[PATCH net-next] packet: Protect packet sk list with mutex
From: Pavel Emelyanov <hidden>
Date: 2012-08-20 14:50:45
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. 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 only the sklist modifications (that already happen in sleeping context) and nothing more. Am I wrong again and a fine-grained atomic locking is required for everything that is reported by packet diag instead? Signed-off-by: Pavel Emelyanov <redacted> ---
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 <linux/spinlock.h> 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..5048672 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c@@ -2308,10 +2308,10 @@ 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); sock_prot_inuse_add(net, sk->sk_prot, -1); - spin_unlock_bh(&net->packet.sklist_lock); + mutex_unlock(&net->packet.sklist_lock); spin_lock(&po->bind_lock); unregister_prot_hook(sk, false);
@@ -2510,10 +2510,10 @@ 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); sock_prot_inuse_add(net, &packet_proto, 1); - spin_unlock_bh(&net->packet.sklist_lock); + mutex_unlock(&net->packet.sklist_lock); return 0; out:
@@ -3766,7 +3766,7 @@ 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;