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 <[email protected]>
Acked-by: Ying Xue <[email protected]>
Signed-off-by: Jon Maloy <[email protected]>
---
net/tipc/node.c | 18 +++++++++---------
1 file changed, 9 insertions(+), 9 deletions(-)
diff --git a/net/tipc/node.c b/net/tipc/node.c
index 9fcc2fb..792bbcb 100644
--- a/net/tipc/node.c
+++ b/net/tipc/node.c
@@ -245,23 +245,23 @@ static void tipc_node_get(struct tipc_node *node)
*/
static struct tipc_node *tipc_node_find(struct net *net, u32 addr)
{
- struct tipc_net *tn = net_generic(net, tipc_net_id);
+ struct tipc_net *tn = tipc_net(net);
struct tipc_node *node;
+ unsigned int thash = tipc_hashfn(addr);
if (unlikely(!in_own_cluster_exact(net, addr)))
return NULL;
rcu_read_lock();
- hlist_for_each_entry_rcu(node, &tn->node_htable[tipc_hashfn(addr)],
- hash) {
- if (node->addr == addr) {
- tipc_node_get(node);
- rcu_read_unlock();
- return node;
- }
+ hlist_for_each_entry_rcu(node, &tn->node_htable[thash], hash) {
+ if (node->addr != addr)
+ continue;
+ if (!kref_get_unless_zero(&node->kref))
+ node = NULL;
+ break;
}
rcu_read_unlock();
- return NULL;
+ return node;
}
static void tipc_node_read_lock(struct tipc_node *n)
--
1.9.1
------------------------------------------------------------------------------
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