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Subject[PATCH 3.2 090/153] netfilter: ipt_CLUSTERIP: fix a refcount bug in clusterip_config_find_get()
3.2.102-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Cong Wang <xiyou.wangcong@gmail.com>

commit db93a3632b0f8773a3899e04a3a3e0aa7a26eb46 upstream.

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>
[bwh: Backported to 3.2: s/refcount/atomic/]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
net/ipv4/netfilter/ipt_CLUSTERIP.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

--- a/net/ipv4/netfilter/ipt_CLUSTERIP.c
+++ b/net/ipv4/netfilter/ipt_CLUSTERIP.c
@@ -135,8 +135,12 @@ clusterip_config_find_get(__be32 cluster
if (c) {
if (unlikely(!atomic_inc_not_zero(&c->refcount)))
c = NULL;
- else if (entry)
- atomic_inc(&c->entries);
+ else if (entry) {
+ if (unlikely(!atomic_inc_not_zero(&c->entries))) {
+ clusterip_config_put(c);
+ c = NULL;
+ }
+ }
}
rcu_read_unlock_bh();

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