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authorJon Paul Maloy <jon.maloy@ericsson.com>2015-02-03 08:59:19 -0500
committerDavid S. Miller <davem@davemloft.net>2015-02-04 16:09:31 -0800
commitb45db71b525d75e520d7ef46c796f49c5d26c07c (patch)
treee19c1c7f6bc27d63e28a1315b7b19ce1d099e02d
parent7d24dcdb3f3132e0ec36f19c49bd004bc874b8aa (diff)
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 <erik.hugne@ericsson.com> Reviewed-by: Ying Xue <ying.xue@windriver.com> Signed-off-by: Jon Maloy <jon.maloy@ericsson.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--net/tipc/discover.c9
-rw-r--r--net/tipc/node.c11
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;
}