tipc: involve reference counter for node structure
TIPC node hash node table is protected with rcu lock on read side.
tipc_node_find() is used to look for a node object with node address
through iterating the hash node table. As the entire process of what
tipc_node_find() traverses the table is guarded with rcu read lock,
it's safe for us. However, when callers use the node object returned
by tipc_node_find(), there is no rcu read lock applied. Therefore,
this is absolutely unsafe for callers of tipc_node_find().
Now we introduce a reference counter for node structure. Before
tipc_node_find() returns node object to its caller, it first increases
the reference counter. Accordingly, after its caller used it up,
it decreases the counter again. This can prevent a node being used by
one thread from being freed by another thread.
Reviewed-by: Erik Hugne <erik.hugne@ericsson.com>
Reviewed-by: Jon Maloy <jon.maloy@ericson.com>
Signed-off-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/tipc/link.c b/net/tipc/link.c
index f5e086c..514466e 100644
--- a/net/tipc/link.c
+++ b/net/tipc/link.c
@@ -854,6 +854,7 @@
if (link)
rc = __tipc_link_xmit(net, link, list);
tipc_node_unlock(node);
+ tipc_node_put(node);
}
if (link)
return rc;
@@ -1116,8 +1117,8 @@
n_ptr = tipc_node_find(net, msg_prevnode(msg));
if (unlikely(!n_ptr))
goto discard;
- tipc_node_lock(n_ptr);
+ tipc_node_lock(n_ptr);
/* Locate unicast link endpoint that should handle message */
l_ptr = n_ptr->links[b_ptr->identity];
if (unlikely(!l_ptr))
@@ -1205,6 +1206,7 @@
skb = NULL;
unlock:
tipc_node_unlock(n_ptr);
+ tipc_node_put(n_ptr);
discard:
if (unlikely(skb))
kfree_skb(skb);
@@ -2236,7 +2238,6 @@
msg.seq = cb->nlh->nlmsg_seq;
rcu_read_lock();
-
if (prev_node) {
node = tipc_node_find(net, prev_node);
if (!node) {
@@ -2249,6 +2250,7 @@
cb->prev_seq = 1;
goto out;
}
+ tipc_node_put(node);
list_for_each_entry_continue_rcu(node, &tn->node_list,
list) {
@@ -2256,6 +2258,7 @@
err = __tipc_nl_add_node_links(net, &msg, node,
&prev_link);
tipc_node_unlock(node);
+ tipc_node_put(node);
if (err)
goto out;