From patchwork Tue Aug 21 11:06:47 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Pavel Emelyanov X-Patchwork-Id: 179040 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 800B12C0099 for ; Tue, 21 Aug 2012 21:07:13 +1000 (EST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756903Ab2HULHB (ORCPT ); Tue, 21 Aug 2012 07:07:01 -0400 Received: from mailhub.sw.ru ([195.214.232.25]:36166 "EHLO relay.sw.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756872Ab2HULG6 (ORCPT ); Tue, 21 Aug 2012 07:06:58 -0400 Received: from [10.30.16.117] ([10.30.16.117]) (authenticated bits=0) by relay.sw.ru (8.13.4/8.13.4) with ESMTP id q7LB6mW9017023 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Tue, 21 Aug 2012 15:06:48 +0400 (MSK) Message-ID: <50336BC7.7030209@parallels.com> Date: Tue, 21 Aug 2012 15:06:47 +0400 From: Pavel Emelyanov User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.1) Gecko/20120209 Thunderbird/10.0.1 MIME-Version: 1.0 To: Eric Dumazet , David Miller , Linux Netdev List Subject: [PATCH net-next] packet: Protect packet sk list with mutex (v2) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Change since v1: * Fixed inuse counters access spotted by Eric In patch eea68e2f (packet: Report socket mclist info via diag module) I've introduced a "scheduling in atomic" problem in packet diag module -- the socket list is traversed under rcu_read_lock() while performed under it sk mclist access requires rtnl lock (i.e. -- mutex) to be taken. [152363.820563] BUG: scheduling while atomic: crtools/12517/0x10000002 [152363.820573] 4 locks held by crtools/12517: [152363.820581] #0: (sock_diag_mutex){+.+.+.}, at: [] sock_diag_rcv+0x1f/0x3e [152363.820613] #1: (sock_diag_table_mutex){+.+.+.}, at: [] sock_diag_rcv_msg+0xdb/0x11a [152363.820644] #2: (nlk->cb_mutex){+.+.+.}, at: [] netlink_dump+0x23/0x1ab [152363.820693] #3: (rcu_read_lock){.+.+..}, at: [] packet_diag_dump+0x0/0x1af Similar thing was then re-introduced by further packet diag patches (fanount mutex and pgvec mutex for rings) :( Apart from being terribly sorry for the above, I propose to change the packet sk list protection from spinlock to mutex. This lock currently protects two modifications: * sklist * prot inuse counters The sklist modifications can be just reprotected with mutex since they already occur in a sleeping context. The inuse counters modifications are trickier -- the __this_cpu_-s are used inside, thus requiring the caller to handle the potential issues with contexts himself. Since packet sockets' counters are modified in two places only (packet_create and packet_release) we only need to protect the context from being preempted. BH disabling is not required in this case. Signed-off-by: Pavel Emelyanov Acked-by: Eric Dumazet --- -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html diff --git a/include/net/netns/packet.h b/include/net/netns/packet.h index cb4e894..4780b08 100644 --- a/include/net/netns/packet.h +++ b/include/net/netns/packet.h @@ -8,7 +8,7 @@ #include struct netns_packet { - spinlock_t sklist_lock; + struct mutex sklist_lock; struct hlist_head sklist; }; diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 226b2cd..79bc69c 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -2308,10 +2308,13 @@ static int packet_release(struct socket *sock) net = sock_net(sk); po = pkt_sk(sk); - spin_lock_bh(&net->packet.sklist_lock); + mutex_lock(&net->packet.sklist_lock); sk_del_node_init_rcu(sk); + mutex_unlock(&net->packet.sklist_lock); + + preempt_disable(); sock_prot_inuse_add(net, sk->sk_prot, -1); - spin_unlock_bh(&net->packet.sklist_lock); + preempt_enable(); spin_lock(&po->bind_lock); unregister_prot_hook(sk, false); @@ -2510,10 +2513,13 @@ static int packet_create(struct net *net, struct socket *sock, int protocol, register_prot_hook(sk); } - spin_lock_bh(&net->packet.sklist_lock); + mutex_lock(&net->packet.sklist_lock); sk_add_node_rcu(sk, &net->packet.sklist); + mutex_unlock(&net->packet.sklist_lock); + + preempt_disable(); sock_prot_inuse_add(net, &packet_proto, 1); - spin_unlock_bh(&net->packet.sklist_lock); + preempt_enable(); return 0; out: @@ -3766,7 +3772,7 @@ static const struct file_operations packet_seq_fops = { static int __net_init packet_net_init(struct net *net) { - spin_lock_init(&net->packet.sklist_lock); + mutex_init(&net->packet.sklist_lock); INIT_HLIST_HEAD(&net->packet.sklist); if (!proc_net_fops_create(net, "packet", 0, &packet_seq_fops)) diff --git a/net/packet/diag.c b/net/packet/diag.c index bc33fbe..39bce0d 100644 --- a/net/packet/diag.c +++ b/net/packet/diag.c @@ -177,8 +177,8 @@ static int packet_diag_dump(struct sk_buff *skb, struct netlink_callback *cb) net = sock_net(skb->sk); req = nlmsg_data(cb->nlh); - rcu_read_lock(); - sk_for_each_rcu(sk, node, &net->packet.sklist) { + mutex_lock(&net->packet.sklist_lock); + sk_for_each(sk, node, &net->packet.sklist) { if (!net_eq(sock_net(sk), net)) continue; if (num < s_num) @@ -192,7 +192,7 @@ next: num++; } done: - rcu_read_unlock(); + mutex_unlock(&net->packet.sklist_lock); cb->args[0] = num; return skb->len;