netfilter: ipt_CLUSTERIP: fix a refcount bug in clusterip_config_find_get()

In clusterip_config_find_get() we hold RCU read lock so it could
run concurrently with clusterip_config_entry_put(), as a result,
the refcnt could go back to 1 from 0, which leads to a double
list_del()... Just replace refcount_inc() with
refcount_inc_not_zero(), as for c->refcount.

Fixes: d73f33b16883 ("netfilter: CLUSTERIP: RCU conversion")
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Pablo Neira Ayuso <pablo@netfilter.org>
Cc: Florian Westphal <fw@strlen.de>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Reviewed-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/net/ipv4/netfilter/ipt_CLUSTERIP.c b/net/ipv4/netfilter/ipt_CLUSTERIP.c
index 1ff72b87a06613e14f82faef02dfcca0527a55b0..4b02ab39ebc54b73f6ec532fa6329fa9df47bb77 100644 (file)
--- a/net/ipv4/netfilter/ipt_CLUSTERIP.c
+++ b/net/ipv4/netfilter/ipt_CLUSTERIP.c
@@ -154,8 +154,12 @@ clusterip_config_find_get(struct net *net, __be32 clusterip, int entry)
 #endif
                if (unlikely(!refcount_inc_not_zero(&c->refcount)))
                        c = NULL;
-               else if (entry)
-                       refcount_inc(&c->entries);
+               else if (entry) {
+                       if (unlikely(!refcount_inc_not_zero(&c->entries))) {
+                               clusterip_config_put(c);
+                               c = NULL;
+                       }
+               }
        }
        rcu_read_unlock_bh();