forked from Minki/linux
tipc: eliminate risk of finding to-be-deleted node instance
Although we have never seen it happen, we have identified the following problematic scenario when nodes are stopped and deleted: CPU0: CPU1: tipc_node_xxx() //ref == 1 tipc_node_put() //ref -> 0 tipc_node_find() // node still in table tipc_node_delete() list_del_rcu(n. list) tipc_node_get() //ref -> 1, bad kfree_rcu() tipc_node_put() //ref to 0 again. kfree_rcu() // BOOM! We fix this by introducing use of the conditional kref_get_if_not_zero() instead of kref_get() in the function tipc_node_find(). This eliminates any risk of post-mortem access. Reported-by: Zhijiang Hu <huzhijiang@gmail.com> Acked-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>
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@ -245,23 +245,23 @@ static void tipc_node_get(struct tipc_node *node)
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*/
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static struct tipc_node *tipc_node_find(struct net *net, u32 addr)
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{
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struct tipc_net *tn = net_generic(net, tipc_net_id);
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struct tipc_net *tn = tipc_net(net);
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struct tipc_node *node;
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unsigned int thash = tipc_hashfn(addr);
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if (unlikely(!in_own_cluster_exact(net, addr)))
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return NULL;
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rcu_read_lock();
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hlist_for_each_entry_rcu(node, &tn->node_htable[tipc_hashfn(addr)],
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hash) {
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if (node->addr == addr) {
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tipc_node_get(node);
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rcu_read_unlock();
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return node;
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}
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hlist_for_each_entry_rcu(node, &tn->node_htable[thash], hash) {
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if (node->addr != addr)
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continue;
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if (!kref_get_unless_zero(&node->kref))
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node = NULL;
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break;
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}
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rcu_read_unlock();
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return NULL;
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return node;
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}
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static void tipc_node_read_lock(struct tipc_node *n)
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