From: Cong Wang <xiyou.wangcong@gmail.com>
Date: Thu, 8 Feb 2018 21:53:52 +0000 (-0800)
Subject: netfilter: ipt_CLUSTERIP: fix a refcount bug in clusterip_config_find_get()
X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?p=pandora-kernel.git;a=commitdiff_plain;h=65b073589499cd4f2e9e3e94f491b6d7b47a8255;ds=inline

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

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>
---

diff --git a/net/ipv4/netfilter/ipt_CLUSTERIP.c b/net/ipv4/netfilter/ipt_CLUSTERIP.c
index db6785cec2dd..cb21acc35b61 100644
--- a/net/ipv4/netfilter/ipt_CLUSTERIP.c
+++ b/net/ipv4/netfilter/ipt_CLUSTERIP.c
@@ -135,8 +135,12 @@ clusterip_config_find_get(__be32 clusterip, int entry)
 	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();