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authorYing Xue <ying.xue@windriver.com>2018-08-07 15:52:32 +0800
committerDavid S. Miller <davem@davemloft.net>2018-08-07 13:15:35 -0700
commit37436d9c0e8f62c3eebe204ff5776ff31fd64658 (patch)
tree432587995f086cb753ff509f8c5a1f57f7d9b12b
parent455f05ecd2b219e9a216050796d30c830d9bc393 (diff)
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tipc: fix an interrupt unsafe locking scenario
Commit 9faa89d4ed9d ("tipc: make function tipc_net_finalize() thread safe") tries to make it thread safe to set node address, so it uses node_list_lock lock to serialize the whole process of setting node address in tipc_net_finalize(). But it causes the following interrupt unsafe locking scenario: CPU0 CPU1 ---- ---- rht_deferred_worker() rhashtable_rehash_table() lock(&(&ht->lock)->rlock) tipc_nl_compat_doit() tipc_net_finalize() local_irq_disable(); lock(&(&tn->node_list_lock)->rlock); tipc_sk_reinit() rhashtable_walk_enter() lock(&(&ht->lock)->rlock); <Interrupt> tipc_disc_rcv() tipc_node_check_dest() tipc_node_create() lock(&(&tn->node_list_lock)->rlock); *** DEADLOCK *** When rhashtable_rehash_table() holds ht->lock on CPU0, it doesn't disable BH. So if an interrupt happens after the lock, it can create an inverse lock ordering between ht->lock and tn->node_list_lock. As a consequence, deadlock might happen. The reason causing the inverse lock ordering scenario above is because the initial purpose of node_list_lock is not designed to do the serialization of node address setting. As cmpxchg() can guarantee CAS (compare-and-swap) process is atomic, we use it to replace node_list_lock to ensure setting node address can be atomically finished. It turns out the potential deadlock can be avoided as well. Fixes: 9faa89d4ed9d ("tipc: make function tipc_net_finalize() thread safe") Signed-off-by: Ying Xue <ying.xue@windriver.com> Acked-by: Jon Maloy <maloy@donjonn.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--net/tipc/net.c4
1 files changed, 1 insertions, 3 deletions
diff --git a/net/tipc/net.c b/net/tipc/net.c
index a7f6964c3a4b..62199cf5a56c 100644
--- a/net/tipc/net.c
+++ b/net/tipc/net.c
@@ -123,15 +123,13 @@ void tipc_net_finalize(struct net *net, u32 addr)
{
struct tipc_net *tn = tipc_net(net);
- spin_lock_bh(&tn->node_list_lock);
- if (!tipc_own_addr(net)) {
+ if (!cmpxchg(&tn->node_addr, 0, addr)) {
tipc_set_node_addr(net, addr);
tipc_named_reinit(net);
tipc_sk_reinit(net);
tipc_nametbl_publish(net, TIPC_CFG_SRV, addr, addr,
TIPC_CLUSTER_SCOPE, 0, addr);
}
- spin_unlock_bh(&tn->node_list_lock);
}
void tipc_net_stop(struct net *net)