From b45db71b525d75e520d7ef46c796f49c5d26c07c Mon Sep 17 00:00:00 2001 From: Jon Paul Maloy Date: Tue, 3 Feb 2015 08:59:19 -0500 Subject: [PATCH] tipc: eliminate race during node creation Instances of struct node are created in the function tipc_disc_rcv() under the assumption that there is no race between received discovery messages arriving from the same node. This assumption is wrong. When we use more than one bearer, it is possible that discovery messages from the same node arrive at the same moment, resulting in creation of two instances of struct tipc_node. This may later cause confusion during link establishment, and may result in one of the links never becoming activated. We fix this by making lookup and potential creation of nodes atomic. Instead of first looking up the node, and in case of failure, create it, we now start with looking up the node inside node_link_create(), and return a reference to that one if found. Otherwise, we go ahead and create the node as we did before. Reviewed-by: Erik Hugne Reviewed-by: Ying Xue Signed-off-by: Jon Maloy Signed-off-by: David S. Miller --- net/tipc/discover.c | 9 ++------- net/tipc/node.c | 11 +++++------ 2 files changed, 7 insertions(+), 13 deletions(-) diff --git a/net/tipc/discover.c b/net/tipc/discover.c index 5b40cb89ff0a..a580a40d0208 100644 --- a/net/tipc/discover.c +++ b/net/tipc/discover.c @@ -1,7 +1,7 @@ /* * net/tipc/discover.c * - * Copyright (c) 2003-2006, 2014, Ericsson AB + * Copyright (c) 2003-2006, 2014-2015, Ericsson AB * Copyright (c) 2005-2006, 2010-2011, Wind River Systems * All rights reserved. * @@ -47,7 +47,6 @@ /* indicates no timer in use */ #define TIPC_LINK_REQ_INACTIVE 0xffffffff - /** * struct tipc_link_req - information about an ongoing link setup request * @bearer_id: identity of bearer issuing requests @@ -163,13 +162,9 @@ void tipc_disc_rcv(struct net *net, struct sk_buff *buf, if (!tipc_in_scope(bearer->domain, onode)) return; - /* Locate, or if necessary, create, node: */ - node = tipc_node_find(net, onode); - if (!node) - node = tipc_node_create(net, onode); + node = tipc_node_create(net, onode); if (!node) return; - tipc_node_lock(node); link = node->links[bearer->identity]; diff --git a/net/tipc/node.c b/net/tipc/node.c index d4cb8c127063..842bd7ad4b17 100644 --- a/net/tipc/node.c +++ b/net/tipc/node.c @@ -96,14 +96,14 @@ struct tipc_node *tipc_node_create(struct net *net, u32 addr) struct tipc_node *n_ptr, *temp_node; spin_lock_bh(&tn->node_list_lock); - + n_ptr = tipc_node_find(net, addr); + if (n_ptr) + goto exit; n_ptr = kzalloc(sizeof(*n_ptr), GFP_ATOMIC); if (!n_ptr) { - spin_unlock_bh(&tn->node_list_lock); pr_warn("Node creation failed, no memory\n"); - return NULL; + goto exit; } - n_ptr->addr = addr; n_ptr->net = net; spin_lock_init(&n_ptr->lock); @@ -123,9 +123,8 @@ struct tipc_node *tipc_node_create(struct net *net, u32 addr) list_add_tail_rcu(&n_ptr->list, &temp_node->list); n_ptr->action_flags = TIPC_WAIT_PEER_LINKS_DOWN; n_ptr->signature = INVALID_NODE_SIG; - tn->num_nodes++; - +exit: spin_unlock_bh(&tn->node_list_lock); return n_ptr; }