier. This ensured that all writes before this point would complete before any writes after this point. However, to determine whether the rules are unused, the sequence counter is read. To ensure that all writes have been done before these reads, a full memory barrier is needed, not just a write memory barrier. The same argument applies when incrementing the counter, before the rules are read. Changing to using smp_mb() instead of smp_wmb() fixes the kernel panic reported in cc00bcaa5899 (which is still present), while still maintaining the same speed of replacing tables. The smb_mb() barriers potentially slow the packet path, however testing has shown no measurable change in performance on a 4-core MIPS64 platform. Fixes: 7f5c6d4f665b ("netfilter: get rid of atomic ops in fast path") Signed-off-by: Mark Tomlinson Signed-off-by: Pablo Neira Ayuso --- include/linux/netfilter/x_tables.h | 2 +- net/netfilter/x_tables.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/include/linux/netfilter/x_tables.h b/include/linux/netfilter/x_tables.h index 5deb099d156d..8ec48466410a 100644 --- a/include/linux/netfilter/x_tables.h +++ b/include/linux/netfilter/x_tables.h @@ -376,7 +376,7 @@ static inline unsigned int xt_write_recseq_begin(void) * since addend is most likely 1 */ __this_cpu_add(xt_recseq.sequence, addend); - smp_wmb(); + smp_mb(); return addend; } diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c index 7df3aef39c5c..6bd31a7a27fc 100644 --- a/net/netfilter/x_tables.c +++ b/net/netfilter/x_tables.c @@ -1389,7 +1389,7 @@ xt_replace_table(struct xt_table *table, table->private = newinfo; /* make sure all cpus see new ->private value */ - smp_wmb(); + smp_mb(); /* * Even though table entries have now been swapped, other CPU's