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 X-Spam-Level: X-Spam-Status: No, score=-19.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 A6EDBC433EF for ; Mon, 13 Sep 2021 13:25:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 91B3C61355 for ; Mon, 13 Sep 2021 13:25:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241487AbhIMN0Y (ORCPT ); Mon, 13 Sep 2021 09:26:24 -0400 Received: from mail.kernel.org ([198.145.29.99]:34832 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240591AbhIMNWJ (ORCPT ); Mon, 13 Sep 2021 09:22:09 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id C55FC6113E; Mon, 13 Sep 2021 13:20:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1631539238; bh=eLJ9Sol2cQltCVDqOhPRp1+wi1Jp3Nz8GOsN49x/vds=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=vh9RA/suusRowSGVGYiRwyUgugJ4eL9Z20cXoXeG5VKND96toOhzbF7gYcpfwqV5q XGnUSirdX9qGGcgnH2tcdo/zmat94a8vNfL/2qPTszkdEYCKnq5OtL2KThX+mibZPM KuDQZgl5ybmgSO1dQqZpBH4p8dsJxD9qCWXQyupg= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Guillaume Nault , "David S. Miller" , =?UTF-8?q?H=C3=A5kon=20Bugge?= Subject: [PATCH 5.4 062/144] netns: protect netns ID lookups with RCU Date: Mon, 13 Sep 2021 15:14:03 +0200 Message-Id: <20210913131050.045276595@linuxfoundation.org> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20210913131047.974309396@linuxfoundation.org> References: <20210913131047.974309396@linuxfoundation.org> User-Agent: quilt/0.66 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: Guillaume Nault commit 2dce224f469f060b9998a5a869151ef83c08ce77 upstream. __peernet2id() can be protected by RCU as it only calls idr_for_each(), which is RCU-safe, and never modifies the nsid table. rtnl_net_dumpid() can also do lockless lookups. It does two nested idr_for_each() calls on nsid tables (one direct call and one indirect call because of rtnl_net_dumpid_one() calling __peernet2id()). The netnsid tables are never updated. Therefore it is safe to not take the nsid_lock and run within an RCU-critical section instead. Signed-off-by: Guillaume Nault Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman Signed-off-by: Håkon Bugge --- net/core/net_namespace.c | 28 ++++++++++------------------ 1 file changed, 10 insertions(+), 18 deletions(-) --- a/net/core/net_namespace.c +++ b/net/core/net_namespace.c @@ -211,9 +211,9 @@ static int net_eq_idr(int id, void *net, return 0; } -/* Should be called with nsid_lock held. If a new id is assigned, the bool alloc - * is set to true, thus the caller knows that the new id must be notified via - * rtnl. +/* Must be called from RCU-critical section or with nsid_lock held. If + * a new id is assigned, the bool alloc is set to true, thus the + * caller knows that the new id must be notified via rtnl. */ static int __peernet2id_alloc(struct net *net, struct net *peer, bool *alloc) { @@ -237,7 +237,7 @@ static int __peernet2id_alloc(struct net return NETNSA_NSID_NOT_ASSIGNED; } -/* should be called with nsid_lock held */ +/* Must be called from RCU-critical section or with nsid_lock held */ static int __peernet2id(struct net *net, struct net *peer) { bool no = false; @@ -281,9 +281,10 @@ int peernet2id(struct net *net, struct n { int id; - spin_lock_bh(&net->nsid_lock); + rcu_read_lock(); id = __peernet2id(net, peer); - spin_unlock_bh(&net->nsid_lock); + rcu_read_unlock(); + return id; } EXPORT_SYMBOL(peernet2id); @@ -962,6 +963,7 @@ struct rtnl_net_dump_cb { int s_idx; }; +/* Runs in RCU-critical section. */ static int rtnl_net_dumpid_one(int id, void *peer, void *data) { struct rtnl_net_dump_cb *net_cb = (struct rtnl_net_dump_cb *)data; @@ -1046,19 +1048,9 @@ static int rtnl_net_dumpid(struct sk_buf goto end; } - spin_lock_bh(&net_cb.tgt_net->nsid_lock); - if (net_cb.fillargs.add_ref && - !net_eq(net_cb.ref_net, net_cb.tgt_net) && - !spin_trylock_bh(&net_cb.ref_net->nsid_lock)) { - spin_unlock_bh(&net_cb.tgt_net->nsid_lock); - err = -EAGAIN; - goto end; - } + rcu_read_lock(); idr_for_each(&net_cb.tgt_net->netns_ids, rtnl_net_dumpid_one, &net_cb); - if (net_cb.fillargs.add_ref && - !net_eq(net_cb.ref_net, net_cb.tgt_net)) - spin_unlock_bh(&net_cb.ref_net->nsid_lock); - spin_unlock_bh(&net_cb.tgt_net->nsid_lock); + rcu_read_unlock(); cb->args[0] = net_cb.idx; end: